Research On The Mechanical Properties Of The Expansive Soil Improved By Industrial Alkali Residue In Southern Shaanxi

As a special soil widely distributed on the land of China,expansive soil is more common in the southern region,and also has some distribution in the northwest region.It has strong adverse properties such as water absorption expansion,water loss shrinkage and water immersion bearing capacity attenuation.Its special engineering nature causes great harm to the engineering construction,disaster prevention and reduction and reinforcement and repair in the expansive land area,which is easy to lead to engineering disasters such as slope instability,subgrade damage and main body deformation,and even cause personnel safety problems and serious economic losses.Therefore,when carrying out construction in the distribution area of expansive soil,it is necessary to improve or modify the relevant characteristics of expansive soil to reduce its harm to engineering construction and meet the requirements of construction.In this paper,the waste industrial alkali residue from ammonia alkali process is used as the improved material,and the research purpose is to improve the mechanical properties and expansibility of expansive soil.By using the industrial alkali residue as the raw material to improve the expansive soil in southern Shaanxi,the industrial alkali residue expansive soil is tested by liquid plastic limit test,free swelling rate test,swelling rate test,triaxial shear test,dynamic triaxial test,SEM test and XRD test,The expansibility and mechanical properties of expansive soil improved by industrial alkali residue in southern Shaanxi and the micro structure of expansive soil after the action of industrial alkali residue were discussed.The main research contents and conclusions are as follows:（1）The effect of industrial alkali slabs for improved expansion soil on the expansion of different dosage ratios were studied,and 0%,10%,20%,30%,40%industrial alkali slag were incorporated into the expansion soil,and the improved Expansive soil for liquid-plastic test,free expansion ratio test,expansion force test,etc.The test results show that industrial alkali can reduce the plastic index of expansive soil;it can effectively reduce the free expansion ratio of expansion soil;and to inhibit the expansion of expansion soil.However,the dosage of industrial alkali slag is not,the better,and the plastic index of improved soil is drawn,and the expansion force is optimally improved in the industrial alkali dregs.（2）The variation of shear strength of improved expansive soil in southern Shaanxi with the content of industrial alkali residue was studied.Triaxial shear tests were carried out on the improved expansive soil with the content of 0%,10%,20%,30%and 40%.The experimental results show that the cohesion and internal friction angle first increase and then decrease with the increase of content.Under the confining pressure of 100KPA,200KPa and 300k Pa,when the content of industrial alkali residue is 20%,the shear strength of industrial alkali residue improved expansive soil is the largest.（3）The dynamic characteristics of expansive soil improved by industrial alkali residue in southern Shaanxi are systematically analyzed,and the action triaxial test of expansive soil improved by industrial alkali residue is carried out.The test results show that when the content of industrial alkali residue is 20%,the maximum dynamic elastic modulus E_dmaxof expansive soil reaches the peak,the damping ratio is the smallest,and the anti vibration capacity and energy dissipation capacity of soil are the best.The system analyzes the dynamic characteristics of industrial alkali to improve expansive soil,and proposes the power characteristics of the industrial alkali-slag improved expansion soil.When the industrial alkali dumping is 20%,the maximum moving elastic modulus of improved expansive soil reaches the maximum,the damping ratio is the smallest,and the movable residue exhibits the best moving stiffness characteristics.（4）The effects of industrial alkali residue on the mesostructure and mineral composition of expansive soil were studied.Industrial alkali residue can agglomerate expansive soil particles to form agglomerated particles,enhance the cementation strength between soil particles,and gradually transform its structural type from point connection structure between particles to surface connection structure between blocks.The addition of industrial alkali residue will destroy the hydrophilic mineral structure of clay particles and produce many compounds with good cementation ability,so as to change its expansibility and soil strength.The above research results provide a certain experimental basis for further research on the improvement of expansive soil by industrial alkali residue.At the same time,it provides theoretical basis for the actual engineering application of industrial alkali-slag improved expansive soil.