Research On Stability And Rapid Detection Of Tailings Subgrade Of Expressway

The quality of subgrade compaction has an important influence on the stability of subgrade.Compaction degree and resilience modulus are two important indexes of subgrade compaction quality.There are some problems with traditional compaction quality detection methods,such as damaged roadbed structure,complex operation process and large error of test data.Based on the engineering background of Zhangjiakou section of Yanchang-Chongqing Expressway,the application of two new non-destructive testing instruments,soil modulus and stiffness tester and PFWD,in stabilization and rapid detection of tailings roadbed is studied in depth.Through the laboratory test of tailings filler,it is concluded that the tailings filler is a well-graded filler.At the same time,the relationship between water content and dry density is obtained,which proves that the tailings filler meets the requirements of subgrade bearing capacity.The equipment characteristics of two new types of testing instruments are studied.The testing principle and flow chart of the two instruments are explained.The linear relationship between pressure and deflection of PFWD under the condition of changing drop weight height is obtained.The reliability of PFWD analysis by linear elasticity theory is verified.At the same time,the logarithmic relationship between the two resilient moduli is obtained by regression analysis.Combined with the actual situation of tailings roadbed construction site,the roadbed construction technology is explained.Aiming at the problem of compactness detection in the process control of tailings roadbed compaction quality construction,based on the construction site of tailings roadbed,the soil modulus stiffness tester,PFWD and surface settlement difference method are used for the first time to detect the location of measuring points one by one.Using regression analysis method in statistics,two kinds of rapid detection equipment resilience modulus index and surface settlement difference index are established.Considering the logarithmic relationship and safety factor,the control standard of resilience modulus in compaction quality construction process based on two kinds of fast detection equipment is proposed.Using soil modulus stiffness tester and PFWD to participate in subgrade compaction quality acceptance,the correlation between the two resilient modulus indexes and the back-calculated modulus and deflection index of Beckman method is established by comparing and analyzing the data with the standard method of Beckman beam in the code.Finally,the standard values of resilient modulus satisfying the requirements of the test section of Yanchong Expressway are determined,and the foundation is put forward.Acceptance criteria for resilience modulus of compaction quality for two kinds of rapid testing equipment.