单轴压缩下岩石蠕变失稳破坏过程数值模拟

在岩石破裂过程分析（RFPA2D）系统的基础上,考虑岩石损伤过程的时间因素影响,引入岩石细观单元蠕变本构方程,建立了考虑流变效应的岩石破裂过程RFPA2D数值模型。应用该模型模拟了恒定荷载作用下岩石的蠕变破坏过程,得到了岩石蠕变破裂的3个典型阶段：初始蠕变阶段、稳定蠕变阶段和加速蠕变阶段,模拟结果同实验室试验所观察到的现象十分吻合。这表明考虑流变效应的RFPA2D数值模型适用于模拟岩石的蠕变破坏这一复杂的、非线性演化问题。此外,数值模拟还揭示了岩石的宏观蠕变破坏实质上是细观层次上单元损伤累计的结果,这些结论对岩石工程的长期稳定性研究具有重要的理论指导和实践意义。     

A new approach to time-load-deformation-stress hypersurface of rocks to stability analysis of underground openings

The most important developments in rock engineering are about time-dependent deformation behavior of rocks under different loads. Many studies have been done for the purpose of identifying mathematically time-load-deformation (TLD) characteristics of the rocks. These studies have made an important contribution to the research on the stability of constructions built in rock masses, and rock material is the main part of the rock mass in which the engineering constructions. When considered from this point of view, the time-dependent deformation behavior of the rocks under different loads is important to determine unstable conditions of the rock constructions in the long term. Researches in rock masses use surfaces based on TLD data. On the other hand, the strength of the rock is also part of these analyzes. The new model developed in this study has four variables such as time, load, deformation, and strength. Therefore, TLD surfaces developed for time-load-deformation has been associated with another variable and three-component (TLD) surfaces eventually transformed into four-component (time-load-deformation-strength; TLDS) hypersurfaces. Hypersurfaces, which illustrate new TLDS behaviors of the rocks, developed in underground openings in different rock constructions in different areas. It is thought that the TLDS hypersurfaces will especially be contributed to the numerical modeling studies of rock construction analysis.     

Visco-Plastic Behaviour around Advancing Tunnels in Squeezing Rock

Summary  The visco-plastic behaviour of rocks plays a relevant role in the tunnelling works, especially for deep tunnels subjected to large initial stresses for which squeezing conditions may develop. A rheological model is discussed that accounts for visco-elastic (primary) and visco-plastic (secondary) contributions to rock creep. The effects of tertiary creep are included in the model by way of a gradual mechanical damage governed by the cumulated visco-plastic strains. The parameters of the intact rock are first identified based on laboratory test results presented in the literature. Then, after scaling them to those of the rock mass, the potential applicability of the model is tested through axisymmetric and plane strain finite element analyses of the full face excavation of a deep circular tunnel. The results are discussed with particular reference to the short term redistribution of stresses around the opening and to its convergence. The analyses show the relevant influence of tertiary creep on the tunnel closure. In addition, those based on an axisymmetric scheme turn out to be crucial for the correct long term prediction of the interaction between the rock mass and the supporting structure of the opening.     

不同渗透水压下完整泥页岩剪切−渗流特性研究

为了探索高压水力浸润带和消落带岩体在压剪荷载与流体入渗双因素耦合作用下剪切渗流特性的衍化规律,利用自主研发的一套新型岩石剪切−渗流耦合试验系统,对饱水泥页岩进行了常法向荷载条件下不同渗透水压的剪切−渗流耦合试验和剪切蠕变−渗流耦合试验。试验结果表明：（1）随着渗透水压力的增加,饱水泥页岩剪切强度峰值、法向变形峰值以及剪切蠕变破坏强度均有所下降,说明渗透水压力对岩样力学强度具有损伤效果。（2）在剪切−渗流耦合试验过程中,岩样剪应力与法向变形在线弹性变化的末期会出现明显的上下波动现象,并伴有水流流出,剪应力和法向变形的突变点在时间上具有一致性。（3）在剪切蠕变−渗流耦合试验过程中,水流渗出速率与渗透水压力大小呈正相关,随着剪切荷载施加等级的提高,岩样蠕变变形量增大,单位时间内累计渗出水量亦有所提升。     

