岩体渗透结构类型的划分及其渗透特性研究

提出了一种计算二维有限变形弹塑性摩擦接触问题形状设计灵敏度的算法. 采用主动 集策略和mortar方法处理接触边线上的约束条件. 在mortar接触边线的切线和法线方向上 采用相同的名义罚函数,提出基于名义罚函数的移动摩擦锥算法来正则化接触约束条件,发 展了一种新的二维多体有限变形摩擦接触算法. 在此基础上, 通过将离散形式的摩擦接触问题 控制方程对形状设计变量微分,得到了该路径相关问题的直接微分法解析设计灵敏度 计算格式, 其节点位移灵敏度方程在每个增量步不用迭代、直接求解. 与国际上现有 的二维多体有限变形摩擦接触问题的解析设计灵敏度算法相比,本算法不需分 解为法向和切向推导,表达式较简洁,便于编程实现. 数值算例验证了算法的精度 和有效性.     

圆板状岩样破坏过程中的渗透特性实验研究

利用一种自行设计的附加渗透试验装置,在MTS815.02岩石力学伺服试验系统上完成了圆板状岩样破坏过程中的渗透特性试验,得到了圆板状岩样渗透率、渗透压差、渗流速度与轴向荷载的关系,并对试验结果进行了分析和讨论。研究表明:1)岩样在渗透的同时发生弯曲变形,岩样的渗透率与其受力状态密切相关,当达到峰值载荷时,渗透率急剧增大,由此验证了突水是伴随着结构破坏的渗流失稳过程;2)岩样在破坏过程中,当轴向载荷达到峰值时,岩样两端压力差急剧减小;3)岩样两端压力差保持0.2MPa,轴向荷载达到峰值时,增压器活塞位移急剧增大,即渗流速度突然变大;4)冲剪破坏为圆板状岩样的主要破坏形式。     

断层内破碎岩石渗透性的实验研究

断层破碎带岩石的渗透性是影响地下工程中由渗流失稳而引发灾害事故的重要影响因素之一。利用一种专门的破碎岩石压实渗透仪,在MTS815.02岩石力学伺服试验系统上测试了取自断层内的破碎灰岩、破碎砂岩、破碎泥岩的渗透系数,得到并分析了轴向压力、岩样粒径、水流速度与渗透系数的关系曲线。研究表明:破碎岩石渗透系数与其压实状态密切相关,随着轴压的增加,渗透系数都相应降低;在相同的轴向压力状态下,岩样粒径越小,其渗透系数也越小,因此,挤压程度和充填程度都较低的小断层导水性好,容易导致突水;破碎岩石的渗透系数随着水流速度的增大呈减小趋势,但水流速度对破碎岩石渗透系数的影响程度有限;在相同的压力、粒径情况下,破碎泥岩的渗透系数比破碎灰岩、破碎砂岩的要小1～2个量级,说明当断层上下盘为坚硬岩石时,断层带渗透性好、易导水。研究结果可为采动过程中评价断层的导水性提供参考。     

Experimental Study of Seepage Properties of Broken Sandstone Under Different Porosities

In coal mining the water flow in broken rock is a very common phenomenon. Study of seepage properties of broken rock is one of the basic subjects required in order to understand the stability of rock surrounding roadways, preventing disasters such as water inrush and gas outbursts and developing underground resources. So far, quantitative studies on the nonlinear seepage properties of broken sandstone under different porosities are not extensive in the research literature. In this article, by means of an electro-hydraulic servo-controlled test system (MTS815.02) and a patent seepage device, the seepage properties under different conditions of porosity were tested on broken sandstone of five different grain sizes. Based on the loading method of controlling the axial compression displacement and steady permeating method, we obtained curves of the relation of pore pressure with time, as well as the relation curves between the pore pressure gradient for steady seepage and velocity. Furthermore, we calculated the permeability k and non-Darcy coefficient β corresponding to different porosities by fitting these curves with the binomial expression. This study indicates that: (1) the seepage properties of broken sandstone are closely related to grain size, load levels, and porosity structure; (2) the permeability k decreases, while the coefficient β increases with a decrease in porosity φ, but both the k − φ and the β − φ curves show some local fluctuations; (3) the permeability k of the broken sandstone has a magnitude of 10⁻¹⁴–10⁻¹² m², while the coefficient β ranges from 10¹⁰ to 10¹² m⁻¹. The results obtained provide some information for further study of the nonlinear seepage behavior of broken rock theoretically.     

