Rock-Socketed Shafts for Highway Structure Foundations (2006)

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111 APPENDIX B Survey Questionnaire and Responses The survey questionnaire is presented in the following pages. Responses to each question are summarized below each ques- tion. Some agencies did not respond to every question.

112 QUESTIONNAIRE NCHRP TOPIC 36-12 USE OF ROCK-SOCKETED DRILLED SHAFTS FOR HIGHWAY STRUCTURE FOUNDATIONS Background and Purpose Drilled shafts socketed into rock are widely used as highway bridge foundations and can provide high load capacity while controlling displacements when designed and constructed appropriately. However, several challenges for design engineers have been identified in the use of shafts socketed into rock and intermediate geomaterials. These can be grouped into three categories: • Geotechnical characterization of the rock or intermediate geomaterial • Analysis and design for axial loading • Analysis and design for lateral loading. The purpose of Synthesis Topic 36-12 is to gather information on how these issues have been addressed in the design of highway structures. To accomplish the objective, there will be a literature review, survey of bridge owners from state departments of transportation (DOTs) and toll authorities, and interviews. This questionnaire is designed to be completed by the state DOT Geotechnical Engineer, assuming that individual has the most knowledge regarding the issues identified above. However, it is recognized that practice varies between states and that other branches within a state DOT may have considerable involvement in drilled shaft engineering. In particular, structural (bridge) engineers responsible for superstructure design may also be involved in foundation design. Therefore, it is recommended that Part V of this questionnaire (Structural Analysis) be completed by the state Bridge Engineer. In addition, it is recommended that Part IV (Design for Axial and Lateral Load) be reviewed by the state Bridge Engineer. Several questions refer to intermediate geomaterials (IGM) as distinguished from rock. For purposes of this survey, these two materials are defined as follows: IGM = cohesive earth material with unconfined compressive strength between 0.5 MPa and 5.0 MPa (5 to 50 tsf) or cohesionless material with SPT N-value (N60) greater than 50. Rock = highly cemented geomaterial with unconfined compressive strength greater than 5.0 MPa (50 tsf). Part I: Respondent Information Geotechnical Engineer Name: Title: Agency: Address: City: State: Zip:

113 Phone: Fax: e-mail: Structural or Bridge Engineer Name: Title: Agency: Address: City: State: Zip: Phone: Fax: e-mail: Please return the completed questionnaire to: John P. Turner Professor, Civil & Architectural Engineering Department 3295 University of Wyoming Phone: 307-766-4265 1000 E. University Ave. Fax: 307-766-2221 Laramie, WY 82071 e-mail: turner@uwyo.edu After completing the survey, if there are issues pertaining to rock-socketed drilled shafts that you believe are important but that are not addressed adequately by the questionnaire, please feel free to contact the author directly. Part II: Defining the Use of Rock-Socketed Drilled Shafts by Your Agency 1. On approximately how many projects per year (average) does your agency deal with drilled shaft foundations socketed into rock or IGMs? None* (1) New Brunswick 1–10 (19) AZ, AL, AR, CT, HI, ID, IL, KY, ME, MI, MN, NH, NJ, NM, SD, TN, UT, VT, WA 10–20 (7) GA, IA, MO, MT, OR, PR, SC More than 20 per year CA, FL, KS, MA, NC, TX * If you answered “None,” skip to Question 5 2. Please indicate the types of rock or intermediate geomaterials that your agency has dealt with when using rock-sockets. (Check all that apply.) Igneous rock types Sedimentary rock types Metamorphic rock types Granite 13 Conglomerate 13 Slate 8 Rhyolite 5 Sandstone 25 Phyllite 5 Obsidian 0 Mudstone/Shale 24 Schist 12 Diorite 7 Limestone 21 Amphibolite 3

114 Andesite 7 Dolomite 15 Gneiss 12 Gabbro 5 Chalk 4 Marble 2 Basalt 11 Other (describe) 3 Quartzite 6 Diabase 4 Serpentinite 3 Peridotite 1 Other (describe) 2 Other (describe) 0 Other Rock Type Descriptions: Hawaii: tuff Minnesota: meta-graywacke Kentucky: interbedded limestone/shale New Mexico: gypsum Massachusetts: argillite North Carolina: partially cemented rock Michigan: iron ore, coal Oregon: diatomaceous siltstone 3. Indicate the range of rock-socket diameters and lengths used on your agency's projects. Range of socket diameters: Alabama (3.5–12 ft) Missouri (3–10 ft) Arizona (2–6 ft) Montana (3.5–10 ft) Arkansas (4–9 ft) New Hampshire (3–7.5 ft) California (2–4 ft) New Jersey (4–6 ft) Connecticut (2.5–7.5 ft) New Mexico (2.5–6 ft) Georgia (4.5–9.5 ft) North Carolina (3 ft min. to 12 ft max.) Hawaii (3–5 ft) Oregon (3–8 ft) Idaho (3.5–5 ft) Puerto Rico (3–4.5 ft) Illinois (2–7 ft) South Carolina (2–8 ft) Iowa (2–10 ft, usually 3.5–4.5 ft) South Dakota (2.5–10 ft) Kansas (3–8 ft) Tennessee (3–8 ft) Ken Florida (3–12 ft) tucky [Typically 4–7 ft (12 ft max.)] Texas (1.5–8 ft) Utah (2.5–4 ft) Intermediate Geomaterials: Alabama clay-shale Arkansas hardclay (8 tsf) California mudstone, sandstone, siltstone, phyllite, slate, and weathered rock Colorado claystone, siltstone, weakly cemented sandstone Florida weathered limestone Georgia partially weathered rock Illinois weathered limestone, hard clay/shale, cemented sand/sandstone Iowa shale, siltstone, sandstone, limestone, dolomite Kentucky weathered shale Massachusetts till Michigan soft shale, hardpan Minnesota noncemented sandstone, highly weathered granite Missouri softshale Montana claystones, siltstones, uncemented sandstones New Jersey v. dense sands with N > 50 New Hampshire glacial till New Mexico Santa Fe Formation (N > 75), of the Rio Grand Rift (indurated, cemented, sands, silts, clay) North Carolina weathered rock Oregon very soft mudstones, highly weathered sandstones, weakly cemented conglomerates Texas clay/shales Utah: weak shales and mudstones Vermont: glacial till Washington Has significant deposits of glacial origin. Many have been overridden and overconsolidated by continental glaciation turning them into IGMs by the definition on page 1. A figure, which can be accessed at http://www.dnr.wa.gov/geology/pdf/ri33.pdf contains the unit descriptions. The first four units are encountered in 75% of our shafts.

