Study On Dynamic Stability Of Railway Silty Foundation Under Wet-dry Cycles

The frequent rise and fall of the underground water level of the railway（highway）foundation in the silty soil area is easy to cause engineering diseases such as subgrade softening,subsidence,slope erosion,slurry and mud,which endangers the safety of railway line operation and increases the cost of railway operation and maintenance.In order to explore the evolution law of silt engineering characteristics under the combined action of train vibration load and wet-dry cycle,master the evolution law of silt cumulative deformation characteristics,dynamic plastic deformation characteristics and critical dynamic stress under wet-dry cycle,and establish a dynamic stability evaluation method of silt soil foundation considering wet-dry cycle effect.It provides theoretical and data support for analysis of service performance and typical diseases of silt soil foundation,design of silt soil foundation and study of disease prevention and control measures.Based on the Xinyi Railway special track project in Jiangsu Province,aiming at the dynamic stability of silty soil foundation under the action of wet-dry cycle,this paper explores the influence of wet-dry cycle on the dynamic characteristics of silty soil by combining laboratory tests and theoretical analysis.The main conclusions are as follows:（1）Under the same vibration frequency,the cumulative plastic strain of silty presented a tendency to increase and then decrease with the increase of wet-dry cycles.Under the same wet-dry cycles and dynamic stress amplitude,the cumulative plastic strain of silty increased first and then became stable with the increase of vibration frequency.（2）Under the condition of the same dynamic stress amplitude,the dynamic elastic strain（dynamic elastic modulus）of silty presented the development trend of first rapidly increasing（decaying）and then stable with the increase of vibration frequency,and its stable value presented the development trend of first increasing（decaying）and then stable with the increase of the wet-dry cycles,and the E_d,stab～ε_e,stab empirical formulas are established.（3）The critical dynamic stress of silty attenuated first and then increased with the increase of wet-dry cycles,and the maximum attenuation range was 56.23%during the wet-dry cycles.（4）On the basis of critical dynamic stress method,which is a long-term dynamic stability evaluation method of railway subgrade,combined with the test results of wet-dry cycle effect of silty,a dynamic stability evaluation method of railway foundation considering wet-dry cycle effect is established.This thesis has 32 figures,12 tables and 96 reference.