STUDY ON STRENGTH WEAKENING OF CARBONATE ROCKS WITH WATER LEVEL FLUCTUATING IN WUXIA OF THREE GORGES RESERVOIR AREA
-
摘要: 三峡库区175 m蓄水以来,巫峡段碳酸盐类岩溶岸坡在周期性水位变动下岩体劣化强烈,新生或加速形成了大量地质灾害。为探讨在周期性水位变动下碳酸盐岩类岸坡的强度弱化规律,文章从岩石(体)物理结构、化学性质、力学性质等方面开展研究,通过在巫峡最具代表性的6处库岸段开展原位岩体回弹强度测试、原位点荷载试验以及室内干湿循环试验、岩石矿物成分分析、岩石表观裂隙扫描等试验,获取水位变动条件下碳酸盐类岩石(体)的强度弱化数据。原位岩体回弹强度测试结果表明,原位岩体单一年度的强度弱化率为0.3%~25.9%,岩体强度弱化主要沿结构面产生;室内干湿循环试验结果表明,在50次干湿循环后,岩石强度弱化率为16.4%~23.9%,变形模量弱化率为17.1%~24.9%;岩石矿物成分分析结果表明,在100次循环后,CaO的溶失量为0.5%~5.6%;岩石表观裂隙扫描结果表明,岩块表面裂纹发育位置发生了水蚀痕迹加重、溶孔变大、裂纹延伸等变形现象。基于干湿循环试验数据,建立岩石强度弱化函数,推导出各点位上的指数函数弱化计算模型。该计算模型可用来预测岩石强度、变形模量与水位循环次数间的数值关系。最后以曲子滩危岩“溃屈”式破坏计算为例,探讨了岩体强度弱化后的灾变效应。研究提出的工作方法和通过试验所得到的数据可为三峡库区岸坡劣化带的防治提供数据和技术支撑。Abstract: Since the impoundment to the elevation 175 m above sea level in the Three Gorges reservoir area, the carbonate karst bank slopes of the Wuxia area have been deteriorating strongly under the periodic water level fluctuations, and a large number of geological disasters have been new-born or developed rapidly. This paper aims to study the law of strength weakening of carbonate bank slopes under cyclical water level fluctuations. It conducted researches from the physical structure, chemical properties, and mechanical properties of the rock(or rockmass). Six most representative reservoir banks in Wuxia area were selected, where in-situ rock rebound strength test, in-situ point loading test and indoor wet-dry cycle test, rock mineral composition analysis, rock apparent fissures scanning test were carried out. Through these tests, the strength weakening data of carbonate rocks(or rockmass) under the condition of fluctuating water were obtained. The results of in-situ rock rebound strength test show that the strength weakening rate of in-situ rockmass is 0.3% to 25.9% per year. The results of indoor dry-wet cycle test show that after 50 dry-wet cycles, the strength weakening rate of rock is 16.4% to 23.9%, and the deformation modulus weakening rate is 17.1% to 24.9%. The results of mineral composition analysis show that the dissolution loss of CaO is 0.5% to 5.6% after 100 cycles. Through the scanning results of rock apparent fissures, new signs of deformation were found on the rock surface, the water erosion marks were aggravated, the solution pores were enlarged and the cracks were extended. Based on the dry-wet cycle test data, the rock strength weakening function is established, and the exponential function weakening calculation model at each point is deduced. Then such functions can be used to predict the numerical relationship between rock strengths, deformation modulus and water level cycle times. Taking the Quzitan dangerous rock as an example, the catastrophic effect of rock strength weakening is discussed. The work methods and the data obtained from the research can provide data and technical supports for the prevention and control of the bank slope deterioration zone in the Three Gorges Reservoir area.
