| The treatment of collapsible loess foundation is an important research topic of special soil treatment in the field of geotechnical engineering.As a collapsible loess treatment technology,fly ash cement grouting reinforced piles can not only solve the problem of fly ash storage,but also reduce the amount of cement.Related theories such as its design method and calculation theory are not perfect.Based on the current standards for foundation treatment of composite foundation and engineering practice experience,the thesis conducts research on the bearing and deformation mechanism of this type of composite foundation through theoretical analysis,indoor scale tests and numerical calculations.The main research contents are as follows:(1)Through theoretical research,systematically analyzed the reinforcement mechanism,settlement theory,and failure modes of composite foundations.Briefly describe the applicable conditions of the formula for compressive modulus of composite foundation,foundation bearing capacity and settlement calculation formula.Based on the existing research results of industrial waste grouting to strengthen collapsible loess,the feasibility of cement-fly ash composite foundation is explained.According to the specifications,two design pile layout schemes with replacement rates of 12.57%and 25.13%are determined to provide a basis for later model tests.(2)The physical and mechanical parameters of the test material are obtained through the geotechnical test,in which the cohesion and the internal friction angle are 44.27 kPa and 29.64°,and the optimal water content is 15.05%,which provides a reference for making indoor models.According to the indoor water immersion test,the collapsibility coefficient of the soil sample after the fly ash cement grouting treatment is significantly reduced.The indoor scale model test was carried out to study the settlement and earth pressure distribution of the grouted fly ash-reinforced pile under the action of vertical load.Solid;the change rule of settlement value at each measuring point of the foundation after treatment is similar.(3)Use ABAQUS software to establish a grouting fly ash cement composite foundation model,and analyze the bearing characteristics of the foundation under static load.Numerical calculations show that the soil settlement and stress are 2.51 times and 1.62 times that of the scaled model test.After treatment,the maximum bearing capacity of the composite foundation can reach 272.5 kPa.The maximum stress ratio of pile-soil is 5.9,which is between CFG pile and cement-soil mixing pile.Analyze the effects of reinforced soil elastic modulus,different treatment depths,different replacement rates,cushion thickness and elastic model on the treatment effect,and provide references for composite foundation design. |
