Study On Sanding Mechanism Of Modified Soil And Application Of Sanding Degree Evaluation Method

In the hardening process of modified soil,the morphology of modified soil is similar to that of fine-grained soil coarsening into sandy soil,so it is also vividly called sanding by engineering and technical personnel.Although the sanding phenomenon of modified soil has long been discovered by the engineering community,there are few reports on the sanding process of modified soil.In order to explore the relationship between particle size and strength of soil and sanding time,this paper studies the use of image method to directly observe and analyze the change of modified soil particles with time,and combined with the experimental study of cone falling depth of modified soil,discusses the change law of cone falling depth and strength of modified soil with time.The experimental results show that the undrained shear strength of modified soil increases linearly with time within 24 hours after adding cement,and the strength increases with the increase of cement content;Similarly,at the same ash content,the median particle size of the modified soil increases linearly with time.At the same time,the particle size increases with the increase of ash content.Therefore,the strength of modified soil increases with the increase of cement content and time,which is also the process of soil particle diameter increasing.In order to analyze the influence of sand content on the strength of cement modified red clay,this paper further carried out the comparative experimental study of modified soil mixed with sand,and tested its unconfined compressive strength by adding different content of standard sand into cement modified red clay.The test results show that with the increase of sand content,the unconfined compressive strength of the modified soil first increases and then decreases,and the strength increases obviously.After further analysis,this paper puts forward a comprehensive evaluation method of sanding degree with grain size and strength as evaluation indexes.In order to explore the effectiveness of the comprehensive evaluation method,taking typical red clay(limestone residual soil and granite residual soil)in Changsha,weak expansive soil of a project in Changsha and silty clay of zhuobegen project in Changsha as examples,this paper carried out the experimental research on the modification effect of different modified soil by using different ash mixing technology,and determined the reasonable ash mixing method of different soil,The comprehensive evaluation method is used to quantitatively evaluate the sanding degree of one of the four kinds of soil.Finally,based on Changsha zhuobegen soft soil treatment project,this paper puts forward a construction method of soft plastic modified soil replacement foundation emergency compaction,and uses ABAQUS finite element software to analyze and compare the foundation bearing capacity before and after modification,so as to illustrate the feasibility of the project and the reliability of the modified construction method.