砂岩峰后卸除围压过程的渗透性试验研究

为了探讨煤层开采引起的围岩卸除围压过程中砂岩渗透性的变化规律,本文用数控瞬态渗透法在电液伺服岩石力学试验系统MTS815.02上进行了砂岩试样的渗透特性试验。得出了试样峰前渗透系数-应变与应力-应变的关系曲线,以及在峰后保持轴向应变一定卸除围压过程中试样的渗透系数-围压与主应力差-围压的关系曲线;对试验砂岩在变形破坏过程中渗透性变化规律进行了总结,重点分析了其峰后卸除围压过程中渗透性的变化规律;并对试验砂岩峰后渗透系数与有效围压关系进行了拟合,得出了拟合方程式,为煤层开采引起的围岩体应力场与渗流场耦合问题提供参考。     

裂隙岩体渗流模型研究现状与展望

裂隙岩体渗流对于边坡、地下工程及基础岩土体的承载能力有显著的制约作用。本文简要地介绍了多种裂隙岩体渗流模型研究现状,评述了几类比较有代表性的渗流模型特点以及存在的不足,为选取合理的数学模型用于求解具体的裂隙岩体渗流问题提供了参考依据,并在上述基础上提出了一些需要进一步研究的问题。指出就目前应用最为广泛的等效连续介质模型而言,裂隙岩体几何参数、有效孔隙度以及等效渗透张量的确定仍有待于更深入的研究,而从细观力学结构入手研究渗流耦合模型将具有重大的理论意义和实用价值。     

充填泥沙裂隙岩石渗流特性的实验研究

对人工充填泥沙裂隙岩石在MTS815.02电液伺服岩石试验系统上进行渗流实验,同时结合岩石孔隙电子显微照片,探讨了泥沙颗粒对裂隙岩石渗透特性的影响规律.实验表明,在泥沙颗粒的作用下,裂隙岩样渗透率明显减小;泥沙颗粒在岩样宏观裂隙中运移达到重新平衡之后,裂隙岩样渗透率随时间逐渐增大并最终趋于稳定.     

煤系地层岩石渗透特性试验研究

基于MTS815.02型岩石伺服渗透试验系统,应用两种实验方法测定了岩石的渗透特性,给出煤系地层中多种岩石全应力-应变过程中渗透率变化范围,对几种岩石的渗透特征进行了分析和讨论。研究表明:1)煤系地层岩石全应力-应变过程的渗透率通常在10-9到10-4Darcy量级之间;2)不同岩石在应力峰值前后其渗透性呈现不同的变化趋势;3)岩石渗透率的离散性很大,即使在相同的试验条件下,渗透率变异系数大多在0.65以上,其离散性按粗砂岩、泥岩、砂质页岩、中砂岩、细砂岩、砾岩、石灰岩顺序逐渐增大;4)在MTS815.02系统上,当所测岩样渗透率小于10-4Darcy量级时,应采用瞬态法,当渗透率量级大于10-4Darcy时,可改用稳态法测定。岩石变形过程中应力场和渗流场的耦合作用十分复杂,渗透率受孔隙压力、围压、试件尺寸、饱和程度等因素影响。     

Analysis of Broken Coal Permeability Evolution Under Cyclic Loading and Unloading Conditions by the Model Based on the Hertz Contact Deformation Principle

