Numerical simulation of a jointed rock block mechanical behavior adjacent to an underground excavation and comparison with physical model test results

Mechanical behavior of a jointed rock mass with non-persistent joints located adjacent to a free surface on the wall of an excavation was simulated under without and with support stress on the free surface using approximately 0.5 m cubical synthetic jointed rock blocks having 9 non-persistent joints of length 0.5 m, width 0.1 m and a certain orientation arranged in an en echelon and a symmetrical pattern using PFC^3D software package. The joint orientation was changed from one block to another to study the effect of joint orientation on strength, deformability and failure modes of the jointed blocks. First the micro-mechanical parameters of the PFC^3D model were calibrated using the macro mechanical properties of the synthetic intact standard cylindrical specimens and macro mechanical properties of a limited number of physical experiments performed on synthetic jointed rock blocks of approximately 0.5 m cubes. Under no support stress, the synthetic jointed rock blocks exhibited the same three failure modes: (a) intact rock failure, (b) step-path failure and (c) planar failure under both physical experiments and numerical simulations for different orientations. The jointed blocks which failed under intact rock failure mode and planar or step-path failure mode produced high and low jointed block strengths, respectively. Three phases of convergence of free surface were discovered. The joint orientation and support stress played important roles on convergence magnitude. The average increment of jointed block strength turned out to be about 10, 7.9 and 6.6 times the support stress when support stresses of 0.06 MPa, 0.20 MPa and 0.40 MPa were applied, respectively. The modeling results offer some guideline in support design for underground excavations.     

Advances in statistical mechanics of rock masses and its engineering applications

To efficiently link the continuum mechanics for rocks with the structural statistics of rock masses,a theoretical and methodological system called the statistical mechanics of rock masses(SMRM)was developed in the past three decades.In SMRM,equivalent continuum models of stressestrain relationship,strength and failure probability for jointed rock masses were established,which were based on the geometric probability models characterising the rock mass structure.This follows the statistical physics,the continuum mechanics,the fracture mechanics and the weakest link hypothesis.A general constitutive model and complete stressestrain models under compressive and shear conditions were also developed as the derivatives of the SMRM theory.An SMRM calculation system was then developed to provide fast and precise solutions for parameter estimations of rock masses,such as full-direction rock quality designation(RQD),elastic modulus,Coulomb compressive strength,rock mass quality rating,and Poisson’s ratio and shear strength.The constitutive equations involved in SMRM were integrated into a FLAC3D based numerical module to apply for engineering rock masses.It is also capable of analysing the complete deformation of rock masses and active reinforcement of engineering rock masses.Examples of engineering applications of SMRM were presented,including a rock mass at QBT hydropower station in northwestern China,a dam slope of Zongo II hydropower station in D.R.Congo,an open-pit mine in Dexing,China,an underground powerhouse of Jinping I hydropower station in southwestern China,and a typical circular tunnel in Lanzhou-Chongqing railway,China.These applications verified the reliability of the SMRM and demonstrated its applicability to broad engineering issues associated with jointed rock masses.     

断裂力学和损伤力学在混凝土中的应用

叙述了断裂力学和损伤力学的形成、应用及发展过程，并将断裂力学和损伤力学引入到混凝土的研究中，探讨了断裂力学和损伤力学在混凝土中的应用。     

A smoke model and its application for smoke management in an underground mass transit station

This paper discusses the development of a smoke model for CFD. The model evaluates smoke visibility based on line of sight. Using a compartment fire, the deficiency in determining visibility by the conventional surface-based approach is first demonstrated. Smoke management in an underground rail station is investigated using the smoke model. For a medium growth rate fire, the results show that the platform is blocked by smoke within 2–3 min. On the mezzanine, the designed smoke exhaust controls the smoke only for a limited time of less than 4 min. The variations of smoke obscuration are quantified at three locations, which are used to start the tunnel ventilation at 4 min. This can be related to a video-based smoke detection. The smoke model would be useful in tenability, egress and other life safety assessments. Future development of the model includes local lighting effects and experimental validation.     