-
表 1 点荷载试验结果一览
Table 1. List of point load test results
采样点 地层代号 岩性 抗压强度计算值/MPa 独龙1号库岸 T1 d4 泥灰岩 45.6 箭穿洞库岸 T1 d4 灰岩 61.6 青石库岸 T1j3 灰岩 75.0 曲子滩库岸 T1j3 灰岩 68.5 板壁岩库岸 T1j3 灰岩 84.0 黄南背库岸 T1j3 灰岩 72.2 黄岩窝库岸 T1j3 灰岩 91.0 表 2 各采样点试验内容及试验分组
Table 2. Test content and group of each sampling point
采样点与试验内容 独龙 箭穿洞 青石 黄南背 板壁岩 曲子滩 黄岩窝 黄南背西段 岩性 T1d4泥灰岩 T1d4灰岩 T1j3灰岩 T1j3灰岩 T1j3灰岩 T1j3灰岩 T1j3灰岩 T1j3角砾岩 抗压试验(风干) 1组 1组 1组 1组 1组 1组 1组 1组 变形 1组 1组 1组 1组 1组 / 1组 / 表 3 岩石强度弱化结果一览表
Table 3. List of rock strength weakening results
采样点 岩性 点荷载强度/MPa 试验初始强度/MPa 干湿循环试验强度值/MPa 强度降低值/MPa 弱化率/% 5次 10次 15次 20次 25次 30次 35次 40次 45次 50次 独龙1号斜坡 泥灰岩 45.6 32.1 29.7 31.9 29.0 28.0 27.1 27.8 26.4 25.9 25.4 25.0 -7.1 22.0 箭穿洞 灰岩 61.6 33.9 30.9 31.4 30.1 30.4 29.1 28.9 28.3 27.9 27.8 27.3 -6.6 19.4 青石顺向坡 灰岩 75.0 34.4 32.9 31.4 30.7 29.7 30.9 28.1 28.1 27.0 26.7 26.3 -8.2 23.7 曲子滩危岩 灰岩 68.5 30.2 30.4 30.0 28.8 28.6 28.0 27.6 26.5 25.3 25.5 25.2 -5.0 16.4 板壁岩危岩 灰岩 84.0 31.0 30.2 28.7 28.5 29.1 27.8 26.8 27.4 26.7 25.5 25.1 -5.9 19.0 黄南背库岸 灰岩 72.2 30.7 31.8 29.0 29.3 27.7 27.4 26.2 25.8 25.3 24.0 24.2 -6.5 21.1 黄岩窝危岩 灰岩 91.0 44.3 43.6 43.1 43.8 41.8 41.3 39.8 38.1 36.9 37.6 36.3 -8.0 18.0 黄南背西段 角砾岩 — 14.5 14.7 13.9 13.3 13.4 12.5 12.2 11.5 11.7 11.0 11.1 -3.5 23.9 表 4 变形参数弱化一览表
Table 4. List of deformation parameters weakening
采样点 岩性 波速段/m·s-1 变形模量值/×104 MPa 弱化率/% 初始值 5次 10次 15次 20次 25次 30次 35次 40次 45次 50次 独龙1号斜坡 泥灰岩 4500~5800 0.768 0.71 0.738 0.709 0.703 0.664 0.646 0.636 0.624 0.615 0.609 20.7 箭穿洞 灰岩 4500~5800 0.633 0.598 0.586 0.560 0.535 0.516 0.504 0.493 0.483 0.480 0.476 24.8 青石顺向坡 灰岩 5800~7000 1.254 1.195 1.214 1.187 1.111 1.094 1.084 1.071 1.060 1.050 1.039 17.1 板壁岩危岩 灰岩 5800~7000 1.568 1.523 1.497 1.496 1.451 1.362 1.309 1.231 1.196 1.186 1.178 24.9 黄南背库岸 灰岩 5800~7000 0.934 0.891 0.863 0.845 0.815 0.780 0.762 0.746 0.733 0.718 0.710 24.0 黄岩窝危岩 灰岩 4500~5800 1.015 0.996 0.948 0.960 0.935 0.905 0.884 0.869 0.847 0.826 0.817 19.5 表 5 试验参数方程一览表
Table 5. List of test parameter equations
采样点与参数 独龙 箭穿洞 青石 黄南背 抗压强度/MPa σc=31.574e-0.005n σc=32.445e-0.004n σc=33.654e-0.005n σc=31.327e-0.006n 变形模量/×104 MPa E=0.7551e-0.005n E=0.613 8e-0.006n E=1.233 3e-0.004n E=0.9147e-0.006n 采样点与参数 板壁岩 曲子滩 黄岩窝 黄南背西段 抗压强度/MPa σc=30.638e-0.004n σc=30.852e-0.004n σc=45.13e-0.004n σc=14.758e-0.006n 变形模量/×104 MPa E=1.596 6e-0.007n / E=1.012 8e-0.004n / 上表所涉及数据分别采用指数、线性、多项式回归模型进行拟合,选择最优拟合式(R2>0.90)作为选用公式 表 6 CaO含量测试统计表
Table 6. Statistical table of CaO content test
试验批次 板壁岩灰岩
CaO含量/%板壁岩灰岩
CaO含量/%黄南背灰岩
CaO含量/%独龙泥灰岩
CaO含量/%曲尺滩灰岩
