堤坝帷幕灌浆效果评价

Quality evaluation of grouting curtain in a dam foundation

防渗帷幕是堤坝中最常见的防渗处理措施,施工后完全位于地下,其施工效果受到多方面因素的影响,因此对防渗帷幕这一隐蔽性工程的灌浆效果评价则显得极为重要。本文以实际工程为例,首先利用压水试验对帷幕断面灌浆后的透水性进行评价;然后利用室内试验对坝基材料的渗透稳定性进行了评价;最后在压水试验和室内试验的基础上,结合数值模拟,分别就帷幕灌浆后的渗透性和局部贯通性缺陷对渗漏量及水力比降的影响进行了敏感性分析。研究发现,帷幕灌浆后,当渗透性低至一定程度时,帷幕渗透性的降低对大坝浸润线和水力比降的分布影响较小,但对大坝的渗漏量依然有一定的影响;当帷幕中有贯通的缺陷时,缺陷处水力比降虽较大,但坝基材料颗粒级配良好,所以不存在渗透破坏的可能性。

As one popular way to prevent leakage, grouting curtain sits underground so it can not be observed directly. Thus its quality evaluation is extremely important. Based on a case study, the quality of grouting curtain in a dam foundation is evaluated. At first, the permeability of grouting curtain is evaluated through water pressure test, and leakage stability is evaluated through particle passing test. At last,based on the results of tests, sensitivity analysis is conducted to evaluate the effect of permeability and local default on quantity of leakage and hydraulic gradient by numerical modelling. Numerical results show that low permeability has a small influence on the water table and hydraulic gradient. Hydraulic gradient is high at local default in the curtain, but the particle gradient is smooth. As a result, hydraulic failure will not happen. This research provides a meaningful reference for the performance evaluation of grouting curtain.