斜坡道节理岩体损伤力学分析

利用损伤力学分析节理岩体的力学特性,对于岩体的不连续性研究从统计上模拟结构面分布状态的方法,对悦洋银矿（武平紫金）230斜坡道岩体节理损伤分析,求得斜坡道围岩的变形状况,为支护手段与参数分析提供理论依据。     

基于Weibull分布的岩石损伤软化模型及其修正方法研究

利用岩石微元强度服从Weibull随机分布的特点，引进能合理描述岩石微元强度的参量，基于岩石三轴应力．应变试验曲线，建立了反映岩石破裂全过程的损伤软化本构模型。在此基础上，探讨了基于Weibull分布的岩石损伤软化模型参数与围压的关系，并结合模型参数对该模型的影响规律以及岩石破裂过程全应力．应变试验曲线的特点，对其参数进行了合理修正，从而建立了更加符合实际的岩石损伤软化本构模型，并与试验结果及前人研究结果进行了对比分析。分析结果显示了该模犁的合理性，表明该模型具有广泛的工程应用前景。     

硬脆性岩石热–力–损伤本构模型及其初步运用

热力作用下岩石本构行为的研究对深部资源开采、地热资源开发、深埋长大地下工程设施建设等岩石工程问题具有重要意义。基于现有岩石损伤劣化统计本构模型研究,引入三参量Weibull分布、热损伤、Drucker-Prager屈服准则和残余强度修正系数,经过严密的数学推导,建立了考虑岩石起裂应力的热–力–损伤本构模型,并确定了其参数表达式。采用围压25 MPa、不同温度(20℃,60℃,130℃)条件下黑云母花岗岩三轴压缩试验结果对模型进行了验证。结果表明:模型理论曲线和试验曲线具有较高的吻合度,能够客观地反映岩石热力破裂应力应变全过程和残余强度,且参数物理意义明确。最后,将本构模型嵌入FLAC数值分析软件,对瑞典APSE隧道开挖过程的热力响应进行了数值分析,计算结果较好地反映了隧道现场围岩的破坏规律。     

巷道裂隙岩体的损伤参数辨识

基于位移反分析理论及几何损伤理论 ,对巷道裂隙岩体的损伤参数进行了辨识。根据岩体中裂隙组数的不同 ,对于含一组裂隙、两组裂隙及多组裂隙情况下损伤参数辨识可靠性问题进行了分析 ,给出了精确辨识的参数组合。针对初值选取对某些参数的辨识精度影响较大的特点 ,采用蒙特卡罗优化法进行初值的优选 ,计算结果显示 ,优选初值下的辨识可靠性有很大提高     

Support design of underground openings in an asphaltite mine

A detailed study to design support systems for underground openings was carried out in this paper. Asphaltite, an energy source for thermal power plants, will be produced from the Uckardesler Asphaltite Vein in southwestern Turkey. This mine will be the first application of underground asphaltite production in the world. Two main geological formations, the Gercus formation and the Midyat formation, form the geological structure of the study area. The Gercus formation is conglomerate, sandstone, mudstone, clay, detritus, such as jibs, and the asphaltite vein located in the formation. The Midyat formation is mostly limestone. The cut and fill stoping method was selected for this mine in accordance with the geometry of the vein, topographic specifications, and expected annual production rates. Asphaltite will be excavated from the underground mine by continuous miners. The shapes and sizes of underground opening, which will include incline and ramp galleries, shafts, crosscut (X/C) galleries, main level galleries, and production galleries, were designed based on production method and rate. Rock mass classification systems and the finite element numerical method were applied to design support systems for the proposed underground openings. In this study, the engineering properties of rock masses were defined from field and laboratory studies for each formation and for asphaltite. Support systems for each underground opening were designed based on the suggestions of the rock mass rating (RMR) system and the Q system of rock mass classification. The suggested support systems were subjected to numerical analysis in order to evaluate their predicted performance. The results of the numerical modeling were analyzed to select the proper support system for each underground opening.     