深层膏质泥岩蠕变特性及非线性蠕变模型研究

泥岩作为油气储层常见复杂介质,在深部高温、高压环境下蠕变力学特性异常复杂,是引起套管损伤破坏的重要因素。以深部油气藏工程含膏质泥岩为研究对象,首先开展了高温为130 ℃、高围压为30 MPa、不同偏应力水平下多试样、单级加载三轴蠕变试验。该泥岩呈显著的时效力学特性,蠕变应力阀值较低,应力和持时对蠕变特性存在显著影响,低应力、长时间作用下泥岩亦呈现明显的稳态蠕变和加速蠕变破坏,且加速蠕变起始时间随应力增加呈指数降低关系。其次探讨了泥岩加速蠕变和强度损伤特性,提出了蠕变损伤起始时间概念,认为泥岩内部蠕变损伤变量可用指数函数予以描述。最后,基于蠕变损伤变量和起始时间,构建考虑泥岩加速蠕变的非线性改进Burgers蠕变模型,对蠕变参数开展辨识和分析,所选模型可准确地对深层膏质泥岩蠕变特性进行描述。研究成果旨在为深部泥岩油气藏套管工程长期稳定分析及安全评价提供可靠的依据。     

孔隙水压力对锯齿状结构面剪切蠕变特性的影响

为探究孔隙水压对岩体结构面剪切蠕变特性的影响,自主研制了结构面一体化制作模具和多功能剪切流变仪,开展了孔隙水压力下锯齿状结构面的剪切蠕变试验,分析了孔隙水压对结构面蠕变变形、蠕变速率和长期强度的影响。试验结果表明：不同孔隙水压力下的结构面先后经历了瞬时变形阶段、减速蠕变阶段和稳定蠕变阶段,并且孔隙水压力的增大促进了结构面非线性特征的发展;随着孔隙水压力的增大,结构面瞬时位移、蠕变位移和稳态蠕变速率逐渐增大,而蠕变时长、破坏应力和长期强度均呈现明显降低的趋势。根据试验结果,考虑孔隙水压力对模型参数的影响,将蠕变模型中的瞬时剪切模量、黏性剪切模量以及黏性系数替换为孔隙水压力的函数,构建了能够反映孔隙水压力影响的结构面蠕变模型,并对模型参数进行辨识,将试验曲线和理论模型曲线进行对比,验证了模型的正确性和适用性。研究成果对富水区岩体长期稳定性分析提供一定的理论指导。     

坝基碎屑岩三轴蠕变特性及长期强度试验研究

基于物理和常规变形特性分析,认为某水电站坝基碎屑岩力学特性异常复杂,故采用岩石三轴伺服仪开展了系列的蠕变力学特性试验研究。首先,探讨了轴向、侧向及体积蠕变特性和速率变化规律;其次,分析了蠕变对偏应力-应变特性影响并开展了破坏岩样微细观电镜扫描试验;最后,在采用等时曲线簇法确定长期强度的基础上,以实际延性扩容为依据,认为岩石侧向体积扩容速率大于轴向压缩速率的临界点为快速蠕变破坏的标志,提出确定长期强度的新方法。结果表明,碎屑岩表现出显著的蠕变特性,蠕变曲线主要分为初始衰减和稳态蠕变两阶段,且最后一级应力施加后呈现加速蠕变现象;应力增加导致蠕变变形加剧,最终破坏表现出轴向压缩变形过大、体积延性扩容明显、稳态蠕变速率较大等特点,且蠕变速率与应力符合指数函数关系。岩样长期强度与三向稳态蠕变速率交点和侧向体积扩容应力阀值基本一致,为常规强度的54%～80%。试验结果旨在为相关岩石工程长期稳定分析及蠕变模型构建提供可靠的依据。     

Creep Damage Characteristics of Soft Rock under Disturbance Loads

This article focuses on the process of rock creep damage and micro-damage evolution properties of gray green mudstone under impacting disturbance load conditions for the first time using the real time computerized tomography (CT) testing technique. The results indicate that axial load comes into limit strength neighborhood, rock micro-crack links into larger crack, creep rate increases in a short time, larger plastic deformation happens; this is called disturbance accelerating creep stage. When rock is within limit strength neighborhood, there occurs creep micro-damage under smaller disturbance load. When disturbance load is larger, rock directly enters into disturbance accelerating creep stage, failure occurs instantaneously. On the basis of experimental research, the CT scanning method was used to describe the creep micro-damage of soft rock, also helpful in the prediction of roadways' service life and evaluation of geotechnicai engineering stability.     

