Analysis of in situ test derived soil properties with traditional and finite element methods

The strength and the stiffness properties of soils from four different insitu tests are examined by studying three types of geotechnical engineering problems: unloading in sheet pile walls; loading in shallow footings; and dynamic loading in Statnamic load test. Two types of calculations were used: the traditional methods, and the FEM with PLAXIS. The results of the analyses greatly depend on the choice of the insitu test and the correlations selected for the soil properties. The analyses were based on the comparison of the measured responses with those predicted.;For cantilevered, strutted, or anchored sheet pile walls, embedded in sands and clays, the SPT test, PMT, and the CPT tests are the preferred insitu tests for design predictions. The equivalent blow count CPT (N) also constitutes a very useful method in estimating the soil properties. The traditional methods did not prove useful, as poor predictions were obtained, and thus are not recommended. The FEM with PLAXIS has better capability and versatility to analyze sheet pile wall problems. Apart from the efficacy of the Hardening Soil model, a good finding was the use of the unload-reload modulus in the Mohr-Coulomb model. The Hardening Soil model is also appropriate to simulate the behavior of very soft clays.;For shallow footings, knowledge of the stress history of sand layers proves highly critical in obtaining good settlement predictions; the insitu tests DMT and CPT are mandatory for estimating the OCR values and/or the K0 values. The SPT, CPT (N ) based traditional methods: D'Appolonia (1970), Schultz & Sherif (1973), and DMT method provide the best predictions. The Mohr-Coulomb model using the CPT data or DMT data is preferable for FEM predictions.;For the Statnamic load test, the Unloading Point Method was shown as a valid alternative to the actual static load test. The method produced the closest load-settlement curve to the actual static test. The CPT ( N) data are useful in estimating the dynamic properties of the soil. The FEM code PLAXIS successfully simulated the Statnamic test.