非开挖与明挖柔性管上土压力与变形对比分析

Comparative study on earth pressure and deformation of trenchless and open-cut pipe

利用PLAXIS 2D数值模拟软件,通过对实际案例的模拟计算验证软件的可靠性与精确性,并针对4种典型地层、不同地下水条件、2种施工方法,揭示明挖与非开挖管线上所受压力与变形的区别及成因,确定管线上压力与变形主要影响因素和作用机理。研究结果表明:管在变形的过程中周围土体对管产生土侧压力,致使PVC柔性管上的最大压力一般出现在管线两侧水平直径处。明挖法施工对土体的扰动范围远大于非开挖法的扰动范围,导致明挖管线上最大压力与变形量远比非开挖管线的大,其中明挖管线上最大压力是非开挖管线的2.6~11.65倍,变形量是非开挖管线的3.96~11.95倍。土体密度是影响明挖法管线上压力与变形的最主要因素,同时,内聚力和泊松比是影响非开挖管线上压力和变形的最主要因素。软黏土地层水位从-2.5 m升高到5.5 m的过程中,由于孔隙压力增大,有效应力减小,明挖管线上的最大压力与变形分别增加18.74%和13.38%,而非开挖管线上最大压力与变形则分别增加615.09%和311.11%,因此,水位的升高对非开挖管线的影响远比对明挖管线的影响大。

In order to analyze the main differences of soil pressure and deformation on open-cut and trenchless pipes,four typical soils,different groundwater depth,open-cut and trenchless construction methods were used.Firstly,PLAXIS2D was used in a field case study to verify its reliability and accuracy.Then groups of models with different conditions were built to calculate the soil pressure and deformation of open-cut and trenchless pipes.Besides,the primary and secondary factors were determined and the mechanism of main factors on soil pressure and deformation were obtained.The results show that because of the lateral soil pressure formed during pipe deformation,the maximum soil pressure on PVC flexible pipe generally appears at the ends of the horizontal diameter.Due to the fact that the disturbance range of open-cut construction is significantly larger than that of trenchless construction,the maximum soil load on open-cut pipe is much larger than that of trenchless pipe.The maximum soil load on open-cut pipe is2.66to11.65times larger than that of trenchless pipe,while the deformation of open-cut pipe is3.96to11.95times larger than that of trenchless pipe.The soil density is the most important factor that affects the soil pressure and deformation of open-cut pipe,while the cohesion and Poisson’s ratio are the most important factors that affect the soil pressure and deformation on trenchless pipe.When ground water table rises from?2.5m to5.5m in soft clay,with the increase of pore pressure and the decrease of effective stress,the maximum soil pressure and deformation on open-cut pipe increase by18.74%and13.38%,respectively.However,the maximum soil pressure and deformation on trenchless pipe increase by615.09%and311.11%,which indicates that the influence of ground water level on trenchless pipe is much larger than that on open-cut pipe.