冻融循环作用下砂岩蠕变特性及损伤模型研究

青藏高原高寒地区岩体长期稳定性受冻融作用影响显著,有必要开展冻融岩石的时效性特征研究。为探讨砂岩在冻融循环作用下的蠕变劣化特性,基于不同冻融循环次数后石英砂岩及红砂岩单轴蠕变试验结果,深入分析了冻融循环对砂岩各蠕变阶段的影响特征。研究表明,在非屈服应力条件下,试样在衰减蠕变阶段的蠕变时长随着冻融循环次数的增加而明显减小,对应蠕变量及蠕变速率增大;在屈服应力条件下,试样进入加速蠕变阶段的应力阈值随着冻融循环次数的增加而逐渐降低,对应从稳定蠕变到加速破坏所经历的时间更短,破坏时累计的应变增量更大;在长期荷载作用下,试样的宏观破裂形态随循环次数的增加逐步由单一斜剪切破坏模式向共轭断面拉剪复合型破坏模式演化。根据试验结果,提出了具有冻融与长期受荷劣化特征的非定常性黏弹性系数损伤演化方程,将其引入西原模型构建了考虑冻融损伤的砂岩蠕变本构模型。利用冻融后红砂岩蠕变试验数据对模型进行了参数辨识与比较分析,验证了模型的正确性及适用性。通过对模型参数进行拟合分析,揭示了黏弹性冻融损伤系数随冻融循环次数的变化规律,表明了长期受荷损伤参数具有控制加速蠕变幅度的重要作用。研究结果对于高寒山区岩体长期稳定性评价具有一定意义。     

一种新的岩石非线性黏弹塑性流变模型

借鉴经典元件组合模型的建模思路,将含分数阶微积分的软体元件与弹簧元件串联,结合一个幂函数黏塑性体,提出一种新的四元件非线性黏弹塑性流变模型,并给出该模型的本构方程和蠕变方程,得到在不同应力条件下的蠕变曲线。可以发现,岩石稳定蠕变阶段的非线性渐变过程和加速蠕变阶段蠕变速率的快慢程度可通过调整蠕变参数进行有效地模拟。在较低应力水平时,模型能够有效地刻画岩石的初始蠕变和稳定蠕变;当应力水平超过岩石的长期强度时,能够反映加速蠕变特性。利用该模型对试验数据拟合的结果表明,含有软体元件和幂函数黏塑性体的非线性流变模型能够有效地描述岩石的蠕变特性,减少组合模型中的元件个数和参数数量。     

The Time-Dependent Reduction of Sliding Cohesion due to Rock Bridges Along Discontinuities: A Fracture Mechanics Approach

Summary In this paper, a fracture mechanics model is developed to illustrate the importance of time-dependence for brittle fractured rock. In particular a model is developed for the time-dependent degradation of rock joint cohesion. Degradation of joint cohesion is modeled as the time-dependent breaking of intact patches or rock bridges along the joint surface. A fracture mechanics model is developed utilizing subcritical crack growth, which results in a closed-form solution for joint cohesion as a function of time. As an example, a rock block containing rock bridges subjected to plane sliding is analyzed. The cohesion is found to continually decrease, at first slowly and then more rapidly. At a particular value of time the cohesion reduces to value that results in slope instability. A second example is given where variations in some of the material parameters are assumed. A probabilistic slope analysis is conducted, and the probability of failure as a function of time is predicted. The probability of failure is found to increase with time, from an initial value of 5% to a value at 100 years of over 40%. These examples show the importance of being able to predict the time-dependent behavior of a rock mass containing discontinuities, even for relatively short-term rock structures. Received November 5, 2001; accepted July 24, 2002; Published online November 19, 2002     

Creep Failure of Roof Stratum Above Mined-Out Area

By taking into account the rheological behavior of the rock mass, the creep failure of a roof stratum seated on pillars in mined-out area is analyzed through a newly developed visco-elastic model. The time-dependent deflection of the roof stratum is obtained by numerical inversion of Laplace transform. The study shows that when creep properties of both the pillars and roof stratum are considered, the expected deflection in the roof stratum increases with time. Consequently, the roof would fail when the critical tensile stress is reached as the result of the increased deflection. To demonstrate the present analytical procedure, the failure time of roof stratum of the Xingtai Gypsum Mine in China was estimated, and the results obtained agreed with the observation. The case study indicates that the analytic approach provides a new way to assess the potential impact of the time-dependence of the roof stratum deformation and is useful in predicting its stability above a mined-out area.     

