多形態裂隙砂巖水力耦合破壞過程與增透機理試驗研究

張英; 郭奇峰; 席迅; 蔡美峰; 倫嘉云; 潘繼良

doi:10.13374/j.issn2095-9389.2022.07.04.004

多形態裂隙砂巖水力耦合破壞過程與增透機理試驗研究

doi: 10.13374/j.issn2095-9389.2022.07.04.004

張英^{1, 2},
郭奇峰^{1, 2},
席迅^{1, 2, ,},
蔡美峰^{1, 2},
倫嘉云³,
潘繼良^{1, 2}

1.
北京科技大學土木與資源工程學院，北京 100083
2.
北京科技大學金屬礦山高效開采與安全教育部重點實驗室，北京 100083
3.
應急管理部信息研究院，北京 100029

基金項目: 國家重點研發計劃資助項目（2021YFC3001301）

詳細信息

通訊作者:
E-mail: xixun@ustb.edu.cn

中圖分類號: TG142.71
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- 文章訪問數: 402
- HTML全文瀏覽量: 102
- PDF下載量: 34
- 被引次數: 0
出版歷程
- 收稿日期: 2022-07-04
- 網絡出版日期: 2022-08-18
- 刊出日期: 2022-10-25

Experimental investigation on hydromechanical coupling-induced failure and permeability evolution for sandstone with multiple-shape prefabricated fractures

ZHANG Ying^{1, 2},
GUO Qi-feng^{1, 2},
XI Xun^{1, 2
, ,},
CAI Mei-feng^{1, 2},
LUN Jia-yun³,
PAN Ji-liang^{1, 2}

1.
School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China
2.
Key Laboratory of High Efficient Mining and Safety of Metal Mines (Ministry of Education), University of Science and Technology Beijing, Beijing 100083, China
3.
Information Institute of the Ministry of Emergency Management of the PRC, Beijing 100029, China

More Information

Corresponding author: E-mail: xixun@ustb.edu.cn

摘要

摘要: 水力耦合激活巖石天然裂隙，誘導裂隙擴展形成復雜裂隙網絡，增加巖石滲透性是礦產地熱共采體系中的關鍵技術。本文通過預制含單裂隙、T型裂隙和Y型裂隙的砂巖試樣，進行三軸水力耦合試驗，研究多形態裂隙砂巖的關鍵閾值（閉合應力、起裂應力、損傷應力、峰值強度）、彈性模量、泊松比以及破壞模式等力學特性，同時開展裂隙漸進演化過程中聲發射和滲透率的演化規律研究，進一步分析水力耦合作用下裂隙巖石增透機理。結果表明：多形態預制裂隙砂巖試樣在水力耦合作用下，既有裂隙均通過拉伸、剪切或混合模式擴展形成次生裂紋，構成裂隙網絡，試樣滲透率顯著增加。單裂隙試樣的次生裂隙以剪切破壞為主，T型和Y型裂隙試樣的次生裂隙為剪切破壞和張拉-剪切破壞兩類。此外，多形態裂隙對試樣強度的影響大于水的弱化作用。隨著軸壓增大，巖石滲透率峰前階段先減小后增大，達到強度破壞時突跳增大。當試樣達到峰值后應力突然下降時，滲透率達到最大值，滲透率增透效果最好。預制裂隙角度和形態的變化對突跳系數的影響幅度較小，單裂隙的平均突跳系數值大于Y型裂隙大于T型裂隙。研究結果有助于理解裂隙破壞和流體流動行為，進而指導礦產地熱共采的工程。
- 水力耦合 /
- 裂隙擴展 /
- 混合型裂隙 /
- 突跳系數 /
- 滲透率增加
Abstract: In mineral and geothermal resource co-mining, the underground rock is often affected by mining stress, and fractures of different shapes, such as single fractures, T-shaped fractures, and Y-shaped fractures, are generated. To increase the reservoir permeability, the existing fractures need to be reactivated, causing them to expand under force and propagate in shear and tension modes, generating new fractures and finally forming a fracture network to increase permeability. Waterjet cutting and wire cutting equipment are used to prefabricate sandstone samples with different inclinations and single, T-shaped, and Y-shaped fractures on standard samples. This paper conducts hydromechanical coupling experiments to investigate the possibility of increasing permeability by expanding and merging fractures in prefabricated fractured sandstone samples under triaxial conditions. In addition, the focus is on mechanical properties, such as critical thresholds (crack closure stress, crack initiation stress, damage stress, and peak strength), elastic moduli, and Poisson's ratio, and the failure modes of multiple-shape prefabricated fracture sandstone samples are mainly studied. Simultaneously, the evolution law of acoustic emission and permeability during the progressive failure of fractured rock is studied, and the mechanism of permeability enhancement of fractured rocks under the action of hydraulic coupling is analyzed. The results show that under the action of hydromechanical coupling, all multi-shape prefabricated fracture specimens form secondary cracks that expand in tensile, shearing, or mixed modes through the existing fractures and generate new fractures or fracture networks, which can effectively increase the flow rate. All single-fracture specimens are shear failures, and the T-shaped and Y-shaped fracture specimens have two types of shear failure and tension-shear failure. Furthermore, the weakening effect of water has a smaller effect on strength than the effect of multiple-shape prefabricated fractures. With increasing axial pressure, the rock permeability first decreases and then increases in the pre-peak stage, and the jump coefficient increases when reaching the strength failure. When the stress suddenly drops after the peak of the sample, the permeability reaches the maximum value, and the permeability enhancement effect is the best. The change in the prefabricated fracture angles and shapes has a small influence on the jump coefficient. The average value of the jump coefficients of a single fracture is larger than that of a Y-shaped fracture, which is larger than that of a T-shaped fracture, and the jump coefficients are more than doubled. These observational and experimental results will help to understand fracture failure and fluid flow behavior, which will guide the engineering applications of mineral and geothermal resource co-mining.
- hydromechanical coupling /
- fracture expansion /
- mixed-mode fracture /
- jump coefficients /
- permeability enhancement

