Study on the delimitation of affected zone of geological environment for karst underground engineering:taking Longgang district, Shenzhen City as an example
-
摘要: 在大量建设城市地下轨道交通及城市更新工程的背景之下,我国城市岩溶地质灾害日趋严重。文章以深圳市3个岩溶地面塌陷事件为例,开展岩溶地下工程地质环境影响区的划定研究。首先运用高频岩溶地下水气压力监测技术对工程影响实际范围进行监测分析,然后结合工程施工参数、岩溶塌陷主要影响因素与水文地质试验参数,采用定性分析和量化计算的综合研究方法,推导出岩溶地下工程地质环境影响范围理论计算经验公式。结果表明:岩溶地下工程影响范围主要与渗透系数、工程深度成正比,与土层厚度成反比,推导的半定量理论公式适用于岩溶承压水条件下,可快速为缺乏地下水监测资料的岩溶地区地下工程安全建设及城市防灾减灾工作提供依据。
-
关键词:
- 岩溶地下工程 /
- 岩溶地下水气压力监测 /
- 工程影响区 /
- 抽水试验 /
- 经验公式
Abstract:The construction of a large number of urban underground rail transit and urban renewal projects has intensified the urban karst geological disasters in our country. As one of the first demonstration areas of national urban construction, Shenzhen has developed rapidly in terms of underground rail transit and urban renewal projects over the years, hence leading to frequent karst collapse disasters due to its location in the karst area. Therefore, the summary of the experience and lessons from the development of karst underground space is of great significance for the engineering construction in karst areas. In this thesis, a preliminary study on the delimitation of the affected zone of geological environment for karst underground engineering is conducted based on three events of karst ground collapse in Shenzhen. The affected zone of geological environment for karst underground engineering refers to the area where disasters are likely to happen due to the disturbance and damage of the rock and soil around the construction site during the construction process. The delimitation of the affected zone is not only conducive to the safe and smooth engineering construction, but also to the clear division of responsibility. The monitoring range of underground engineering construction in karst area usually reaches only tens of meters at the current stage. But when a disaster happens, the actual range influenced by engineering will often exceed hundreds of meters. Therefore, the current construction specification about the affected zone of geological environment for karst underground engineering is unreasonable and uncertain in some degree, and the relevant provisions are greatly challenged. For instance, it is stipulated that the engineering monitoring should be conducted within the plane range that is only 3 times as deep as the foundation pit during construction , and the description of the expansion of the monitoring range in the karst development area is not detailed. Therefore, the further research on the affected zone of geological environment for karst underground engineering is very necessary, so the actual affected range of the project can be effectively judged, and then the corresponding prevention and control measures can be taken. On the basis of fully mastering the regional geological background and the geological conditions of site engineering, a preliminary study is conducted in this thesis. Firstly, the actual affected range of the project is monitored and analyzed by the high-frequency monitoring technology of karst groundwater pressure. The monitoring scheme should be formulated according to local conditions. The monitoring frequency should capture the disturbance changes of regional karst groundwater with more than 3-month monitoring cycle. The results of monitoring and data measurement of water levels indicate