The Analysis And Study About The Method For Determining Bearing Capacity Of Cement-soil Mixing Pile Group Piles Composite Foundation

With the rapid development of national economy and the constant enlargement of the basic construction project,it will often encounter harmful foundation problems in project. Reinforcing the foundation soil, improving the engineering characteristic of the foundation soil, increasing the shear strength of the foundation, and lowering the compressibility of the foundation decrease settlement and differential settlement reduce of foundation can meet the demands of the buildings. The cement-soil mixing pile composite foundation is one of methods to the foundation treatment, because of some advantages, such as the short construction period and the short pre-compression period, the little after-construction subside, no noises, no vibration, no sewage disposal, conservation of steel and so on, which has widely used . However, it is the fundamental issue which is the pile-soil interaction mechanism and bearing capacity determination has not been satisfied in the cement-soil mixing pile composite foundation design.In the light of determination of the cement-soil mixing pile composite foundation's bearing capacity determination,the paper explore the problems as follows:1. Expatiate the development and applied of the cement-soil mixing pile composite foundation.2. The soil-cement pile on the mechanism of action and the impact of the mechanical properties of cement-soil factors are discussed, and soil-cement pile composite foundation bearing mechanism is analyzed.3. This paper researched into the field test of cement-soil mixing pile composite foundation, and focus on the method for determining bearing capacity of cement-soil mixing pile composite foundation in accordance with existing norms in the actual project.4. Using ANSYS combined an example simulate the static load test in the light of cement-soil mixing pile single pile composite foundation. It show that the calculate result fits better with that of field test.5. The pressure and deformation of cement-soil mixing pile group piles composite foundation of settlement are simulated , and the bearing capacity of single pile and that of group piles composite foundation are comparative analyed. The result prove that the bearing capacity of group piles composite foundation is more less than that of single pile composite foundation, which illustrates it is unsafe to define the bearing capacity of group piles composite foundation with the test of single pile composite foundation in engineering testing. 6. In the base of the above, simulate the settlement characteristics of the cement-soil mixing pile composite foundation and analyze factors of the different modulus of pile, different length and different replacement ratio on the bearing capacity of composite foundation. The result is that the bearing capacity of composite foundation increase with the Increase of pile's modulus, however it is stable when the modulus continues to increase, which illustrates that the modulus has an optimum range. And the bearing capacity of composite foundation increase with the Increase of pile's length, however it is stable when the pile's length continues to increase, which illustrates that the pile's length also has an optimum range. The bearing capacity of composite foundation increase with the Increase of replacement ratio, however the settlement is stable when the replacement ratio continues to increase, which illustrates that the replacement ratio has an optimum range too. So this paper prove that the optimum range of pile's modulus is 200-300MPa,valid pile's length is about 10m and the optimal replacement ratio is about 20% by analyzing.