Analysis Of Influencing Factors And Micro Mechanism Of Unconfined Compressive Strength Of Lime Soil

Lime soil is composed of lime and soil,two kinds of materials with complex engineering characteristics.Improving and optimizing the preparation of lime soil is of great significance to ensure the safety of road engineering implementation and the stability of operation in China.Accurate determination of its strength is the basis of optimal preparation,and unconfined compressive strength is one of the important aspects.But in practice,because of the complexity of materials and the limitation of design,lime soil often disintegrates and destroys.These problems directly affect the development of unconfined compressive strength test,making it impossible to accurately measure the value of unconfined compressive strength.Therefore,in order to ensure the accuracy of the unconfined compressive strength test value,it is necessary to study the influencing factors and mechanism of the unconfined compressive strength of lime soil,so as to ensure the smooth progress of the unconfined compressive strength test.In this paper,based on the unconfined compressive strength test,the factors influencing the strength are determined from the reinforcement mechanism,and then the orthogonal test method is used to study the influence of these factors on the strength.Finally,the scanning tunneling microscope is used to study the micro mechanism,and the following research results are obtained:(1)The mixing ratio,curing period and soaking time have decisive influence on the unconfined compressive strength of lime soil.(2)With the increase of lime mixing ratio,the unconfined compressive strength of lime soil increases gradually,but when the lime content is more than 7%,the strength also increases,but the increase range also decreases.With the increase of curing time,the strength of lime soil gradually increases,but when the curing time exceeds 28 days,although the strength also increases,the growth rate also gradually decreases.With the increase of soaking time,the unconfined compressive strength of lime soil decreases.Taking the soil sample with 5% lime as an example,when the soaking time increases from 12 h to 48 h,the absolute value of unconfined compressive strength decreases by 0.23 mpa,with a range of about 16%.(3)Under the same conditions,the microstructure of lime soil is denser than that of plain soil.With the increase of lime content,the compactness first increases and then decreases.No matter what the lime mixing ratio is,the greater the compactness is,the greater the compactness is.The structure of lime soil is not consistent with different curing age.When the curing period is short,the soil particles are small and aggregate to form a large aggregate structure.When the curing period is longer,the particles are bonded together under the action of cementitious materials.With the increase of soaking time,the proportion of large particles increased gradually,and the proportion of less than 2um decreased gradually,indicating that the soil particles gradually powdered.(4)In order to enhance the unconfined compressive strength of lime soil,it is necessary to increase the cementitious substances produced by lime and minerals in the soil or reduce the consumption of these substances.In engineering,in addition to increasing the lime mixing ratio,improving the curing time and reducing the soaking time,additives are commonly used to increase the production of cementitious substances.Diammonium hydrogen phosphate(DAP)is an excellent additive.Regardless of the amount of DAP,the unconfined compressive strength increases with the increase of curing time.Compared with several groups of test data,when the DAP content is 2%,the effect is the best,not only the early strength increases faster,but also the strength keeps increasing after 28 days.There are 37 pictures,15 tables and 48 references.