The permeability of the caved zone in a longwall operation impact many issues related to ventilation and methane control, as well as to interaction of gob gas ventholes with the mining environment. Insofar as the gob is typically inaccessible for performing direct measurements of the stresses and permeability, the latter values of the caved zone have to be assessed indirectly, which requires the application of the most reliable prediction techniques. To study the permeability evolution of the broken coal and its influencing factors during the coal seam group repeating mining, the particle deformation of the broken coal sample (BCS) is assessed in this study based on the Hertz contact deformation principle. Using the experimental results of the BCS cyclic loading and unloading seepage tests, the effect of BCS parameters on the stress sensitivity for permeability is analyzed. The laboratory test results imply that the re-crushing, re-arrangement, and compressional deformation of particles in the loading process lead to a drastic drop in the caved zone porosity causing the permeability reduction. During the unloading process, only the permeability loss caused by the particle deformation can be recovered. The secant modulus of BCS during unloading is stable and can be assessed by fitting the permeability stress curves. The stress sensitivity of the BCS permeability during unloading process drops with an increase in the secant modulus, while the re-crushing capacity and re-arrangement ability of BCS particles gradually deteriorate due to an increase in the secant modulus with the number of loading cycles. The effect of Poisson’s ratio on the permeability stress sensitivity at the later loading/unloading stages is found to be quite feeble, while the stress sensitivity is indirectly related to the particle size via the secant modulus: the greater the particle size, the higher the unloading stress sensitivity.     

Experimental Investigation on the Permeability Evolution of Compacted Broken Coal

Given the importance of airflow seepage properties to coal self-oxidation in gob, this paper develops a method and self-designed apparatus to assess seepage properties of compacted broken coal. This study mainly focuses on the strain, porosity and permeability evolution under the different conditions of particle size, vertical stress and temperature. The studied results show: (1) The strain, porosity and permeability were enlarged when the particle size increased under the same loading stress. The porosity and permeability reduced when the vertical stress increased. (2) The non-Darcy coefficient was negative in all tests, but the absolute value of the non-Darcy coefficient generally increased when the vertical stress increased. (3) The experiment results indicated that the larger the particle was, the easier to be compacted. The larger the grain diameter was, the lower the porosity and permeability were, which shown that the void volume in broken coal with larger grain diameters could be easily compacted. (4) The permeability was reduced when the temperature increased, which indicated the permeability of the compacted broken coal decreased during low-temperature oxidation in gob. (5) By the effects of stress and the particle size diameter on the porosity and permeability, the vertical stress recovery and generally increase are advantageous to reduce the porosity and permeability in gob. It is favorable to reduce the porosity and permeability and prevent coal self-heating by reducing the degree of fragmentation and percentage of small particles or consolidate the small particles.     

三峡库区云阳—江津段危岩形成的影响因素及稳定性评价

三峡库区云阳—江津段高陡岸坡地质环境复杂,危岩极其发育,其破坏具有突发性,致灾具有毁灭性。危岩稳定性影响因素具有复杂性及模糊性特点,河流或沟谷强烈下切产生的岸坡岩体卸荷作用、软硬相间的岩层组合以及高强度的降雨或较大的日温差变化是三峡库区危岩形成的基本条件。本文选取地形地貌、地层岩性、岩体结构、危岩体规模、水文地质、风化作用、土地利用类型7个因子作为评价指标,建立危岩稳定性评价指数模型。根据稳定性指数将危岩稳定性分为4级:稳定、基本稳定、稳定性差、稳定性极差。结合实例,对万州黑岩脚危岩体进行了稳定性模糊评价,结果与实际调查情况基本一致。研究结果表明,本文提出的危岩稳定性评价指数模型,考虑的信息量丰富,数据通过野外调查容易获得; 评价指标权选取和分级合理,稳定性模糊评价结果与与实际调查情况基本符合,为三峡库区危岩稳定性分析、治理和监测提供了重要依据。     

