Study Of Several Problems In Support Design Of Excavation Adjacent To Existing Buildings

The excavation adjacent to existing buildings has very strict requirements ondeformation control. At the same time, it makes a lot of support system not applicablehere that the width of soil outside the foundation is narrow. Based on the existingresearch results, through theoretical analyses and numerical simulations, severalproblems on the support design for this kind of foundation pit are studied systemically.In the first several chapters the calculation methods of soil pressure in differentconditions are discussed, and then the support design is analyzed. Research workincludes the followings:(1)Through theoretical analysis and numerical simulation, it makes furtherdiscussion about the soil pressure on retaining structures in the current code ofrelevant local load, and the effect of soil parameters c and φ on additional earthpressure of elastoplastic solution. It is found that additional pressure and staticearth pressure coefficients has proportional relationship. Distribution of earthpressure of layered soil is analyzed by the finite element method; the influenceof the depth on additional earth pressure is also analyzed. By using the normaldistribution curve fitting of the additional pressure of underlying stratum, thecalculation formulas of additional earth pressure caused by additional surchargeis introduced.(2)Between retaining wall and the existing building foundation the finitesoil is formed, where soil pressure calculation by using Rankin theory orColumn theory cannot be used directly. In this paper complete mechanicalanalysis of the limited soil is conducted, which has considered the lateral andtangential forces between the limited soil and the wall. Then the equations forcalculating the active earth pressure are established, and a simplified formulafor this case is presented finally. It is verified by the finite element results thatthe simplified formula derived in this paper has relatively simple form and highprecision. In the process of application of formula, the effect of displacementfactors and intermediate principal stress should be taken into account, so theseproblems are also discussed in this chapter. (3)The effect of water on the earth pressure is analyzed, includinginfluence of seepage on earth pressure, and different earth pressure caused byshear strength of unsaturated soils.(4)It makes the supporting pile cantilever structure that the anchor cannotbe constructed, so looking for other measures to reduce the deformationbecome the focus of attention. Through the three-dimensional numericalsimulation of different supporting scheme, some methods decreasing thedeformation are found: the upper soil nailing wall can effectively reducecantilever length of the pile; double-row piles have a certain advantage insupport design of this kind of foundation; making full use of the originalsupporting system of the surrounding building etc. At the same time, theselection of pile diameter, slope depth were also studied. A new support schemeis proposed, by limiting the torsion of the pile, it can reduce the deformationeffectively.