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

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