Manual on Subsurface Investigations (2019) / Chapter Skim
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From page 94... ...
94 C H A P T E R 6 Drilling and Sampling of Soil and Rock Introduction When formulating a plan for the subsurface exploration program, the geotechnical engineer or project geologist must carefully evaluate the variety of equipment, methods, and procedures available for drilling and sampling soil and rock. This careful evaluation of drilling and sampling options will assist with optimizing this phase of the subsurface exploration program to acquire the required information at the least cost.
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From page 95... ...
95 Table 6-1. Rotary drill rigs Type of Rig Applications Truck-mounted Sites with easy access All-terrain Soft ground and difficult terrain Track-mounted Swampy soft ground and heavily wooded terrain Skid-mounted Steep terrain With conventional rotary methods, the drill rods are lowered down the borehole and removed repeatedly to change drill bits and obtain samples.
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From page 96... ...
96 Borehole Advancement Methods A borehole (boring) is a vertical hole advanced into the ground to determine the depths, layers, zones, types, and thicknesses of the geomaterials (soil and rock)
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97 6.3.3 Auger Drilling Augering is a simple method to advance a borehole. There are two types of augers: solid-flight augers and HSAs.
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98 Source: Jeff Farrar Figure 6-1. HSA methods: drill rod (left)
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99 Source: Paul Mayne Figure 6-2. Rotary drilling techniques in comparison with other borehole methods Several types of drill rods and bits are available for different types of overburden and rock materials encountered, and the driller can change drill rods and bits as the situation demands.
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100 used in Europe than in the United States at present and is described in an International Organization for Standards (ISO) standard (ISO 22476-15)
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101 Soil Sampling Soil sampling devices are divided into two broad categories based on the condition of the samples they recover: • Disturbed samples • Undisturbed samples 6.4.1 Split-Spoon (Disturbed Samples) The SPT uses an open-ended drive sampler (i.e., split-spoon or split-barrel sampler)
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102 6.4.2.1 Continuous Hydraulic Push Samplers Using an anchored hydraulic pushing system, geoprobe or powerprobe rigs can direct push a long steel mandrel in strokes of 2–6 ft (0.6–1.8 m) to obtain continuous soil samples (Figure 6-4)
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From page 103... ...
103 Source: Boart Longyear Figure 6-5. Example of recovered sonic soil samples 6.4.2.3 Vibracore Samplers Vibracoring is a simple means to obtain soil samples at the bottom of a body of water.
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From page 104... ...
104 • Laval samplers • Piston samplers • Rotary core samplers 6.4.3.1 Shelby Tube Thin-Wall Open Sampler The thin-walled sampling method, more commonly referred to as Shelby tube from the manufacturer's tradename, may be any thin-wall tubing or casing that is beveled to form a tapered cutting edge. The tubes are usually available in diameters ranging from 2 to 5 in.
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105 Source: AASHTO Figure 6-7. Components of a fixed-piston sampler The piston can be locked and fully sealed at the bottom of the thin-wall tube so that it can be lowered into the borehole without contamination.
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106 additional skin friction to develop between the sample and the tube, which minimizes potential for sample loss during recovery. Osterberg Sampler.
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107 and mechanics of these core barrels, which are commercially available under a variety of trade names. Denison and Pitcher samplers are discussed in the following sections.
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From page 108... ...
108 Pitcher Sampler. The Pitcher rotary core barrel sampler is a modification of the Denison sampler and consists of a single-tube, swivel-type core barrel with a self-adjusting, spring-loaded inner thin-wall sample tube that telescopes in and out of the cutter bit as the hardness of the material varies.
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109 6.5.2 Core Barrel Types Core barrels are manufactured in three basic types: single tube, double tube, and triple tube (Figure 6-10) with diameters that range from 1 to 10 in.
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110 to the core barrel system minimizes the amount of drilling fluid and its contact with the sample which further decreases sample disturbance. Numerous sizes of cores can be obtained in rock, with the most common size for geotechnical explorations from rotary wash being NX with a diameter of 2.16 in.
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111 of samples taken, types of samples (drive or tube) , how the boring was advanced (auger, rotary wash, or direct push)
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112 Source: Geosyntec Consultants, Inc. Figure 6-12.
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113 6.5.6 Logging Rock Core The recovered rock core is logged in the field using at least three measures: (i) rock type, (ii)
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114 Measured RQD Quality 90% to 100% Excellent Source: Goodman (1989) Source: Paul Mayne Figure 6-13.
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115 with expendable tips and other technologies. A review of the various techniques is given by Lutenegger et al.
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From page 116... ...
116 Chapter 6 References Clayton, C.R.I., N.E. Simons, and M.C.
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