崩落法开采引起的岩层移动时效性研究

崩落法开采的金属矿山往往会伴随着一系列的地质灾害现象。为保证矿区安全生产,开展崩落法开采引起的岩层移动的时效性研究具有重要意义。以程潮铁矿西区下盘为研究对象,通过将地表10多年GPS监测数据的整理分析,并与现场破坏调查结果和工程地质条件相结合,进而探究不同分区下岩层移动的时效行为。研究结果表明：岩层移动的时效行为与其破坏过程有着密切的关系,不同分区下的岩层移动的时效行为是不同的,可分为初始变形、渐进变形、加速变形和残余变形共4个阶段,分别对应着稳定状态、临界状态、失稳状态以及采矿结束后的蠕变状态;初始变形阶段对应着岩体的初始蠕变过程,渐进变形阶段反映了岩体抵抗自身变形的过程,加速变形阶段与深部破坏面的形成和强烈的应力释放有关;崩落碎石在采矿作业停止后失去了流动空间,在岩体变形挤压下会对围岩提供支撑力进而限制了岩层移动的进一步发展;残余变形时间由岩体的蠕变特性和崩落碎石的压密过程所控制,倾倒滑移区因需要经历一个额外的碎石压密过程而导致残余变形时间更长。     

张开穿透型单裂隙岩体三轴卸荷蠕变特性试验

高应力条件下较多岩体工程在开挖卸荷过程中表现出显著的时效变形特征。为研究裂隙岩体在卸荷状态下的蠕变特征,以锦屏I级水电站大理岩为原样制备模型试样,开展了恒轴压分级卸围压三轴卸荷蠕变试验。试验结果表明：试件在破坏时对应应力差最小的是倾角为30°裂隙试样,其次为倾角为60°裂隙试样,倾角为90°裂隙试样最大。从破坏形式来看,完整试件与倾角为90°裂隙试件均呈整体剪切破坏模式,倾角为30°和60°裂隙试件均从裂纹尖端扩展至破坏。变形特征方面,均可采用Burgers模型对各裂隙试样不含加速蠕变阶段的蠕变曲线进行拟合,试样在不同裂隙类型和应力水平下的变形特点则通过参数数值加以区分。该结论与Lemaitre应变等效原理和Sidoroff能量等价原理中有关损伤材料和无损材料间相关关系的基本观点一致。基于此,提出了裂隙岩体损伤蠕变模型,该模型建立了完整岩石与裂隙岩体间的相关关系,对裂隙岩体时效变形特征的进一步研究具有较好的参考价值。     

A new rock mass failure criterion for biaxial loading conditions

To simulate brittle rocks, a mixture of glastone, sand and water was used as a model material. Thin galvanized sheets of thickness 0.254 mm were used to create joints in blocks made out of the model material. To investigate the failure modes and strength, both the intact material blocks as well as jointed model material blocks of size 35.6 × 17.8 × 2.5 cm having different joint geometry configurations were subjected to uniaxial and biaxial compressive loadings. A new intact rock failure criterion is proposed at the 3-D level. This criterion is validated for biaxial loading through laboratory experimental results obtained on intact model material blocks. Results obtained from both the intact and jointed model material blocks are used to develop a strongly non-linear new rock mass failure criterion for biaxial loading. In this failure criterion, the fracture tensor component is used to incorporate the directional effect of fracture geometry system on jointed block strength. The failure criterion shows the important role, the intermediate principal stress plays on rock mass strength.     

预制节理岩体试件强度及破坏模式的试验研究

采用相似材料模型试验对不同节理倾角、节理贯通度、节理组数、载荷应变率、试件长径比、节理充填物厚度及类型等7种工况下的预制节理岩体在单轴压缩下的峰值强度及破坏模式进行了研究。结果表明：节理岩体的破坏模式及峰值强度与节理构造形态密切相关。贯通节理岩体将产生沿节理面的剪切破坏或穿切节理面破坏,且与第1种破坏模式对应的岩体峰值强度更低。非贯通节理岩体的强度介于完整岩体和贯通节理岩体之间。随着平行节理组数的增加,岩体峰值强度逐渐下降。随着载荷应变率的增加,岩体峰值强度逐渐增大,相应地试件的破坏模式也变得更加复杂。试件长径比基本没有改变其破坏模式,完整试件仍主要是以张拉破坏为主,而节理试件仍以剪切破坏为主。随着长径比增加,试件峰值强度逐渐增大。随着节理充填物厚度增加,试件峰值强度降低。不同节理填充物对试件峰值强度也有一定影响。     

Deep-seated rockslide-avalanches preceded by mass rock creep of sedimentary rocks in the Akaishi Mountains, central Japan

