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METHODS OF SUBSURFACE EXPLORATION 1. TEST PITS excavate by hand or with backhoe usually dig a relatively narrow trench shallow depths, usually < 10 to 20 feet See Figure 3.15 in Coduto Advantages: Engineer can view soil profile directly. 2. Large quantities of soil available for testing. 3. Can hand carve undisturbed samples. 4. Can perform field test in pit, such as plate-load test. Disadvantages: Economically limited to 10 to 20 ft. depth. Dewatering required below water table. 3. Numerous test pits disrupt the site. 4. Cost of excavation in rock may be prohibitive. 5. Dangerous, trenches prone to collapse. 2. BORINGS a. Hand Auger (Figure 3-3 Coduto) augers 2 to 4 inches in diameter possible to drill 20 - 30 feet, sometimes deeper, depending on soil conditions can use where access is poor Advantages: Low cost. Portable. Can use with minimal headroom. Can use in almost any topography. Disadvantages: Maximum depth of drilling is restricted. 2. No means for obtaining undisturbed samples. 3. Cannot drill through rock, hard clay, gravel, or sand below the water table. 4. Slow, labor-intensive work. Page lof6
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b. Truck-Mounted Power Auger (Figures 3.6, 3.9 Coduto) usually continuous flight augers 4-6 inches diameter auger flights in sections (5 ft long) augers may have solid or hollow stems, most are solid most rigs are truck-mounted with 7 to 22 ft derricks can drill to depths as great as 150 ft., but rarely used for borings over 80 to 100 ft. depth Advantages: 1. Very little set-up time required. 2. Fastest technique for relatively shallow holes (depth < 50 ft. or so). 3. Can log cuttings conveniently. 4. Can obtain soil samples by removing augers from hole and lowering sampler down on steel rods.
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This note was uploaded on 09/23/2011 for the course CIVIL ENGI CE 3400 taught by Professor Rosenblad during the Spring '11 term at Missouri (Mizzou).

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