115 Maine (4.5–7.5 ft) Massachusetts (Typical 2.5–4 ft; extreme case10 ft) Michigan (3–5 ft) Minnesota (3–10 ft) Vermont (5–10 ft) Washington (3–10 ft, with understanding that 6 ft and greater may need specialized equipment or methods) Range of socket lengths: Alabama (Geotechnical Foundation Design generally recommends 1 diameter into competent rock. Bridge structures personnel generally drop this tip elevation to 1.5–2 diameters.) Arizona (10–30 ft) Montana (5–50 ft) Arkansas (8–30 ft) Missouri (15–120 ft) California (15 ft to >300 ft) New Hampshire (3–30 ft) Connecticut (5–15 ft) New Jersey (8–16 ft) Georgia (5–15 ft) New Mexico (6–30 ft) Hawaii (5–10 ft) North Carolina (10–120 ft) Idaho (5–12 ft) Oregon (up to 120 ft) Illinois (Typically 5–10 ft, range 3–40 ft) Puerto Rico (10–20 ft) Iowa (up to 30 ft) South Carolina (2–25 ft) Kansas (4.5–20 ft) South Dakota (30–90 ft) Kentucky (Typically 6–15 ft, approx. 30 ft max.) Tennessee (10–30 ft) Maine (5–23 ft) Texas (1–3 shaft diameters) Massachusetts (Typically 6 ft; several ft extr. case >50 ft) Utah (2–10 ft) Michigan (5–17 ft) Vermont (5–22 ft) Minnesota (5–160 ft) Washington (Usually 2 shaft diameters, so 6–20 ft depending on shaft size) 4. What group or person in your agency has primary responsibility for design of rock-socketed drilled shafts? (If more than one group within your agency is responsible, please describe briefly the division of tasks below.) Geotechnical Branch (30) AL, AZ, CA, CO, CT, GA, HI, ID, IL, IA, KS, KY, ME, MA, MI, MN, MO, MT, NH, NJ, NM, NC, OR, SC, SD, TN, TX, UT, VT, WA Geology Branch (4) AZ, CA, KS, MN Bridge Engineering (structural) (20) AL, AR, CA, CO, CT, GA, ID, IA, KS, KY, MA, MI, MN, MO, NH, OR, SD, TN, UT, VT Outside Consultant (11) CT, FL, HI, ID, IL, IA, KY, MA, NB, NM, PR Other (explain): Iowa (Input from FHWA) Division of tasks (if applicable): AL: Geotechnical is responsible for axial capacity. Bridge is responsible for lateral stability. CT: All our drilled shaft projects to date have been designed by outside consultants. If we were doing the design in-house, the responsibility would be shared between the geotech and bridge designer. CO: Geotech provides geotechnical design parameters. Bridge performs design. FL: Axial—Geotechnical; Lateral—Structural. GA: Geotechnical—Selection of shafts is recommended foundation type or alternate; bearing pressures, rock- socket length, and tip elevations. Bridge—Selection of shaft diameters, lateral analysis, and possible revision of tip elevations. KS: Geotechs set base of shaft elevation and recommend side shear and end bearing strengths. Florida (3–30 ft)

116 KY: Geotechnical Branch and/or Geotechnical Consultant—Geotech investigation, axial capacities, tip elevations. Division of Bridge Design and/or Structures Consultant—Structural design and detailing, structure plans. MA: Geotechnical—Dimensions and capacities based on loadings and soil/rock properties. Structural—rebar, concrete, connection designs. MI: Geotechnical characterizes rock formation and determines rock-socket diameter and length. Bridge Design determines shaft location, shaft loading, and sizes reinforcement. MN: Geotech determines design bearing capacities and soils and rock properties with consultation with geology. Structures designs final shaft dimensions. MO: Geotechnical Office provides design criteria and evaluates shaft design based on materials encountered and proposed shaft configuration. Bridge Engineering proposes the layout of foundation units and designs the shaft itself (size, steel configuration, etc.). NM: Geotechnical Section approves outside consultant designs. UT: Geotech Branch—rock resistance, L-pile; Structures—structural design. VT: Geotechnical capacity and lateral analysis is done by the geotechnical branch and structural design is done by the structures group. WA: Geotechs assess capacity and settlement and provide p-y input parameters to bridge office. The structural designer in the bridge office performs the structural design of the shaft assessing shear, moments, and rebar/concrete requirements. They also perform the seismic design using the geotech’s p-y parameters. 5. In the next 3 years, do you anticipate that the use of rock-socketed drilled shafts by your agency will: Increase (8) ID, KS, MA, MO, NB, PR, SC, TN Remain approximately the same (25) AL, AZ, AR, CA, CT, FL, GA, HI, IL, IA, KY, ME, MI, MN, MT, NH, NJ, NM, NC, OR, SD, TX, UT, VT, WA Decrease (none) 6. Please add any comments you feel would be useful, pertaining to the use of rock-socketed drilled shafts by your agency. CA: Most result in claims due to the requirement to include “Differing Site Conditions” on all contracts. IA: Use of drilled shafts has been more frequent in past 2–3 years (above historic use), but may fall off again within next 2–3 years. KS: Used on high tower lighting and sign structure footings. Used as a contractor’s option on some structures. Ease of construction around highway and railway facilities. MS: Combination of new codes and loadings, issues of scour, and extreme events, are driving the use of deep and/or rock-socketed shafts. MO: Use is increasing in part due to more consultant bridge design and MoDOT bridge designers gaining more experience in shaft design. Shaft design is cost-competitive with driven pile in many cases and construction in urban areas causes less noise and vibration than driven pile. New Brunswick: We are beginning to recognize the potential of this type of foundation as an option for bridge foundations in our province. We currently have two projects in the design stage that will use drilled shaft foundations. Where we have limited design experience in-house; most of the questions in the survey are left unanswered. We look forward to reviewing the results as a way to see how other agencies approach these designs, as we move toward the consideration of drilled shafts as an option in the future. NH: Emphasize that the design of drilled shafts should include consideration of the drilled shaft construction methods and constructability issues. OR: Most of our shafts are socketed into bedrock, either with or without end bearing resistance. Many times we need rock embedment to resist high lateral loads associated with high seismic loading conditions, sometimes coupled with soil liquefaction. SC: Finding some way to equate different rock drilling rigs/equipment capabilities to varying rock strengths. SD: 99% of the drilled shafts done in this state are done in shale bedrock.

117 WA: When we want to have a rock socket of a certain length and recognize that the rock may be variable in elevation we include the following provision in our shaft special provision. With this special in place, the contractor can tie the reinforcing cage prior to excavating, excavate to rock, construct the rock socket, and trim the cage to fit. Excavation to tip elevation, cage placement, and the concrete pour can be complete in one shift this way. We pay for the steel that is cut off from the bottom of the cage, but feel that it is well worth the investment by lowering our risk of a blow-in or caving as the shaft does not have to sit open for days while the cage is tied. When the contract requires a minimum penetration into a bearing layer, as opposed to a specified shaft tip elevation, and the bearing layer elevation at each shaft cannot be accurately determined, add subsection 3.05.E as follows: For those shafts with a specified minimum penetration into the bearing layer and no specified tip elevation the Contractor shall furnish each shaft steel reinforcing bar cage, including access tubes for cross-hole sonic log testing in accordance with subsection 3.06 of this Special Provision, 20% longer than specified in the plans. The Contractor shall add the increased length to the bottom of the cage. The contractor shall trim the shaft steel reinforcing bar cage to the proper length prior to placing it into the excavation. If trimming the cage is required and access tubes for cross-hole sonic log testing are attached to the cage, the Contractor shall either shift the access tubes up the cage or cut the access tubes provided that the cut tube ends are adapted to receive the watertight cap as specified. Part III: Characterization of Rock or Intermediate Geomaterial (IGM) 7. Check the methods used by your agency to determine depth to bedrock for the purpose of drilled shaft foundation engineering. Standard Penetration Test (SPT) refusal (22) AR, CA, CO, FL, GA, HI, IL, IA, KS, MA, MI, MN, MO, MT, NJ, NM, NC, OR, PR, SC, UT, VT Cone Penetration Test (CPT) refusal: (3) KS, MN, MO Coring and inspection of core samples (30) AL, AZ, AR, CA, CO, CT, FL, GA, HA, ID, IL, IA, KS, KY, ME, MA, MI, MN, MO, NH, NJ, NM, NC, OR, PR, SC, TN, UT, VT, WA Geophysical methods (specify) AZ, CA, ID (seismic refraction), KS, KY (currently using resistivity and microgravity on a project where we are considering drilled shaft foundations. We have not previously used geophysical methods for drilled shaft investigations), MT, UT, (seismic refraction), WA Other (specify—provide details if possible) CA (2.25 in diameter terry cone driven to refusal. Please note that no one method is solely relied upon), IL, IA (laboratory UC or other tests), MN (pressuremeter), NJ (point load strength test), NM (RQD/RMR/joint orientation/water/polymer slurry only), SD (California retractable plug sampler to extract samples), TX (Texas Cone Penetrometer—for information see the following websites: http://txdot-manuals/dynaweb/colbridg/geo—go to Chapter 2, Section 4, Field Testing for Design Charts—go to Chapter 4, Design Guidelines: http://txdot- manuals/dynaweb/colmates/soi/@Generic__BookView;cs=default;ts=default; go to Section 32 Tex—132-E Texas Cone Penetration Test). 8. How does your agency distinguish between rock, soil, and intermediate geomaterials? Defined in the same way as stated on page 1 of this questionnaire (24) AL, AR, CA, CO, FL, HI, ID, IL, KS, KY, ME, MI, MN, MO, MT, NM, OR, PR, SC, SD, TN, UT, VT, WA Other: summarize below AZ: Typically, we classify as either soil or rock only by the use of test borings.

