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黄金科学技术 ›› 2023, Vol. 31 ›› Issue (5): 752-762.doi: 10.11872/j.issn.1005-2518.2023.05.036

• 采选技术与矿山管理 • 上一篇    下一篇

热冲击对花岗岩动态断裂行为的影响研究

王卫华(),李凯(),黄瑞新   

  1. 中南大学资源与安全工程学院,湖南 长沙 410083
  • 收稿日期:2023-03-03 修回日期:2023-04-06 出版日期:2023-10-31 发布日期:2023-11-21
  • 通讯作者: 李凯 E-mail:50973993@qq.com;LK15200721534@163.com
  • 作者简介:王卫华(1976-),男,湖南长沙人,教授,从事岩体动力学、爆破及安全工程研究工作。50973993@qq.com

Study on the Effect of Thermal Shock on Dynamic Fracture Behavior of Granite

Weihua WANG(),Kai LI(),Ruixin HUANG   

  1. School of Resources and Safety Engineering,Central South University,Changsha 410083,Hunan,China
  • Received:2023-03-03 Revised:2023-04-06 Online:2023-10-31 Published:2023-11-21
  • Contact: Kai LI E-mail:50973993@qq.com;LK15200721534@163.com

摘要:

为了研究热冲击对加热花岗岩的影响,使用3种冷却方法来提供不同的冷却速率,对花岗岩试样施加不同程度的热冲击作用。通过分离式霍普金森压杆(SHPB)系统对热冲击处理后的花岗岩半圆盘中心直裂纹三点弯曲(NSCB)试样进行冲击断裂试验,并利用高速摄像机记录了试样的断裂模式。试验结果表明:随着试样温度和冷却速率的提升,试样的干密度和纵波波速显著下降,试样的孔隙率加大。试样的断裂韧度变化及破坏模式表明热冲击作用使花岗岩试样受到冲击力时抗裂纹扩展的能力下降,尤其在冲击载荷的加载率高于130 GPa·m0.5/s时下降尤为明显。

关键词: 热冲击, 花岗岩, Ⅰ型动态断裂韧度, NSCB, 冷却方法, 断裂模式, SHPB系统

Abstract:

In engineering operations such as geothermal development and utilization in high-temperature rock formations,underground coal gasification,multiple oil extractions,underground disposal of high-level radioactive waste,and protection and restoration of important buildings after fires,rocks often experience thermal shock due to drastic temperature changes.Thermal shock refers to the phenomenon where an object undergoes a large amount of heat exchange in a short time due to rapid heating or cooling,resulting in the generation of thermal shock stress within the object.To investigate the impact of thermal shock on the dynamic fracture behavior of high-temperature granite,the granite was heated to three different temperature levels of 100,300,600 ℃,followed by cooling using three different methods of furnace cooling,air cooling,and water cooling to provide different cooling rates,resulting in varying degrees of thermal shock within the granite samples.The notched semi-circular bend (NSCB) specimens of the granite samples subjected to thermal shock treatment were tested using a split Hopkinson pressure bar (SHPB) system for dynamic fracture behavior.The fracture pattern of the specimens was recorded using a high-speed camera.The results show that with the increase in specimen temperature and cooling rate,the dry density and longitudinal wave velocity of the specimens decrease significantly,and the porosity increase.Under thermal shock,the dynamic fracture toughness value of the specimens decreased significantly.At the same loading rate level,the dynamic fracture toughness value of the water-cooled specimens is lower than that of the air-cooled specimens,indicating that the crack propagation resistance of rock materials decrease when subjected to dynamic impact.Furthermore,at loading rates higher than 130 GPa·m0.5/s,the effect of thermal shock on fracture toughness is more pronounced.By analyzing the relationship between dynamic fracture toughness and loading rate,a power law function with a good fitting degree is obtained,revealing the impact of thermal shock on dynamic fracture toughness.Therefore,this study provides valuable reference for the stability of rock formations in cooling treatment projects involving high-temperature rocks,contributing to the design and management of engineering operations such as geothermal development and utilization,underground coal gasification,multiple oil extractions,underground disposal of high-level radioactive waste,and protection and restoration of important buildings after fires.

Key words: thermal shock, granite, mode I dynamic fracture toughness, NSCB, cooling method, fracture patterns, SHPB system

中图分类号: 

  • TD315

图1

NSCB试样尺寸示意图"

图2

热处理中的温度变化曲线"

图3

分离式霍普金森压杆试验系统"

表1

SHPB系统主要参数"

参数数值参数数值
杆径/mm50弹性模量/GPa240
入射杆长度/mm2 000泊松比0.28
吸收杆长度/mm500纵波波速/(m·s-15 400
投射杆长度/mm1 500杆密度/(kg·m-37 800

图4

NSCB试样两端受到的动态加载力"

图5

NSCB试样的动态应力强度因子(SIF)时程曲线in NSCB specimen"

图6

未处理试样与热冲击处理后的试样"

表2

NSCB试样的平均干密度"

温度

/℃

炉内冷却空气冷却水冷却
ρsσρaσρwσ
1003.1850.00243.1810.00253.1740.0020
3003.1630.00463.1610.00533.1490.0018
6003.1250.00183.1140.00123.1010.0050

图7

NSCB试样的干密度"

表3

NSCB试样的平均纵波波速"

温度

/℃

炉内冷却空气冷却水冷却
VsσVaσVwσ
1003 333.4318.143 356.3145.053 167.2565.46
3002 793.4256.802 618.8151.702 493.0157.04
6001 395.5717.661 338.2842.941 278.827.08

图8

NSCB试样的纵波波速"

表4

NSCB试样的平均孔隙率"

温度/℃炉内冷却空气冷却水冷却
PsσPaσPwσ
1001.340.041.370.131.890.19
3001.470.081.520.241.920.08
6001.890.081.660.082.230.16

图9

NSCB试样的孔隙率"

图10

3种温度下NSCB试样动态断裂韧度与加载率的关系"

表5

动态断裂韧性与加载率拟合函数参数"

冷却方式温度/℃abR2
未处理250.3690.6280.969

炉内冷却

1000.2590.9820.964
3000.4630.5150.932
6000.1820.7010.886

空气冷却

1000.4850.9410.977
3000.1290.7590.949
6000.4540.4790.827

水冷却

1000.2700.6360.883
3000.2650.6130.908
6000.1230.7130.971

表6

空气冷却和水冷却过程中的平均降温速率"

温度/℃空气冷却速率/(℃·min-1水冷却速率/(℃·min-1
1003.46975.00
30011.591137.50
60022.577143.75

图11

动力冲击试验中出现的2种破坏过程注:图(b)是在加载率为132.86 GPa·m0.5/s的条件下进行试验"

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