高温加热-液氮冷冲击处理后花岗岩声发射演化特征及损伤本构模型  

Acoustic emission evolution characteristics and constitutive model for damage of granite after high-temperature heating and liquid nitrogen cold shock treatment

作　　者：薛熠 张智豪 刘嘉[1] 蔡承政[2] 张志镇[2] 高峰[2] 时旭阳 张云 XUE Yi;ZHANG Zhihao;LIU Jia;CAI Chengzheng;ZHANG Zhizhen;GAO Feng;SHI Xuyang;ZHANG Yun(State Key Laboratory of Eco-hydraulics in Northwest Arid Region,Xi'an University of Technology,Xi'an 710048,China;State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology,Xuzhou 221116,China)

机构地区：[1]西安理工大学西北旱区生态水利国家重点实验室,陕西西安710048 [2]中国矿业大学深部岩土力学与地下工程国家重点实验室,江苏徐州221116

出　　处：《岩土工程学报》2024年第9期1849-1859,共11页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(52274096,12202353,12002270)。

摘　　要：通过液氮(LN_2)压裂在储层中形成大规模裂隙网络,可以有效提高干热岩储层的热能提取效率。为研究液氮冷冲击作用对不同温度储层的压裂机理和致裂效果的影响,对经过高温加热(25℃~400℃)和液氮冷冲击处理后的花岗岩试样进行单轴压缩试验,分析了花岗岩力学强度及声发射等多项参数的演化特征,并进一步构建了考虑声发射参数的损伤本构模型,用于评价和预测高温加热-液氮冷冲击处理后花岗岩的变形和强度特征。结果表明:高温和液氮冷冲击的联合作用显著劣化了花岗岩力学性能,峰值强度逐渐降低,最大降幅达到32.8%。同时随着加热温度的升高,不同矿物颗粒之间的热膨胀变形存在差异,导致矿物颗粒之间变形不协调。随着初始加热温度的升高,声发射最大b值平均值显著上升,最大增幅达到32.2%,且声发射振铃计数的初始静默阶段对应的应变量大幅度降低,最大降幅达到54.3%。随着加热温度的升高,液氮冷冲击作用使得微裂纹的生长更为密集,花岗岩在外部荷载作用下,微裂隙不断扩展贯通,更容易形成剪切变形,发生剪切破坏的起始应力水平逐渐下降,最大降幅达到62.3%,同时RA-AF散点值在剪切区域占比增加,最大增幅达到29.5%。此外,本文以声发射振铃累计计数为变量构建了考虑声发射参数的损伤本构模型,能够描述不同高温和液氮冷冲击处理后花岗岩各力学参量在变形破坏过程中的演化特征。By using the liquid nitrogen(LN2)fracturing to create a massive network of fractures in the reservoir,the thermal energy extraction efficiency of hot dry rock reservoirs can be effectively improved.To investigate the effects of LN2 cold shock treatment on the fracturing mechanism and fracture effects of reservoirs at different temperatures,the uniaxial compression tests are conducted on the granite samples undergone high-temperature heating(25℃~400℃)and liquid nitrogen cold shock treatment.The evolution characteristics of the mechanical strength and acoustic emission parameters of granite are analyzed,and an acoustic emission constitutive model for damage of granite is further established to evaluate and predict the deformation and strength characteristics of granite after high-temperature heating and liquid nitrogen cold shock treatment.The results indicate that the combined effects of high-temperature heating and LN2 cold shock significantly degrade the mechanical properties of granite,with the gradual decrease in the peak strength and the maximum reduction of 32.8%.Meanwhile,with the increase in the heating temperature,there are differences in the thermal expansion deformation between different mineral particles,resulting in a lack of coordination in deformation between mineral particles.With the increase in the initial heating temperature,the average maximum b-value of acoustic emission significantly increases,with the maximum increase of 32.2%,and the strain corresponding to the initial silent stage of acoustic emission ringing counts decreases significantly,with the maximum reduction of 54.3%.With the increase in the heating temperature,the LN2 cold shock treatment causes the microcracks to grow more densely.Under the external loading,the microcracks continuously expand and penetrate,making it easier for the granite to undergo shear deformation and for the initial stress level of shear failure to gradually decrease,with the maximum reduction of 62.3%.Meanwhile,the proportion of RA-AF scatter plot values

关 键 词：花岗岩 声发射 高温加热-液氮冷冲击 损伤破坏 本构模型 

分 类 号：TU45[建筑科学—岩土工程]