118 CT: We generally do not try to quantify IGMs. We may have some glacial tills/weathered bedrocks overlying a hard bedrock that would be an IGM, but we do not usually spend much time defining its’ engineering properties for the design of drilled shafts. CO: Some very weathered claystone is classified as rock even if it is weaker than IGM, as described in the background and purpose section above. GA: Soil-drilled and sampled with earth augers, SPT < 50±, drilled shaft bearing pressure < 30– 40 ksf; IGM-drilled with earth and/or rock augers, SPT > 50±, drilled shaft bearing pressure > 40 ksf, < 75 ksf; rock material below auger refusal sampled with diamond core drilling, drilled shaft bearing pressure > 75 ksf. IL: Experience combined with field observation of drilling operation (difficulties, change of drilling tools, etc.) IA: Classify as IGM? Rock if of “sedimentary rock” geologic origin. Classify as soil if of glacial, alluvial, similar deposition. KY: We have very few IGMs and if we have them, they are typically a weathered zone of shale in a transition from residual soil to interbedded limestone and shale. This material is typically neglected for drilled shaft design. MA: We have a clear distinction between rocks and soils, based on coring use. ME: NH: For classification purposes on test boring logs, differentiation of bedrock vs. IGM or soil based on geologic interpretation of boring samples. For drilled shaft analysis, would generally use the definitions on page 1 (e.g., weathered bedrock would be classified on the boring log as bedrock, but would be analyzed as an IGM). NJ: Based on the coring results, RQD and recovery, and engineering judgment; e.g., RQD < 30% may be considered as IGM not sound rock. NC: Definition of Rock—SPT and refusal—“Rock” is defined as a continuous intact natural material in which the penetration rate with a rock auger is less than 2 in. (50 mm) per 5 min of drilling at full crowd force. This definition excludes discontinuous loose natural materials such as boulders and man-made materials such as concrete, steel, timber, etc. TX: Our design methodology does not require specific designation of rock, soil, or IGM. Design is generally based on the strength testing, regardless of material designation. The following is a list of rock properties that may be required or recommended to apply design methods specified in the FHWA Drilled Shaft Manual, as well as for other published design methods used for rock-socketed drilled shafts: qu = unconfined compressive strength (units of F/L2) RQD = Rock Quality Designation φRC = effective stress angle of friction between the rock or IGM and concrete Ecore = Young's modulus of rock or IGM core (units of F/L2) Rock Mass Quality as defined in terms of: RMR = Rock Mass Rating (Bieniawski 1974) Q = Norwegian Geotechnical Institute rating (Barton 1974) c'i and φ'i = instantaneous values of cohesion and friction angle for Hoek–Brown nonlinear strength criteria of fractured rock masses 9. For each rock property, check the appropriate box indicating whether your agency determines this property for rock-socket design and, if so, the method used to determine the property: qu Always Never Varies Always: (23) AL, AZ, CT, FL, HI, ID, IL, KS, ME, MA, MI, MN, MO, MT, NJ, NM, OR, SC, SD, TN, UT, VT, WA Never: (0) Varies : (10) AR, CA, CO, GA, IA, KY, NH, NC, PR, TX

119 Method: ASTM D2938 or AASHTO T-226: Uniaxial Compressive Strength (14) AL, AZ, IA, KY, MN, MO, NH, NM, OR, SC, TN, TX, UT, VT Point Load Tests and/or Uniaxial Compression of intact core: (3) MA, MI, WA Maine (ASTM D7012-04) ?? RQD Always Never Varies Always: (28) AL, AZ, AR, CA, CO, CT, GA, HI, ID, IL, IA, KS, ME, MA, MI, MN, MO, MT, NH, NJ, NC, OR, PR, SC, TN, UT, VT, WA Never: (1) SD Varies: (3) FL, KY, TX φRC Always Never Varies Always: (2) KS, MT Never: (23) AL, AR, CT, FL, GA, HI, ID, IL, KY, ME, MA, MI, MN, NH, NM, NC, OR, PR, SC, SD, TX, UT, VT Varies: (7) AZ, CA, CO, IA, NJ, TN, WA Method: AL (Relies on charts), AZ (Estimate from AASHTO Manual), IA (theoretical), WA (Usually use published textbook values based on rock type) Ecore Always Never Varies Always: (5) KS, ME, MN, UT, VT Never: (11) AL, AR, CA, HI, ID, MT, NM, PR, SC, SD, TX Varies: (16) AZ, CO, CT, FL, GA, IL, IA, KY, MA, MI, NH, NJ, NC, OR, TN, WA Method: AL: Correlation charts between qu and E IA: Theoretical KY: Correlation with UC strength ME: ASTM 7012-04 MA: Goodman, Jack, and tables/charts MI: Calculated from Ultrasonic Velocity test (ASTM D2845) or approximated from figures and tables in section 4 of the AASHTO Standard Specs MN: ASTM D3148 NH: Eintact determined from qu test, then correlated to Ein situ through RMR or other methods OR: From ASTM D2938 results with measured strains UT: either unconfined compression test or from AASHTO table VT: ASTM D3148 WA: Usually use published textbook values based on rock type RMR Always Never Varies Always: (5) MA, NH, NM, TN, UT Never: (15) AL, AR, FL, HI, IL, KY, ME, MI, MN, MT, NJ, PR, SC, SD, TX Varies: (12) AZ, CA, CO, CT, GA, ID, IA, KS, NC, OR, VT, WA

120 Q Always Never Varies Always: none Never: (29) AL, AZ, AR, CA, CO, CT, FL, GA, HI, ID, IL, IA, KY, ME, MA, MI, MN, MT, NH, NJ, NM, OR, PR, SC, SD, TX, UT, VT, WA Varies : (3) KS, NC, TN c'i and φ'i Always Never Varies Always: none Never: (24) AL, AR, CT, FL, GA, HI, ID, IL, IA, KS, KY, ME, MA, MI, MN, MT, PR, SC, SD, TN, TX, UT, VT, WA Varies : (8) AZ, CA, CO, NH, NJ, NM, NC, OR 10. List below any in situ test methods that are used by your agency to correlate with rock or IGM properties or to correlate directly to rock-socket design parameters (e.g., side or end bearing resistance). In Situ Test State Property or Design Parameter Standard Penetration Test (SPT) CA not stated HI strength IL inch penetration per 100 blows (no property stated) MO correlation to qu NH side and end bearing resistances WA friction angle for IGMs FL strength Pressuremeter Test (PMT) AZ shear values CA rock mass modulus MN stiffness (rock mass modulus) OR correlation with p-y curves Borehole (Goodman) Jack MA rock mass modulus Dilatometer CA rock mass modulus TxDOT Cone Penetrometer TX correlate to side and tip resistances 11. Indicate by marking the boxes whether your agency uses any of the following tools for evaluating characteristics of rock below base elevation: Coring into the rock below the bottom of the shaft after the excavation to base elevation is complete; if so, to what depth? AZ: 3B or minimum of 10 ft AL: typically 10 ft unless specified otherwise FL: >10 ft GA: 6 ft MO: 10 ft below the bottom of the shaft for end bearing design; not required when designed for side friction only MT: 50 ft NJ: not stated NM: 3 diameters NC: 5 ft TX: at least 5 ft deep or a depth equal to the shaft diameter, whichever is greater.

