Reservoir dam foundations in the deep-cut valleys of the Loess Plateau in Northwest China typically exhibit geological characteristics such as "overlying collapsible wet loess, underlying fractured sandstone, and a deep-buried relative impermeable layer". These conditions result in technical bottlenecks during curtain grouting construction, including difficulty in controlling borehole deviation, severe leakage of grout, and challenges in meeting impermeability standards. Taking Tianshuibao regulation reservoir in Gansu province as a case study, this paper systematically reveals the spatial distribution patterns of the thickness of the strongly weathered zone in the bedrock (1.3~16.6 m) and the burial depth of the roof of the relative impermeable layer (q<5 Lu, 25~90 m) in the dam site area, based on detailed geological survey data. To address these geological deficiencies, a three-dimensional seepage control system comprising "two rows of main curtains + three rows of reinforcement grouting + 50-meter extensions on both sides of the mountain slopes" is proposed. Additionally, dynamic grout mixture ratio models and grouting pressure gradient control models based on the permeability characteristics of the strata are established. Practice shows that in the water pressure tests conducted on 22 sections of inspection boreholes after grouting, the average permeability has decreased to 1.2 Lu, with a maximum permeability of only 2.9 Lu, and no borehole sections with q>5 Lu are found; the seepage volume behind the dam has decreased from 0.85 L/s before grouting to 0.12 L/s. These study results validate the effectiveness of the technical approach and can provide a technical reference for seepage control and reinforcement of projects under similar geological conditions in Northwest China.

curtain grouting, deep-cut valley, sandstone fractures, grouting pressure, grout mix ratio, Tianshuibao regulation reservoir

西北黄土高原深切沟谷区的水库坝基多呈现“上覆湿陷性黄土、下伏裂隙发育砂岩、相对隔水层埋深大”的地质特征，导致帷幕灌浆施工面临钻孔偏斜难控、浆液漏失严重、防渗指标难以达标等技术瓶颈。笔者以盐环定扬黄甘肃专用工程——甜水堡调蓄水库为例，基于详尽的工程地质勘察资料，系统揭示了坝址区基岩强风化带厚度（1.3~16.6 m）与相对隔水层（q<5 Lu）顶板埋深（25~90 m）的空间分布规律。针对地质缺陷，提出了“双排主帷幕+三排加强区+两岸山体延伸50 m”的立体防渗体系，建立了基于地层渗透特性的浆液动态配比模型与灌浆压力梯度控制模型。工程实践表明：灌后检查孔22段压水试验中，透水率平均值降至1.2 Lu，最大透水率仅为2.9 Lu，且无q>5 Lu的孔段分布；坝后渗漏量由灌浆前的0.85 L/s降至0.12 L/s。研究成果验证了技术方案的有效性，可为西北类似地质条件下的防渗加固提供技术参考。

帷幕灌浆, 深切沟谷, 砂岩裂隙, 灌浆压力, 浆液配比, 甜水堡调蓄水库