地下石油储备库岩体力学参数研究

在工程施工巷道围岩基本特征分析和岩体质量级别确定的基础上,采用广义Hoek-Brown强度准则,估算了Ⅲ级岩体
的强度参数,并按Hoek(2006)的公式估算了变形参数;根据巷道的拱顶沉降和净空收敛变形监测,按正交试验设计原理进行了有
限元位移反演,获得了Ⅲ级岩体强度和变形参数。通过两者的对比发现:估算结果与反演结果基本一致,最终根据反演结果的岩
石材料常数mi值较准确,以及估算结果的岩体变形模量Em 值较准确的原则,确定了Ⅲ级岩体的强度参数和变形参数。      

广西石林概述

在广西,石林的景区(景点)分布广泛,类型多样,各具特色,具有一定的美学观赏价值和科学研究价值。按照《岩溶学词典》阐述,石林是由密集林立的锥柱状、锥状、塔状岩体组合而成的自然景观。一般认为是土壤水沿着质纯厚层的石灰岩表面及节理裂隙的溶蚀作用而使裂隙扩大,然后岩石又经剥落而形成,其岩体上部受到雨水的淋滤改造,便形成形态各异的石峰。由众多的石峰连成片即成石林。     

Hoek-Brown准则在岩石强度各向异性评价中的应用

完整岩石强度随非连续界面角度发生变化而变化,因此具有各向异性。修正的Hoek-Brown准则可以对岩石的强度各向异性特征进行合理预测。通过对沉积岩及变质岩两大岩类、共23组岩样单、三轴测试结果进行分析,获取相应强度各向异性参数K_β及R_c,结果表明:岩石各向异性强弱与原岩类型、压实和胶结等沉积成岩作用、微裂隙发育程度及变质作用等因素有关。对于结构完整的沉积岩石,煤岩的各向异性最强,其次为页岩,而砂岩、泥岩和灰岩的各向异性相对较低。变质岩中板理发育的板岩各向异性最强,片麻岩次之,片岩和大理岩的各向异性相对较低。K_min与R_c间满足幂指数关系,K₉₀/K_min与R_c间满足线性关系,建立了各向异性岩石K_min分类标准。最后利用Londe转换和σ_cβ预测效果验证了修正的Hoek-Brown准则方程具有较高预测精度,结果可靠,从而为岩石强度各向异性更深入研究提供参考和依据。      

广西晚元古代本洞和三防花岗岩类岩体Nd、Sr同位素特征

广西晚元古代本洞和三防花岗岩类岩体的εNd(T)平均值分别是-5.0±0.38(7)和-6.7±0.68(8)。εSr(T)变化很大。本洞岩体Nd模式年龄T_(DM)~(Nd)平均值为2120Ma。根据两个岩体在εSr(T)—εNd(T)和εNd(T)—T两个图上的分布特征,推断它们的成因类型基本相同,来源于同一岩浆库。该岩浆库是10亿年前由下地壳物质完全重熔产生,但是在演化过程中,本洞岩体中有少量亏损性地慢物质加入,三防岩体同化混染了大量沉积岩。以四堡群为代表的下地壳形成年龄大于2120Ma。岩浆期后自交代和气成热液作用导致岩石的Rb/Sr比增高,εSr(T)降低和Sm—Nd系统再次分异。     

基于损伤分区与统一强度理论的岩石本构模型

自然界中岩石内部均存在一定程度的损伤,损伤的持续演化过程对岩体的稳定性极为不利。为了研究岩石的损伤演化过程,将岩石分为未损伤部分、闭合裂隙部分与张开裂隙部分,采用统一强度理论与统计损伤理论分析岩石微元强度的分布,通过分析变形协调条件下各部分的应力-应变特征得到岩石的损伤本构模型与损伤演化模型,与巴东组紫红色泥岩三轴压缩试验结果对比验证后将模型应用于某反倾层状岩质边坡的破坏深度分析。分析结果表明:提出的损伤本构模型可以较好地模拟巴东组紫红色泥岩的三轴压缩应力-应变特性,提出的损伤演化模型可以较好地分析巴东组紫红色泥岩的损伤演化过程,且模型参数具有明确的物理意义;此外,根据基于损伤演化模型的反倾层状岩质边坡破坏深度修正模型计算得到的结果偏保守,用于岩土工程设计偏安全。      

桂阳台子上蚀变岩体型锡矿床地质特征及找矿意义

该矿床赋存于大义山复式岩体中侏罗纪三江口序列花岗岩最晚期次的介头单元中心部位.矿体呈似层状,中心部位隐伏,NE端长约500 m,宽400m,平均厚15.30 m,Sn平均品位0.5%;南西段长400 m,宽240 m,厚4～25 m,Sn平均品位0.7%.矿区有蚀变细粒花岗岩型和云英岩型两类锡矿.矿石矿物主要是锡石,次有黑钨矿、辉钼矿、铌钽铁锰矿等,脉石矿物主要是长石、云母、石英等.围岩蚀变发育,类型多样,其中云英岩化、黄玉化、萤石化和褐铁矿化是重要的找矿标志.岩浆上侵的前锋位置且多组节理、裂隙的交汇处,是有利的储矿空间.介头单元等晚期岩体的顶盖及其前锋部位,是寻找该类型锡矿的有利地段.     