CaO含量/%箭穿洞灰岩
CaO含量/%青石灰岩
CaO含量/%黄南背角砾岩
CaO含量/%黄岩窝灰岩
CaO含量/%1 93.1 91.6 92.2 84.5 91.1 94.1 90.2 93.4 86.5 2 93.0 91.3 91.7 84.3 90.7 93.9 89.9 93.4 84.2 3 91.7 91.3 91.0 83.3 90.7 93.9 88.9 92.2 81.9 4 91.6 91.1 91.0 82.1 90.7 92.5 88.4 92.0 81.8 5 91.2 90.9 90.9 80.3 90.6 92.3 86.6 91.4 80.9 总溶失量 1.90 0.70 1.30 4.20 0.50 1.80 3.60 2.00 5.60 -
Chen X T, Huang B L, Li B, et al. 2020. Karstification and slope failure in carbonate areas of Three Gorges Reservoir[J]. Carsologica Sinica, 39 (4): 567-576. Collins B D, Stock G M. 2016. Rockfall triggering by cyclic thermal stressing of exfoliation fractures[J]. Nature Geoscience, 9 : 395-400. doi: 10.1038/ngeo2686 Corvo F, Reyes J, Valdes C, et al. 2010. Influence of air pollution and humidity on limestone materials degradation in historical buildings located in cities under tropical coastal climates[J]. Water Air and Soil Pollution, 205(1-4): 359-375. doi: 10.1007/s11270-009-0081-1 Dai Z W, Yin Y P, Wei Y J, et al. 2016. Deformation and failure mechanism of outang landslide in Three Gorges Reservoir Area[J]. Journal of Engineering Geology, 24 (1): 44-55. Ding Q, He Z, Yu J W, et al. 2017. Factors controlling carbonate rock dissolution under high temperature and pressure[J]. Oil & Gas Geology, 38 (4): 784-791. Deng H F, Li J L, Zhu M, et al. 2012. Experimental research on strength deterioration rules of sandstone under saturation-air dry circulation function[J]. Rock and Soil Mechanic, 33 (11): 3306-3312. Dochez S, Farid L, Christian F, et al. 2014. Multi-scale analysis of water alteration on the rockslope stability framework[J]. Acta Geophysica, 62 (5): 1025-1048. doi: 10.2478/s11600-014-0232-7 Dong H G, Chen L D, Huang C S. 2010. Influence factors and stability assessment of dangerous rocks in Yunyang-Jiangjin on Three Gorges Reservoir[J]. Journal of Engineering Geology, 18 (5): 645-650. doi: 10.3969/j.issn.1004-9665.2010.05.006 He K. 2015. Research on collapse mechanism of tower rock[D]. Xi'an: Chang'an University. Huang B L, Yin Y P, Li B, et al. 2020. Rock mass deterioration and its catastrophic effect of karst bank slope in the Three Gorges Project Reservoir Area[J]. Hydrogeology & Engineering Geology, 47 (4): 51-61. Huang B L, Yin Y P, Zhang Z H, et al. 2019. Study on deterioration characteristics of shallow rock mass in water level fluctuation zone of karst bank slope in Three Gorges Reservoir Area[J]. Chinese Journal of Rock Mechanics and Engineering, 38 (9): 1786-1796. Ion R M, Fierascu R C, Fierascu