| In order to solve the problem of frost damage of canal system engineering in seasonally frozen soil area,this paper takes the frozen and thawed silty clay in Weishan Irrigation Area as the research object,and the samples with different dry density,moisture content and salt content are prepared for different freeze-thaw treatment.After the end of freeze-thaw cycle,the direct shear test is carried out on the soil samples.According to the test data,the change rule of its mechanical properties is summarized and analyzed.Using MATLAB software to build RBF neural network and the test data are trained,combining with the principle of statistics,the sensitivity of influencing factors of mechanical properties of freeze-thaw silty clay and the interaction between them are studied.The sensitivity of influencing factors of mechanical properties of freeze-thaw silty clay is classified,and the regression equation is established based on the sensitivity analysis results.The conclusion is as follows:?1?Under the action of moisture content,dry density,salt content and freeze-thaw cycle,the stress-strain curve of freeze-thaw silty clay is similar,that is,the stress increases proportionally with the increase of shear displacement in the early stage of shear,and when the shear stress reaches the peak value,the growth rate becomes slower and even negative,and finally tends to be stable.The peak shear stress and residual strength of soil are negatively correlated with water content and salt content,positively correlated with dry density;under the freeze-thaw cycle,the peak shear stress of low-density soil increases by 4.8%,and the peak shear stress of high-density soil decreases by 9.76%.?2?The cohesion of freeze-thaw silty clay is negatively correlated with water content and salt content,positively correlated with dry density.The cohesion of soil is bounded by the optimal moisture content of 16.7%,and the decreasing trend is fast first and then slow.When the dry density is less than 1.57 g.cm-3,the cohesion increases by 55.1%,and when the dry density is greater than 1.57 g.cm-3,the cohesion increases by 68.9%,the rising trend is slow first and then fast.Under the action of freeze-thaw cycle,the cohesion of soil with different moisture content has a negative correlation with the number of freeze-thaw cycles.The cohesion of low-density soil increases and that of high-density soil decreases under the action of freeze-thaw cycle.The cohesion of plain soil is negatively related to the number of freeze-thaw cycles.The cohesion of soil with quantitative sulfate increases first and then decreases with the number of freeze-thaw cycles,and the cohesion reaches the peak value after one freeze-thaw cycle.?3?The internal friction angle of freeze-thaw silty clay has a negative correlation with water content and a positive correlation with dry density.The change trend of soil internal friction angle with water content is fast first and then slow.When the dry density of soil is greater than 1.57 g.cm-3,the internal friction angle changes only by 0.048°,and the change amplitude decreases obviously.The internal friction angle of soil decreases first and then increases with the increase of salt content.When the salt content is less than 2%,the internal friction angle decreases.When the salt content is greater than 2%,the internal friction angle increases,and there is a significant threshold within the designed salt content.Under the action of freeze-thaw cycle,the internal friction angle of soil is decreasing as a whole,but the decline of internal friction angle of soil with different moisture content,dry density and salt content reflects different forms.?4?Regardless of the interaction factors,the sensitivity of soil cohesion and the order of influence quantity are:dry density B?70.491%?>salt content C?8.2674%?>moisture content A?5.2165?>freeze-thaw cycles D?3.4783?.Considering the sensitivity and influence quantity of the factors of the second order interaction,the order is:B*C?11.6336%?>A*B?11.5845%?>B*D?6.6397%?>C*D?5.6178%?>A*C?3.4088%?>A*D?1.9347%?.Considering the sensitivity of each factor of the third order interaction and the order of influence quantity is:A*B*C?1.32%?>B*C*D?0.6613%?>A*B*D?0.5285%?>A*C*D?0.403%?.Through regression analysis,the sensitivity ranking of the influencing factors is verified.On the basis of direct shear test,this study not only summarizes the relationship between the mechanical properties of freeze-thaw silty clay and the influencing factors,but also uses RBF neural network to quantitatively analyze the sensitivity between the influencing factors of the mechanical properties of freeze-thaw silty clay.In the test process,through continuous improvement and debugging of the direct shear equipment,a strain controlled direct shear system and data optimization method are invented,which makes the collection of test data more efficient and accurate,and greatly improves the test efficiency.Therefore,this study has a certain innovation in the analysis method,and the conclusion has a certain reference value for the research of frost prevention of canal system engineering in seasonally frozen soil area. |
PDF Full Text Request