渗流-应力耦合下侏罗系红砂岩力学及渗透特性试验研究

三峡库区广泛分布侏罗系红砂岩, 在水库运行期间红砂岩的渗流-应力耦合特性关乎库区内多数滑坡和岩质边坡的稳定性。借助岩石多场耦合三轴试验系统, 对三峡库区侏罗系红砂岩开展了不同围压、不同渗透压下的三轴压缩试验, 系统研究了红砂岩的三轴压缩力学特性和渗透率演化特征。研究结果表明: ①红砂岩的峰前应力-应变曲线可分为孔隙压密阶段、弹性变形阶段、微裂隙稳定发展阶段和非稳定发展阶段。红砂岩的力学参数与渗透压的关系呈负相关, 与围压呈正相关。②随着围压升高, 红砂岩的破坏模式由张拉破坏过渡到剪切破坏。③不同渗透压下, 渗透率曲线呈平稳发展→缓慢上升→快速上升3阶段演化规律; 不同围压下, 渗透率曲线先降低后升高。④从能量角度分析了渗透压和围压对岩石的作用, 验证了渗流对岩石的劣化效应以及围压对裂纹发展的抑制作用。本试验对鲜有报道的侏罗系红砂岩的强度、变形和渗透特性做了系统的研究, 对渗流-应力耦合课题有补充意义。其工况根据三峡库区边坡岩体的应力水平来确定, 试验结果对分析库区边坡稳定性具有指导意义。      

辽宁省三股流花岗岩地质特征及成因探讨

三股流花岗岩呈椭圆形出露在前震旦系结晶基底中。岩体中捕虏体甚多,接触交代作用不明显。花岗质岩石具似斑状结构,钾长石斑晶分布极不均匀。副矿物类型为榍石型。岩体的氧化系数小。岩石化学成分Al_2O_3/(Na_2O+K_2O+CaO′)为1.01,A.R.为2.51,(Na_2O+K_2O)/Al_2O_3为0.51,为钙碱性花岗岩。据岩体的岩石化学,矿物特征,以及岩体与岩石的稀土配分、锶同位素~(87)Sr/~(86)Sr初始值、δ~(34)S组成范围应属重熔型花岗岩。在岩体周边形成的金矿和金矿化点,显然其成矿与三股流岩体有关。     

高应力区砂岩加卸载条件下能量变化规律及损伤分析

根据高应力区砂岩三轴压缩试验和峰前卸围压试验的结果,分析了砂岩在不同应力路径下的能量变化规律。试验结果表明,相同围压下,峰前卸围压试验的各能量指标(总吸收能、弹性应变能、耗散能)均小于三轴压缩试验,能量变化特征与其初始应力路径密切相关,且随围压的增大而增大。峰前储存的弹性应变能比耗散能多,耗散能只在临近峰值点处才迅速增加。能量的耗散会导致岩石产生损伤,并且使岩性劣化、丧失强度,从能量角度定义的损伤变量,可以得出结论:开始卸荷低围压下的损伤变量大于高围压下,临近破坏时高围压下的损伤变量大于低围压下;卸围压使岩样束缚减小,加速了损伤的发展,岩样所受的应力状态愈趋不平衡。因此,基于能量的角度来表征岩石的损伤演化更符合实际。      