I, et al. 2014. Influence of Fantanita Lake(Chalk Lake) water on the degradation of Basarabi-Murfatlar Churches[C]// Engineering Geology for Society and Territory. Switzerland: Springer. Jian W X, Li S J, Tao L. 2015. Deterioration mechanism of shear strength of Badong formation soft rocks in the hydro-fluctuation belt of Three Gorges Reservoir[J]. Geological Science and Technology Information, 34 (4): 170-175. Liu X H, Zhu J B, Zeng P, et al. 2015. Deteriorating effect of wetting and drying cycles on bank slope's siltstone properties[J]. Journal of Yangtze River Scientific Research Institute, 32 (10): 74-77, 84. Liu X R, Fu Y, Wang Y X, et al. 2008. Deterioration rules of shear strength of sand rock under water-rock interaction of reservoir[J]. Chinese Journal of Geotechnical Engineering, 30 (09): 1298-1302. doi: 10.3321/j.issn:1000-4548.2008.09.006 Nicolas A, Fortin J, Regnet J B, et al. 2016. Brittle and semi-brittle behaviours of a carbonate rock: influence of water and temperature[J]. Geophysical Journal International, 206 (1): 438-456. doi: 10.1093/gji/ggw154 Tang M G, Yang H, Xu Q, et al. 2019. Permeability and parameters of landslide bodies in Three Gorges Reservoir Area[J]. Journal of Engineering Geology, 27 (2): 325-332. Tecer L. 1999. Laboratory experiments on the investigation of the effects of sulphuric acid on the deterioration of carbonate stones and surface corrosion[J]. Water Air & Soil Pollution, 114(1-2): 1-12. Wang J, Yu Q. 2018. Experimental investigations of the process of carbonate fracture dissolution enlargement under reservoir temperature and pressure conditions[J]. Geofluids: 1-19. Wang L F, Li L G, Yang X. 2018. Instability initiation mechanism of gravel soil slope in Three Gorges Reservoir: case study of Hongyanzi Landslide in Wushan County[J]. Chinese Journal of Geotechnical Engineering, 40 (S2): 209-214. Wen J M, Ni H Y, Wang C S, et al. 2018. Study on the evolution and failure characteristics of the interbeded slope of sand and mudstones-taking the Three Gorge Reservoir Area(Changshou-Fengdu) as an example[J]. Journal of Engineering Geology, 26 (S): 76-84. Xia D. 2014. Study on damage mechanics of soaking rock and application in mines containing water[D]. Shenyang: Northeastern University. Xiao J F, Li Y A, Cai J M. 2020. Model test research on response characteristics of outang landslide under water level fluctuation[J]. Journal of Engineering Geology, 28 (5): 1049-1056. Yin Y P. 2005. Human-cutting slope structure and