拉日线峡谷区地应力分布特征的分析

介绍了拉日线峡谷区地应力分布特征的概况,分析了雅鲁藏布江峡谷区地应力的特征,进行了峡谷区水压致裂原地应力测量,探讨了高地应力对工程的影响,提出了高地应力的应对措施和选线原则具有一定的参考价值。     

金川矿区地应力规律与人工神经网络预测研究

介绍了对金川矿区地应力变化规律的研究与预测结果,在矿区地应力测试资料的基础上,开发了矿区地应力神经网络预测模型.借助于该模型,进行矿区三维空间的地应力预测和分析,给出了由此获得的主要结论.     

深钻孔地应力测试技术与地应力场分析方法

本文概述了深钻孔地应力的量测和依据不同深度的实测资料进行地应力场分析的原理和方法,并介绍了某抽水蓄能电站地下厂房区进行地应力量测和地应力场分析的某些成果。     

引汉济渭工程黄三隧洞地应力测试研究

通过地应力现场测试,研究引汉济渭工程黄三隧洞地应力场特征。首先介绍水压致裂法基本原理,然后分析现场测试结果得到了水平主应力量值和最大水平主应力方向,讨论了地应力场特征及地应力对隧洞轴向选择的影响。测试区域内,地应力属于中低应力水平,σ_Hσ_hσ_Z;地应力方向在浅部符合河谷区应力分布一般规律,深部主要受区域构造应力场影响。从地应力角度分析,隧洞轴线选择方向对围岩稳定较为有利。     

南水北调玛柯河～阿柯河段地应力场分析研究

南水北调西线工程区内工程地质条件十分复杂,初始地应力场研究是决定工程设计的重要工程地质条件.借用南水北调工程区其他的现场地应力实测资料,建立的西线各个分段沿深度线性表达的地应力概化模型,得出地应力回归方程预测区间,利用玛柯河～阿柯河段有限的两个测孔地应力资料,采用均匀试验设计,全面考虑可能影响因素,同时大大减小试验次数,以最小方差作为衡量标准,分析了该段地应力的最优回归方程,即地应力和深度的具体关系式,分析了地应力大小分布规律和地质构造、地形地貌、地震断裂带、岩石力学性质等因素的关系,并给出了第一主应力沿洞轴线分布图.     

基于BP神经网络的铁路长深隧道地应力三维反演技术研究与应用

针对区域地应力评估难度大,难以通过实测方法获得区域地应力真实情况的问题,在实测点状地应力数据基础上,使用优化的BP神经网络与数值模拟相结合的方法,对浩吉铁路阳山隧道工程范围内岩体的区域地应力状态进行了预测与模拟,实现了对区域地应力水平更贴近现实情况的预测和评估。通过对比优化的BP神经网络与回归分析2种方法可知,前者能够更好地克服地应力反演结果离散性大的问题。通过实例验证可知,采用优化的BP神经网络与数值模拟相结合的方法进行区域地应力评价是可行的     

平顶山一矿地应力分布特征研究

初始地应力是地下工程围岩稳定与支护结构设计的一个基本参数。详细介绍了平顶山一矿的地应力计算原理，并根据矿区实测地应力资料，得出了计算区域初始地应力场相应的应力回归公式，并且分析了矿井地应力的分布特征．     

岩芯饼化的应力分析

作者应用光弹、电测和电算方法,对地质钻探过程中岩芯地应力的释放进行了研究,找出了地应力释放后,岩芯中剩余应力的波及范围和分布规律。在此基础上,应用能量原理,推导出了一维和二维地应力的计算公式。同时,还用试验方法建立了一个一维地应力的计算公式。应用这些公式,根据岩芯饼化的特征参数;岩饼直径D、厚度t和长短轴差△D,可以计算出地应力的大小,从而大大简化了现有的地应力的测量工作。本文对几种地应力计算公式进行了分析比较,并用二维计算公式,对二滩电站实测岩饼资料进行了计算,得出二滩电站岩芯饼化地层的地应力为700kg/cm~2左右,中国科学院武汉岩体土力学研究所实测结果为650kg/cm~2,二者接近。     

隧道穿越复杂岩体的水文工程地质原因分析

低地应力是地下工程中经常被忽视的一种应力状态,低地应力对地下工程稳定性有重要影响.结合白鹤隧道复杂地质段施工,本文详细分析了其工程地质特征,并结合低地应力的地质标志,得出了低地应力为该复杂地质段主控制因素的结论,为进一步设计施工提供参考.     