121 Coring into rock below bottom elevation prior to excavating the shaft. (27) AL, AZ, AR, CA, CT, FL, GA, HI, ID, IL, IA, KS, KY, MA, MI, MN, MO, NH, NJ, NM, NC, OR, PR, TN, UT, VT, WA Inspection of core holes at the bottom of the socket using “feeler rods.” (5) AL, GA, MA, NC, TN Inspection of core holes using fiberoptic cameras. (5) AZ, NJ, NM, NC, UT Other: CA: Visually inspect drilled hole and cores and/or cuttings that are removed. IL: Visual inspection and classification of rock core by an experienced geologist. ME: Camera inspection of rock-socket base and extending borings during design stage to depth below expected bottom of rock socket. NC: 10 lb weight, SID camera, or use temporary casing to inspect the base by the engineer or the contractor. SC: Corings into rock below shaft bottom during design represent expected rock below base. UT: Visual inspection; many times, the rebar cage is designed to go to the bottom of the boring (in shorter shafts)—this verifies depth. 12. If your agency has experience in the design and construction of rock sockets with any of the materials listed below, please check the appropriate box and provide information on test methods (field or laboratory) that you have used to characterize the material properties Weak lime rock (11) AZ, FL, GA, IA, KS, MN, MO, NC, SC, TX, UT State: Property; Test Method; Correlations Used AZ: This applies to all rock types listed below: shear and end bearing; unconfined compressive strengths and RQD; AASHTO Guidelines FL: Coring, qu, qt, RQD, Recovery (%), SPT GA: Coring, RQD, compressive tests, split tensile IA: Strength, skin friction/end bearing; lab UC on cores, O-cell tests KS: Core, RQD RMR qu MN: Strength and stiffness; unconfined compression MO: Compressive strength; qu on core sample NC: Typically we core the rock and perform unconfined compression tests SC: Unconfined; load test TX: qu, skin friction, point bearing; ASTM, Tex-132-E; TxDOT Geotechnical Manual correlations UT: Same mentioned in Question 9 Soft shales or marls (14) AL, AZ, CA, GA, IA, KS, KY, MI, MO, NM, SC, SD, TX, UT State: Property; Test Method; Correlations Used AL: Rock strength, thickness and spacing of discontinuities; unconfined compression testing where possible, logged by a professional geologist from the cored rock (for all rock types checked) CA: Unconfined strength; triaxial test GA: Coring, RQD, compression tests IA: Strength skin friction/end bearing; lab UC on cores and O-cell tests KS: As above KY: Unconfined compression, slake durability index MI: Unconfined compressive strength; ASTM D2166 MO: Compressive strength; qu on core and correlations with SPT; Texas DOT correlations modified by

122 MoDOT NM: qu/triax shear; AASHTO T296; Alpha method SC: Triaxial; load tests SD: Soil strengths; unconfined compression test; skin resistance compared to pull test on steel pk rod TX: qu, skin friction, point bearing; ASTM, Tex-118-E, Tex-132-E; TxDOT Geotechnical Manual correlations UT: Same as mentioned in Question 9 Weathered and highly fractured rock (20) AL, AZ, CA, GA, HI, IA, KS, KY, MA, MI, MN, MO, NM, NC, OR, SC, SD, TX, UT, WA State: Property; Test Method; Correlations Used AR: Visual observations of rock condition GA: Coring, RQD, compression tests HI: Strength; unconfined compression IA: Strength skin friction/end bearing; lab UC on cores and O-cell tests KS: As above KY: We may use Slake Durability Index in shale and sometimes sandstone MA: RMR/qu MI: Unconfined compressive strength; Point Load Test ASTM D5731; correlations included in test procedure MN: Strength and stiffness; SPT or pressuremeter MO: RQD NM: phi'; N60; Mayne and Harris OR: Shear strength; SPT, judgment based on experience, often treated as very dense granular soil; Meyerhof or Peck, Hanson, Thornburg SC: SPT SD: Soil strengths; unconfined compression test; skin resistance compared to pull test on steel pk rod TX: qu, skin friction, point bearing; ASTM, Tex-132-E; TxDOT Geotechnical Manual correlations UT: Same mentioned in Question 9 WA: RQD and unconfined compressive strength; drilling and Point Load Karst (9) AL, AZ, FL, GA, KS, KY, MI, NM, TX State: Property; Test Method AZ: Core into rock after the excavation to check for voids FL: Coring, qu, qt, SPT GA: Coring, RQD, compressive tests, split tensile KS: Seismic KY: Rock Core Recovery NM: Discontinuities; test pits/seismic shear wave TX: qu, skin friction, point bearing; TxDOT Geotechnical Manual correlations Rock with steeply dipping discontinuities (7) AL, AR AZ, CA, GA, NM, WA State: Property; Test Method; Correlations AR: Visual observations of rock condition AZ: Down-the-hole camera to check for poorly oriented joint sets GA: Coring, RQD, compressive tests NM: Modulus; RMR WA: RQD and unconfined compressive strength; drilling and Point Load Interbedded rock with alternating strong and weak strata (11) AL, AR, AZ, CA, GA, IA, KS, KY, MO, NM, TX State: Property; Test Method

123 AR: Visual observations of rock condition GA: Coring, RQD, compressive tests IA: Strength skin friction/end bearing; lab UC on cores, O-cell tests KS: Core, qu, RMR, RQD KY: Unconfined compression, Slake Durability Index MO: Compressive strength; qu from representative core samples NM: Side shear/modulus; Rowe and Armitage TX: qu, skin friction, point bearing; ASTM, Tex-118-E, Tex-132-E Hard, intact rock (22) AL, AZ, CA, CT, GA, HI, ID, IA, KY, ME, MA, MI, MN, MO, NH, NM, NC, OR, SC, TX, VT, WA State: Property; Test Method; Correlations AL: AZ: CA: CT: Unconfined compressive strength GA: Coring, RQD, compressive tests HI: Strength; unconfined compression ID: Unconfined compressive strength; ASTM D2938 IA: Strength skin friction/end bearing; Lab UC on cores O-cell tests KY: Unconfined compression ME: qu and E; D 7012-04 MA: qu; point load: Ip; 25 Ip = qu MI: Unconfined compressive strength; ASTM-C42 MN: Strength and stiffness; unconfined compression test MO: Compressive strength; qu from core samples NH: Intact compressive strength; unconfined compression test NM: qu; RMR NC: OR: Unconfined compressive strength; ASTM D2938 SC: Unconfined; FHWA methodology TX: qu, skin friction, point bearing; ASTM, Tex-132-E; TxDOT Geotechnical Manual correlations VT: qu; ASTM D2938; FHWA IF-99-025 WA: RQD and unconfined compressive strength; drilling and point load 13. Identify any other issues pertaining to IGM or rock characterization that you think should be addressed by the Synthesis. MO: Limited Osterberg load cell testing has indicated that we significantly overdesign shafts in IGMs based on compressive strength values from qu testing. We need low cost in situ or other test methods for obtaining ultimate capacities in IGMs. NC: NCDOT and the NC State University conducted research to determine p-y curves for soft weathered rock loaded horizontally. OR: In Question 9, is anyone actually measuring or estimating the “s” and “m” dimensions of the rock mass for the Carter and Kulhawy equation? Also, is anyone estimating borehole “roughness” and using the Horvath (1983) equation? We are not because we have no real way of knowing if this can be accomplished in the field. UT: How are states handling discontinuities in design; how are strength values of the discontinuities being determined, etc.? WA: In Washington State, our shaft lengths are rarely designed to carry the applied axial loads. Most shafts have very significant lateral capacity demand owing to earthquake loading. Tip elevations are often set to meet lateral capacity requirements. Very little information is available on the lateral capacity or lateral behavior of shafts in IGMs subjected to lateral loads. The effects of group loading in IGMs are also not well-documented.

