The Lanzhou-chongqing Railway Abandon Slag Used As Subgrade Filling Water Tunnel Experiment Research

Lanyu Railway, as a newly-constructed railway in Western China, demands a subgrade with such engineering properties as higher strength, stability and durability, but lower deformations. However, there was little qualified Group A and Group B fillings for the railway embankment near the Qingshui Tunnel on Lanyu Railway within the Qinling orogenic belt. If we completely rely on the transported fillings from other areas far away, it will not be economical and reasonable. Therefore, it would be an effective method to use cement which has been widely used in railway construction to improve the in situ filling, while its construction quality is affected by many factors very difficult to control. Since the study on improved phyllite spoil is badly needed both at home and abroad, it is really necessary to study the nature of improved phyllite spoil.To solve the actual needs of the Lanyu Railway construction, the following researches have been carried out:1. The test plans for basic properties of original and improved phyllite spoil were designed. Through the laboratory experiments, the main factors affecting the compression strength of cement improved phyllite spoil were found out. The relationship between the compression strength of cement improved phyllite spoil and other factors were also studied.2. According to the experimental data, the patterns and mechanism of compression strength of the cement improved phyllite spoil were anlysed. In view of the deficiency of existing data about the strength formation mechanism of cement improved phyllite spoil, the microscopic image before and after the quantization process were calculated by using the image processing software. The the regression analysis on the relationship of micro parameters of phyllite spoil and compression strength were also conducted. The improving mechanism of phyllite spoil by cement was discussed, and the the actual engineering improving method was determined.3. Through the laboratory test data regression, the simulation parameters were obtained. Numerical finite element simulations by using the MIDAS/GTS software on the roadbed before and after the improvement were conducted under dynamic loads induced by the trains at different speeds. The influence of dynamic load induced by the trains on the subgrade before and after the improvement of phyllite spoil was compared, which verified the rationality and feasibility of the design plan above.The results showed that during the application of recommended improvements, cement improved phyllite roadbed can form the better rigid skeleton, stronger roadbed, and higher strength. Under the dynamic load induced by the trains, the deformation of the improved subgrade is much small, which can meet the practical requirements of roadbed stability, reduce the investment and minimize the impact of spoil on the environment.