Soil Consolidation during Construction Essay Example | Topics and Well Written Essays - 1250 words

Soil Consolidation during Construction - Essay Example Generally, any undrained loading or unloading will produce excess pore pressures in the loading area. Hence, construction of any type of infrastructure generates pressure on the soil on which the construction takes place. The excess pore pressures may be positive or negative, depending on the long term steady state pore pressures. In time, these excess pore pressures give rise to hydraulic gradients which cause seepage flow which then results to changes in the volume of the soil. Hence, the changes in soil volume are based upon the changes of effective stress as the excess pore pressures disperse. The gradual reduction in volume of a fully saturated soil of low permeability which is caused when stress is what consolidation refers to. More specifically, consolidation is the union of seepage caused by hydraulic gradients with compression due to the flow of the leakages and changes of effective stress placed against the soil. Consolidation leads to drainage of some of the pore water, which triggers the continuity of soil consolidation until the excess pore water pressure caused by the stress against the soil has completely dispersed. Through the test of time, consolidation leads to settlement of foundations or constructions due to the gradual softening of soil in excavations. Therefore, consolidation settlement is basically the vertical dislocation of the construction as a result of the volume change of soil during the consolidation. Hence, if a building is built over a layer of saturated clay, consolidation settlement will cause a stratum overlying a clay layer. Likewise, if an excavation is made in a saturated clay, crowding, the reverse of settlement, can be observed in the bottom of the excavation. This, on the other hand, is due to swelling of the clay resulting to a gradual increase in volume of the soil. The most basic case of consolidation is that of one-dimensional on which the strain generated against the soil is zero-lateral. One-dimensional consolidation occurs when all seepage flow and the effective stress placed against the soil is vertical. Hence, there should be no radial seepage or strain. If effective lateral stress is placed against the soil, the settlement will occur faster. This is because of the deformation of the soil under undrained conditions, in addition to consolidation settlement. Immediate settlement can be estimated using the results from elastic theory, which will be able to determine the elastic properties of the soil. Furthermore, before a structure is completely conceptualised, the magnitude and the rate of consolidation settlement should first be predicted using effective tools. One of the popular processes used in predicting the progress of consolidation is by setting up piezometers in order to document the change in pore water pressure with time. The scale of consolidation settlement can be determined by recording the levels of appropriate reference points on a construction and in the surface on which it will be built. In such measurement, levelling of the reference points should be accurate, working from a point of reference which is not subject to any type of settlement. During this process, every output should be documented, as this will determine the competence of theoretical methods to be used. The attributes of a soil during one-dimensional consolidation can be measured through oedometer test. This test, developed