124 Part IV: Design for Axial and Lateral Load Note: The terms “base resistance,” “tip resistance,” and “end-bearing resistance” are used by various agencies; all refer to the resistance developed beneath the tip of a deep foundation. 14. When designing for axial load of rock-socketed shafts, does your agency account for: Both side and base resistances (25) AL, AZ, CA, CO, CT, FL, GA, IA, KS, KY, ME, MI, MN, MO, MT, NM, NC, OR, PR, SC, TN, TX, UT, VT, WA Side resistance only (10) CA, HI, ID, MA, MN, MO, NH, NJ, SD, TN Base resistance only (7) AR, CA, ID, ME, MA, MO, TN Comments: AZ: Rely mainly on side resistance with reduced end bearing. CA: Depends on anticipated methods of construction. IL: Depends on the elastic deformation. Generally, not both side and end. MO: Evaluated on a case-by-case basis. Typically end bearing only in hard rock and side resistance only in alternating hard and soft rock layers. NH: Rock-socket lengths typically controlled by lateral load with sufficient geotechnical capacity provided by side shear only. Would consider using a portion of the end bearing geotechnical capacity in combination with full side shear, if needed, to avoid extending socket length beyond what may be needed for lateral loads. NC: Depends on our design; we might use base or side resistance but most of the time we use both. OR: Combine side and base resistance only in very ductile rock formations as described in the FHWA Drilled Shaft Design Manual. TN: Geotech Section provides parameters for both. Structure designer decides which to use. UT: In wet conditions we will, many times, discount base resistance; with the current LRFD code we have been using either side resistance only (most of the time) or base resistance, based on deflection. 15. For calculating side resistance of rock sockets, please indicate the reference(s) associated with the method(s) used by your agency (mark all that apply): O'Neill and Reese (1999) Publication No. FHWA-IF-99-025, Drilled Shafts: Construction Procedures and Design Methods (26) AL, AZ, CA, CT, GA, HI, ID, IA, KS, KY, MA, MI, MN, MO, MT, NH, NJ, NM, NC, OR, PR, SC, TN, UT, VT, WA Horvath and Kenney (1979) (8) CA, HI, ID, IL, ME, OR, SC, TN Rowe and Armitage (1984) (1) NM Carter and Kulhawy (1988) (6) CA, IL, ME, NC, SC, WA Other (please cite reference or provide a brief description) (6) AZ: (AASHTO 2002) KS: (Results from O-cell tests) FL: McVay et al. (1992) NH: (2002 AASHTO bridge code)

125 OR (not stated) TX (TxDOT Design Method—See Chap. 4 of the Geotechnical Design Manual (website) 16. What, if any, computer programs are used by your agency for analysis of rock-socket response to axial loading? SHAFT (14) AL, AZ, CA, GA, KS, MN, MT, NJ, NM, NC, OR, PR, SC, UT FBPIER (6) CT, FL, MN, NC, TN, VT ROCKET (0) CUFAD (0) Other (name of program) (4) FL: FB Deep IL: In-house spreadsheet based on Pells and Turner KY: In-house spreadsheets TX: WinCore–TxDOT program for the design of drilled shafts 17. Specify the range of values used by your agency for either Factor of Safety (FOS) or Resistance Factor ( φs) applied to rock-socket ultimate side resistance in design (if applicable, specify by rock type). AL: FOS 3.0 MI: All, FOS 3 AZ: All, FOS 2.5 NH: All, FOS 2.5 CA: Hard rock, FOS 2.0–2.5 or φs 1 or 0.75 NJ: All rocks, FOS 2 CT: AASHTO ASD, LFD, or LRFD recommended NM: All, FOS 2.0 values regardless of rock type NC: All, FOS 2.5–3.00, We reduce the GA: Weak IGM or hard granite FOS 2.5 FOS if we perform a load test HI: Tuff, φs 0.65 OR: All, FOS 2.5 ID: Igneous (basalt), φs 0.55–0.65 : All, FOS 2–3, φs 0.4–0.7 IL: All, FOS 2.5 SD: Shale, FOS 2.0? IA: IGM and “Rock,” FOS 2–2.5 TX: All, FOS 3 KY: All, FOS 2 (if load tested) to 3 UT: All types, φs 0.55 MA: All, FOS 2–2.5 or φs 0.55–0.65 VT: All, FOS 2.5 ME: Schist, FOS 2.5 WA: All, FOS 3.0 Static, 1.65 Seismic FL: By AASHTO LRFD 18. For calculating base resistance of rock sockets, please indicate the reference(s) associated with the method(s) used by your agency (mark all that apply): O'Neill and Reese (1999) Publication No. FHWA-IF-99-025, Drilled Shafts: Construction Procedures and Design Methods (24) AL, AR, CA, CT, GA, ID, IA, KS, KY, ME, MA, MI, MN, MO, MT, NH, NJ, NM, NC, OR, PR, UT, VT, WA Canadian Foundation Engineering Manual (1979) (3) CA, IL, ME Zhang and Einstein (1998) (2) ID, MA Carter and Kulhawy (1988) (3) AR, CA, WA Other (please cite reference or provide a brief description) AZ: AASHTO 2002 KS: O-cell tests results KY: Experience and judgment SC

126 NH: 2002 AASHTO Bridge code NM: Rowe and Armitage TN: Use Soils and Geology Allowables and Section 4 of AASHTO Specs. TX: TxDOT Design Method—See Chap. 4 of the Geotechnical Design Manual (website) WA: AASHTO LRFD Manual 19. Specify the range of values used by your agency for either Factor of Safety (FOS) or Resistance Factor (φs) applied to rock-socket ultimate base resistance in design: AL: FOS 3.0 MI: All, FOS 3 AR: Sandstone or shale, FOS 2.5 MN: FOS 2.5 AZ: All, FOS 2.5 NH: All, FOS 2.5 CA: All, FOS 2.0 or φs 1 or 0.75 NJ: All rocks, FOS 2 CT: AASHTO ASD, LFD, or LRFD recommended NM: All, FOS 2.0 values regardless of rock type NC: All, FOS 2.5–3.0 GA: Weak IGM or hard granite, FOS 2.5 OR: All, FOS 2.5 ID: Igneous (basalt), φs 0.5 : All, FOS 2–3, φs 0.4–0.7 IL: All, FOS 2.5 : Shale, FOS 2.0? IA: IGM and “rock,” FOS 2–2.5 TN: All, FOS 2.5 KY: All, FOS 2 (if load tested) to 3 TX: All, FOS 2 MA: All, FOS 2–2.5 or φs 0.5 UT: All types, φs 0.5 ME: Schist, FOS 2.5 VT: All, FOS 2.5 WA: All, FOS 3.0 Static, 1.65 Seismic 20. If you include both side and base resistances in design of rock sockets, explain briefly how you account for the relative contribution of each to the socket axial resistance CA: Must determine the amount of each that can be mobilized at our allowable movement at the top of the pile. CT: The relative contributions would be based on the computed displacement/strain of the drilled shaft. If load test data were available, the strain compatibility would be validated or refined based on the actual test data. FL: Based on compatibility. IL: For weak IGM. IA: Both are typically limited by settlement criteria for both allowable and ultimate loads. KS: In good hard rock most of the load is stripped off in side shear. In shales, we assume that side shear and end bearing act together; either O-cell testing at site or extrapolation of previous testing. KY: Evaluate strain compatibility if O-cell load test is run. If no load test, use higher FS (3). ME: Two projects were designed in accordance with AASHTO 4.6.5.3, assuming that axial loads are carried solely by end resistance, as the strains required for full mobilization of both end and side resistance is incompatible. This design approach was later altered on one project to assume conservative, simultaneous mobilization of both end and side frictional resistance. That design approach ignored side resistance in the upper 5 to 15 ft may (based on a minimum required value of RQD and qu, determined by the geotechnical engineer). For the remainder of the side walls, partial contribution is assumed, in addition to partial mobilization of full end bearing. MI: Seek to design socket to have side friction capacity 2.0 to 2.5 times applied load. When end bearing contribution is added, seek to show FS greater than or equal to 3.0. NM: Osterberg and Gill (length/modulus ratio). NC: This assumption will depend on engineering judgment and the method of construction. OR: According to methods described in FHWA manual; determine the resistance available from the side and base independently based on a given relative shaft settlement and then add them together. SC: Assume side fully mobilized and 5% diameter settlement not necessary to mobilize end resistance in rock. TN: Geotech Section opinion is that with the rock type and strength we have and using a safety factor of 2.5, a relatively small mobilization of side and end bearing occurs; therefore, it is okay to use a SC SD combination of both. Structures Designer typically uses just one or the other. FL: Side/end: 0.55; side only: 0.60