Seven large rockslide-avalanches of sedimentary rocks are known in Japan. Almost all of these major landslides were preceded by gravitational deformation of rocks (mass rock creep, MRC), as inferred from geologic and geomorphic investigations of five rockslide-avalanches in the Akaishi Mountains. The MRC that preceded the rockslide-avalanches in the Akaishi Mountains was characterized by a slow but steady downslope bowing of steeply dipping foliations, which accompanied intensive deformation and fragmentation of the rock mass by shearing along foliations. This deformation and fragmentation of the rock mass provides a basic cause for the occurrence of rockslide-avalanches, which occur when a creeping rock mass has lost its support from the lower part of a slope by stream erosion. This type of MRC continues for a long time after a part of the creeping area has slid and results in longterm generation of debris by the landslide sear of the rockslide-avalanche.     

缓倾斜层状岩体单轴压缩力学行为的颗粒流数值模拟

针对不同层理面强度的缓倾斜层状岩体在单轴压缩试验中产生不同破坏形式的问题,以室内原岩单轴压缩试验结果为依据,采用颗粒流程序建立了缓倾斜层状岩体单轴压缩数值模型,研究了不同层理面强度条件下的缓倾斜层状岩体强度及破坏形式变化特征,并分析了不同工况时缓倾斜层状岩体微裂纹发育及演化规律和细观颗粒的位移演化规律,研究表明:当层理面强度远小于层理面间完整岩体强度时,层理面在一定程度上降低了层状岩体的整体强度,宏观破断面为沿层理面和贯穿层理面的折线型破断面;当层理面强度与层理面间完整岩体强度相近时,宏观破断面主要为光滑单斜面;当层理面强度远大于层理面间完整岩体强度时,层状岩体的强度由层理面间完整岩体的强度决定,宏观破断面主要为X型共轭破坏面。     

冻融循环下花岗岩剪切蠕变试验与模型研究

为探讨冻融对寒区工程岩石剪切蠕变特性的影响,以吉林省辉白隧道花岗岩为研究对象,对经历不同冻融循环次数的试样开展细观特征分析和剪切蠕变试验。试验结果表明：（1）随着冻融次数的增加,试样裂隙、孔隙不断扩展,岩石表面损伤现象愈发明显;（2）试样主要以中小孔隙为主,孔隙度随着冻融次数的增加呈非线性增长趋势;（3）随着冻融循环次数增加,蠕变变形量和蠕变速率逐渐增大,而蠕变时长、破坏应力和长期强度均呈现明显降低趋势。根据试验结果,进行冻融岩石非定常蠕变参数的表达,提出了冻融岩石损伤黏性元件,构建了花岗岩冻融剪切蠕变本构模型。将蠕变试验曲线和理论模型拟合曲线进行对比,验证了模型的正确性和适用性。通过对蠕变参数进行敏感性分析,研究了其对花岗岩蠕变变形的影响,并给出了蠕变参数随冻融循环次数的变化规律。该研究结果对于寒区岩体工程长期稳定性评价具有指导意义。     

万福煤矿不同含水率砂岩蠕变力学特性试验研究

为研究深部巷道围岩在地下水作用下的长期蠕变力学特性,采用自主研制的深部软岩五联流变试验系统,开展不同含水率(0%、0.8%、1.6%、2.4%、3.3%)下砂岩吸水软化单轴压缩试验及单轴蠕变试验。通过试验结果研究表明：砂岩的单轴抗压强度、弹性模量和蠕变破坏应力与含水率呈指数下降关系,蠕变破坏应力与单轴抗压强度的比值在0.76～0.84之间;砂岩衰减蠕变阶段时间随着含水率的增加而减少,随应力水平的增加而增加。径向应变比轴向应变先进入稳态蠕变阶段,破坏应力下径向应变的加速蠕变阶段开始时间要先于轴向应变;基于稳态蠕变速率曲线确定了砂岩的长期强度,径向稳态蠕变速率确定的值略小于轴向,长期强度与含水率之间满足负指数关系;将蠕变试验中径向应变与轴向应变之比定义为μ_c,提出了基于μ_c值的岩石长期强度确定方法且μ_c值与含水率无关,对于本次砂岩样品可以认为μ_c值大于0.3时样品会在一定时间内发生加速蠕变破坏;随着含水率的增加,样品破坏形态由单斜面剪切破坏逐渐演变至X状共轭斜面剪切破坏。研究结果为地下水作用下巷道长期稳...