Research On Consolidation Settlement And The Control Of Stability For Soft Clay Ground Treated With Plastic Drains

As an effective method of the soft clay ground treatment, plastic band drain preloading is developed from sand drain preloading method. With the development of economy, it is widely used in several kinds of the soft clay ground improvement projects, such as road, heap, port, airport and so on. After reviewing the principal and development of this method in brief, this thesis gives a systematic research on consolidation settlement and stability problems in the soft ground treatment based on the results of field test of Zhoushan National Oil Reserve Base improved by plastic band drain preloading.Firstly, Multi-stage preloading of one-dimensional nonlinear consolidation analytical solution is obtained on the basis of single-stage preloading of one-dimensional nonlinear consolidation analytical solution, according to the equation degeneration and a simple instance, the analytical solution is verified.According to the general situation of Zhoushan National Oil Reserve Base preloading test area, the preliminary preloading and field test plan is designed. By analyzing the results of field test, the regulations about settlement, pore pressure & lateral displacement develop with time and loading are induced.Based on the results of field test, the degree of consolidation which is calculated by traditional consolidation theory, one-dimensional nonlinear consolidation theory and prediction methods between ideal drain and non-ideal drain with partially penetrated is contrast of 15%-20%, the degree of consolidation calculated by prediction methods is between that of obtained by ideal drain and non-ideal drain, besides it is in line with the degree of consolidation calculated by one-dimensional consolidation theory. By using four settlement prediction methods, immediate settlement and final settlement can be obtained and compared to get the settlement coefficient m varied from 1.12 to 1.16. The settlement calculated by one-dimensional nonlinear consolidation theory is well agreed with the results of field test.Finally, the paper analyzes the control of stability during the field test, it is mainly from the stability coefficient calculation and the data of field test analysis.When calculating the stability coefficient, the increase of shear strength in the soft clay ground must be considered, and the reduction coefficient in the field test is calculated to varied from 0.83 to 0.96. When using the data got from the field test to control the preloading process, it is suggest to give attention to three norms, including settlement rate, lateral displacement rate and pore pressure.