127 TX: TxDOT Design Method—See Chap. 4 of the Geotechnical Design Manual (website cited above). WA: See the attached pdf discussing WSDOT procedures for designing drilled shafts in rock and IGMs. 21. When a bridge is supported on a shallow footing that is supported on a rock-socketed drilled shaft (as opposed to a mono shaft), does your design procedure account for the contribution of the footing to the foundation capacity? Yes (none) No (25) AL, AR, CA, CT, FL, GA, HI, IL, IA, KS, KY, MA, MI, MN, MT, NH, NM, NC, SC, SD, TN, TX, UT, VT, WA Not applicable (6) AZ, ID, ME, NJ, OR, PR If you answered “Yes,” please provide a brief description of your analysis to account for the footing contribution: (none) 22. For analysis of rock-socketed shafts under lateral loading, please indicate the methods and/or references associated with methods used by your agency (mark all that apply). Equivalent Cantilever Method (Davisson 1970) (5) KS, MA, NH, NC, SC Broms Method (Broms 1964) (5) KY, MT, OR, SC, TN p-y method of analysis (26) AZ, AR, CA, CT, FL, GA, HI, IL, IA, KS, KY, MA, MI, MN, NH, NJ, NM, NC, OR, PR, SC, TN, TX, UT, VT, WA Characteristic Load Method (Duncan et al. 1994) (none) Zhang, Ernst, and Einstein (2000) “Nonlinear Analysis of Laterally Loaded Rock-Socketed Shafts” (1) MA Reese, L.C. (1997) “Analysis of Laterally Loaded Piles in Weak Rock” (8) GA, ID, MI, MT, NJ, NC, OR, TX Carter and Kulhawy (1992) “Analysis of Laterally Loaded Shafts in Rock” (1) NJ Other (please cite reference or provide a brief description) ME: FB Pier evaluation SC: Some lateral load resisting WA: S-Shaft Program developed by M. Ashour and G. Norris of UNR along with J.P. Singh of J.P. Singh & Associates. Model is based on strain wedge theory 23. What, if any, computer programs are used by your agency for analysis of rock-socket response to lateral loading? LPILEPLUS (23) AL, AZ, CA, GA, HI, ID, IA, KY, MA, MI, MN, MT, NH, NJ, NM, NC, OR, PR, SC, TX, UT, VT, WA COM624P (17) AR, CA, CT, GA, ID, IL, IA, KS, KY, ME, MA, NJ, NC, OR, PR, TX, VT FBPIER (8) FL, MI, MN, NJ, NC, TN, TX, VT Finite-Element Method (specify program) NC: Flac

128 Other (provide name of program) NH: Group 6.0 WA: S-Shaft Program developed by M. Ashour and G. Norris of UNR along with J.P. Singh of J.P. Singh & Associates. Model is based on strain wedge theory 24. If you use the p-y method of analysis, describe briefly how you determine the p-y relationships for rock Published correlations between rock properties and p-y curve parameters (4) CA, KY, NJ, VT Reference(s): CA: LPILE Manual Correlations built into computer code (specify program) (22) AZ, AR, CA, CT, FL, GA, HI, IL, IA, MA, MI, MN, NH, NM, NC, OR, PR, SC, TN, TX, UT, VT (all of the above states use LPILE) In-house correlations based on agency experience (2) NC, OR Educated guess (2) MA, OR Other (describe) CA: Pressuremeter Testing MN: in situ test NC: Research OR: Limited pressuremeter data in soft rocks WA: Reese p-y curves for vuggy limestone are derived using elastic theories. For basalt, using engineering judgment, we typically define y as 0.01B, assuming 0.5% strain is the typical range over which basalt behaves linearly and that is the rock within 2B that resists the load. Therefore, y = 0.005(2B) or 0.01B. We then use correlations or published values to determine Young’s modulus E. Typically, this is about 10,000 ksi for basalt. We then use the unconfined compressive strength from point load tests along with E to define the curve. For example, if qu is 22.8 ksi we would take the 10,000 ksi (E) value and divide by the qu to get about 440. The p-y curve would then be defined by a straight line beginning at the origin with a slope of 440 qu. In highly fractured rock, the engineer would use judgment to change strain that defines y1, thus flattening the p-y curve. 25. On projects completed by your agency, which of the following design considerations control rock-socket length (approximately)? Axial capacity AL Not really KS 50% NJ 65% AZ 99% KY 30% NM 80% CA 70% ME 100% NC 30% CT 50% MA 30% OR 35% HI 100% MI 50% SC 40% ID 100% MN 90% SD 100% IL 50% MT 50% TX 95% FL 70% UT 80% Lateral load response AL: KY: 60% NC: 70%

129 AZ: 1% MA: 60% OR: 60% AR: 100% MI: 50% SC: 60% CA: 20% MN: 10% TN: CT: 50% MT: 50% TX: 5% GA: 10% NH: 90% UT: 20% IL: 40% NJ: 35% VT: 100% KS: 50% NM: 10% WA: 100% FL: 30% Construction-related CA: 10% IL: 10% MA: 10% GA: 90% KY: 10% Sharing of load between drilled shaft and footing Puerto Rico: 100% Other (explain) IA: No information available KS: Minimum of 1.5 x shaft diameter NM: 10% scour OR: 5% scour TN: 1.5 x socket diameter 26. Please identify any other issues pertaining to rock-socket analysis/design that you feel should be addressed in this synthesis. FL: In karst, check for voids below tip. IL: Bureau of Bridges and Structures, and consultants. KS: Pertaining to Question 17, at the LFD load, the settlement should be less than some acceptable value. We are using an arbitrary value of approximately 1⁄4 in. This will vary depending on the bridge type and span length. MA: The design/analysis of highway structures foundation (traffic signals, etc.). Construction practices and QA/QC and their influences on design assumptions. NH: Provide additional guidance for using side shear and end bearing in combination and provide simplification of side resistance equations for cohesive soils contained in FHWA-IF-99-025. OR: What agencies are using the AASHTO methods for drilled shaft design in rock? UT: Concerns with appropriate lateral analysis methods; that is, is LPILE appropriate to be using with rock sockets? Part V: Structural Analysis 27. What branch or group within your agency is responsible for structural design of rock-socketed drilled shafts? AL: Bridge Bureau ME: Bridge Program AZ: Bridge Group MN: Bridge Office AR: Bridge Design MT: Bridge CA: Division of Engineering Services/ NH: Bridge and Geotechnical Sections Structure Design NJ: Structural and Geotechnical Engineering Units CT: No drilled shaft design has been done NM: Bridge Section with in-house engineering staff OR: Technical Services, Region Technical Centers GA: Office of Bridge Design PR: None, done by consultants HI: Bridge Design Section or Structural Consultants SC: Bridge Design Section ID: Bridge Design SD: Bridge Design

