Abstract:Taking the double-row steel sheet pile cofferdam in the excavated section of the Pingtian Lake Tunnel as the engineering background, and aiming at the problem that the traditional deterministic design fails to reflect the influence of the uncertainty of soil parameters and water level conditions on the stability, a study on the parameter sensitivity and safety reserve of cofferdam stability is carried out. Based on the anti-overturning and anti-uplift checking models specified in the current codes, the single-factor disturbance parameter sensitivity analysis method is adopted, and the dimensionless sensitivity coefficient and safety reserve coefficient are introduced to systematically evaluate the influence laws of changes in internal friction angle, cohesion, soil density, rock penetration depth and water level difference on the stability safety factor. And the quantitative statistics is conducted on the safety margin. The results show that the cofferdam stability is the most sensitive to the internal friction angle and cohesion, followed by the rock penetration depth and water level difference, and the soil density has a relatively minor influence. Within the reasonable range of parameter disturbance, the overall requirements of the codes are satisfied, yet there is a certain conservative space under local working conditions. The research results can provide a reference for the design value selection and risk control of cofferdams under similar complex hydrogeological conditions.
