Passenger Line Of The Red Clay Foundation Settlement Numerical Analysis And Experimental Research

Red clay is a stronger regional special soil type. It is considered that red caly is a good natural foundation and good building materials. At the same time, there are a lot of engineering problems because it has obvious shrinkage, cracks and uneven distribution, etc. With China's western development strategy implementation, there would be inevitably more and more questions about red clay when a lot of high-speed railways will be built on red clay ground in the southwest, central and southern China areas. State-of-the-art research of red clay is still difficult to meet the strict requirements of the high-speed railway ballastless track. So the further research about engineering properties of red clay is of important theoretical and engineering practical significance. In this thesis, we carried out research combined the practical needs of the building of Wuhan-Guangzhou Passenger Line with the major research topic of the Ministry of Railways. Based on the comprehensive analysis of the domestic and international research in this field, combining soil experiments, in-situ testing, field engineering monitoring with theoretical analysis and numerical simulation methods, it has been discussed that deformation law of red clay with over-consolidation characteristics and some the practical problems in engineering application. Some conclusions and research achievement are obtained as follows.(1) Based on the engineering geological investigation report of Wuhan-Guangzhou Passenger Dedicated Line and the results of many soil tests, the engineering properties parameters of typical red clay were obtained. Using the method of probability and statistics, this thesis has discussed the spatial variability of soil parameters. Many experiment relationships among these indicators have been set up. It was found that the change law of many indexes increased with depth increasing at red clay natural profile, such as water content, void ratio, liquid limit, plastic limit, liquid index, plasticity index, compression modulus, pre-consolidation pressure, etc.(2) Through a large number of compression tests and triaxial shear tests, it has been studied systematically that the stress-strain characteristics at different stress levels and the change regularity of intensity changes of the parameters under the different consolidation states. Also, it has discussed some factors influencing the red clay strength and deformation is discussed, such as soil depth, confining pressure and others.(3) Through the plate load tests and cone penetration tests on the red clay ground in typical region, the settlement deformation curves and deformation rules of red clay ground under load are obtained. Compared the parameters of different depths soil gotten by cone penetration test with those gotten by soil experiments in room, some relationships between parameters have been obtain. According to the results described above, consolidation behavior of red clay foundation can be judged.(4) In view of the over-consolidation characteristics of red clay, the influence of stress history on consolidation settlement of red clay ground has been taken into account fully. Several consolidation behaviors may occur when over-consolidation red clay foundation is under load. The critical pore water pressure is used at the time of consolidation of state changes. The level of pore water pressure dissipation is used to represent the extent of its dissipation.(5) Considering the changes of over-consolidation ratio with the soil depth increasing, it is built to analyse the nonlinear consolidation equations of over-consolidation saturated red clay. The numerical solution of consolidation equation has been obtained by means of Finite difference method and FORTRAN program. Combined the method suggested by this paper and test results, it has been analyzed that consolidation characteristics of red clay and its influences under load.(6) In engineering applications, there is 373 days in-site monitoring the roadbed of the Wuhan-Guangzhou Passenger Dedicated Line integrated test section. According to the results of site monitoring, it is discussed that development and change regularity of red clay ground surface subsidence, layered settlement and pore water pressure. In addition to the method suggested, Finite Element Method is also taken to numerical simulate using software ADINA. Theoretical calculation results are compared with the site monitoring value, which shows that theoretical value are more in line with the field test results. (7) This thesis derives the formula of settlement modified coefficient using Bayesian theory. Uniform distribution of the experience distribution is used as prior distribution. Under conditions that in situ test the datum are very limited, the posterior distributions of the probability density function are set up using Bayesian analysis of small samples. And posteriori probability densities of the samples are analog by means of Markov Chain Monte Carlo (MCMC) method and Gibbs sampling method, which makes fully use of limited sample information to infer posteriori distribution of settlement modified coefficient. The tradition settlement modified coefficient has been optimized through this method. In this way, the past experience has been used farthest extends, which fully reflects its objectivity. This approach coincides with the actual statistics process of the geotechnical parameters and has a high application value. In addition, it can provide alternative way to carry out settlement calculation for similar projects.