Model Experimental Research On New Structure Of Lateralseepage Control In Deep Collapsible Loess Ground Embankment

According to the distribution, collapsible loess has a large portion in C hina. The characteristic of collapsible loess is its collapsibility. When immersed in the water, the collapsible loess will become less solid rapidly, which is followed by some engineering disasters, such as collapses and subsidences. They will greatly affect the normal use of tracks and buildings. In the area of collapsible loess, especially in northwestern C hian, it is particularly important to lessen or eliminate the collapsibility. In the practical engineering, the commonest way to eliminate the collapsibility is using seepage prevention treatment. Therefore, a lateral-constraint and seepage structure is designed considering the collapsibllity of the loess, and the theoretical analysis and indoor model test are combined to study the effects of lateral-constraint and seepage structure. The main content of this thesis include:Firstly, the basic characteristics of loess and the theory of loess collapsibility are described. In order to provide a theoretical reference for the subsequent model test, the strengthening mechanism of compaction pile and seepage prevention are also analyzed.Secondly, indoor model tests are carried out based on the theoretical analysis, and three groups are designed with different test conditions. They are the first group(without any handling), the second group(with lime-soil compaction pile) and the third group(with lime-soil diaphragm wall). After the tests, the last two groups are compared with the first group, and the results are: In the second and third groups, the permeability decreases obviously and the anti-seepage performance improved significantly, which is because, after the handling of lime-soil compaction pile and lime-soil diaphragm wall, the compactness of the pile increases and the coefficient of permeability decreases. Besides, the material itself also has some certain waterproof effect, so the anti-permeability effect of the subgrade is greatly improved. What's more, the lime-soil underground diaphragm wall has better effect than the lime-soil compaction pile, which is resulted from the proper pile spacing. In the test, 2.5 times pile spacing is adopted, and with the space decreasing, the seepage control effect becomes better and better.Finally, the changes of moisture content are analyzed. Meanwhile, the subgrade settlements in different test situations are also compared. The results are: the third group has the least settlement, and the second group has less settlement than the first group. That is because the better the anti-permeability effect is, the less the water infiltrate the subgrade and the smaller the amount of the collapsible deformation will be.