130 IA: Office of Bridges and Structures TN: Division Structures KS: Bridge Design Section TX: Geotechnical Branch KY: Division of Bridge Design UT: Structures Division MA: Bridge Designer (either in-house or consultant) WA: Bridge and Structures Office after consultation with Geotechnical Section FL: Geotech for resistance; Structures for structure design 28. Mark all of the applicable references/codes used by your agency in the structural design of rock-socketed drilled shafts: O'Neill and Reese (1999) Publication No. FHWA-IF-99-025, Drilled Shafts: Construction Procedures and Design Methods (15) AR, CA, CT, FL, ID, IA, KS, KY, MA, NH, NJ, NC, OR, PR, VT ACI 318, Building Code Requirements for Structural Concrete (3) IL, NJ, WA AASHTO, Bridge Design Specifications (26) AZ, AR, CA, CT, FL, GA, HI, ID, IL, IA, KS, KY, MA, MN, NH, NJ, NM, NC, OR, SC, SD, TN, TX, UT, VT, WA ACI 336, Design and Construction of Drilled Piers (2) NJ, WA 29. For structural design of drilled shafts, does your agency currently use Load Factor Design (LFD), Load and Resistance Factor Design (LRFD), or Allowable Stress Design (ASD)? SLD (allowable stress, or Service Load Design) LRFD (Load and Resistance Factor Design) LFD (Load Factor Design) Mixed approach (SLD for foundation capacity and LFD or LRFD for load calculation) SLD: (7) AZ, AR, GA, NM, NC, PR, TX LRFD: (8) CT, FL, HI, ID, ME, SC, UT, WA LFD: (6) CA, KS, MA, KS, NC, WA Mixed: (10) (a) stated “mixed” only, no explanation: MN, NH, OR, SD, VT (b) SLD for foundation capacity and LFD or LRFD for load calculation: KY, IL, IA, NJ, TN 30. For structural design purposes, how would you best describe the analysis method used to obtain the distribution of moment and shear with depth? A “point of fixity” is assumed; shaft is then treated as a structural beam-column. (11) CT, KS, KY, MA, NJ, NM, NC, SD, TN, TX, UT Soil/Structure Interaction analysis is conducted using one of the following computer codes: p-y method by COM624 or LPILEPlus (21) AZ, AR, CA, GA, HI, ID, IL, IA, KS, ME, MA, MN, NJ, NM, OR, PR, SC, TX, UT, VT, WA FBPIER (5) FL, ME, MN, NC, VT

131 Other (2) NH, WA (S-Shaft Program see above) Elasticity solution (1) KS Numerical methods such as finite element, boundary element, or finite difference specify computer program: none Other method (explain briefly). NM: Interaction with Geotechnical Section. TN: Triangular stress distribution limited to side bearing capacity of rock and McCorkle side resistance equations. TX: Point of fixity is used for simple, “typical” structures. P-y method is used for more complex structures. 31. Please indicate whether you have encountered difficulties associated with the design or analysis issues listed below and, if so, summarize the circumstances (shaft dimensions, depth of soil over rock, rock or IGM type): Unexpectedly high computed shear in the rock socket when using the p-y method of analysis. CA: “When the moments go from a maximum to zero over a relatively short length, then the corresponding shear demands that are reported are large.” Difficulties or questions in applying p-y analysis to relatively short socket lengths CA, IA, NM NH: “One question is whether the drilled shaft length can be terminated even though the p-y analysis indicates some minor shear, moment, or deflection at the base of the shaft.” Questions regarding transfer of moment to the rock socket or development length for reinforcing bars extending into the rock socket. IA, MA 32. Please identify any other issues pertaining to structural analysis/design that you feel should be addressed in this synthesis. MA: “Should seismic design of rock-socket length be adequate to develop full plastic hinge moment in reinforced concrete shaft?” OR: “Not specifically related to rock sockets, but a design with about 60–70 ft of overlying silt was difficult to analyze. Resulting moments at superstructure were opposite direction of what would be expected, did not tend to converge on a solution during seismic modeling runs. I chased it all over the place (using LPILE, WinSTRUDL, ODOT BRIG2D software).” Part VI: Construction and Field Testing of Rock-Socketed Drilled Shafts 33. Indicate whether the measures described below are included in construction specifications for rock or IGM sockets designed by your agency: Roughening of the sides of the socket by grooving or rifling (6) AZ, IA, KS, ME, MA, MN Restrictions on the use of slurry in sockets (14)

132 CA, FL (no polymer), GA, HI, KS, KY, ME, MA, MN, NM, NC, TX, UT, VT Specifications for rock excavation by blasting (4) CA, ME, NC, OR 34. Does your agency specify requirements for cleanliness at the bottom of the excavation prior to concrete placement? Yes (28) AL, AZ, AR, CA, FL, GA, HI, ID, IL, IA, KS, KY, ME, MA, MN, MT, NH, NJ, NM, NC, OR, SC, SD, TN, TX, UT, VT, WA No (1) CT If you answered “Yes,” please provide a brief summary of the following: Requirements for cleanliness: Six states (FL, HI, IL, NH, NC, and SC) gave the following: “minimum 50% of base area to have less than 0.5 in. and maximum depth not to exceed 1.5 in.” AR: No more than 1 in. of loose material. CA: Specification simply states that the contractor verifies that the bottom is clean. CT: Not written into specification, but generally following recommendations in FHWA Drilled Shaft Manual. GA: No loose sediment or debris. ID: Less than 2 in. thick for end bearing shafts; less than 6 in. for side friction shafts. IA: Minimum 50% of base to have less than 0.5 in. and maximum depth not to exceed 1 in. KS: Just prior to placing concrete, a minimum of 75% of the base must have less than 0.5 in. of sediment; CSL also used for wet pours. KY: Maximum 0.5 in. of sediment. MA: End bearing <1 in., skin friction <3 in. ME: Minimum of 50% of the base of shaft should have <0.5 in. of sediment at time of concrete placement. MN: From our drilled shaft special provision: loose material shall be removed from drilled shafts prior to placement of reinforcement. After the shafts have been cleaned, the engineer will inspect the shafts for conformance to plan dimensions and construction tolerances. If permanent casing is damaged and unacceptable for inclusion in the finished shaft, the casing shall be replaced at the contractor’s expense. If a portion of a shaft is underwater, the contractor shall demonstrate that the shaft is clean to the satisfaction of the Engineer. This shall include inspection by a diver, at no cost to the department, if considered necessary by the Engineer. Dewatering of the drilled shafts for cleaning, inspection, and placement of reinforcement and concrete will not be required. If the drilled shaft contractor chooses to dewater the shafts for convenience of construction, this work shall be done at the contractor’s expense. NJ: Less than 0.5 in. of sediment. NM: <1 in. of loose material. OR: No more than 2 in. of loose material for end-bearing; no more than 6 in. of loose material for friction shafts. Assume end-bearing if not specified. SD: Make sure the bottom of the shaft is free of loose material. TN: No loose soil or rock cuttings allowed. TX: From Specification 416 Drilled Shafts—“remove loose material and accumulated seep water from the bottom of the excavation prior to placing the concrete.” UT: Remove all lose material from the bottom of drilled holes before placing concrete. WA: The contractor shall use appropriate means such as a cleanout bucket or air lift to clean the bottom of the excavation of all shafts. No more than 2 in. of loose or disturbed material shall be present at the bottom of the shaft just prior to placing concrete for end bearing shafts. No more than 6 in. of loose or disturbed material shall be present for side friction shafts. End bearing shafts shall be assumed unless otherwise noted in the contract. Shafts specified as both side friction and end bearing shall conform to the sloughing criteria specified for end bearing shafts.