that the affected range of the project is closely connected with the karst groundwater drawdown funnel. The obvious anisotropy of karst aquifer medium at each site is indicated in the groundwater flow field, which is mainly controlled by karst development and structure. The maximum affected ranges of the three projects are 560 m, 820 m and 850 m respectively. Then, the analysis on the formation mechanism of karst collapse is conducted. Results indicate the collapse mechanism. The excavation and precipitation of foundation pit leads to the change of groundwater hydrodynamic internally caused of strong karst development, the change of hydrodynamic conditions disturbs karst groundwater or gas, and the force generated by karst water disturbance acts on the overburden floor through karst pipeline or crack. As a result, the overburden soil mass collapses and loses gradually, until the roof becomes unstable and damaged for the insufficient collapse resistance. Finally, the Gehart’s empirical formula of influence radius of confined water pumping hole is used for reference, combined with engineering construction parameters, main factors of karst collapse and hydrogeological test parameters. The mixed research method of qualitative analysis and quantitative calculation is adopted to theoretically deduce the empirical calculation formula of the affected zone of geological environment for karst underground engineering. Research results indicate that the affected range of karst underground engineering is mainly in direct proportion to the permeability coefficient and engineering depth. However, it is inversely proportional to the thickness of soil layer. The deduced semi-quantitative theoretical formula is suitable for the calculation of a relatively thick aquifer between the Quaternary and the karst aquifer. If the depth of foundation pit is greater than that of rock surface and of confined karst water in underground engineering, this fomular can be used to quickly provide the basis for safety construction of underground engineering as well as urban disaster prevention and reduction in the karst area lacking groundwater monitoring data. -
表 1 工程参数及岩溶发育指标一览表
Table 1. Engineering parameters and karst development indicators
基坑
工程基坑
长度/m基坑
宽度/m地面原
标高/m工程
深度/m土层
厚度/m岩溶发育
深度/m钻孔
/个见洞率/% 线岩
溶率/%数码城站 512 16~56 43.0 22.3 6~23 9~24 1876 42.9 24.8 5#地更新工程 200 150 35.0 19.8 7~25 10~25 1452 29.4 26.8 龙平站 191 28 35.8 27.0 7~24 9~22 1367 39.2 21.4 注:依《建筑地基基础设计规范》GB50007-2011表6.6.2划分标准,判定研究区岩溶强发育。 表 2 工地监测信息统计表
Table 2. Statistical table of site monitoring information
工程
场地监测点
数量/个监测点
平均间距/m监测面积/
km2监测
频率/min工程实际
影响半径/m地下水降落漏斗影响范围
形成日期/年.月.日数码城站基坑 19 200 0.52 2~5 850 2020.10.24 5#工地 74 100 0.85 2~5 560 2020.04.27 龙平站基坑 8 180 0.31 2~5 820 2021.02.02 表 3 龙岗区塌陷点覆盖层厚度统计表
Table 3. Statistical table of overburden thickness on collapse point in Longgang area
塌陷编号 T01 T02 T03 T04 T05 T06 T07 T08 T09 覆盖层厚度/m 6 20.6 14 8 9.3 11.6 14.4 9.3 14.8 表 4 场地抽水试验成果表
Table 4. Results of site pumping tests
试验场地 钻孔编号 试验段
埋深/m静止水位
埋深(h)/m水位降深
(s)/m涌水量
(Q)/m3·d−1影响半径
(R)/m平均渗透系数 $\bar {\rm{K}}$/