Design methodology for the safety of underground rock engineering

In order to optimise the safety of underground rock engineering construction and the long-term security of the resultant facilities, it is necessary to have a knowledge of the likely hazards. These risks or hazards fall into the four categories of known beforehand and relatively easily addressed, known beforehand and not easily addressed, not known beforehand and relatively easily addressed, and not known beforehand and not easily addressed. This paper describes how these four types of hazard can be incorporated into a design methodology approach, including the process by which the relevant mechanical rock mass parameters can be recognised for modelling and hence predictive purposes. In particular, there is emphasis on the fact that information and judgement are the keys to safety——whether the hazards are known or unknown before construction proceeds.     

钢桥面沥青混合料铺装体系疲劳特性的损伤力学分析

用损伤力学原理及方法,从力学近似法角度分析了单纯的沥青混合料铺装层矩形截面梁疲劳损伤特性,推导出梁的应变场和疲劳寿命预测公式。按抗弯刚度等效简化原则,将疲劳试验复合梁模型中的实际桥面用钢板简化为沥青混合料铺装层叠加到下面的沥青混合料铺装层上,共同组成准单纯的沥青混合料铺装层矩形截面梁,应用该原理及方法推导出梁底缘的应变场,以南京长江第二大桥钢桥面环氧沥青混凝土铺装体系复合梁疲劳试验为例,进一步推导出复合梁的疲劳寿命预测公式。通过实例分析,表明损伤力学原理及方法可用于分析钢桥面沥青混合料铺装体系疲劳特性,其疲劳寿命预测结果是较为精确的,它的实际应用还需给出相应的修正,此外指出了环氧沥青混凝土铺装具有很好的抗疲劳性能。     

非连续变形分析（DDA）法及在岩石力学中的应用

指出非连续变形分析（DDA）方法是近年来发展起来的一种分析不连续介质力学的岩土工程数值模拟方法,根据相关文献,叙述了DDA法的基本理论和求解方法,介绍了DDA法研究现状、在岩石力学及相关领域的研究和发展现状,并对今后的发展方向提出了一些看法。     

结构力学计算机应用教学的实践与认识

计算机应用对结构力这有巨大的影响,本介绍了为开展结构力学计算机应用所作的课程建设和程序设计等教学实践情况,谈了对程序设计教学的深层次认识。     

川东北碳酸盐岩酸化损伤及力学特性试验研究

通过岩芯静态酸蚀试验并结合矿物微观组构分析和岩石力学特性试验,从不同尺度和性质研究了酸液对碳酸盐岩储层岩石力学特性损伤问题及其规律,并通过压裂室内模拟试验研究了裂缝起裂和扩展演化规律以及酸液化学作用对体积缝的影响。该研究有助于指导现场储层酸压改造设计及优化技术参数,对于提高碳酸盐岩储层深度酸压增产改造技术具有重要的工程意义。试验结果表明:酸液对碳酸盐岩试样主要以表面溶蚀为主,微细观结构形成了溶蚀缝洞和微裂隙,矿物含量方解石由73.43%减至47.51%,方解石含量高且易酸化,属可压性较高储层;酸液对岩石物理力学特性劣化衰减具有明显的时间效应,酸岩反应后试样纵波波速迅速降低,岩石单轴抗压强度和弹性模量均随酸化时间增长而降低,破坏模式仍呈现拉伸劈裂破坏,但破坏方式有脆性向延性转化的趋势;碳酸盐岩水力压裂和酸化压裂的泵注压力随时间演化和声发射特征具有一定的相似性,但酸压裂缝更为复杂,裂缝表现出粗糙的溶蚀孔缝,且酸压起裂泵压明显小于水压起裂泵压。     

上海地区地下工程专用混凝土的应用研究

耐久性混凝土的胶凝材料用量少,抗裂性高减少了后期修补费用,既满足耐久性要求,又兼顾绿色化。随着上海轨道交通和隧道工程的迅速发展,地下工程混凝土对耐久性的要求越来越高。本文简述了聚羧酸类外加剂配制的耐久性混凝土在上海地区地下工程的应用情况、存在的问题及解决方法。     

