Study On Interaction Between Lateral Limited Subgrade And Raft Foundation And Design Of Raft Foundation

The bearing capacity of the natural base itself is small,so that making the raft foundation bending moment and settlement on the natural base are increased.When designing the raft foundation on the natural base,it shall be overall considered the bearing capacity and safety requirements of the foundation,it is found that the raft foundation has a large base thickness and a large amount of steel bars,and the construction is more complicated.In order to solve the problem of the natural base bearing capacity is small lead to excessive settlement of raft foundation and the related design problem.It has been tried to adopt the lateral limited subgrade to treat and make good economic results.The lateral limited subgrade not only solves the problem of insufficient bearing capacity and excessive settlement in the natural base,but also reduces the economic loss in the process of foundation treatment.The raft foundation is based on the lateral limited subgrade and the support form is different from that on the natural base.The multi-point support form of the lateral limited subgrade greatly reduces the foundation settlement of the raft foundation,at the same time reduces the raft bending moment.When the raft foundation is carried out on the lateral limited subgrade,it is necessary not only to study the interaction between the both,but also to determine the relevant parameters of the design raft foundation.The factors such as reinforcing bars,thickness,strength,as well as the length of the lateral limited subgrade of raft foundation shall affect the design of raft foundation on the lateral limited subgrade.In this paper,the interaction between the lateral limited subgrade and raft foundation is analyzed,and also parameter values of raft thickness and strength are studied deeply.In this paper,indoor unit test and analysis are carried out on the interaction between the lateral limited subgrade and raft foundation first.Its unit numerical simulation and overall numerical simulation are respectively carry out on this basis,then the interaction characteristics and laws are verified by engineering examples.The following main achievements have been obtained through the above three main studies:(1)Through the static load test in the indoor unit,it is conclude that raft thickness and the strength of unit upper raft changed,strain variation regularity of raft plate and lateral limited body.According to the static load test of indoor unit,the strain distribution diagram of raft plate on the lateral limited subgrade is obtained,and also concluded that the raft foundation is in the damage form of "+" type.(2)The numerical simulation of the unit is performed according to the indoor unit test.The consistency of the both conclusions is obtained through the comparison and analysis of the raft thickness and strength variation in the unit model.The numerical simulation of the unit verifies the correctness of the indoor test results.(3)The overall numerical simulation is carried out according to the actual project.Comparative analyzing the influence of upper layer construction on stress and settlement of raft foundation and lateral limited subgrade.At the same time,analyzing the influence of the upper layer construction on the lateral limited body confining stress and settlement.In this paper,the stress magnitude of lateral limited unit at different positions in rectangular lateral limited subgrade is analyzed and studied.(4)In the overall simulation,analyzing the influence of different raft plate thickness on the settlement and stress of raft plate and lateral limited body,and concluding the economical and reasonable range value of raft plate thickness on the lateral limited subgrade.(5)In the overall simulation,analyzing the influence of different raft plate strength on the settlement and stress of raft plate and lateral limited body,and selecting the strength of raft foundation on the lateral limited subgrade.