基于临界水力梯度接近度的工程管涌危险程度量化研究

工程中管涌发生严重时会导致工程失稳。文章基于土体发生管涌的水力条件, 提出临界水力梯度接近度指标, 以定量分析土体管涌发生的危险性, 进而划分出管涌危险区并提出相应的防治建议。以施工过程中发生 2 次管涌事故的某船闸基坑为工程实例, 采用 FLAC3D 软件构建三维数值计算模型, 利用 FISH 语言编程并分析该基坑施工过程中水力梯度以及临界水力梯度接近度分布随管涌产生和基坑防渗加固的演化规律, 进而探讨该基坑涌水机制。结果表明: 基坑发生管涌时, 坑底发生管涌位置土体的水力梯度以及临界水力梯度接近度数值均表明该处发生了管涌, 此外临界水力梯度接近度还可以划分出除管涌位置外整个场地内其他管涌危险区域; 基于管涌危险区分布提出的防渗加固建议, 可以有效降低坑底土体发生管涌的风险。该临界水力梯度接近度的提出为工程中管涌预测以及防治提供了一种新的管涌危险性评价的量化方法。

Serious piping will lead to instability of engineering. Based on the hydraulic condition of soil piping, the approach degree of critical hydraulic gradient is proposed to quantitatively analyze the risk of soil piping, which can distribute the piping risk area and put forward corresponding prevention suggestions. Taking a ship lock foundation pit with two piping accidents during construction as an engineering example, FLAC3D software is used to construct a three-dimensional numerical model, FISH language programming is used to analyze the evolution law of the hydraulic gradient and the approach degree of critical hydraulic gradient distribution with piping and foundation pit anti-seepage reinforcement during construction, and then the water inflow mechanism of the foundation pit is explored. The results show that when piping occurs in the foundation pit, both the hydraulic gradient and the approach degree of the critical hydraulic gradient of the soil at the location where piping occurs indicate that piping occurs there, in addition, the approach degree of the critical hydraulic gradient can divide other piping risk areas in the whole site except the piping location; the anti-seepage reinforcement suggestions based on the distribution of piping risk areas can effectively reduce the risk of piping in the soil at the bottom of the pit. The proposed approach degree of critical hydraulic gradient provides a new quantitative method of piping risk assessment for the prediction and prevention of piping in engineering.