Triaxial compression tests on a crushable sand in dry and wet conditions

A calcareous sand from the Persian Gulf is subjected to a series of dry and fully drained saturated triaxial shear tests. The samples are prepared at relative densities of 65% and either left dry or saturated. They are consolidated to confining pressures ranging from 50 to 750 kPa, and sheared until shear strains of 20%. It is shown that the stress-strain and strength characteristics of crushable sand are significantly affected by the presence of water. During shearing of wet samples, there is less dilation, the peak is postponed and a lower shear strength is reached compared to dry samples. Crushability is assessed by comparing the granulometry before and after the triaxial tests. While both dry and wet samples show breakage, the wet sand is consistently more crushable. It is stated that the higher crushability of the wet sand suppresses its dilation during shearing

Effects of grain size distribution on the initial strain shear modulus of calcareous sand

The soil’s small strain shear modulus, Gmax or G0, is applied in dynamic behavior analyses and is correlated to other soil properties (density and void ratio) for predicting soil dynamic behavior under seismic loadings such as earthquakes, machinery or traffic vibrations. However, for calcareous sands, selecting representative samples for the field conditions is difficult; therefore, almost all measured soil parameters (post-seismic properties) do not reflect exactly the soil state before seismic loading. In some cases of dynamic loading, a change in grain size distribution (GSD) of soils, especially for calcareous sands might occur. Moreover, many of these sand types behave differently from silica sands owing to their mineralogy, particle characterization, soil skeleton, and the continuous changing of particle size. For this reason, a series of isotropic consolidation tests in ranges of confining pressure from 25 to 300 kPa as well as bender element measurements on a calcareous sand and on a reference silica sand were performed in this study. The effects of differences in gradation and in the type of material on the soil’s small strain shear modulus, Gmax, are discussed

Load-settlement behaviour of three pile groups: a case study

The paper presents the case study on the construction of three 48m diameter steel tanks, each founded on a group of 422 displacement cast in-situ piles. The three tanks are close enough to each other to induce interaction. The movements of the tank foundations have been monitored during the hydro-testing of the steel tanks, and during the subsequent working stage of the tanks. The bearing layer for the pile group is a 5 m thick stiff sand layer at a depth of about 20m, overlain by a very heterogeneous soft fill containing sand pockets, and underlain by a very thick slightly overconsolidated clay. The authors present some short and long term settlement prediction for the tanks, based on soil parameters derived from CPT on site, and compare this to the measured settlements. The initially derived soil parameters are re-evaluated in order to predict the long term settlement for the full life span of the construction

Discussion of an instrumented screw pile load test and connected pile group load settlement behavior

The aim of the paper is to discuss a fully instrumented screw pile load test up to failure, in difficult heterogeneous soil conditions along the shaft. The pre-stressing of the pile during its installation process has been brought to attention as an important item to assisting in explaining the differences in pile capacity and load settlement curve on the one hand, and the data as registered from the pile shaft instrumentation. In the second part of the paper, starting info on the registered load settlement data of the foundation slabs of each of the three, closely positioned, oil tanks of 48m diameter and 19m of height are shared and briefly analyzed