failure pattern at the Three Gorges Reservoir[J]. Journal of Engineering Geology, 13 (2): 145-154. Zhang Z H, Du C L, Yu S, et al. 2018. Stability analysis and design of control works on Jianchuandong dangerous rockmass in Wuxia Gorge, the Three Gorges Reservoir[J]. The Chinese Journal of Geological Hazard and Control, 29 (2): 48-54. Zhu H. 2015. Experimental study on mechanical properties of constrained argillaceous dolomite with drying-wetting cycles[D]. Guiyang: Guizhou University. 陈小婷, 黄波林, 李滨, 等. 2020. 三峡水库碳酸盐岩区岩溶作用与斜坡破坏[J]. 中国岩溶, 39 (4): 567-576. https://www.cnki.com.cn/Article/CJFDTOTAL-ZGYR202004012.htm 代贞伟, 殷跃平, 魏云杰, 等. 2016. 三峡库区藕塘滑坡变形失稳机制研究[J]. 工程地质学报, 24 (1): 44-55. doi: 10.13544/j.cnki.jeg.2016.01.006 邓华锋, 李建林, 朱敏, 等. 2012. 饱水-风干循环作用下砂岩强度劣化规律试验研究[J]. 岩土力学, 33 (11): 3306-3312. https://www.cnki.com.cn/Article/CJFDTOTAL-YTLX201211018.htm 董好刚, 陈立德, 黄长生. 2010. 三峡库区云阳-江津段危岩形成的影响因素及稳定性评价[J]. 工程地质学报, 18 (5): 645-650. http://www.gcdz.org/article/id/8607 贺凯. 2015. 塔柱状岩体崩塌机理研究[D]. 西安: 长安大学. 黄波林, 殷跃平, 李滨, 等. 2020. 三峡工程库区岩溶岸坡岩体劣化及其灾变效应[J]. 水文地质工程地质, 47 (4): 51-61. https://www.cnki.com.cn/Article/CJFDTOTAL-SWDG202004007.htm 黄波林, 殷跃平, 张枝华, 等. 2019. 三峡工程库区岩溶岸坡消落带岩体劣化特征研究[J]. 岩石力学与工程学报, 38 (9): 1786-1796. https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX201909006.htm 简文星, 李世金, 陶良. 2015. 三峡库区消落带巴东组软岩抗剪强度劣化机理[J]. 地质科技情报, 34 (4): 170-175. https://www.cnki.com.cn/Article/CJFDTOTAL-DZKQ201504025.htm 刘小红, 朱杰兵, 曾平, 等. 2015. 干湿循环对岸坡粉砂岩劣化作用试验研究[J]. 长江科学院院报, 32 (10): 74-77, 84. https://www.cnki.com.cn/Article/CJFDTOTAL-CJKB201510017.htm 刘新荣, 傅晏, 王永新, 等. 2008. (库)水-岩作用下砂岩抗剪强度劣化规律的试验研究[J]. 岩土工程学报, 30 (9): 1298-1302. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC200809008.htm 汤明高, 杨何, 许强, 等. 2019. 三峡库区滑坡土体渗透特性及参数研究[J]. 工程地质学报, 27 (2): 325-332. doi: 10.13544/j.cnki.jeg.2018-011 王林峰, 李林刚, 杨洵. 2018. 三峡库区碎石土质岸坡失稳启动机制研究——以龙江红岩子滑坡为例[J]. 岩土工程学报, 40 (S2): 209-214. https://www.cnki.com.cn/Article/CJFDTOTAL-YTGC2018S2044.htm 温金梅, 倪化勇, 王春山, 等. 2018. 砂泥岩互层斜坡演化及失稳特征研究-以三峡库区(长寿-丰都段)岸坡为例[J]. 工程地质学报, 26(增): 76-84. doi: 10.13544/j.cnki.jeg.2018121 夏冬. 2014. 浸水岩石损伤演化过程试验研究及在大水矿山中的应用[D]. 沈阳: 东北大学. 肖捷夫, 李云安, 蔡浚明. 2020. 水位涨落作用下藕塘滑坡响应特征模型试验研究[J]. 工程地质学报, 28 (5): 1049-1056. doi: 10.13544/j.cnki.jeg.2020-326 殷跃平. 2005. 三峡库区边坡结构及失稳模式研究[J]. 工程地质学报, 13 (2): 145-154. http://www.gcdz.org/article/id/9101 张枝华, 杜春兰, 余姝, 等. 2018. 三峡库区巫峡箭穿洞危岩体稳定性分析及防治工程设计[J]. 中国地质灾害与防治学报, 29 (2): 48-54. https://www.cnki.com.cn/Article/CJFDTOTAL-ZGDH201802008.htm 朱珩. 2015. 干湿循环作用下约束泥质白云岩力学特性试验研究[D]. 贵阳: 贵州大学. -