基于结构面网络模拟的龙门石窟擂鼓台渗水产生机理研究

Analysis of the mechanism of the water seepage damage formation at Lei Gutai,Longmen grotto,based on discontinuity network modeling

渗水病害在龙门石窟擂鼓台中发育明显,为明晰擂鼓台区渗水机理,现场对石窟内外共149条裂隙开展了调查。基于此数据样本,运用Monte-Carlo随机模拟生成了擂鼓台斜坡区结构面三维网络图。模拟结果显示,擂鼓台三窟中主要连通途径是由倾向NNW的层面和倾向SW和SE的两组近直立结构面构成,在石窟中部和南部结构面连通率分别高达87.1%和83.6%。综合该模拟结果及窟内外裂隙发育特征,可将擂鼓台北、中、南三洞渗水机理归结为:北洞SW、NWW倾向裂隙J12、J4加速2号平台滞水进入石窟顶部,洞内大量发育的倾向SW、SE裂隙向上与J12、J4连通,方便地表水渗入至洞内;中洞渗水受裂隙J12及J35控制,洞内大量发育的SW、SE倾向裂隙与J12、J35相通构成窟内主要渗水通道,其中J12与JM1直接相连是中洞渗水关键;南洞因山体缺失不存在沿层面渗水,地表水主要沿砌体与山体间隙及SE、SW倾向的J11、J31、J30等构造裂隙渗入,后在洞内连通程度较高的SW倾向裂隙引导下流至窟内表。本研究所取得的经验可为同行在以后类似工程中所应用。

Water seepage damage is prevalent at the Lei Gutai grotto of Longmen grotto. To better understand the mechanism of water seepage, 149 discontinuities at this area were investigated. Taking these discontinuities as sample parameters, a 3D rock discontinuity network model was built, which aids the study of rock mass innerbody connectivity. Using this discontinuity network it is found that the major connective path at Lei Gutai consisted of three group discontinuities：one stratum （trending NNW） and two high dip discontinuities （trending） and that their degrees of connectivity are up to 87.1% and 83.6% at middle and south parts of Lei Gutai, respectively. Combining these results with the 3D model, inside and outside field discontinuities are investigated, and finally developed a mechanism for water seepage formation at the Lei Gutai grotto. The north grotto has two discontinuities, J12 （trending SE） and J4 （NNW）, that pass through the No. 2 reserving rainfall platform, which allows surface runoff to infiltrate into the upper rock mass of the grotto. Next, the internal discontinuities, trending south east （SE） and south west （SW）, stretch upward and intersect with J12 and J4. Consequently, surface runoff along those internal discontinuities seeps into the north and middle grottos. J12 and J35 control the entrance of surface runoff into it, and many internal discontinuities, trending SW and SE, connect with its seepage channel. When it rains, surface water permeates into the top of the grotto through J12 and J35, and then flows through internal discontinuities onto the internal surface of the grotto. For the south grotto, considering mountain is deficiency, rainfall cannot infiltrate into the grotto along with stratum, and water arriving into internal surface is from the interval of manual brickwork and mountain, and discontinuities such as Jll （trend SE）, J31, J30 （trend SW）. Once rainfall through these cracks infiltrates unto the grotto above, internal connective discontinuities of south grotto （most trend SW） will guide water seeping to its surface.