EVALUATION OF COARSE GRAINED ALLUVIUM BEHAVIOR BASED ON PRESSUREMETER TESTS

The pressuremeter test can be considered one of the most important in situ tests in geotechnical engineering projects. The pressuremeter consists of two main elements: a radially extendable cylindrical probe, which is placed inside the borehole at the desired test depth, and a monitoring unit, which remains on the ground surface. These two parts are connected by cables and hoses. Coarse grained alluvium layers are major subsurface layers in urban areas, such as Tehran, the capital of Iran. Prediction of the behavior of these layers in geotechnical engineering problems is very important. Based on this, and for better predicting the constitutive behavior of coarse grained alluvium with cementation, physical modeling has been undertaken. For this evaluation, we used the pressuremeter test (PMT) in a laboratory chamber designed and constructed for this purpose. Insitu tests play an important role in any geotechnical engineering investigation. This test is capable of properly estimating the geotechnical and de ection parameters of soil. These parameters are the elasticity modules (E), the shear modules (G), the in situ horizontal stress (h), limit pressure (PL), undrained shear strength (Cu) for clay, over the consolidated ratio (Em/PL) and the reaction modules (Ks). Furthermore, the number of parameters of these constitutive models (in many cases) inhibits their incorporation into general purpose numerical codes, thus, restricting their usefulness in geotechnical engineering practice. There are several dierent kinds of pressuremeter that dier mainly by the way the probe is placed in the ground. These pressuremeter tests have been done using a preboring method. Then, for assisting the cementation eect on the behavior of these layers, some pressuremeter tests have been undertaken in a laboratory chamber constructed for this purpose. This instrument was constructed for modeling under in situ conditions without cementation to inspect the eects of cementation on the coarse grained alluvium layers. Afterwards, the results of the pressuremeter tests on the chamber are compared with each other and the geotechnical parameters of the coarse grained alluvium are reported. These pressuremeter stress-strain curves are compared with the eld test curves, and the constitutive parameters have been recalculated. Based on these curves, the elasticity modules and limit pressure were presented. Other parameters have been calculated in this paper. Finally, the results of the pressuremeter tests in the eld and the PMT in the chamber are compared with each other and the cementation eect is reported.