藏东南某大型水电站工程区地应力状态及反演分析

李征征; 杨文超; 张鹏; 李常虎; 范玉璐

doi:10.12090/j.issn.1006-6616.20232912

藏东南某大型水电站工程区地应力状态及反演分析

doi: 10.12090/j.issn.1006-6616.20232912

1.
中国电建集团西北勘测设计研究院有限公司，陕西西安 710065
2.
中国地质科学院地质力学研究所，北京 100081

详细信息

作者简介:
李征征（1991—），男，硕士，工程师，主要从事水电工程地质勘察工作。E-mail: lizhengzh@nwh.cn

通讯作者:
张鹏（1986—），男，博士，副研究员，主要从事地应力测量与监测工作。E-mail: zhangpeng0713@163.com

中图分类号: TV221；P315.72+7
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出版历程
- 收稿日期: 2023-03-23
- 修回日期: 2023-05-18
- 录用日期: 2023-05-25

In-situ stress measurement and inversion analysis of a large hydropower project in southeast Tibet

1.
Northwest Engineering Corporation Limited, Xi’an 710065, Shannxi, China
2.
Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China

摘要

摘要:
某水电站作为西藏易贡藏布流域的控制性调节工程，对满足西藏电网的用电需求发挥重要作用。为查明该水电站现今地应力环境，掌握地下厂房、引水隧洞等关键位置地应力分布特征，保障其工程安全，文章综合考虑工程区构造地质背景、岩体条件等，通过布设钻孔开展水压致裂法地应力测量工作，获得4个测点（8个孔）的地应力数据；依据现有地质条件，建立有限元三维地质模型；通过测得的应力状态，获得加载条件，进行工程区应力场反演分析。结果表明：二维地应力测试结果显示最大水平主应力为4.17～16.93 MPa，三维地应力测试结果显示最大主应力为14.20～16.23 MPa，最大水平主应力方位为NE 38°～NE 47°，现今构造应力场以北东向为主导；电站地下厂房区域2995 m高程水平面最大主应力σ₁应力值为11.70～12.12 MPa，中间主应力σ₂应力值为9.81～10.74 MPa，最小主应力σ₃应力值为5.22～6.85 MPa；引水隧洞沿线最大主应力值σ₁为11.8～14.05 MPa，中间主应力值σ₂为10.13～12.83 MPa，最小主应力值σ₃为4.56～8.49 MPa；该水电站地下厂房轴线方向和引水隧洞轴线方向与实测最大主应力方向呈小角度相交，地应力场对工程洞室的稳定性有利。后期施工过程中应综合考虑实际地质情况，采用适宜的隧洞施工技术并加强施工监测，从而确保工程安全建设。
- 藏东南 /
- 水电站 /
- 水压致裂法 /
- 地应力测量 /
- 应力场反演分析 /
- 工程稳定性
Abstract:
As a control and regulating project, the hydropower station in the Yigongzangbu basin of Tibet plays a vital role in meeting the electricity demand of the Tibetan power grid. Identifying this hydropower station’s present-day in-situ stress environment and understanding the characteristics of in-situ stress distribution at critical locations such as underground plants and diversion tunnels are essential to ensure its engineering safety. Based on the tectonic and geological background and rock conditions of the project area, we carried out hydraulic fracturing in-situ stress measurements by placing boreholes and obtained in-situ stress data from 4 measurement points (8 boreholes). A finite element three-dimensional geological model was established according to the existing geological conditions. The measured stress state revealed the loading conditions, and the inverse analysis of the stress field in the engineering area was made. The maximum horizontal principal stress ranges from 4.17 to 16.93 MPa in the 2D test and 14.2 to 16.23 MPa in the 3D test. The maximum horizontal principal stress orientation is NE 38°to NE 47°, and the NE direction dominates the present-day tectonic stress field. In the 2995-meter elevation horizontal plane of the underground plant area of the power station, the stress values of σ1, σ2, and σ3 range from 11.70 to 12.12 MPa, 9.81 to 10.74 MPa, and 5.22 to 6.85 MPa, respectively. The maximum principal stress value of σ1, σ2, and σ3 along the diversion tunnel range from 11.8 to 14.05 MPa, 10.13 to 12.83 MPa, and 4.56 to 8.49 MPa, respectively. The axis direction of this hydropower station’s underground plant and the diversion tunnel’s axis direction intersect at a slight angle with the direction of the measured maximum principal stress, and the ground stress field is favorable to the stability of the project cavern. It is necessary to consider the actual geological conditions and adopt suitable tunnel construction technology in the later construction process. The construction monitoring should also be strengthened to ensure the project’s safe construction.
- southeast Tibet /
- hydropower station /
- hydraulic fracturing /
- in-situ stress measurement /
- inverse analysis of in-situ stress /
- engineering stability

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图 1 区域主要活动断裂及地震震中分布图

Figure 1. Distribution map of main active faults and seismic centers in the research area

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图 2 测点地应力典型曲线

Figure 2. Typical curves of in-situ stress test in each test point

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图 3 测点印模定向示意图

Figure 3. Schematic diagram of impression orientation at different frature section

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图 4 工程区有限元计算模型

Figure 4. FEM model of the engineering area

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图 5 工程区主应力分布云图

Figure 5. Nephogram of principal stress distribution in the engineering area

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图 6 2995 m高程水平面（地下厂房所在层）应力云图

