大跨度地下洞室拱顶稳定性及支护措施研究

拟建的金沙江下游一水电站引水发电系统地下洞室群规模巨大且布置复杂，其圆筒型阻抗式调压井高度达100 m，直径达50 m，洞室在同类工程中罕见，拱顶稳定及支护措施问题突出。针对复杂地质条件下，尾调顶拱围岩潜在的应力型破坏和结构面导致的变形与坍塌两类不同性质的问题，采用工程地质分析与三维数值模拟3DEC等相结合的方法，深入探讨圆筒形尾调室围岩应力集中范围、程度和高应力破坏风险；说明软弱层间错动带对围岩变形稳定影响及其安全性。研究表明：圆筒形尾调室总体受力特征良好，拱顶应力集中水平(30～44 MPa)相对不高，高应力破坏问题不突出；但层间错动带对拱顶稳定影响明显，沿层间错动带的错动变形较大且NNE向浅层7 m范围发生剪切屈服。采用系统支护与混凝土置换的加强支护措施后，可以明显减小层间带的错动变形，提高层间带的安全储备。

STUDY OF STABILITY AND SUPPORTING MEASURES OF CHAMBER ARCH CROWN FOR LARGE SPAN UNDERGROUND CAVERNS

The proposed hydropower station which is located on lower reaches of Jinsha River is characterized by the large scale and complex arrangement. The height of cylindrical throttled surge chamber is about 100 m，and the diameter reaches 50 m. The stability and supporting measures of chamber arch are the noteworthy factors needed to be considered. In order to analyze potential stress-type failure，deformation and collapse caused by structure planes of tailrace surge chamber arch crowns under complex geological conditions，engineering geological analysis and three-dimensional numerical simulation(3DEC) are adopted to study the stress concentration arrange，stress concentration degree and risk of high stress failure，and the effects of interlayer fault zones on stability of surrounding rock are demonstrated. The results show that the overall stability of cavern satisfies the engineering requirements，and the relatively stress concentration degree(30–44 MPa) of arch crown doesn?t cause prominent issue of high stress failure. However，bedding fault zones reduce the stability of surrounding rock distinctly，thus large sliding deformation occurred along the bedding fault zones and shear yield occurred in NNE direction from surface to 7 m superficial zone. After strengthened reinforcements including system supporting and concrete replace are adopted，sliding deformation of bedding fault zones is reduce obviously，and interlaminar band security reserve is improved.