基于弹塑性分析的浅埋盾构隧道地表沉降控制

目的为更准确地预测浅埋盾构隧道引起的地表沉降，探求相应的沉降控制措施．方法基于均质半无限空间假定，将浅埋单孔盾构隧道二向非等压初始地应力场分解为均匀应力场和单向应力场。利用弹塑性力学的Lame公式和Kiersch公式及摩尔一库仑屈服准则，定义了弹塑性解的位移边界条件．将控制地表沉降两大措施成功地应用于北京地铁十号线浅埋盾构隧道地表沉降预测及控制．结果得出适合浅埋隧道地表沉降预测的弹塑性计算式，对弹塑性计算式的分析显示，隧道围岩的弹性模量E和黏聚力c越大，地表沉降越小；泊松比纵内摩擦角φ和膨胀角沙越大，地表沉降也越大．提出通过减少围岩扰动和提高围岩性质两种控制盾构隧道地表沉降的方法．结论研究成果能较好地应用于浅埋盾构隧道的地表沉降预测及控制．

Prediction and Control of Shallow Shield Tunneling-Induced Ground Settlement with Elasto-Plasticity Analysis

For predicting the shallow shield tunneling -induced ground settlement more accurately and studying the relevant settlement controlling methods, a newly - modified shield tunneling - induced ground settlement calculation method is presented which is based on the hypothesis of homogeneous half - plane, with the use of Molar - Coulomb plastic yielding criteria and classic Lame and Kiersch elastic equations by separating the non -uniform stress field to uniform and uniaxial stress field, and by defining corresponding boundary condition of the ground loss pattern around shallow tunnel. The numerical results show that the ground settlement is decreasing with the increase of the Young＇s modulus E and cohesion c, and increasing with the rise of Poisson＇s ratio ,internal friction angle and dilation angle of surrounding rock/soil. The settlement controlling method through reducing the disturbance of surrounding soil and strengthening the surrounding soil of tunnel is proposed by analyzing the influence factors of the newly - modified ground settlement prediction method for shield tunneling engineering. It is applied in the case of Beijing metro shield tunneling project. The analytical results show good agreements with insite observed data.