m·d−1数码城站 SMSW01 8.3~24.8 1.95 6.0 392.1 133.2 6.63 4.0 336.5 98.8 2.0 262.4 59.5 数码城站 SMSW02 4.0~28.0 1.90 6.0 442.5 502.3 67.87 4.0 302.2 330.9 2.0 156.8 161.3 数码城站 SMSW03 12.0~14.2 2.20 9.0 38.7 159.6 2.70 6.0 23.9 99.3 3.0 10.8 44.5 龙平站 LPSW01 4.0~29.5 4.51 6.6 527.2 167.8 6.33 5.6 450.3 140.8 4.7 375.6 115.9 龙平站 LPSW02 4.0~10.8 4.40 3.0 373.0 77.3 23.14 2.0 262.4 48.6 1.0 145.9 22.9 龙平站 LPSW03 15.0~20.0 4.00 10.2 5.3 32.6 0.09 6.8 3.3 20.4 3.4 1.5 8.8 龙平站 LPSW04 11.0~15.6 3.40 7.5 130.3 200.9 7.75 5.0 98.0 138.9 2.5 57.9 72.2 龙平站 LPSW05 13.6~17.0 3.10 10.5 590.9 510.4 28.30 7.0 496.5 375.4 3.5 302.2 199.6 5#地块 SW102 17.5~99.5 3.7.0 2.4 151.9 144.3 37.40 表 5 经验系数α反演结果
Table 5. Inversion results of empirical coefficient α
区域 工程深度
H/m初始水位
埋深h/m土层平均
厚度d/m区域渗透
系数K/m·d−1实际影响
半径R/m理论影响
半径R′/m范围
误差/%经验
系数(α)平均经验
系数( $\bar \alpha$数码城站 22.27 1.9 12.97 37.25 850 848 0.2 5.9 5.9 龙平站 27.0 3.1 13.31 25.72 820 806 1.7 6.0 5#地块 19.84 2.38 16.91 37.4 550 559 1.6 5.8 -
[1] Lei M, Jiang X, Gao Y. Current Status and Strategic Planning of Sinkhole Collapses in China[J]. Engineering Geology for Society and Territory, 2015, 5:529-533. [2] 蒙彦, 雷明堂. 岩溶塌陷研究现状及趋势分析[J]. 中国岩溶, 2019, 38(3):411-417.MENG Yan, LEI Mingtang. Analysis of situation and trend of sinkhole collapse[J]. Carsologica Sinica, 2019, 38(3):411-417. [3] 张建全, 闫宇蕾,宋伟超,王彪,张克利. 地下工程施工工程影响分区综合研究与应用 [J]. 施工技术, 2020, 49(7):65-67,108.ZHANG Jianquan, YAN Yulei, SONG WEichao,WANG Biao,ZHANG Keli. Comprehensive study and application of underground engineering construction influence zoning[J]. Construction Technology,2020,49(7):65-67,108. [4] 崔庆龙,沈水龙,吴怀娜,许烨霜. 广州岩溶地区深基坑开挖对周围环境影响的研究 [J]. 岩土力学, 2015, 36(S1):553-557.DOI: 10.16285/j.rsm.2015.S1.096.CUI Qinglong, SHEN Shuilong, WU Huaina,XU Yeshuang. Field investigation of deep excavation of metro station on surrounding ground in karst region of guangzhou[J]. Rock and Soil Mechanics, 2015, 36(S1):553-557. DOI: 10.16285/j.rsm.2015.S1.096. [5] 历立兵, 侯兴民, 李远东. 一种基坑降水影响半径的有限元计算方法[J]. 岩土力学, 2021, 42(2):574-580.LI Libing, HOU Xingmin, LI Yuandong. A finite element method for calculating the influence radius of foundation pit dewatering[J]. Rock and Soil Mechanics, 2021, 42(2):574-580. [6] 建筑基坑工程监测技术规范 [S]. 中华人民共和国国家标准. 2009: 94p: A4.Technical code for monitoring of building excavation engineering[S]. National standards of the People's Republic of China. 2009:94p:A4. [7] 城市轨道交通工程监测技术规范 [S]. 中华人民共和国国家标准. 2014: 0p: A4.Code for moilit}ring measurement of urban rail transit engineering [S]. National standards of the People's Republic of China. 2014: 0p:A4 [8] Gary M K. Maryland's zone of dewatering influence law for limestone quarries [C]. Hydrogeology and engineering geology of sinkholes and karst:1999: 273-277. [9] Maryland.gov. Press Release. [EB/OL]. (1998-03-30).https://mde.maryland.gov/programs/Pressroom/Pages/399.aspx [10] Maryland.gov. Press Release. [EB/OL]. (1998-04-29).https://mde.maryland.gov/programs/Pressroom/Pages/393.aspx [11] Aston R L. Maryland limestone producers protest discrimination[J]. Engineering and Mining Journal, 1998, 199(4):32RR. [12] United States Court of Appeals, Fourth Circuit. Laurel Sand & Gravel, Inc. v. Wilson. [EB/OL]. (2008-03-05) [2022-03-25].https://www.courtlistener.com/opinion/1025180/laurel-sand-gravel-inc-v-wilson/ [13] Dr S F . The Practical Impacts of Karst Regulations on the Communities that Implement Them - a Pair of Case Studies[J]. Springer Netherlands, 2009. [14] Brezinski D K. Geologic and anthropogenic factors influencing karst development in the Frederick region of Maryland[J]. Environmental Geosciences, 2007, 14(1):31-48. doi: 10.1306/eg.01050605014 [15] Lv Yuxiang, Jiang Yongjun, Hu ei, Mao Yang. A review of the effects of tunnel excavation on the hydrology, ecology, and environment in karst areas: Current status, challenges, and perspectives[J]. Journal of Hydrology, 2020, 586:124891. doi: 10.1016/j.jhydrol.2020.124891 [16] 刘鹏瑞, 刘长宪, 姜超, 王芳, 陈钰, 贾龙. 