HTML全文

圖 1 預制裂隙砂巖試樣加工流程. (a) 試樣模型示意圖; (b) 砂巖試樣實物圖

Figure 1. Processing flow of sandstone samples with prefabricated fracture: (a) sample models; (b) physical images of sandstone samples

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圖 2 水力耦合試驗設備. (a) MTS815伺服剛性試驗機; (b) Teledyne ISCO D-Series 泵; (c) 聲發射探頭分布圖

Figure 2. Test equipment: (a) MTS815 rock mechanics testing machine; (b) Teledyne ISCO D-Series pumps; (c) distribution map of acoustic emission probes

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圖 3 完整和單裂隙試樣不同閾值、應力比率與傾角關系. (a)不同閾值與傾角關系;(b)應力比率與傾角關系

Figure 3. Relationship of fracture inclination with different thresholds and the stress ratios of intact and single-fracture samples: (a) relationship between different thresholds and fracture inclination; (b) relationship between stress ratios and fracture inclination

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圖 4 完整和T型裂隙不同閾值、應力比率與傾角關系. (a)不同閾值與傾角關系; (b)應力比率與傾角關系

Figure 4. Relationship of fracture inclination with different thresholds and the stress ratios of intact and T-shaped fracture samples: (a) relationship between different thresholds and fracture inclination; (b) relationship between stress ratios and fracture inclination

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圖 5 完整和Y型裂隙不同閾值、應力比率與傾角關系. (a)不同閾值與傾角關系; (b)應力比率與傾角關系

Figure 5. Relationship of fracture inclination with different thresholds and stress ratios of intact and Y-shaped fracture samples: (a) relationship between different thresholds and fracture inclination; (b) relationship between stress ratios and fracture inclination

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圖 6 完整和單裂隙、T型、Y型裂隙彈性模量、泊松比傾角關系. (a)彈性模量與傾角關系; (b)泊松比與傾角關系

Figure 6. Relationship between the elastic modulus and Poisson's ratio of intact and single fracture, T-shaped, and Y-shaped fracture samples: (a) relationship between the elastic modulus and fracture inclination; (b) relationship between Poisson's ratio and fracture inclination

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圖 7 單裂隙(a)、T型(b)和Y型(c)裂隙試樣應力和振鈴計數與時間關系

Figure 7. Relationship between stress, the ringing count of single (a), T-shaped (b), and Y-shaped (c) fracture specimens, and time

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圖 8 水力耦合作用下誘發裂隙擴展規律：單裂隙(a)、T型(b)和Y型(c)裂隙試樣破壞模式

Figure 8. Propagation law of induced cracks under the action of hydraulic coupling: failure modes of single (a), T-shaped (b), and Y- shaped (c) fracture specimens

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圖 9 單裂隙(a)、T型(b)和Y型(c)裂隙試樣應力、滲透率與時間關系

Figure 9. Relationship between stress, permeability, and time of single (a), T-shaped (b), and Y-shaped (c) fracture specimens

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表 1 裂隙砂巖試樣試驗方案

Table 1. Test scheme of fractured sandstone samples

Fracture inclination, α/(°)	Sample No.			Confining pressure/MPa	Water pressure/MPa
Fracture inclination, α/(°)	Single fracture	T-shaped fracture	Y-shaped fracture	Confining pressure/MPa	Water pressure/MPa
0	SF0	ST0	SY0	10	3
15	SF15	ST15	SY15	10	3
30	SF30	ST30	SY30	10	3
45	SF45	ST45	SY45	10	3
60	SF60	ST60	SY60	10	3
75	SF75	ST75	SY75	10	3
90	SF90	ST90	SY90	10	3

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表 2 完整砂巖試樣試驗方案

Table 2. Test scheme of intact sandstone samples

Name	Sample No.	Confining pressure/MPa	Water pressure/MPa
Intact sample without water pressure	W1	10
Intact sample with water pressure	W2	10	3

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表 3 多形態裂隙與完整砂巖試樣峰值強度對比

Table 3. Peak strength comparison between multiple-shape prefabricated fractures and intact sandstone samples

Fracture inclination, α/(°)	Percentage drop in peak strength compared with intact samples without water pressure/%			Percentage drop in peak strength compared with intact samples with water pressure/%
Fracture inclination, α/(°)	Single fracture	T-shaped fracture	Y-shaped fracture	Single fracture	T-shaped fracture	Y-shaped fracture
0	19.29	34.89	43.85	14.82	31.28	40.74
15	30.60	33.79	37.91	26.75	30.12	34.47
30	41.53	46.09	43.07	38.28	43.11	39.91
45	37.54	39.32	43.32	34.08	35.95	40.17
60	40.39	47.23	44.30	37.08	44.31	41.21
75	44.31	42.76	37.28	41.23	39.59	33.80
90	36.45	36.02	43.92	32.93	32.47	40.81

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