Study On Mechanical Properties Of Guiyang Red Clay Treated By Alkali

Alkali solution reinforcement is the main chemical method to treat special ground.As a kind of special soil mass,red clay is widely distributed in guizhou province.At the same time,the research group has found that the mechanical properties of the red clay after lye erosion have changed significantly in the previous study,which is mainly manifested by the increase of shear strength and compression modulus.This provides a new idea for the reinforcement of red clay.This paper analyzes the reinforcement effect of alkali treated red clay under different conditions through indoor unconfined compression test from the dry density,reinforcement method and temperature of soil.At the same time,the stress-strain control triaxial shear tester was used to analyze the soil strength characteristics,stress-strain relationship and pore water pressure changes of red clay under three conditions of loading,unloading and unloading while loading after alkali treatment.Finally,the possibility of extended application of the stress-strain relationship of the strength-producing surface theory to alkali-treated red clay was studied.The main research results are as follows:?1?Alkali treatment method for different dry density of red clay are reinforcing effect,for the optimum moisture content is 36%,the maximum dry density of soil sample is 1.299 g/cm³ conditions reinforcement effect is best;Through the way of mixing alkali treatment has the highest strength of red clay soil samples;Under the environment of high temperature curing of reinforcement effect is much better than low temperature environment.?2?Compared with the sample before treatment,the peak failure strength of CTC,TC,and RTC is significantly higher than that of the sample before alkali treatment.Among them,the peak damage strength is higher under the CTC path,the strength under the RTC path is relatively low,and the TC path is between the two.Between,the shear strength index becomes higher.However,when the red clay sample undergoes a small strain after alkali treatment,the sample will fail.At the same time,as the structure of the red clay sample is enhanced after the alkali treatment,the pore pressure change amplitude and the strain value at the time of failure under the three different stress paths are less than that before the treatment,and the effective stress path of the red clay sample after the alkali treatment The deflection that occurs compared to the total stress path is smaller than the sample before treatment.?3?The stress-strain curve under different stress paths can be normalized to obtain the?₁/??₁-?₃???₁ relationship curve,which is linear.But as a result of red clay as a special kind of over-consolidated soil,simple Duncan-chang model was applied to alkali treatment before and after the stress strain relationship have some applicability,the initial tangent modulus of Ei,though a rise with confining pressure increasing,but the Rf value far in excess of the normal range,can further follow-up studies,modified Duncan-chang model.?4?Based on the Extended SMP theory,the?_SMP/?_SMP?-d?_SMP/d?_SMP relationship curve of red clay under three stress paths of CTC,TC and RTC before and after alkali treatment is a straight line with high fitting degree;However,the?_SMP/?_SMP?-?_SMP/?_SMPcurve is not a simple linear relationship.In the early stage,when the-?_SMP/?_SMP value is small,?_SMP/?_SMP grows slowly.?_SMP/?_SMP growth accelerated in the medium term,almost a straight line of growth;With the increase of-?_SMP/?_SMP value in later period,?_SMP/?_SMP value did not increase or even decreased.?5?Further analysis of the characteristics of the red clay on the Extend SMP surface before and after alkali treatment shows that the growth trend of?_SMP/?_SMPvalue in?_SMP/?_SMP??₁ curve has a high similarity to the change of stress and strain curve,and the curve of rapid growth followed by slow growth finally tends to be stable or fall down.At the same time,the(?_SMP/?_SMP)_max values of the red clay samples before and after alkali treatment under the same stress path and different confining pressures are close to each other,and the?₁-?₃ values corresponding to the(?_SMP/?_SMP)_max values are almost all equal to the peak failure intensity of the samples.Therefore,it can be said that under the same stress path,the?_SMP/?_SMP value of the red clay sample before and after alkali treatment will reach a specific range on the Extend SMP surface with the increase of axial strain,and the principal stress difference on the soil is close to the peak failure strength of the sample.