砂箱弥散试验尺寸效应及弥散度尺度效应

砂箱弥散试验结果的应用受弥散度尺度效应及砂箱尺寸效应限制。为导向性分析砂箱尺寸效应和尺度效应对弥散度影响及二者关系,以中、细砂构建孔隙含水层,采用尺寸为1.0 m(长)×0.4 m(宽)×0.6 m(高)、0.5 m(长)×0.2 m(宽)×0.3 m(高)的大、小尺寸比为2倍的砂箱各两个,开展NaCl示踪砂箱弥散试验,观测分析10、20、30和40 cm等4个尺度的弥散度。结果表明:①小砂箱弥散度大于大砂箱,具体为(4.26±0.94)cm(1.21±0.30)cm、(5.66±1.42)cm(1.66±0.42)cm、(4.33±1.32)cm(1.45±0.50)cm和(3.08±0.11)cm(2.81±0.03)cm;②以大砂箱为表征,弥散度尺度效应为0.045 7;③与大砂箱相比,尺寸效应使小砂箱的弥散度分别增大(2.51±0.39)倍、(2.41±0.50)倍、(1.99±0.57)倍和(0.10±0.05)倍;④尺寸效应(E_(size))和尺度(x)关系为E_(size)=0.153 2x-7.731 8。综上所述,砂箱尺寸越大,尺寸效应越小;尺度越大,尺寸效应越不明显。该研究为消除尺寸效应对砂箱试验测定土体弥散度影响,及实现砂箱尺度测得弥散度的野外尺度外推提供参考。     

Finite element analysis for blasting law of jointed rock mass

On the basis of Mises strength theory, rock models are built including vertical, horizontal and diagonal joints to simulate jointed rock mass under blasting load by using FEM. The dynamic procedures of jointed rock mass under blasting are quantified and the effective stress-time curves of typical elements are compared to analyze the barrier of joints to the stress wave. The blasting law was studied according to the process of computer simulation and the effect of blasting, and some suggestions were given for solving the problems of overbreak and underbreak.     

Finite element ana lysis for blasting law of jointed rock mass

On the basis of Mises strength theory, rock models are built including vertical, horizontal and diagonal joints to simulate jointed rock mass under blasting load by using FEM. The dynamic procedures of jointed rock mass under blasting are quantified and the effective stress-time curves of typical elements are compared to analyze the barrier of joints to the stress wave. The blasting law was studied according to the process of computer simulation and the effect of blasting, and some suggestions were given for solving the problems of overbreak and underbreak.     

A modified Hoek-Brown failure criterion considering the damage to reservoir bank slope rocks under water saturation-dehydration circulation

After water is impounded in a reservoir, rock mass in the hydro-fluctuation belt of the reservoir bank slope is subject to water saturationdehydration circulation (WSDC). To quantify the rate of change of rock mechanical properties, samples from the Longtan dam area were measured with uniaxial compression tests after different numbers (1, 5, 10, 15, and 20) of simulated WSDC cycles. Based on the curves derived from these tests, a modified Hoek- Brown failure criterion was proposed, in which a new parameter was introduced to model the cumulative damage to rocks after WSDC. A case of an engineering application was analyzed, and the results showed that the modified Hoek-Brown failure criterion is useful. Under similar WSDC-influenced engineering and geological conditions, rock mass strength parameters required for analysis and evaluation of rock slope stability can be estimated according to this modified Hoek-Brown failure criterion.     

Estimating the properties of weathered bedrock and pilerock interaction from the geological strength index

The effect of variable rock mass properties on pile-rock interaction poses a great challenge to the design of stabilizing piles and numerical analysis of pile-rock interaction. The paper presents a novel method to estimate the properties of weathered bedrock, which can be applied to routine design of landslide-stabilizing piles for collivial landslides. The Ercengyan landslide located in the Three Gorges Reservoir, China, is the area of interest for this study. A geological investigation and triaxial tests were conducted to estimate the basic parameters, including Geological Strength Index(GSI), uniaxial compressive strength σ_(ci) and Hoek-Brown constant m_i of intact bedrock in the study area. Hoek-Brown criterion was used to estimate mechanical properties of the weathered rock, including elastic modulus E_m, cohesion c, friction angle Φ, and normal ultimate lateral resistance p_(max). A parametric study was performed to evaluate the effect of parameterizations of GSI, σ_(ci) and m_i on the bedrock properties and p-y curves. The estimated rock mass properties were used with PLAXIS 2D software to simulate pile-rock interaction. Effect of GSI on stress at the pile-rock interface and in the rock, pile bending moment, pile shear force, and p-y curve were analysed.     

Deformation features and failure mechanism of steep rock slope under the mining activities and rainfall

Underground mining activities and rainfall have potential important influence on the initiation and reactivation of the slope deformations, especially on the steep rock slope. In this paper, using the discrete element method (UDEC), numerical simulation was carried out to investigate deformation features and the failure mechanism of the steep rock slope under mining activities and rainfall. A steep rock slope numerical model was created based on a case study at the Wulong area in Chongqing city, China. Mechanical parameters of the rock mass have been determined by situ measurements and laboratory measurements. A preliminary site monitoring system has been realized, aiming at getting structure movements and stresses of unstable rock masses at the most significant discontinuities. According to the numerical model calibrated based on the monitoring data, four types of operation conditions are designed to reveal the effect of mining excavation and extreme rainfall on the deformation of the steep rock slope.     