Cost optimization of the underground gas storage

The paper presents the cost optimization of an underground gas storage (UGS), designed from lined rock caverns (LRC). The optimization is performed by the non-linear programming (NLP) approach. For this purpose, the NLP optimization model OPTUGS was developed. The model comprises the cost objective function, which is subjected to geomechanical and design constraints. The geotechnical problem is proposed to be solved simultaneously. Geomechanical rock mass parameters are determined from geological conditions of a selected suitable UGS location and a special FE model is generated. The rock mass strength stability and safety of the system are then analyzed for various combinations between different design parameters like inner gas pressures, cavern depths, cavern diameters and cavern wall thickness. As a result, geomechanical constraints are approximated and put into the optimization model OPTUGS. This way, the optimization enables not only the obtaining of an optimal solution but also that the rock mass achieves sufficient strength stability and safety. The optimization is proposed to be performed for the phase of preliminary design. The numerical example at the end of the paper demonstrates the efficiency of the introduced optimization approach.     

露天煤矿冻岩边坡饱和砂岩冻融损伤试验与劣化模型研究

 高海拔多年冻土区露天煤矿岩质边坡常年处于冻融交替环境中,边坡浅部病害显著。为了分析边坡上岩石在冻融环境中的劣化规律,利用采集于木里地区露天矿边坡钻孔中的砂岩试样进行了室内饱和冻融循环试验,并建立了饱和岩石冻融劣化的理论模型。岩样冻融循环试验结果显示随着冻融循环次数的增大,饱和砂岩的微裂隙率逐渐增大,单轴和三轴抗压强度以及表示岩石质量的常见物理参数逐渐降低。基于岩石在冻融循环过程中的微裂隙变化,提出并推导了微裂隙扩展因子,理论建立了岩石强度随冻融循环变化的劣化模型和本构关系,利用劣化理论模型所计算的岩石强度与试验结果吻合较好。分析岩石微裂隙的变化规律,可以获得饱和砂岩在冻融循环环境中的劣化是由于岩石内部的微裂隙在水成冰相变过程中产生的巨大复合应力超过了岩石微裂隙开裂强度,而导致微裂隙逐渐失稳扩展,岩石整体性被削弱等结论。     

岩石的高温动态统计损伤本构模型研究

结合连续强度理论和随机统计分布假设,在常温统计损伤演化方程的基础之上引入温度影响因素,推导了大理岩的高温统计损伤演化方程;采用组合建模的方法,以损伤力学为基础,将统计损伤体引入到粘弹性本构模型中,构建了能够反映温度影响效应的大理岩高温动态统计损伤本构模型。利用带高温装置的分离式霍普金森压杆试验系统进行了大理岩在不同高温与不同加载速率共同作用下的动态力学试验,基于试验结果,确定大理岩高温动态统计损伤本构模型的参数,并对理论模型进行验证,拟合程度较好,可为岩石类脆性材料动态本构关系的进一步研究和工程应用提供参考依据。     

三轴多级荷载下盐岩声波声发射特征与损伤演化规律研究

 采用岩石声波、声发射一体化监测装置,系统地研究三轴多级循环荷载作用下盐岩超声波波速与声发射变化特征。结果表明：(1) 岩石的超声波波速和声发射活动与应力状态呈现出良好的一致性。加载阶段,超声波波速上升,声发射活跃,卸载阶段,超声波波速下降,声发射平静,应力级数越高,这一特征越显著。(2) 盐岩的声波、声发射特征与试验围压应力密切相关。围压水平越低,应力循环试验中岩石波速变化率越大,声发射事件数量越多;围压水平越高,岩石超声波波速变化率越小,声发射事件数量越少。五级应力荷载试验中,围压条件为5,10,15,20 MPa时盐岩的声发射事件数量分别为1 026,703,361和206个,显示了“围压致密效应”。(3) 分别应用卸载模量、裂隙密度和Felicity比表征盐岩的损伤演化。结论认为：盐岩的裂隙密度和Felicity比变化与岩体承载破坏特征较为一致,可以较好地反映盐岩的损伤破裂过程,而利用卸载模量表征盐岩损伤误差较大,这是由于盐岩特殊的黏塑性变形特征造成的。