| With the rapid development of our economy,the city building is more and more intensive,which put forward a higher requirement for the excavations in the city.Besides,our country is widely distributed soft soil,poor engineering property of soft soil makes the excavations face more challenge.In soft soil area,the heave-resistant stability analysis of excavations is an important basis for evaluating the safety of excavations.Due to the complexity of excavations,the current analysis method is too conservative,so it is necessary to deeply study the theory of the heave-resistant stability of excavations in soft soil area,putting forward a simplified calculation formula that can be applied to practical engineering,and analyze the factors affecting the heave-resistant stability of excavations.In this paper,the method of checking the stability of excavations against heave in soft soil area and the influencing factors of the safety factors of excavations against heave are systematically studied by means of theoretical analysis,numerical simulation and comparative analysis of engineering examples.The main work and conclusions are as follows:The formula of checking the heave-resistant stability of excavations is improved by considering the width and depth of the heave,the beneficial effect of the shear force on the vertical sliding surface of the soil outside the excavation and the influence of the width of the excavations.A simplified calculation method suitable for soft soil area is presented,and the complete calculation formula and checking diagram are given.Then,based on some excavation examples,the improved formula is verified by comparing different formulas with the improved formula.Based on the engineering example,the finite element model is established.On the basis of verifying the accuracy of the model,the law of excavation heave deformation is analyzed and studied.And it is found that the width of excavations is positively correlated with the heave of the bottom.When the width to depth ratio of excavations is greater than 3,the width effect of excavations can be ignored.Plaxis2D numerical simulation software is used to compare and verify the improved formula,and the rationality of the improved formula is further tested.The improvement method of finite element can be applied to engineering checking calculation,which has the significance of engineering practice and popularization.In addition,in the process of using finite element method for calculation,it is found that the strength reduction calculation can improve the efficiency on the premise of ensuring the calculation accuracy by using Mohr-Coulomb model.A generalized analysis model of excavations is established,and the finite element method,the specification method and improved method are used to calculate at the same time.The influence of calculation parameters on the safety factor of the heave-resistant stability of excavations is studied by control variable method.It is found that the elastic modulus and Poisson’s ratio of soil have no effect on the stability analysis of anti-heave.After comparing the improved method with the finite element method and the normative method,it is concluded that among the many influencing factors,the internal friction angle has the greatest influence on the calculation result of the improved formula,followed by the insertion ratio of the supporting structure,and the soil weight has the least influence. |