133 Method(s) and tools used to verify cleanliness requirement: AZ: Visual and hand probe. AR: Video equipment or person in hole with suitable lighting and ventilation. CA: Contractor submits a concrete placement plan for approval. Usually, they will use a clean out bucket to clean the bottom of hole. There is inspection of the drilling slurry at bottom of the shaft prior to placing concrete. Caltrans occasionally will verify the bottom of end bearing shafts with a camera. CT: Probing of the rock-socket bottom. FL: Probing, sometimes use SID. GA: Hand cleaned and inspected. HI: Weighted tape. ID: Cleaning buckets or air lift. IA: Weighted tape, camera inspection (rare), sediment deposition “trial run” in open-top clean-out bucket. KS: Visual on dry pours, sounding (using probes) underwater. KY: Judgment of inspector. MA: Weighted rods, visual check by use of cleaning equipment spoils. ME: Weighted tape and remotely operated cameras. MN: See above. NH: Weighted tape or solid rod. NJ: Sounding by weighted tape. NM: Weighted tape/sounding. NC: 1. Visual Inspection. 2. Steel Probe (10 lb weight). 3. SID shaft inspection device. OR: Weighted tape, rod probe or visual. SD: Visual inspection if the shaft is dry, otherwise use a clean-out bucket. TN: Visual inspection. TX: Visual, clean-out bucket. UT: Visual. WA: The excavated shaft shall be inspected and approved by the Engineer prior to proceeding with construction. The bottom of the excavated shaft shall be sounded with an airlift pipe, a tape with a heavy weight attached to the end of the tape, or other means acceptable to the engineer to determine that the shaft bottom meets the requirements in the contract. 35. Does your agency use construction specifications or special provisions that account for construction of sockets in a particular rock type? Yes No Yes: (3) AZ, ID, KY No: (25) If “Yes,” please provide a brief description. Rock type and special provision: AZ: Limestone; drill below tip elevation to check for karst conditions. ID: Special provisions for IGMs and hard rock. KY: Soft shale; sometimes require contractors to use polymer slurry in wet holes with soft shales subject to slaking in the presence of water. CA: Different pay items for Cast-in-Drilled-Hole concrete piling and Cast-in-Drilled-Hole (Rock Socket) concrete piling. 36. Have you observed any methods, equipment, or materials used for socket construction that you believe are a source of construction problems? Yes No

134 Yes: (10) CA, FL, KS, KY, NH, NC, SD, TN, UT, VT No: (16) AL, AZ, AR, CT, GA, HI, ID, IL, IA, ME, MA, MN, OR, SC, TX, WA If yes, please explain: CA: We design for low bidding contractors to get the contract and the construction problems that will result. Rock may be harder than the contractor thought when bidding and planning the job. Thus, the drilling equipment brought out is often unable to drill or very slow to drill the rock. This results in costly contractor claims. FL: Improper equipment or size; full-length casing reduces skin friction. KS: In wet pours, inadequate sealed tremie or no pig in the concrete pump supply line. Loss of slump in the concrete during placement. Dirty bottoms were observed with Sonic testing. KY: Reverse circulation drilling methods used in conjunction with polymer slurry when used as described in Question 35. NH: Certain clean-out buckets cannot always meet the cleanliness requirements. NC: Various methods used to force a dry pour. SD: If not done properly using pump trucks to place concrete can cause soft bottoms in the shafts. TN: We have significant depths of interlayered rock layers and soil that makes it difficult to use either an auger or a core barrel. UT: Concerns with use of drilling fluids instead of casing. VT: In holes cased through the overburden soils into bedrock we have had problems seating the casing into rock. This was true when the contractor used a casing diameter that was essentially the same as the rock-socket diameter. The casing was vibrated into the rock-socket hole, which resulted in more rock drilling than expected, because the casing “followed” the socket. This resulted in longer overall shaft lengths than planned, particularly when the upper portion of the rock was fractured or weathered. 37. Please identify any other construction-related issues for rock or IGM sockets that you believe should be addressed in this synthesis. FL: What is rock, where does it start, quality. KS: Pertaining to Question 35—Our special provision accounts for a wet or dry pour (cased or uncased) rather than rock type. MA: Define “Top of Rock,” which generally can be a discrepancy between borings and construction drilling. NH: Effect of slurry on side friction. OR: If during construction the top of rock elevation is found to be different than what was assumed in design, what is the effect? How different does it have to be to have a significant effect on design? 38. Indicate whether your agency has used any of the following field load testing methods on rock-socketed drilled shafts. Conventional static axial load test (7) CA, FL, GA, IA, NC, TX, UT Conventional lateral load test (5) CA, FL, MA, NJ, NC Osterberg Cell for axial load test (18) CA, CT, FL, GA, HI, IL, IA, KS, KY, ME, MA, MN, NJ, NM, NC, PR, SC, TX Osterberg Cell for lateral load test (1) SC Statnamic test for axial load (6) CT, FL, IA, NC, PR, SC Statnamic test for lateral load (3) AL, FL, SC

135 High strain impact (3) FL, KS, MA If your agency has used the Osterberg Cell (O-cell) for axial load tests on rock-socketed shafts, please answer the following: 39. Were you able to measure both side and tip resistances of the socket independently? Yes No Yes: (17) CA, CT, FL, GA, HI, IL, IA, KS, KY, ME, MA, NJ, NM, NC, PR, SC, TX No: (1) MN 40. Was the test used to determine Ultimate side resistance (of socket) Ultimate base resistance Proof load only 41. Additional comments regarding use of O-cell for load testing of rock sockets. IL: Too expensive. IA: None. KY: We have typically failed shafts in side resistance and mobilized enough base movement to extrapolate the ultimate base resistance. ME: Did not mobilize ultimate base resistance on either project. MN: Was also used to develop p-y curve. NM: Use was for IGM Santa Fe Formation. TX: For information on recent O-cell testing in rock contact Dr. Vipu and University of Houston. If your agency has experience with Statnamic testing of rock-socketed drilled shafts please answer the following: 42. Which of the following performance parameters were determined by the test? (Check all that apply.) Socket side resistance Socket base resistance Total socket resistance (side and base) Axial load displacement response Lateral load-displacement response 43. Additional comments regarding Statnamic testing of rock-socketed drilled shafts. FL: Limit on size that can be tested. NC: Test is very expensive; we need to find another method with less cost. 44. Do you have results of load tests on rock-socketed drilled shafts and, if so, are you willing to receive follow-up contact regarding the possibility of using your results for the synthesis? Yes, I have previously unpublished load test results (9) CA, GA, IA, KS, KY, ME, MA, NC, SC (5) FL, AL, IA, NC, SC (4) FL, NC, PR, SC (3) FL, NC, SC (5) CT, FL, IA, NC, SC (5) AL, FL, NC, PR, SC (8) IL, FL, IA, KS, KY, NC, SC, TX (4) HI, NJ, PR, SC (14) CA, CT, FL, GA, IA, KS, KY, ME, MA, MN, NM, NC, SC, TX

136 Yes, I am willing to receive follow-up contact (11) CA, CT, GA, IA, KS, KY, ME, MA, NM, NC, PR If previously published, please give a reference: ME: Loadtest, Inc., performed all O-cell tests on the Bath–Woolwich and Hancock–Sullivan bridges in Maine. MN: Transportation Research Record 1633. 45. Indicate which of the following nondestructive testing methods are used on a regular basis by your agency for rock-socketed shafts. gamma-gamma (3) AZ, AR, CA crosshole sonic logging (20) AZ, AR, CA, CT, HI, ID, IA, KS, KY, ME, MA, MN, NJ, NM, NC, OR, PR, SC, SD, VT sonic echo (1) AR impulse response (1) AR parallel seismic other (3) CA (downhole camera), NC (Osterberg load cell), VT (CSLT— one project) 46. Based on your experience, are there any special considerations or issues related to the use of NDT-NDE, specifically for rock-socketed shafts? If so, explain. FL: Results are iffy. IA: None. KY: No. MA: The configuration of the test pipes within the socket (if diameter is smaller than shaft) and the possible influence of rock material properties on the data results. NM: Sonic echo not utilized. NC: Technology is not 100% accurate. PR: We bought the equipment (CSL) last month. 47. Do you have case histories of design, construction, or testing of rock-socketed drilled shafts that, in your opinion, could provide useful information to your colleagues and, if so, are you willing to be contacted by the author of the synthesis to discuss your case histories further? Yes, I have useful case histories (9) CA, CT, IA, KS, KY, ME, NM, NC, WA Yes, I am willing to receive follow-up contact (8) CA, CT, GA, IA, KS, KY, ME, NM