Experimental Investigation on the Strength, Deformability, Failure Behavior and Acoustic Emission Locations of Red Sandstone Under Triaxial Compression

Conventional triaxial compression and “reducing confining pressure” experiments were carried out for red sandstone by an MTS815 Flex Test GT rock mechanics experimental system. Our results show that the post-peak axial deformation characteristics of red sandstone changed as the confining pressure was increased from 5 to 65?MPa. Young’s modulus of red sandstone increased nonlinearly with increasing confining pressure, but Poisson’s ratio remained unaffected. Using our new data, the compactive and dilatant behavior, strength and failure characteristics of sandstone under triaxial compression are further discussed. For our data, the nonlinear Hoek-Brown criterion better reflects the peak strength properties than the linear Mohr-Coulomb criterion. However, the residual strength shows a clear linear relationship with confining pressure, which can be best described using the linear Mohr-Coulomb criterion. The peak and residual strengths were not directly related to the two different loading paths. The onset of dilatancy (C′), the switch from compaction-dominated to dilatant-dominated behavior (D′) and the stress at zero volumetric strain all increased linearly with the confining pressure. In our conventional triaxial compression experiments, the failure mode changed from mixed tension and shear fracture (single shear fracture) to shear fracture with double slippage planes with increasing confining pressure. However, the failure mode in our “reducing confining pressure” experiments was more complicated and results mainly from the unstable failure characteristics of the rock during the reduction in confining pressure. Finally, based on our acoustic emission (AE) locations, at a confining pressure of 35?MPa, a detailed analysis of the evolutionary process of internal cracks is presented for the entire loading process.     

Research on Damage and Acoustic Emission Properties of Rock Under Uniaxial Compression

Geotechnical and Geological Engineering - In this paper, the YSSZ-500A rock biaxial rheological tester was used to investigate the acoustic emission characteristics of coal seam roof rock under...     

声发射预报地震的岩体力学分析

岩体受压破坏是由于岩体内裂纹扩展及新的宏观裂纹产生不断积累的结果,大规模岩体受压破坏前会发生局部岩体的先前断裂破坏。裂纹起裂、快速扩展和止裂会产生声发射现象,局部岩体断裂破坏会产生强烈的声发射现象,通过对岩体声发射的监测分析可以预报受压岩体破坏的时间。因此,通过对地壳岩体声发射的监测分析,可以进行地震的短期和临震预报。通过对岩体受压应力分布规律的分析,得出通过监测地壳浅部地应力和地形变预报地震是没有实际意义的结论。     

On Tension Failure of 2-D Rock Specimens and Associated Acoustic Emission

Summary To understand the failure mechanism of quasi-brittle materials like rock under tensile stress, observations on the failure process of granite and marble plate specimens under tension are summarized and presented. Micro- and macro-failure properties of rock plates under uniaxial tension have been characterized by using an acoustic emission technique. Acoustic emission signals associated with micro-fractures are captured to locate the sources. An algorithm based on arrival time difference is developed for this purpose. The results reveal clearly the failure processes of rock which include initiation, nucleation and propagation of micro-fractures when the axial stress is close to the peak strength of rock. It is believed that the difference in heterogeneity between granite and marble specimens leads to different fracture shapes and different behaviors of associated acoustic emissions. Numerical simulation of acoustic emissions for two-dimensional tensile test is also carried out. The simulated characteristics are in good agreement with the experimental results.     

考虑温度效应的岩石损伤内时本构关系

本文根据岩石类材料受载时的损伤破坏机理,首次引入两个损伤变量 D_1和 D_0用以反映外载荷体量和偏量的作用,在内时理论的基础上建立起考虑温度效应的岩石损伤本构方程,并导出具有明确物理意义的本构方程增量型关系式。在不同温度下用大理岩试样进行了压缩实验和声发射实验。根据实验所得结果,确定了本构方程中材料的所有参数,得到了大理岩材料受温度影响其性质发生变化的一些有意义的结论。     

Three Dimensional Statistical Damage Constitutive Model of Rock Based on Griffith Strength Criterion

Geotechnical and Geological Engineering - According to the damage mechanics theory and Lemaitre strain equivalence theory, because most rock materials are brittle materials, Griffith strength...     