Study on engineering geological stability of rock mass at Shanmen silver deposit

The natural balance conditions will be disturbed and produce a series of problems when mineral deposit has mined.This paper has researched the engineering rock masses have been researched in this study,structural planes,the distribution characteristics of tectonic geological factors and the stability of engineering structures according to the theory and research methods of rock mechanics,it will provide the engineering geological evidence for mining area exploited,meanwhile pledge the safety production.Shanmen silver deposit is a large epithermal deposit,it is controlled by NE to NNE strike faults.The stability of rock mass is acted on the tectonic movement and hot metalliferous brine in long-term.Especially,strength of rock mass becomes softened,muddy and loosed under the action of water,so the lower stability of rock mass is,the easier it can take place for harm of disaster threatening production safe of mining.For this reason,it is very important that drawing up a plan to lower harm for mine and protect.     

Study on engineering geological stability of rock mass at Shanmen silver deposit

The natural balance conditions will be disturbed and produce a series of problems when mineral deposit has mined. This paper has researched the engineering rock masses have been researched in this study, structural planes, the distribution characteristics of tectonic geological factors and the stability of engineering structures according to the theory and research methods of rock mechanics, it will provide the engineering geological evidence for mining area exploited, meanwhile pledge the safety production. Shanmen silver deposit is a large epithermal deposit,it is controlled by NE to NNE strike faults. The stability of rock mass is acted on the tectonic movement and hot metalliferous brine in long-term. Especially,strength of rock mass becomes softened, muddy and loosed under the action of water,so the lower stability of rock mass is,the easier it can take place for harm of disaster threatening production safe of mining. For this reason,it is very important that drawing up a plan to lower harm for mine and protect.     

冻融循环作用下砂岩单轴压缩破坏断口特征分形研究

寒区岩石的力学特征往往受到冻融循环和荷载的共同影响,冻融岩石单轴压缩破坏断口蕴含着与冻融循环和荷载有关的损伤演化信息,冻融岩石单轴压缩破坏断口研究对冻融岩石断裂破坏机理分析有重要价值。为研究冻融岩石单轴压缩破坏断口形貌特征及其与宏观力学参数之间的关联性,通过摄影观测经历不同次数冻融循环的砂岩单轴压缩破坏断口形貌,采用像素点覆盖法计算断口分维值,探究了断口分维值与宏观力学参数之间的关系。结果表明:随着冻融次数的增加,冻融砂岩的力学性能劣化,单轴抗压强度、弹性模量、断口分维值、耗散能密度逐渐减小,峰值应变增大;单轴抗压强度、弹性模量、耗散能密度均与断口分维值之间存在指数关系,断口分维值越大,对应的单轴抗压强度、弹性模量、耗散能密度越大。冻融岩石单轴压缩破坏断口分维值可作为寒区岩体断裂破坏机理分析的有效参数。      

橡胶纤维-砂混合料力学特性的离散元三轴试验研究

橡胶砂作为一种轻质填料在岩土工程中具有良好的应用前景，为揭示橡胶纤维-砂混合料强度特性、偏应力-轴向应变曲线及微观结构的变化规律，开展了橡胶纤维-砂不同配比的三轴剪切试验，基于颗粒流理论和PFC3D程序，对橡胶纤维-砂混合料的三轴剪切试验进行了数值模拟，并与室内试验结果进行了比较。结果表明:随着橡胶含量的增加，试样的应力-应变关系由应变软化型向应变硬化型过渡，试样剪切过程中体变形式逐渐由体胀型变为体缩型；同一围压下橡胶纤维含量高的试样变形模量小，表明橡胶材料的掺入有助于增强试样的压缩性能。      

Preliminary slope stability analysis and discontinuities driven susceptibility zonation along a crucial highway corridor in higher Himalaya,India

Identification of failure susceptible slopes through different rock engineering approach is highly valuable in landslide risk management along crucial highway corridors in the high mountainous region. In this study, a critical highway(NH-5) segment in higher Himalaya has been investigated using the various rock mass characterization schemes based on detailed field observations. Since the highway corridor is highly susceptible to discontinuities-driven failures, consisting of jointed rock masses;Mean and Combined kinematic feasibility analysis has been performed for 20 highway slopes. Observed slope mass classes have been compared to the feasibility percentage of discontinuities driven failures(wedge, toppling, and planar) and accordingly the kinematic feasibility zonation along highway segment has been done for each as well as overall failure types. Based on the slope mass conditions and discontinuities driven failures probability(%), responsive remedial measures have been proposed for individual highway slopes to ensure safe and uninterrupted transportation.