Research On Settlement Characteristics Of Completely Decomposed Granite

To ensure the train run smoothly and safely in the high-speed passenger line, the most important things that must pay attention to is the design and calculations for Foundation on specific geological conditions. In this paper, the completely decomposed granite is the research object.By conducting in-situ test, laboratory test and field soil pressure and settlement deformation monitoring test. The stress distribution of subgrade basement, the settlement and deformation characteristics of the completely decomposed granite foundation,the additional stress decay mode of foundation are studied. By using the above methods the settlement of the foundation was calculated and then compared with the measured values,we found that these methods derived from this paper is rationality and feasibility.The key findings are as follows:1,Through a series of on-site tests, the engineering geological characteristics and the basic physical and mechanical properties of the soft soil and completely decomposed granite were identified in detail. The foundation modulus and bearing capacity values were obtained too.Then,the bestest on-site test method which was adequate to the foundation of completely decomposed granite was established.2,The influence of subgrade, foundation modulus and Poisson's ratio on the subgrade basement stress were studied using FLAC3D software. The greater of Poisson's ratio of foundation,the smaller of the subgrade basement stress of the roadbed center.The margin of the Subgrade and foundation modulus had a certain influence on the subgrade stress distribution and size of the subgrade basement. When the subgrade modulus is greater than the foundation modulus happened, the diffusion of subgrade basement stress will be faster. It can also reduce the stress of the middle subgrade basement, but the slope's stress will be increased.3,By monitoring the on site subgrade basement soil pressure and comparing with the stress calculated by the existing method, the subgrade basement soil pressure distribution and the calculation method were obtained. From the monitoring data we can learned that the stress of subgrade basement and its distribution which calculated by the method paper proposed were basically consistent with the actual stress.Based on the Boussinesq theory, this paper created an additional stress attenuation formula in the foundation.4,Through the monitoring of the pile and soil between piles pressure and elongation geogrids of cement mixing pile composite foundation, it shows the displacement that cement mixing pile pierced to the cushion is very small, pile-soil stress ratio is also smaller. From the monitoring data of the geogrids, it can be learned that the Japanese calculation method were more reasonable used in the calculation of geogrid soil arch height and geogrids elongation.5,based on the above method, the settlement of the test sections of the subgrade were calculated. Compared with the on site measured settlement, we can find that this method is more realistic and has a certain value in subgrade foundation design. Considering the foundation consolidation and the irregular subgrade load, a new foundation settlement evaluate method is derived. By comparing the current settlement forecasting model, the new settlement forecasting model which was suitable to the completely decomposed granite was proposed.