声发射检测技术在冰川上的应用

根据声发射检测技术，研制了专用的检测仪器。在乌鲁木齐河源冰川７个测点上进行了声发射信号检测和分析。证实了冰川上存在着丰富的声发射信号。信号有突发型和连续型两种基本类型。信号主频率为：１２．５－２５Ｈｚ，６０－８５Ｈｚ，１１０－１２５Ｈｚ。冰川上水流动振动信号频带为６２５－１５００Ｈｚ。此外，用爆破手段测得天山乌鲁木齐河源１号冰川东支纵波的传播速度为３．７５±０．０５ｋｍ／ｓ。     

基于小波包分析的岩石声发射测量地应力

根据目前岩石声发射确定Kaiser点存在的问题采用小波包分析研究方法,在单轴加载岩石声发射试验的基础上,首先提出了基于小波包变换的Kaiser点信号的信噪分离方法,其次确定了Kaiser点信号的频率范围,最后利用小波包分析对岩石声发射信号的能量分布特征进行研究,得到了砂岩Kaiser点信号的特征频带。结果表明,小波包分析是处理岩石声发射Kaiser点信号的一种有效的方法,进而为AE法测量地应力确定Kaiser点奠定了一定的试验基础。     

冰体材料损伤与断裂破坏的本构理论

冰体材料对应变速率很敏感, 存在一个韧脆转变区和转变速率εR, 当ε<εR时冰体为韧性性质, 当ε>εR时, 冰体为脆性性质.因此可按冰体的不同性态分段描写本构模型, 对冰体的韧性性质给出了损伤模型, 对冰体的脆性性质给出了断裂模型.分别用损伤模型预测韧-脆转变区的起始速率, 用断裂模型预测韧-脆转变的终点速率及相应的破坏应力.     

Failure and Acoustic Emission Characteristics of Jointed Rock Masses with Different Joint Inclination Angles and Combination Mode

Geotechnical and Geological Engineering - In order to analyze the characteristics of the mechanical property, failure mode and acoustic emission of the columnar jointed rock masses,...     

Damage and Acoustic Emission Characteristics of Combined Rock Mass with Anchor Under Different Inclination Angles and Combination Modes

Geotechnical and Geological Engineering - Soft and hard rock assemblages and anchor solids have important effects on rock mechanics properties under different inclinations and assemblages, so it is...     

Progressive Failure Analysis of Slope Water Damage Based on Improved Green-Ampt Infiltration Model

Geotechnical and Geological Engineering - In order to get the law of rainwater infiltration and the law of progressive water damage, the slope of Tianshang bridge foundation in Yunnan Province of...     

深基坑工程变形预报神经网络法的初步研究

提出了深基坑变形预报的人工神经网络法,详细介绍了该方法的建模和应用实例。预报结果与实测值较为吻合,从而表现在深基坑工程中利用该方法进行变形预报是可行的。     

地震波动力学参数在砂体预测中的应用

随着勘探程度的不断提高，未发现的大型构造油气藏已越来越少，因而寻找油藏的岩性油藏是一项紧迫的任务，利用地震资料识别砂岩是完成这一任务的关键。已有的预测砂岩的方法都要求地层厚度在调谐厚度以内，对厚层无法准确预测。针对松辽盆地南部泥岩薄互层的地质特点，从地震数据中提取并优选地震波动力学参数，利用神经网络方法学习，训练，准确识别预测砂岩的厚度，即使其厚度大于调谐厚度也适用。     

致密砂岩气层压裂产能及等级预测方法

致密砂岩储层孔隙度小、渗透率低、含气饱和度低,基本上没有自然产能,需要进行压裂,因此进行压裂产能的预测很有必要。笔者研究了鄂尔多斯盆地苏里格东部地区盒8段致密砂岩气层的压裂产能及等级预测。利用反映储层流动性质的测井参数(电阻率、自然伽马、声波时差、中子、密度)与反应压裂施工情况的压裂施工参数(单位厚度砂体积、砂比、砂质量浓度、单位厚度排量、单位厚度入井总液量),选择数学统计方法神经网络法进行致密砂岩气层压裂产能等级预测。分析比较Elman神经网络、支持向量回归(SVR)、广义回归神经网络(GRNN)3个神经网络预测致密砂岩气层压裂产能模型的网络结构参数、回判及预测精度以及运行耗费时间。结果表明:3个模型中,GRNN网络参数只有1个,回判和预测精度最高,运行时间小于1 s。因此,选择GRNN模型预测致密砂岩气层压裂产能,并用于苏里格东部地区致密砂岩气层压裂产能的等级预测。等级预测准确率达到90%。     

岩石声发射技术的应用现状

介绍了我国内外岩石声发射技术在测定地应力、钻进监测、岩石力学与岩石破碎学研究、坑道岩体稳定性监测等方面的应用现状及发展趋势。     

岩石蠕变声发射特性研究现状与展望

蠕变是岩石一种重要的力学特性,与工程的长期安全稳定和安全密切相关。声发射技术作为一种无损检测手段,被广泛应用于岩石变形破坏研究领域。本文阐述了近年来基于声发射技术开展岩石蠕变特性方面的研究进展,主要包括不同岩性、加载方式、应力水平下岩石蠕变声发射特性,岩石蠕变破坏声发射前兆特征。在此基础上,提出了几点今后需要进一步深入研究的问题。