The Analysis Of Locally Supplying Strength To Shallow Foundation Of Structures

After put into operation, multi-storey buildings often appear different forms of diseases due to such factors as the structure design, construction, and bearing capacity of foundation. In the light of the influencing factors of the damage to the shallow foundation from the existing structures, this paper analyzes on the reinforcement effects and influencing factors. It mainly carries out the following researches:(1) It summarizes the recent researches on the design, deformation, destruction and the bearing capacity of shallow foundation, also concludes reinforcement methods and reinforcing measures.(2) It analyzes the influencing factors of the damage to the shallow foundation from the existing structures. It also analyzes respectively on the grouting method, root pile method, grouting and micrpile mixed method.(3) Combined with practical engineering cases, this paper analyzes each unit parameters of the models, establishes analysis model and verifies its correctness by applying numerical simulation software PLAXIS under the environment of Mohr-Coulomb constitutive model. In the grouting reinforcement method, the researcher selectes grouting range and depth of grouting for shallow foundation deformation, shear stress and normal stress of soil impact, and draws reasonable design parameters. It concludes that as the grouting range stays in a certain range, the foundation settlement and the maximum shear strain linearly decreases with the increase of the depth of grouting. When grouting depth stays, in the basal plane within the scope of 0.75 ~ 1.5 times of pressure grouting, the control the subsidence effect significantly increases; in the basal 1.5 ~ 2 times, within the limits of grouting plane, it reaches the optimal reinforcement effect. In the basal plane within the scope of 0.75 ~ 1.75 times of pressure grouting, the maximum shear strain linearly decreases, and its reinforcement effect significantly increases; in 1.75 times of the width of the basal reinforcement range, the maximum shear strain has no obvious change.(4) Combined with practical engineering cases in micropile reinforcement method, the researcher selectes micropile to set length and angle to analyze shallow foundation deformation, shear stress and normal stress of soil impact, and proposes reasonable design parameters. In terms of pile length, with the increase of pile length and the strengthening effect of root pile, pile soil stress ratio increases. But when pile length exceeds 2.5 m, reinforcement effect flatten out, with the increase of pile length and the change rule of shear strain is nonlinear decreasing. Considering the influence of the angle aspect, for the purpose of effectively control of foundation settlement and maximum shear strain, the optimal range should be 30°to 45°. In the 0 ° to 45 °interval, at the bottom of the foundation, the soil normal stress decreases with increasing angle.(5) Combined with practical engineering cases.This paper establishes grouting and micropile mixed method by selecting grouting reinforcement, scope, micropile angle and length to make an orthogonal analysis and establish numerical model groups. By adopting the orthogonal analysis of impact on the different design parameters on the basis of the displacement and the influence of shear strain of soil, the researcher finds out the affects of parameters and concludes that the parameters from importance rank as depth of grouting, length of micropile, grouting flat-field, angle of micropile.