破碎岩石气体渗透性的试验测定方法

为了测试采矿工程中松散破碎岩体的气体渗透特性,设计了与MTS815.02岩石力学伺服机配套的气体渗透仪和测试系统。依靠MTS伺服机改变压力和位移条件,渗透仪用以稳定破碎岩石并连接气体测试系统,接入气源、组成回路和测试气透特性等由测试系统完成。通过对几组破碎砂岩岩样氮气渗透性能的测试,结合考虑状态方程的渗透率换算公式,得出破碎砂岩气体渗透率随压力和粒径条件的变化规律。该测试方法和测试结果在研究采动破碎岩体瓦斯等气体流动规律方面具有重要意义。     

振动对充填裂隙渗透率影响的实验研究

为了研究振动和充填泥沙的共同作用对裂隙岩石渗透率的影响,通过对裂隙试件在充填和振动后条件下的渗流实验,得到了频率和振幅与充填裂隙岩石渗透率的关系曲线。结果表明,充填泥沙后的相对渗透率低于充填前,最小降幅为10.19%,最大降幅为59.74%。在相同的振幅下,试件的相对渗透率随频率的增加都基本呈下降趋势;振动后的渗透率低于振动前的渗透率;充填试件在较大频率振动下,渗透率减小的更为显著。在相同的频率下,充填试件振动后的渗透率基本上都减小了,最小降幅为8.90%,最大降幅为51.23%;而未充填试件振动后的渗透率与振幅存在一定关系;相对渗透率与振幅的变化之间存在拐点,相对渗透率并没有随着振幅的增加而一直减小。     

岩体系统渗流场与应力场耦合的广义双重介质模型的应用研究

本文通过实验资料分析, 提出了裂隙岩体应力与渗流之间的分形几何关系式。以研究区岩体系统结构为基础, 提出了岩体系统应力场与渗流场耦合的广义双重介质模型, 并将该模型应用于某水利水电工程的渗流与控制中, 对坝区岩体进行了应力场和渗流场的耦合分析, 取得了比较满意的结果。     

模拟不同节理粗糙度对单裂隙渗流的影响

在研究岩体裂隙间的渗流特性时,节理粗糙度会影响裂隙水流的渗流特性和路径,因此需要对粗糙表面进行恰当的描述。本文选取伸长率、最大起伏高度、最大起伏角和分维数4个参数刻画粗糙度。结合分维数的计算方法,选择当最大起伏高度为2.5mm、节理宽度为5mm时,随机生成4组直线和曲线节理边界。建立二维模型模拟发现,最大起伏角、伸长率和分维数是影响水流流速分布的敏感因素。在节理最高起伏处的下边界,流速值最大。此外,粗糙度的方向性对渗流影响较大。同等节理条件下,可发现沿水流方向,最大起伏高度的位置越靠后,越能抑制最大流速值,从而减小渗流破坏。最后,根据规则锯齿状的节理试验分析表明,在外力条件下,渗流量一定时,节理通道一旦发生改变,内部形成的漩涡便与水流的有效路径呈现负相关关系。     

沥青混凝土级配曲线的数值设计方法与对有效弹性模量影响的研究

沥青混凝土有效性能的预测和评估是其在道路工程与大坝防渗等应用中的关键问题。本文利用细观随机建模技术和有限元方法研究了级配曲线对沥青混凝土有效弹性模量的影响。首先,基于改进的蒙特卡洛法分别实现了服从工程筛分级配曲线或给定函数级配曲线的沥青混凝土细观随机模型的高效生成;然后,利用建立的模型分析了骨料的含量、弹性模量和试样尺寸对沥青混凝土的有效弹性模量的影响,并与实验结果进行对比,验证了所建模型的可靠性;从而,预测了在AC-13级配范围内级配曲线的凹凸程度,即粗细骨料的组成比例对沥青混凝土有效弹性模量的影响。结果表明,级配曲线的凹凸程度对其有效弹性模量影响存在较大差异,级配曲线的下凹(粗骨料占比增大)会导致有效弹性模量迅速增大,级配曲线的上凸(细骨料占比增大)也会引起有效弹性模量略有上升;另外提出的随机建模方法可实现对级配曲线,即对粗细骨料组成比例的定制设计.     