Figure 6. Horizontal stress nephogram at 2995-meter elevation

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图 7 引水隧洞轴线沿线主应力分布云图

Figure 7. Nephogram of stress distribution along the diversion tunnel

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表 1 测试钻孔基本信息

Table 1. Basic parameters of the test boreholes

测点编号	孔号	钻孔方位角/（°）	钻孔倾角/ （°）	孔口高程（埋深）/m	孔深（水位）/m
ST-1	ZK59	/	90	3139.1（214.0）	200.8（78.4）
ST-2	ZK66	/	90	3100.0（112.0）	151.6（100.3）
ST-3	ZK54	/	90	3022.5（334.5）	101.0（0）
	ZK54-1	58	−3		30.8（/）
	ZK54-2	168	−3		31.0（/）
ST-4	ZK56	/	90	3022.5（442.5）	80.8（0）
	ZK56-1	17	−3		30.8（/）
	ZK56-2	119	−3		30.7（/）

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表 2 各测点压裂试验测试深度

Table 2. Depth of each measuring point for fracturing test

测点编号	孔号	有效数据/段	测试深度/m
ST-1	ZK59	6	31.00、56.00、81.00、132.00、155.00、192.50
ST-2	ZK66	5	49.00、82.50、101.00、119.40、138.50
ST-3	ZK54	5	12.90、37.00、61.50、87.30、92.00
	ZK54-1	5	10.50、14.50、20.40、24.30、27.50
	ZK54-2	6	6.84、11.70、14.80、18.36、24.06、27.00
ST-4	ZK56	4	36.50、50.50、64.54、74.00
	ZK56-1	3	14.90、20.40、24.30
	ZK56-2	4	10.70、17.80、24.30、25.57

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表 3 ST-1、ST-2二维地应力测试结果

Table 3. The results of two dimensional in-situ stress measurement (ST-1&ST-2)

测点编号	钻孔编号	深度H/m	压裂特征参数/MPa			主应力值/MPa			S_H方位
测点编号	钻孔编号	深度H/m	破裂压力P_b	重张压力P_r	关闭压力P_s	S_H	S_h	S_v	S_H方位
ST-1	ZK59	31.00	9.32	3.92	2.49	4.17	2.80	6.47
		56.00	8.94	4.41	3.14	6.13	3.70	7.13
		81.00	9.37	5.89	4.04	7.82	4.85	7.79	NE38°
		132.00	13.42	8.26	6.32	12.80	7.64	9.14	NE45°
		155.00	14.03	8.58	6.63	13.64	8.18	9.75
		192.50	15.01	9.55	7.45	15.51	9.38	10.75	NE41°
ST-2	ZK66	49.00	21.80	12.17	7.49	11.28	7.98	4.27
		82.50	16.57	12.11	8.24	14.26	9.07	5.15	NE39°
		101.00	15.51	9.07	7.32	14.90	8.33	5.64	NE43°
		119.40	17.93	12.91	9.06	16.47	10.25	6.13
		138.50	18.76	13.57	9.37	16.93	10.76	6.64	NE47°

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表 4 ST-3、ST-4三维地应力测试计算结果

Table 4. The results of three dimensional in-situ stress measurement (ST-3&ST-4)

测点编号	埋深/m	最大主应力σ₁			中间主应力σ₂			最小主应力σ₃
测点编号	埋深/m	量值/MPa	方位角/（°）	仰角/（°）	量值/MPa	方位角/（°）	仰角/（°）	量值/MPa	方位角/（°）	仰角/（°）
ST-3	334.5	14.20	235.4	−18.2	12.56	152.5	19.6	9.07	106.0	−62.0
ST-4	441.5	16.23	248.0	−22.8	14.28	167.0	20.0	7.68	114.0	−58.0

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表 5 地应力实测数据与反演值对比表

Table 5. Comparison of in-situ stress data and inversion data

测点编号	序号	深度/m	S_H/MPa		S_h/MPa		S_v/MPa
测点编号	序号	深度/m	实测	反演值	实测	反演值	实测	反演值
ST-1	1	31.00	4.17	15.11	2.80	2.45	6.48	9.21
	2	56.00	6.13	15.53	3.70	3.84	7.14	9.86
	3	81.00	7.82	14.72	4.85	4.95	7.80	10.36
	4	132.00	12.80	15.44	7.64	6.93	9.15	11.08
	5	155.00	13.64	15.30	8.18	7.59	9.76	11.32
	6	192.50	15.51	15.15	9.38	8.84	10.76	11.79
ST-2	7	49.00	11.28	11.86	7.98	7.54	4.31	2.02
	8	82.50	14.26	14.11	9.07	9.34	5.19	3.45
	9	101.00	14.90	14.93	8.33	10.25	5.68	4.59
	10	119.40	16.47	15.22	10.25	10.94	6.17	5.83
	11	138.50	16.93	15.10	10.76	11.29	6.68	6.57
ST-3	12	12.90	8.27	11.56	5.36	5.28	9.18	9.89
	13	37.00	10.07	12.07	6.51	6.09	9.82	10.47
	14	61.50	13.11	12.43	8.20	6.76	10.47	10.91
	15	87.30	13.73	12.81	8.50	7.50	11.15	11.38
	16	92.00	13.70	12.88	9.23	7.69	11.28	11.49
ST-4	17	36.50	13.97	11.90	9.63	7.10	12.72	10.84
	18	50.50	17.38	12.10	11.24	7.40	13.09	11.04
	19	64.54	14.11	12.33	10.34	7.74	13.46	11.28
	20	74.00	17.74	12.49	11.79	7.99	13.71	11.44

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