武汉市工程施工引发岩溶塌陷机理分析[J]. 中国岩溶, 2017, 36(6):830-835. doi: 10.11932/karst20170605LIU Pengrui, LIU Changxian, JIANG Chao,WANG Fang,CHEN Yu,JIA Long. Mechanism of karst collapse caused by engineering construction in Wuhan City[J]. Carsologica Sinica, 2017, 36(6):830-835. doi: 10.11932/karst20170605 [17] 黄健民,吕镁娜,郭宇,陈小月. 广州金沙洲岩溶地面塌陷地质灾害成因分析 [J]. 中国岩溶, 2013, 32(2):167-174.HUANG Jianmin, LV Meina, GUO Yu,CHEN Xiaoyue. Research on the reason for geologic disaster by karst surface collapse at Jinshazhou in Guangzhou[J]. Carsologica Sinica,2013,32(2):167-174. [18] 耿光旭. 深圳岩溶地区的岩土工程问题及对策[C]. 广东省首届地球科学与工程学术大会论文集. 2017: 99-107.GENG Guangxu. Problems and countermeasures of geotechnical engineering in Shenzhen Karst area[C]. Proceedings of the first Earth Science and Engineering Conference of Guangdong Province. 2017:99-107. [19] 蒙彦, 郑小战, 雷明堂, 李卓骏, 贾龙, 潘宗源. 珠三角地区岩溶分布特征及发育规律[J]. 中国岩溶, 2019, 38(5):746-751.MENG Yan, ZHEN Xiaozhan, LEI Mingtang, LI Zhuojun, JIA Long, PAN Zongyuan. Karst distribution and development in the Pearl River Delta[J]. Carsologica Sinica, 2019, 38(5):746-751. [20] 蒋小珍, 雷明堂. 岩溶塌陷灾害的岩溶地下水气压力监测技术及应用[J]. 中国岩溶, 2018, 37(5):786-791.JIANG Xiaozhen, LEI Mingtang. Monitoring technique and its application of karst groundwater-air pressure in karst collapse[J]. Carsologica Sinica, 2018, 37(5):786-791. [21] 蒋小珍, 雷明堂, 管振德. 湖南宁乡大成桥充水矿山疏干区岩溶系统水气压力监测及突变特征[J]. 中国岩溶, 2016, 35(2):179-189. doi: 10.11932/karst20160207JIANG Xiaozhen, LEI Mingtang, GUAN Zhende. Character of water or barometric pressure jump within karst conduit in large strong drainage area of karst water filling mine in Dachengqiao,Ningxiang,Hunan[J]. Carsologica Sinica, 2016, 35(2):179-189. doi: 10.11932/karst20160207 [22] 王晓明,王秀辉,文望,李功宇. Dupuit稳定井流公式的模型分析 [J]. 煤田地质与勘探, 2014, 42(6):73-75,81WANG Xiaoming, WANG Xiuhui, WEN Wang,LI Gongyu. Model analysis of Dupuit’s steady well flow formula[J]. Coal Geology & Exploration,2014,42(6):73-75,81. [23] 王军辉,王峰. 论抽水的降落漏斗范围、影响半径与环境影响范围 [J]. 水利学报, 2020, 51(7):827-834WANG Junhui, WANG Feng. Discussion on the range of groundwater depression cone,radius of influence and scope of environmental impacts during pumping[J]. Journal of Hydraulic Engineering,2020,51(7):827-834. [24] 凤蔚,王晓燕, 刘振英, 李文鹏, 李海涛.松散岩类承压含水层影响半径计算方法 [J]. 人民黄河, 2017, 39(12):57-61.FENG Wei, WANG Xiaoyan, LIU Zhenying,LI Wenpeng,LI Haitao. Calculating Methods of Influence Radius in the Confined Aquifer of Loose Stuff[J]. Yellow River,2017,39(12):57-61. [25] 钱学溥,于义强. 引用影响半径理论公式及其应用 [J]. 工程勘察, 2019(6):43-49.QIAN Xuepu,YU Yiqiang. Theoretical equation on quoted influence radius and its application[J]. Geotechnical Investigation & Surveying,2019(6):43-49. [26] Zhou Z, Xu Y L, Zhu C Q, Xu M T,Jin Z Y. Collapse Mechanism of Shallow-Buried Karst Cave Under the Effect of Mining[J]. Geotechnical and Geological Engineering, 2021, 39(2):1521-1532. doi: 10.1007/s10706-020-01573-2 [27] 潘宗源, 陈学军, 杨鑫, 宋宇, 张铭致. 湖南郴州地区岩溶塌陷分布规律及其影响因素浅析[J]. 中国岩溶, 2021, 40(2):221-229.PAN Zongyuan, CHEN Xuejun, YANG Xin,SONG Yu,ZHANG Mingzhi. Distribution and influence factors of sinkholes in the Chenzhou area, Hunan Province[J]. Carsologica Sinica, 2021, 40(2):221-229.