Test On Dynamic Properties Of Composite Drainable Waterproof Plate Based On Medium-weak Expansive Soil Subgrade Of Yun-Gui Railway

Abstract:Expansive soil is a kind of special clay widely distributed at home and abroad. With its special engineering characteristics such as overconsolidation, multiple discreteness, repeated dilatability and contractibility, and dampness-heat sensitivity, it brings great harm to the railway engineering.Currently high-speed railway is tending tofull-scale acceleration, overload and high intensity, however, the problematic dynamic properties of expansive soil subgrade under the train load become one of the most important constraints against the high-speed railway development.To guarantee safety, stability and comfort of the train in operation, higher requirements are put forward to the stability of expansive soil cutting bed. Therefore, it is absolutely necessary to study the dynamic characteristics of high-speed railway subgrade in the expansive soil areas.With the support of scientific and technological project of the ministry of Railways (2010G016-B) and the national natural science foundation (51278499), the paper focuses on the medium-weak expansive soil subgrade in test section of the newly-built Yun-Gui railway. Through laboratory test and statistical analysis,the physical-mechanical properties of expansive soil are analyzed; through the field vibration test, the dynamic response characteristics of expansive soil cutting bed and the effect of drainable waterproof plate are studied. The main research work of this paper are concluded as follows:(1) Based on a lot of laboratory tests on the field undisturbed samples, the engineering property parameters of typical expansive soil are achieved. Firstly, the SPSS statistical software is applied to analyze the routine physical-mechanical indexes of the two expansive soil sections, Guangxi and Yunnan, and to gain the average value of each index, the confidence interval of95%,98%and the correlation between the index variables. Secondly, the hierarchical clustering method is also used in the expansive soil of the two sections, and it shows that the routine physical-mechanical indexes of expansive soil can be generally classified into three kinds:structural index, strength index and status index. Thirdly, the principal component analysis indicates that the properties of medium-weak expansive soil can be reflected by the values of the seveal unrelated index variables.(2) The test sections of medium-weak expansive soil are selected according to the advance field investigation of Yun-Gui railway. First of all, the paper introduces the filling materials, group A and B, used in the bottom layer of subgrade bed, and it also introduces the filling processes and testing standards of graded broken stone used in the surface layer of subgrade bed. Moreover, it elaborates the application of composite drainable waterproof plate in the medium-weak expansive soil subgrade of the newly built Yun-Gui railway, including its composition, main parameters, construction technology, matters needing attention and’(4) By investigating the conditions of the typical medium-weak expansive soil in the test sections of newly-built Yun-Gui railway, the dynamic response properties are measured; using the high-speed railway subgrade in-situ dynamic test system, the different dynamic responses of1million times vibration under the imitated natural condition and rainfall condition are collected and analyzed respectively, through which, some statistics are inferred, for example the time history curve of dynamic response with the change of the vibration frequency, dynamic stress, vibration acceleration, vibration velocity along the direction of depth of the subgrade, the attenuation law of the lateral subgrade. What’s more, the dynamic displacement subgrade is also inferred at the same time. Though the humidity monitoring of the subgrade bed by vibration experiment under the rainfall conditions and after the rainy season, it shows that the surface water can penetrate into the subgrade bed through lap seams between the drainable waterproof plates. Therefore, it can be concluded that the composite drainable waterproof plate is inadequate to repelling and draining water in the medium-weak expansive soil cutting bed.The paper includes80figures,61tables and138referances.