The Constitute Law of Gas Seepage in Rock Fractures Undergoing Three-dimensional Stress

This paper is based on the research we have done in recent years of the constitute law of gas seepage in rock fractures. Both experiments and theoretical derivations will be discussed. The gases used in our experiments include methane and CO₂, both of which are highly adsorptive. The experiments were conducted mainly in coal fractures. The results reveal that the permeability coefficient of gas in rock fractures varies parabolically with respect to fracture pore pressure. When the pore pressure is below a certain value, the permeability coefficient decreases while the pore pressure increases. It is different from the water seepage law in fractures. Analysis shows that this abnormality is caused by adsorption. It is also concluded that the tangent deformation has the same effects as normal deformation on gas seepage law. The permeability of gas in fractures has a negative exponent relationship with both normal deformation and tangent deformation.     

非达西渗流拟启动压力梯度推算

岩体启动压力梯度的大小是石油开采,工程防渗处理等方面需要考虑的影响因素。非线性渗流现象已被广泛所认同,低渗透性岩渗流存在启动压力梯度,它基本代表了流体产生渗流时的压力梯度大小。试验对试样进水端水压进行长期稳定控制,出水端采用精确测定流出水体积变化量的方法进行流量测定; 当渗出端水体积的变化量与时间呈直线关系时,即认为该时段渗透特征符合达西定律。通过对具有不同渗透性的软弱岩系统的试验测试,根据实测渗透系数与压力梯度的正相关关系,提出了拟启动压力梯度推算的"三次平均法",即:首先统一调整实测渗透系数值,然后确定绝对渗透系数值,再根据该值确定V0值, 3次取平均推算拟启动压力梯度的方法。分析表明:拟启动压力梯度随围压升高而增大,随岩石的绝对渗透系数降低而增大; 在渗透压差增大过程测得的拟启动压力梯度大于降低过程的拟启动压力梯度,这些都与理论分析结果相吻合。实例说明拟启动压力梯度推算"三次平均法"较为合理,易于推广使用。这为通过室内试验确定工程岩体启动渗流压力梯度的大小,提出了一种新的思路。     

岩石破裂过程THMD耦合数值模型研究

从岩石的细观非均匀性特点出发,应用损伤力学、热力学和渗流力学理论,建立了岩体热(温度)-水(渗流)-岩(应力)-损伤耦合数值模型(THMD model),把岩石(体)THM耦合问题的研究从应力状态分析深入到损伤、破坏过程分析之中。探讨了THM耦合作用下岩石材料的细观结构损伤及其诱发的材料力学性能演化机制,并运用所提出方法计算温度-渗流-应力耦合作用下井筒近场围岩的稳定性,模拟得到的岩体破坏过程、应力分布、AE特性及渗流特性变化与现场标定结果有着一致的规律性,初步证明了该数值模型的合理性和有效性。THMD模型以简单的数值模型表征了岩石(体)中热、水、岩及损伤之间复杂的作用关系,为从细观损伤演化揭示宏观岩体温度-渗流-应力耦合破坏机制提供了一种新的数值分析方法。     

裂隙岩体渗透系数确定方法研究

裂隙岩体渗透系数以及渗透主方向的确定对研究岩体渗透性大小及各向异性具有重要意义。高放废物地质处置库介质岩体的渗透性能将直接影响其使用安全性。本文运用离散裂隙网络模拟的方法对我国高放废物处置库甘肃北山预选区3#钻孔附近裂隙岩体进行了渗透性质分析。通过对3#钻孔1715～1780m段压水试验数据的反演,标定了离散裂隙网络渗流模型中的裂隙渗透参数(导水系数T)。利用标定的离散裂隙网络模型对场区裂隙岩体进行了渗流模拟,确定了该区域裂隙岩体的渗流表征单元体(REV)的尺寸大小以及渗透主值和主渗透方向。运用离散裂隙网络模型计算得出的渗透主值的几何均值与现场压水试验计算结果较接近,证明了计算结果的有效性。