Study On Stress And Deformation Characteristics About Composite Foundation Of Main Building And Annex Building Which Have The Same Foundation

This paper mainly studies the following content:(1)study on the characteristics of pile and soil stress of rigid CFG pile composite foundation, and the proportion of the stress of pile and soil;(2)Analysis of engineering entity composite foundation at different depths settlement characteristics, and find out the composite foundation deformation occurrence reason and control factors;(3) Analysis of characteristics of settlement in different parts of the foundation of buildings, especially the settlement characteristics of the two part of the core barrel inside and outside;(4) The influence of different layout of the core tube and its periphery on the foundation deformation is studied;(5) New calculation method of settlement and deformation of rigid pile composite foundation and foundation. The ultimate aim is to stress and deformation characteristics of composite foundation of the main building of the common base, to provide the experimental basis for the foundation treatment and the optimization design of the foundation.In order to complete the research, a method for measuring the displacement of pile and soil is designed, by this method, the displacement of pile top and soil pile can be obtained, it can also be used to measure the pile and soil stress with the pressure box. Through field test, the stress and deformation of the pile and the pile in the composite foundation with rigid piles can be obtained.The measured data show that the settlement of the soil pile is significantly larger than that of the pile, this shows that under the action of the upper load, deformation of the top of the pile occurs, cushion local flows, always keep the contact with the surface soil pile, In order to transfer the upper load to the soil between piles, the cushion is the premise of existence conditions of pile soil to bear the upper load. The deformation of the measured pile shows that the load is increased to a certain extent, deformation of pile keeps stability, this is not consistent with the deformation regularity of single pile static load test of pile, the single pile bearing capacity is not fully played in the composite foundation load test, the thickness of the cushion effect degree of ultimate bearing capacity of single pile. The deformation of the pile is measured, and the deformation of the soil around the pile is larger than that of the soil around the edge of the load plate, this is due to the lack of load plate bending deformation caused by warping, at the same time, it also reflects the influence of the foundation stiffness on the deformation of the pile, under the action of rigid foundation, deformation of soil between piles tends to be uniform; Under the flexible foundation, deformation of piles in the load center, the deformation of the pile with the load margin is small.Summarizes and analyzes the geological conditions of Beijing area which has a strong representation of the high-rise building in the composite foundation, the size and regularity of the settlement deformation. The main control factors of composite foundation deformation are analyzed and studied, the main effect of the deformation of the underlying layer on the deformation of composite foundation is proposed; And according to the time characteristic of deformation development, it is pointed out that the settlement and deformation of the initial stage of the construction is relatively large, about the structure of the total settlement of the first double. It sums up at present, the empirical coefficient of settlement calculation is only suitable for the calculation of the deformation of the foundation center point.For the calculation of the corner and edge points of composite foundation is not applicable, the calculation result is obviously small, the correction coefficient can be improved by 2.5 to 3.5 times based on the proposed value of "building foundation treatment technology standard", besides, analyses When the pile end is in the relatively weak cohesive soil, the relationship between the depth of the pile and the deformation of composite foundation, to point that there is no obvious corresponding relationship between the two, and, it is found that the deformation of the composite foundation is larger than the theoretical value, besides, summarized the influence of the pile end bearing stratum selection on the settlement of composite foundation, the pile end bearing stratum should choose the hard formation with low compressibility, it can obviously reduce the deformation of foundation, at the same time, the deformation and stability time is relatively short.Comparative analysis and calculation of different distribution patterns, under the precondition of satisfying the bearing capacity of composite foundation, proposed for core tube parts, as far as possible the use of a long pile of cloth pile model, it is better to control the total settlement of foundation settlement.Combined with previous research results, developed a method for settlement calculation of composite foundation based on Mindlin solution and Boussinesq solution, at the same time, we can consider the effect of the base plate, the analysis and calculation of the interaction between the foundation and the foundation, and the corresponding finite element calculation program is worked out. At the same time,it has been well applied in the work. At the same time, the internal force and displacement of the raft can be calculated, and it can provide a reference for the optimization design of raft.