Study On The Mechanism And Model Test For Vacuum Preloading With Heating

Soft clay is widely distributed in coastal areas of China.With the development of social economy,many buildings have to be built on the soft clay foundation.The settlement of untreated soft soil foundation is large and its stability is poor.Therefore,the construction treatment of soft soil foundation has become one of the scientific and technical research topics in the field of geotechnical mechanics of geotechnical engineering in China.Among the existing methods to deal with soft soil foundation,the vacuum preloading method is widely used in soft soil foundation management with the advantages of low construction cost and small impact on the environment.However,the consolidation rate is slow and the reinforcement effect is limited.Through mechanism analysis and model test,this paper discusses the feasibility and rationality of vacuum preloading combined with thermal drainage consolidation method,and discusses the effect of intermittent heating and continuous heating on the consolidation effect of the combined method,in order to provide reference for engineering practice.The main contents and understanding of this paper include:(1)combing the existing studies on thermal drainage consolidation method and vacuum preloading method,discussing the mechanism of action of vacuum preloading combined with thermal drainage consolidation method,and analyzing the feasibility and rationality of the combined method.Combined with the classical shaft foundation consolidation theory and considering the influence of heating on soil parameters,the settlement,pore pressure and consolidation degree of soft soil foundation at different temperatures are analyzed,and the expansion and settlement phenomena of soft soil foundation during heating are reasonably explained.(2)a series of vacuum preloading combined with heating consolidation tests were carried out based on the self-made heating model bucket,and the effects of different temperatures on the treatment effect of soft soil foundation were studied.The results showed that: in a certain temperature range,the higher the temperature,the greater the settlement and the faster the consolidation rate.When the temperature is high,the heating will lead to changes in the material of the plastic drainage plate,and the permeability of the plastic drainage plate will be reduced due to the heating,which will hinder the transfer of vacuum degree to the depth of the foundation.Therefore,the excessive heating temperature will have the opposite effect on the consolidation of the vacuum pre-pressure drainage.The experimental results show that the heating temperature of about 50℃ combined with vacuum preloading is the best.In addition,based on the test results and theoretical analysis,the permeability coefficients of soils at different temperatures are inversely analyzed.(3)the soft soil foundation model test of vacuum preloading combined with intermittent heating was carried out.The results showed that the vacuum preloading settlement using intermittent heating at 40℃ increased by 25% compared with the conventional vacuum preloading settlement,and decreased by 5.22% compared with the continuous heating vacuum preloading settlement.The difference between intermittent heating and continuous heating is not big,and the intermittent heating saves 1/3 energy.From the perspective of engineering reinforcement effect and economy,the vacuum preloading combined with intermittent heating is more suitable to be popularized in practice.