Research On Bearing Capacity Of Mudstone Foundation Based On The Improved Rock Loading Test And Displacements Back Analysis

Foundation bearing capacity is an important design basis of foundation and foundation engineering, and a concern in engineering practice either, especially the foundation bearing capacity of soft rock, such as mudstone. Due to the particularity of mudstone, the recommended methods of specification often fail to completely and truly reflect the bearing capacity characteristic, it will result in the use of this method to determine the bearing capacity of mudstone foundation what lead to the cost put in foundation treatment and foundation engineering greatly increased. This paper is based on rock foundation bearing capacity test method recommended by standard, improved rock plate loading test to simulate the loads of overlying soil. Research in the edge load(depth), the characteristics of mudstone foundation bearing force variation, and try to obtain the correction factor and correction formula of the bearing capacity of mudstone foundation. Due to the limitation of objective conditions, unable to obtain substantial improvements batholite load test data, so the numerical simulation method is used for mudstone foundation bearing capacity research. Then make a comparison and analysis of indoor uniaxial compressive strength test and load test results. Using the finite difference method and displacement back analysis, import the support vector machine(SVM) and particle swarm optimization(PSO) algorithm to simulate the load test to inversion of mechanical parameters of mudstone and draw the load at different edge load(depth) the variation of bearing capacity of mudstone foundation. The main results obtained are as follows:(1) Under the condition of applying 200 kPa edge loads, the bearing capacity of mudstone has the 0.7 to 0.9 times increase compare with applying no edge loads, there needs to have the modification of depth for mudstone. Derived the formula of the standard and made an inverse calculation to get depth modified coefficient. Combining the rock loading test results with the results of indoor rock uniaxial compressive strength test, to do inverse computation of reduction factor according to the standard method which draw the conclusion that the value of the standard proposal is conservative. When the bearing capacity of mudstone in Chengdu is determined by the uniaxial compressive strength test, the value of reduction factor could be improved appropriately.(2) Using the numerical method to simulate batholite load test, the p-s, lgp-s curve, displacement vector and shaping figure of test analysis showed that because the load side load limiting the damage to both sides of the mudstone, what forcing the stress and strain to deeper and farther extended range so that can play mudstone capacity increased. Under the action of loads, the elastic deformation and the plastic stage are extended accordingly, so that the bearing capacity of mudstone is improved.(3) Using back analysis of displacements to get the parameter of the mudstone, apply ?-SVR(support vector machine) which based on the particle swarm optimization algorithm. By the amount of load test measured displacement extrapolation "optimal" parameter of the mudstone, what make the p-s curve can achieve good fitting with the field test when using this set of parameters to simulation calculation.(4) Using the inversion parameters to simulate the rock foundation loading test under the condition of different edge. From the simulation results, we can see that mudstone proportional limit load and limit load with side load increases but the increasing trend is tends to a maximum value. Description on the edge of the load increases to a certain degree, the mudstone of the proportional limit load and limit load will not increase; Depth correction coefficient with the carrier to sideband increases decreases. And according to the test results, the depth correction coefficient and the correction formula of the bearing capacity of mudstone are obtained.