Research On The Effect Of Vacuum Field On The Properties Of Unsaturated Cohesive Soil

Grouting technology is an effective way to reinforce the formation and plugging water.Because of its simple construction process and wide range of applications,so it has been applied in many projects.Grouting process is generally used in the layer which has big porosity or rock fissures.However,in practical engineering,when use the traditional hydrostatic grouting process for construction,often encountered the sand layer whose porosity is very small.Not only the diffusion radius of the slurry cannot meet the requirements,but also the grouting pressure is so large that it cause the ground uplift,cracking and other phenomena,it has brought a lot of trouble to the construction.In recent years,some scholars have studied a new grouting process-vacuum grouting,a mean that can apply in fine sand layer,and achieved good results,but in the less permeable clay this related research is lacking.Due to the particularity of the clay itself,its permeability is not only related to the size of the pores,but also has a great relationship with the bound water on the surface of the clay and electric double layer’s thickness.Based on this situation,it is very important to study the experimental of vacuum grouting for unsaturated clay strata.In this paper,the influence of vacuum field on the properties of unsaturated viscous soils was analyzed by indoor simulation test.The diffusion law of slurry in unsaturated clay was obtained and the relationship between vacuum field and clay permeability was demonstrated.The main contents of this paper include:(1)Based on the characteristics of unsaturated clay and the characteristics of vacuum grouting test,a miniature vacuum model box was designed independently.(2)The proper ratio of acid water glass slurry was determined by laboratory test.The influence of temperature on the gel time and viscosity of acidic water glass slurry was analyzed.Through this data the appropriate slurry ratio could be selected according to the laboratory temperature.(3)The influence of different vacuum time and vacuum degree on the bonding water and electric double layer in clay was analyzed by micro-vacuum simulator,and the influence law was measured by thermo gravimetric analyzer and Zeta potentiometer.(4)The experiments of vacuum grouting were carried out.The slurry diffusion radius,diffusion time and shape of grouting consolidation were analyzed under different pumping time and different vacuum degree in the grouting test.And the effect of vacuum field on the permeability of unsaturated cohesive soil is demonstrated.