Passenger Line Red Clay Foundation Consolidation Deformation And Pile Network Reinforcement Mechanism Of Field Trials

Red clay is a kind of special soil with strongly regional characteristic. On the vertical section of natural red clay foundation, consistency state of red clay could be divided into three types:hard plastic stateâ†'plastic stateâ†'soft flow～mould state. Generally, the layers with hard plastic state or plastic state are thicker than the soft flow-mould state layers. For normal constructions, it is considered that red clay is a good natural foundation and good building material. However, there are a lot of engineering problems because of it's obvious dilatability and contractibility, large discreteness of its physical and mechanic parameters and uneven distribution, etc. With high-speed railway network plan has been carried out, the work of high-speed railway construction is now in full swing, and red clay engineering problems in construction are increasing.Red clay is widely distributed in southwest, southern, central china areas. Research productions of red clay which have been obtained are difficult to meet the strict requirements of ballastless track of high-speed railway. To guarantee the quality, designers use pile-net composite foundation to reinforce red clay foundation. Researchers at home and abroad have done lots of works about pile-net composite foundation. Different soil has different engineering characteristics, so the work-mechanism of pile-net composite foundation will change with soil type. On the stage, there is rarely data about red clay pile-net composite.So the further research about engineering properties of red clay is of important theoretical and practical significance. In this thesis, combined with the practical needs of Wuhan-Guangzhou passenger dedicated railway, we have carried out researches with the supports of national natural science foundation of china and Ministry of Railways. The main achievements are as follows:(1)Based on the engineering geological investigation report of Wuhan-Guangzhou passenger dedicated railway and the results of many soil tests, the engineering properties parameters of typical red clay have been obtained. using the Theory of Multivariate Statistical Analysis, through statistic analysis, mean and 95% Confidence Interval for mean of each parameter are obtained. What more, many experimental relationships among these parameters have been set up. Hierarchical cluster analysis indicates the property of red clay can be divided into three parts:structural index, strength index and status index. Principal component analysis indicates that values of comprehensive principal component can be used to assess road performance of red clay.(2) Embed single-point settlement sensors and pressure gauges at different depth of red clay foundation to measure deformation and pore pressure. Combined with results of consolidation and swell-shrinking test, system analysis of red clay foundation deformation character and its mechanism have been done.(3) In a cross section of red clay foundation where reinforced by CFG piles, flexible displacement meters have been fixed on the geogrid of pile top and between piles location to monitor the geogrid deformation as load and time change. Combined with monitoring results, the deformation mechanism has been analysis deeply.(4) The concrete strain meters have been buried in CFG piles to monitor the deformation. Combined with the results of laboratory tests, the behaviors of CFG pile which were changed with load and time and the internal interaction mechanics between pile and red clay are studied.(5) Through investigating computational model of soil arching effect of subgrade with Composite Foundation, limitions of these models have been analyzed. Considering that fill heights of most subgrads are not tall, and their fill materials are granular materials, a new computational model of soil arching effect has been established in this thesis. But there are a lot of works need to do to improve the model.