江边水电站厂区初始地应力场研究分析

锦屏二级水电站位于雅砻江干流锦屏大河湾上,是雅砻江干流上的重要梯级电站,厂区内地形起伏较大,属于典型的“V”型河谷。由于厂区靠近河谷,因此其地应力场的量级应该较高,并且地应力方向分布较为复杂。为了掌握厂区地应力场的分布规律和量级,利用厂区的地应力测值,根据河谷演化理论和神经网络对厂区的地应力场进行了回归分析,回归结果表明,厂区的地应力应在20~30MPa,属于中偏高地应力场,可以诱发岩爆现象,同时验证了河谷演化理论和神经网络相结合的方法是反演深切河谷地应力场的有效手段。     

十年来韩国隧道施工的地应力水压致裂法测试经验

自1994年以来,韩国的土木工程师们首次接触到水压致裂法,在仪器开发、解释技法领域均有长足进展。在仪器开发方面:第一代水力致裂试验装备为管道形状,操作较为困难,之后简化到管线状,至今已研制出更加小型化、便于操作的设备。在解释技法领域也取得很多成就:水力致裂应力曲线中最难判读的龟裂闭锁压力曲线,也可以利用各种分析方法自动锁定。通过过去10a年来的探测经验,韩国已积累了国内大部分地区地应力的检测结果,而且这些参数资料一直在隧道工程的各种设计中得到应用。因此,考虑到沿岸地区的地应力测试固有的局限性,路域地区的测试资料可作为较好的参考资料,将其应用于海底隧道工程的设计当中。     

深切河谷区地应力场分布规律研究

 基于对南水北调西线工程7个坝址区水压致裂法地应力测试结果的统计分析,初步得出深切河谷区最大水平主应力量值随深度呈分段线性关系的结论。分析结果还表明在河谷埋深较浅部位(即应力释放区),最大水平主应力值随深度的增加幅度较小,而在较深部位(即应力集中区),最大水平主应力值随深度的增加幅度较大。此外,利用有限差分程序FLAC3D,对阿达坝址区的地应力场进行反演。研究结果表明：(1) 河谷卸荷作用对浅部谷坡的地应力场影响较大,在该区域采用水压致裂法确定地应力场误差可能会比较大;而对河床区域应力场方向的影响较小,采用水压致裂法来确定河床区域的应力场是可行、可靠的;(2) 不仅河谷区地应力场存在3个分区即应力释放区、应力集中区和应力平稳区,岸坡地应力场也存在上述3个分区;(3) 阿达坝址区河谷底应力集中范围在河床下60～140 m范围内;(4) 深切河谷区应力集中区的深度受岩体卸荷强弱程度和地形地貌的差异影响较大。     

基于不同岩石抗拉强度值确定最大水平主应力的对比分析

水压致裂原地应力测量系统的柔性对最大水平主应力的结果会产生很大的影响,提高最大水平主应力的测量精度对各种地下等工程设计都具有重要意义。通过进行直接拉伸试验、“垫条加载”和“角锥荷载”形式的圆盘劈裂实验、弯曲拉伸实验获得岩石抗拉强度,结合实测破坏压力、孔隙压力数据及相关理论计算出最大水平主应力,并与利用经典水压致裂公式计算得到的最大水平主应力进行数据对比分析。结果表明:通过“角锥荷载”圆盘劈裂实验、直接拉伸试验、“垫条加载”圆盘劈裂实验、三点弯曲实验所获得的最大水平主应力均大于经典水压致裂公式计算得到的最大水平主应力,且偏差依次增大,由此也说明测试系统的柔性会导致利用经典公式计算的最大水平主应力偏小。4种实验中,通过“角锥荷载”圆盘劈裂实验所获得的数据较其他3种方法更接近经典公式计算得到的最大水平主应力,且偏差较小,可以作为估算最大水平主应力的一种替代方法。在未来的工作研究中,可以为避开系统柔性对实测最大水平主应力的影响、提高测量精度提供方法参考。     

遗传算法在确定钻孔裂缝产状中的应用

精确确定钻孔内裂缝产状是地应力测量和微观构造研究中的一项重要工作。利用遗传算法的反演拟合确定各种规则形态和不规则复杂形态钻孔裂纹的产状，提供了确定裂缝产状的一种效果较好的具有通用性的反演程序。     

Application of Weibull's theory to estimating in situ maximum stress σH by hydrofracturing

Hydrofracturing is a widely used and established method for rock stress measurement and is especially valuable at great depths. In conventional hydrofracturing (Haimson, Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 15 (1978) 167), dealing with an axi-parallel fracture, the horizontal minimum stress σ_h is obtained as the shut-in pressure and the maximum stress σ_H is calculated from the breakdown pressure or reopening pressure. It has been pointed out, however, that σ_H is not as reliable as σ_h. This paper therefore presents a new approach for estimating σ_H. In this approach the probabilistic aspects of tensile failure are considered as new sources of information, because the probability density of fracture direction may provide valuable information concerning the stress difference σ_H−σ_h. As the basic theory to describe the tensile failure of rock, we adopted the Weibull’s weakest link theory. The applicability of the theory is first verified via tensile tests on rock specimens of different shape and size, then the probabilistic approach is applied to hydrofracturing to give the probability function of breakdown and the probability density function for the fracture direction. The applicability of the proposed method is presented through numerical calculations and an example in which σ_H−σ_h is estimated from the probabilistic variability of the fracture direction.     

