<p><p><strong>Reference(s):</strong></p><p><em>Leets and Chuaqui (2003)<br>Baker (1983)<br>Brachman et al. (2003)<br>Karol (2003)<br>Waller et al. (1983)</em></p><p><strong>Method Summary</strong></p><p>Penetration tests such as Standard Penetration Tests (SPT), Cone Penetration Tests (CPT), and Dynamic Cone Penetration (DCP) tests can be used to assess the improvement in the soil strength by comparing post-treatment results with pre-treatment results.</p><p>The SPT is described in ASTM D1586. SPT is a dynamic in-situ penetration test which uses a thick-walled sampling tube (with outside diameter of 50 mm, inside diameter of 35 mm and length of about 650 mm) that is driven into the ground by a slide hammer (about 64 kg) falling from a height of about 760 mm. At each testing depth, the number of blows required to drive the tube for three consecutive 150 mm (6-inch) intervals is recorded, and the values for the last two intervals are added to give the SPT penetration resistance, or N-value, in blows per foot. These blow count values have been correlated to soil shear strength parameters; however correlations for cohesive soils are not reliable and not recommended (Kulhawy and Mayne 1990). Disturbed soil samples acquired from the tube are used to classify the soils and obtain soil stratigraphy information.</p><p>The CPT is described in ASTM D3441. CPT involves pushing an instrumented cone tip with following friction sleeve into the ground at a controlled rate and recording the sleeve friction and tip resistance of the cone almost continuously (about every 2 cm). Some modern electronic CPT cones now employ a pressure transducer to record pore water pressure data and is commonly referred to as CPTu method. One advantage of CPT over SPT is that it can provide a more continuous profile of soil parameters. The sleeve friction and tip resistance values have been correlated to soil classification. Major disadvantage with CPT is that it does not provide a sample for visual identification and may not be feasible if the layers are very stiff/hard to penetrate.</p><p><strong>Accuracy and Precision</strong></p><p>The accuracy of SPT values is highly variable, with a coefficient of variation (COV) ranging from 15 to 100 % depending on calibration of the equipment and type of soil (Kulhawy and Mayne, 1990). However, the test is repeatable, provided the same equipment and crew are used, and thus can be used as a qualitative indication of improvement. CPT is much more reliable with a COV of 7 to 12 % (Kulhawy and Mayne, 1990).</p><p><strong> </strong><strong>Adequacy of Coverage</strong></p><p>Sufficient evaluation requires many tests. The number of tests depends on the variability in subsurface conditions. A high frequency of measurements is needed to accurately determine grouted zone geometry.</p><p><strong>Implementation Requirements</strong></p><p>The SPT method is relatively easy to implement with limited additional cost. CPT methods require a greater amount of training, experience, and increased initial equipment investment.</p><p><strong>General Comments</strong></p><p>This method has an advantage over other methods due to the familiarity of the method in the geotechnical community and ease of implementation. This can be an effective QA method.</p></p>