基于修正Peck公式的软土地层超大直径顶管施工地表沉降特性研究

Study on surface subsidence characteristics of super large diameter pipe jacking construction in soft ground based on modified Peck formula

依托深圳市超大直径钢顶管清污分流项目,研究了复杂软土地层地表沉降规律﹒首先,基于现场地表沉降50组实测数据对Peck公式进行修正,推导出拟合函数表达式,并给出了软土地层地表沉降Peck曲线上限和下限解;然后,采用有限元方法精细化模拟顶管施工动态过程,进行摩阻力、机头压力和土体弹性模量参数敏感性分析,总结出横、纵断面地表沉降失稳破坏区范围和影响参数临界值;最后,采用半解析半数值法,确立了修正Peck公式各参数间的函数关系﹒结果表明:修正后的Peck公式可准确预测复杂软土地层地表沉降,其地层损失率取值范围为0.130%~0.238%;地表沉降与摩阻力呈正相关,与弹性模量呈负相关;顶管摩阻力和机头压力临界值应分别控制在15 kN和0.2 MN;横向地表沉降扰动区范围为2D~2.5D,纵向隆起区分布范围为1.25D~2D;沉降槽宽度i与覆跨比(H/D)呈指数函数关系,S_(max)/g~H/D关系可用修正Clough公式进行描述.

Relying on the cleaning and diversion project of super-large diameter steel jacking pipe in Shenzhen,the law of surface subsidence in complex soft soil stratum is studied.First,based on 50 sets of measured data of on-site surface subsidence,Peck's empirical formula is modified,the fitting function expression is deduced,and the upper and lower solutions of the Peck curve of surface subsidence in soft soil are given.Second,the dynamic process of pipe jacking constructionis finely simulated by finite element analysis,and the sensitivity analysis of friction resistance,machine head pressure and soil elastic modulus parameters is carried out,and the range of the surface subsidence instability damage zone in the transverse and longitudinal sections and the critical value of the influencing parameters are summarized.Finally,the semi-analytical and semi-numerical method is used to establish the functional relationship among the parameters of the modified Peck formula.The results show that the modified Peck formula can accurately predict the surface subsidence of complex soft soil strata,and the range of formation loss rate is 0.130%to 0.238%.There is a positive correlation between surface subsidence and friction resistance,and a negative correlation between surface subsidence and elastic modulus.The critical values of pipe jacking friction resistance and head pressure should be controlled at 15 kN and 0.2 MN respectively.The range of transverse surface subsidence disturbance area is 2D to 2.5D,and the distribution range of longitudinal uplift area is 1.25D to 2D.The width of the settlement tank has an exponential function relationship with the span ratio(H/D),and the relationship between S_(max)/g and H/D can be described by the modified Clough formula.