Research On Basal Stress Of Geotechnical Deposits

To ensure project quality and proper use, to calculate settlements of subsoil layers, to design the maximum height of deposits, it should be quite aware of the basal stress state (stress distribution and value) of geotechnical deposits, which has important engineering significance. The approximate solution and numerical solution of basal stress of geotechnical deposits have been studied in this thesis with the Rayleigh-Ritz method and finite difference software FLAC3D, as follows:1. To study basal stress state of geotechnical deposits, three cases are considered:no constraints from the horizontal direction; constraints from the horizontal direction; allowable vertical displacement on the base;2. The partial differential equations and boundary conditions, which should be satisfied in case no constraints from the horizontal direction and case constraints from the horizontal direction, of the basal stress state from the theory of elasticity are analyzed. Though it is impossible to get the theoretical solution, I succeed to get the approximate solution with the Rayleigh-Ritz method and minimum potential energy principle;3. To study basal stress state (σy) of geotechnical deposits in case no constraints from the horizontal direction with the help of FLAC3D, the following situations are considered:the cross-section of geotechnical deposits either triangular or trapezoidal; six different slope ratio; six different Poisson’s ratio; three different width/height ratio. With the slope ratio increasing, the depression of basal stress is decreasing. Compared to slope ratio, Poisson’s ratio has less influence on basal stress. The depression is much smaller and will disappear at width/height=0.5when the cross-section is trapezoidal;4. To study basal stress state (σy and τxv) of geotechnical deposits in case constraints from the horizontal direction with the help of FLAC3D, the following situations are considered:the cross-section of geotechnical deposits either triangular or trapezoidal; six different slope ratio; six different Poisson’s ratio; three different width/height ratio. The phenomenon of depression of basal stress is much more obvious when there is the horizontal constraint. With the slope ratio increasing, both the value of the maximum τxy and its x-coordinate are decreasing. Poisson’s ratio will only have influence on the value of τxy. The depression is much smaller and will disappear at width/height=1when the cross-section is trapezoidal;5. To study basal stress state (σy and σxy) of geotechnical deposits in case c with the help of FLAC3D, six different stiffness ratio are considered. The lower of the value of stiffness ratio, the more obvious of the phenomenon of depression of basal stress. On contrary, results will be like the case constraints from the horizontal direction. The value of τxy will be very large at the foot of the slope. The depression is much smaller and will disappear at width/height=2when the cross-section is trapezoidal;6. To compare results of the basal stress state (σy and τxy) by the approximate solution and the numerical solution, results have good agreement;7. With a coal pile project, to illustrate the application of the basal stress state of geotechnical deposits. The settlement calculated with the basal stress in this article is3～5%smaller than the settlement calculated with the trapezoidal distribution of basal stress, indicating the feasibility of trapezoidal distribution of basal stress in projects;...