Disturbance Caused by In Situ Strength Testing

Use of in situ testing equipment to obtain strength data encounters many actual or potential problems. Most of these problems cause a reduction in strength. A summary of instrumental sources of strength degradation for CPT and vane tests is listed in Table 4.4. 

Soil disturbance occurs during in situ testing as a result of primarily three factors drilling operation, probe insertion, and test procedure. The actual magnitude of strength reduction is hard to predict without having specific information on equipment, soil, operating procedures, and so on. 

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