Research On The Mechanism Of Mud Pumping Of Heavy Haul-railways

Because of the low controlling standard in construction period of existing heavy haul railway in our country, subgrade has not been put as a geotechnical structures to deal with the construction. As a long operation, the train axle, the traffic volume, and the increased speed, mud pumping has been very serious. Many sections have been formed when it rains, and a white scene after the rain, and it also increases significantly the maintenance costs. The railway works departments can only ease the occurrence of the disease in a short time, but it still exist a lot of problems to be completely resolved. Mud pumping is the most serious troubled problem when all the railway subgrades work. So far, it has not gotten a unified conclusion about the mechanism of the mud pumping in the field of geotechnical engineering. The process of mud pumping is the benevolent see benevolence and the wise see wisdom. Therefore, it is particularly important to study fundamentally the mechanism of the mud pumping. it also provides a theoretical basis for resolving the problem fundamentally and the subgrade design of the new line.In this paper, it relies on the research of science and technology development program of Railways project. “The research on the key technology of Existing Railway in the big axle- Subgrade detection and Enhancement Technique of existing railway in the big axle and the heavy haul railway(2012G011-B)”. First of all, it carried out a dynamic test about the disease investigation of the Datong-Qinhuangdao heavy railway, and studied real conditions of disease occurrence and which affected relationship among dynamic stress, axle load, and speed, and it provided a basis for setting future triaxial test parameters. Secondly, it developed a new measuring method based on "Vanderbilt Law" triaxial measurement of water content of soil samples in the laboratory. The method was combined with dynamic triaxial tests in order to explore each depth of the triaxial soil sample with the increased number about variation, and the variation about soil water content in the depth direction, in order to explore the basic body of the subgrade under dynamic stress fundamentally. The main contents and results of this paper are included in the following aspects:(1) The paper investigates the disease of heavy railway on the scene, indoor physical analysis test, and subgrade dynamic test on the scene. It studies the occurrence of disease manifestations, and grading situation on diseases section of road and with normal grading along with the increase of depth direction, and the influence of dynamic stress on the axle and speed. The results indicate: mud pumping of Datong-Qinhuangdao heavy railway is basically a mud-pumping. Fine-grained soil of Roadbed is composed with Locomotive blast, Cinder and the Grated powder. From the surface to deepth is increasingly well-graded. And it is better than which is under the rail joints; with the increasing in big axle, all the dynamic stress of the subgrade basically changes linearly. The impact of speed about the dynamic stress is not very clear.(2) The paper develops a new test system for using electrical resistivity to determinate of the water content. Calibration tests are carried out of all kinds of influence factors such as the number of washing soil with soil samples, solution concentration, height of sample and the resistivity- moisture calibration test. It is included that:This test system has good test accuracy and time effects, and it also has a good correspondence between resistivity and water content.(3) The paper researches immersion dynamic triaxial tests through using GDS cyclic triaxial combined with self-developed water content test system. It tests the effect of deformation degree and dynamic stress amplitude on deformation and water invasion law. In the loading process, the paper tests distribution of riaxial soil moisture in the depth direction and the water content distribution of soil samples at different times on each deepth, and explores the moisture migration In the role of dynamic load thing-in-itself of subgrade. It shows that: With the degree of compaction increases, dynamic stress amplitude decreases, axial deformation Cumulative and the amount and rate of flooding decrease. On the contrary, the indicators corresponding increase; Bladders, which displays the mud pumping generation, are formed by the dynamic load and water coupling.