Failure pressure calculation of fracturing well based on fluid-structure interaction

Failure pressure is a key parameter in reservoir hydrofracturing operation. Existing analytical methods for calculating the failure pressure are based on the assumption that borehole fluid is under two extreme conditions: non-infiltration or complete infiltration. The assumption is not suitable for the actual infiltration process, and this will cause a great error in practical calculation. It shows that during the injection process, the dynamic variation in effective stress-dependent permeability has an influence on the infiltration, and the influence also brings about calculation errors. Based on the fluid-structure interaction and finite element method (FEM), considering partial infiltration during injection process, a numerical model for calculating rock failure pressure is established. According to the analysis of permeability test results and response-surface method, a new variation rule of rock permeability with the change of effective stress is presented, and the relationships among the permeability, confining pressure and pore pressure are proposed. There are some differences between the dynamic value of permeability-effective-stress coefficient observed herein and the one obtained by the classical theory. Combining with the numerical model and the dynamic permeability, a coupling method for calculating failure pressure is developed. Comparison of field data and calculated values obtained by various methods shows that accurate values can be obtained by the coupling method. The coupling method can be widely applied to the calculation of failure pressure of reservoirs and complex wells to achieve effective fracturing operation.     

Failure pressure calculation of fracturing well based on fluid-structure interaction

Failure pressure is a key parameter in reservoir hydrofracturing operation. Existing analytical methods for calculating the failure pressure are based on the assumption that borehole fluid is under two extreme conditions: non-infiltration or complete infiltration. The assumption is not suitable for the actual infiltration process, and this will cause a great error in practical calculation. It shows that during the injection process, the dynamic variation in effective stress-dependent permeability has an influence on the infiltration, and the influence also brings about calculation errors. Based on the fluid-structure interaction and finite element method (FEM), considering partial infiltration during injection process, a numerical model for calculating rock failure pressure is established. According to the analysis of permeability test results and response-surface method, a new variation rule of rock permeability with the change of effective stress is presented, and the relationships among the permeability, confining pressure and pore pressure are proposed. There are some differences between the dynamic value of permeability-effective-stress coefficient observed herein and the one obtained by the classical theory. Combining with the numerical model and the dynamic permeability, a coupling method for calculating failure pressure is developed. Comparison of field data and calculated values obtained by various methods shows that accurate values can be obtained by the coupling method. The coupling method can be widely applied to the calculation of failure pressure of reservoirs and complex wells to achieve effective fracturing operation.     

煤巷锚杆支护成套技术研究与实践

介绍煤巷锚杆支护技术的最新进展与研究成果。在支护理论方面,认为锚杆支护的主要作用在于控制锚固区围岩的离层、滑动、张开裂隙等扩容变形与破坏,最大限度地保持围岩完整性,避免有害变形出现;围岩地质力学测试仪器包括小孔径水压致裂地应力测量装置、围岩强度原位测量装置及钻孔窥视仪的技术特征与使用方法;论述锚杆支护动态信息设计方法的特点与设计步骤,及面向现场工程技术人员使用的支护设计软件组成与功能;分析高强度锚杆支护材料的力学性能,包括锚杆、锚固剂、W型钢带和锚索;最后,介绍井下应用实例,通过监测数据,评价支护效果。实践证明,锚杆支护是目前最适合煤巷的高效、经济的支护方式。     

超声波成象钻孔电视及其在岩石工程中的应用

本文主要介绍了超声波成象钻孔电视的工作原理,并以实例说明了地层节理裂隙的取得及计算分析方法,和在生产、科研工作的应用。文中对超声波钻孔电视用于观测钻孔崩落确定现今应力场方向,定向岩芯的获取,井下探头的安装,油田深部的套管变形和压裂前后射孔及套管的变化等作了报导．     

2D-numerical analysis of hydraulic fracturing in heterogeneous geo-materials

A geo-material failure process analysis (F-RFPA2D), considering the coupling of stress distribution, fluid flow, and element damage evolution, is used to investigate the mechanisms of crack initiation and propagation around a 2-D cylindrical cavity in heterogeneous stiff soils during hydraulic fracturing. A large number of numerical analysis on hydraulic fracturing in stiff soil with pre-existing injection cavity have been carried out to study the mechanism of hydraulic fracturing in stiff soil. In addition, the characteristic of acoustic emission (AE) due to hydraulic fractures are studied by numerical simulations. The results provide a better understanding of the crack initiation and propagation mechanisms during hydrofracturing. The simulation software package can be a powerful tool for study of soil behavior during hydraulic fractures.