筋土界面相互作用参数和加筋垫层处理软基的性状研究

Study on the Interaction Parameters between Geogrid and Expansive Soil/Sand and Performance of Soft Ground Improvement with Reinforced-mat

Settlement control and short supply of embankment filling are two technical problems influencing the construction and development of highspeed railway and highway, and the chances to solve these two problems may arise by applying geosynthetic to embankment engineering. It may be practical to treat the expansive soil (as filling of embankment) with geogrid, and it is hoped to control the (residual) settlement of embankment by using reinforcedmat with other methods in groundimprovement. Given that the aim of those two technical problems is the same, i.e. deformation controls, the key problem is how to gain the reasonable interaction parameters between geogrid and soil (IPBGS) through further investigation in the interaction mechanism between reinforcement and soil. Thus, in order to meet the deformation requirement in the application of reinforced techniques, this paper, based on extensive research of these subjects at home and abroad, systematically tests research (selection principle of testing methods, the steps of pullout tests and some relative criteria, and analysis method etc.) on IPBGS, corresponding tests (extension tests for geogrid and geotechnical properties tests of soil), and model tests of the performance of ground improvement with reinforced mat were carried out. Therefore, the main conclusions are as follows:1. Selection Principle of Testing Method for the IPBGS. Based on the state of the art research of IPBGS at home and abroad, the principal selection for testing the IPBGS is set up. The steps of pullout tests whose mode is strain control and some relative criteria are concluded.2. Analysis of IPBGS and its relative results by research. Based on the pullout tests data between geogrids and expansive soil/sands arranged by the orthogonal table L9 (34) , the following conclusions are reached:(1) The displacementproperties of pullout tests depend on the pullout speed. (2) Applying the method of ″process analysis″ to analyze pullout data, and with the concept of ″equivalent pullout displacement (χ)″ brought forward, the pull out tests are divided into two processes: a. ″main process (when χ≤10)″ and ″residual process (when χ≥10)″, and b. three stages: static friction resistance stage, slip friction resistance stage, and residual friction resistance stage.(3) The value of friction coefficient between reinforcement and soil varies with their definitions, but each factor influencing IPBGS and its rule remain almost the same during the whole tests process. (4) Corresponding tests for pullout tests: It has been put forward that quality index of geogrids should be the tensile strength, strain, and strain rate, and the size of geogrid sample for strain test is suggested.3. Further research on the performance of ground improvement with reinforced mat by model tests: Three kinds of springs are used to simulate the different lateral stiffness of soft ground, and special drawers with sliding path are modeled as lateral displacement pile of embankment during its filling periods, with the function of reinforcedmat considered. On the basis of the data of tests designed by thogonal table L9 (34), three kinds of (factor, depth of layer, loading) state matrixes are obtained which could be used for process analysis by making use of the principle of information matrix conformation. Moreover the relationship between the affecting degrees of factors influencing the lateral displacement (pile) rate and the depth of layer is researched by process analysis of loading, and the one between the affecting degree of factors and loading is analyzed in terms of the matrix factors and the matrix of layers. The general rules of affecting degree of factors influencing lateral displacement rate with the depth of layers, in every layer and during loading process, are gained. And the confinement effects (lateral restrained) of the sandmat and reinforcedmat with loading are presented. In addition, their differences, after a period of loading, also illustrated by comparing each other?