Abstract

Field and laboratory testing was carried out for the construction of a 100 m long cable stayed bridge situated in the foothills of the Alps in the south of Germany, a region dominated by deep post-glacial, fine-grained sediments. Due to the sensitivity and associated challenges with retrieving undisturbed soil samples in situ tests and their evaluation proved to be essential for the geotechnical design of the bridge foundation. This contribution focuses on the analytical and numerical interpretation of Cone Pressuremeter Tests (CPM). The non-linear 𝐺-𝛾 relationship and undrained shear strength (using both the limit pressure and reverse plasticity contraction analysis) were determined analytically. Numerical investigations were carried out as verification using both the Finite Element method (FEM) using both 1D (cavity expansion) and 2D simulations (where the penetration of the probe was modelled) as well as using the Finite Difference (FD) method. 2D simulations demonstrated that the assumption of the cylindrical cavity expansion is appropriate for modelling the CPM tests. The interpreted undrained shear strength showed good agreement with other field tests, including CPTu, vane shear (FVT) and seismic cone penetration (SCPT) tests, as well as with the results of laboratory tests on disturbed samples. CPM tests with strain rate jumps were conducted during pressuremeter expansion, wherewith it was possible to quantify the viscous response of the soil. Based on the holistic interpretation of the field and laboratory results involving both numerical simulations and analytical methods the parameters for the material model Viscohypoplasticity were calibrated.

Abstract

The inner bay of the city of Puno has been the subject of various investigations that seek to recover and enable floodprone areas, through strategic urban development projects (urban infrastructure) and protection works. On the other hand, the characteristics of soft soil deposits, such as those in the inner bay of Puno, represent a risk of problems with excessive settlement of the infrastructure. This study presents an engineering characterization of the lacustrine soil deposits in the inner bay of the city of Puno, around Lake Titicaca. The site lies around the Pier of Puno city at Lake Titicaca, the highest navigable lake in the world, approximately a few hundred meters in front of the National University of the Altiplano of Puno (UNAP) and a few hundred meters to the southward of the Pier of Puno city. Physical, strength, and deformation properties were determined from standard laboratory tests. The material studied corresponds to the shallow layers of the study area, corresponding to sedimentary soils of the lacustrine units and fluvial-alluvial deposits of the inner bay of Puno. These lacustrine soils are classified as highly plastic silts and organic clays (MH and OH). The results show the significant influence of the quality of soil samples, due to the sampling method and storage time, on consolidation and resistance parameters. Finally, this study provides valuable insights into the influence of sample quality on consolidation parameters and shear strength of the lacustrine soils in the inner bay of Puno city around Titicaca Lake.