Study On Mechanical Mechanism Of Cement-soil In Erosive Environment

In recent years,with the expansion of China's industrial layout and urban development scale,especially in the eastern coastal areas,in the face of the growing metropolitan area and more and more tense construction land,a large number of new projects have to be built on the soft soil foundation with poor engineering properties.As a common material for soft foundation treatment,cement soil has the advantages of simple construction and low cost,which is very popular in the field of soft foundation treatment,but it also brings some problems such as the change of engineering properties of cement soil under seawater erosion environment.Predecessors have also found this problem,but their research is mostly based on the ideal laboratory environment,and the research results are often slightly different from the actual engineering problems.Therefore,in this paper,a series of experimental studies were carried out around the changes of mechanical properties of soil in the erosion environment and combined with the actual engineering conditions.The main work and research results are as follows:(1)The change law of unconfined compressive strength of cement soil samples under seawater simulated by mocledon with different concentrations was studied,the experimental results show that: With the increase of curing time,the strength of cement soil samples in different concentrations of seawater solution is also increasing;The strength of cement soil samples is the highest under 40% seawater solution,and the low or high concentration of seawater solution is not conducive to the stable improvement of cement soil strength.(2)The stress-strain evolution of soil cement samples under different confining pressures during triaxial compression tests is studied,the experimental results show that: With the increase of curing age,the strength of cement soil samples under different confining pressures is also increasing;At the initial stage of curing(7d),with the increase of the confining pressure,the peak value of the large principal stress of the sample first increases and then decreases,and the peak value of the principal stress of the cement soil sample is the largest under the confining pressure of0.04MPa;In the middle and later stage of curing(14d,28d),with the increase of confining pressure,the peak value of large principal stress of the specimen first increases,then decreases,and then increases.The peak value of principal stress under0.08 mpa confining pressure is the largest.(3)The mineral composition of cemented soil in 40% seawater solution and0.04 MPa confining pressure was analyzed by X-ray diffraction(XRD),the experimental results show that: No matter in the environment of 40% seawater solution or 0.04 MPa confining pressure,the main diffraction peaks of cement soil samples are not changed with the increase of maintenance age,and Si O2 is the main content,while the content of calcium silicate hydrate and calcium hydrolase aluminate increases with the continuous hydrolysis hydration.(4)Scanning electron microscope(SEM)tests were carried out on samples cured with different concentrations of seawater solution and different confining pressures,the experimental results show that: The overall structure of cement soil sample in40% seawater solution is the best;At the early stage of curing(7d),the structural integrity of cement soil under 0.04 MPa confining pressure is the best,while at the middle and late stage of curing(14d,28d),the structural integrity of cement soil under0.08 mpa confining pressure is the best.