Study On Technique Of Control For Differential Settlement Embankment In Expressway Widening Project

In freeway widening, sub-grade difference settlement is inevitable. How to take action to reduce the differential settlement between new and old ground becomes the key problem of freeway design and construction. Against the existing control measures of difference settlement in widening project, the harmony and control of sub-grade deformation is the important objective with the clue of the capacity to digest treating differential settlement of new and old ground. Through the finite element simulation analysis,geotechnical engineering centrifuge test,design optimization and observational analysis of engineering example, this dissertation studies on the control technology of differential settlement between the new and old ground.Based on the Visual-Fortran flat, the dissertation does the second development of the large common finite element MARC programme using finite element method and geotechnical theory. The subroutines is programmed including initial and release stress subroutine, void element disposal subroutine, motion load subroutine, changing parameter nonlinear elasticity model subroutine, three-dimensional and contact interface element subroutine, and so on. This dissertation establishes computation model of widening the bottom of asphalt concrete road surface, and puts forward the control standard of differential settlement between new and old ground using numerical analysis method. Take this as the standard, this dissertation analyzes the settlement and deformation behavior of the new and old ground, studies on the adaptiveness of treatment measure in convergence zone of widening sub-grade. The result indicated that reinforcement treatment effect is limitation, especially for the deep weak sub-grade, the reinforcement treatment cannot effectively solve difficult engineering problem, taken by differential settlement between new and old ground.This dissertation establishes computation simplification pattern of ground settlement, designs the laying down position, the layer number, the overlap length of the reinforcement treatment technology by numerical analysis method. This dissertation analysis the influence of pile modulus,pile length and exchange rate of pre-stressed pipe pile compound foundation on the settlement characteristic of compound foundation. The result shows that the piles' space,pile stiffness,cushion compression modulus,treatment scope and arrangement way of pipe pile compound foundation has influences on differential settlement between new and old ground. Therefore, this dissertation obtains optimization design parameter about reinforcement treatment of widening sub-grade convergence zone and the treatment of pre-stressed pipe pile compound foundation, and puts forward the optimization design measures.This dissertation installs load device,stress and displacement measurement system using medium centrifuge equipment. This dissertation simulates the improvement of the deformation and treatment technology to sub-grade settlement,stress concentration and overall stability in sub-grade widening.Base on numerical analysis and the centrifuge model test, this dissertation put forward reasonable calculation methods of pipe pile foundation settlement by the stress and deformation of the compound foundation pile-soil, combined with mechanism of the pre-stressed pipe pile. Through observing the application of the pipe pile compound ground in Zhengzhou-Luoyang Expressway Extension Project test section, this dissertation proves the veracity of the calculation methods about pipe pile foundation settlement, and proves the rationality of the control technology of differential settlement between the new and old ground.