基于非线性规划的岩质边坡有限元塑性极限分析下限法研究

结合塑性极限分析下限法理论、有限元离散技术以及非线性数学规划手段,将有限元塑性极限分析法运用于岩质边坡的稳定性分析。基于非线性Mohr-Coulomb屈服条件、平衡条件、边界条件以及间断面应力连续条件,提出塑性极限分析中无厚度节理单元、等厚度节理单元的有限元模式,建立带节理单元的有限元塑性极限分析非线性数学规划模型,并提出非线性规划的求解策略。最后对3个岩质边坡的稳定性进行分析,验证该方法的可行性。     

竖向节理分布特征对岩质边坡稳定性影响的数值模拟研究

以广州某工程岩质边坡为例,采用有限元软件Midas建立模型,并考虑了不同节理间距布置下工况,对边坡稳定性影响进行分析。结果表明：(1)在竖向节理广泛分布的岩质边坡中,节理发育分布越密集,岩体整体稳定性越差。每条节理裂隙对边坡稳定性影响不尽相同,而边坡稳定性的破坏往往是多条节理裂隙破坏共同作用的结果;(2)变形通常会出现在竖向节理发育处,对岩质边坡来说,竖向节理可看成一软弱夹层,对岩体整体安全稳定性产生不利影响;(3)节理发育处抗剪强度降低,抵抗滑裂面产生的能力下降;容易产生岩体局部大变形乃至崩塌。     

考虑平动–转动力学效应的露天矿山节理岩质边坡塑性极限分析

露天矿山节理岩质边坡的失稳破坏一般同时包含平动和转动力学效应。本文将塑性极限分析理论、多自由度的刚性块体单元离散技术、拟静力法原理和数学规划方法结合起来,研究矿山节理岩质边坡平动滑移破坏或倾倒破坏时的稳定性。根据拟静力法原理计算单元形心地震惯性力,以结构面的法向力、剪力、弯矩为决策变量,构建节理岩质边坡静力许可应力场,建立节理岩质边坡稳定性分析的下限法数学规划模型;同时以单元形心的平动速度、转动速度为决策变量,构建节理岩质边坡机动许可速度场,建立节理岩质边坡稳定性分析的上限法数学规划模型;最后运用优化算法求解这两个数学模型,获得节理岩质边坡安全系数的上、下限解和对应的破坏机构。     

岩质边坡稳定塑性极限分析方法——斜分条法

基于塑性极限分析上限定理,依据岩质边坡沿某一滑裂面滑动破坏时,在其内部产生沿陡倾角结构面(断层、节理和层面)的剪切破坏现象,建立了岩质边坡极限分析斜分条法破坏模式。进一步根据滑体处于极限状态时的虚功率方程,推导得出了斜分条后岩质边坡的塑性极限分析稳定系数计算公式。采用超载系数的方法,将稳定系数表示在块体所受的极限荷载,避免了隐式出现,有效地简化了公式推导。以锦屏一级水电站右岸边坡为例进行了稳定性分析。计算表明,结论较为合理,对于具有倾斜界面的岩质边坡稳定性评价具有重要意义。     

具有外倾节理岩质边坡开挖与支护FLAC~(3D)数值模拟分析

该文结合具有一组平行外倾节理面的岩质边坡工程实例,通过FLAC3D建立数值计算模型,分析了该类边坡的稳定性以及开挖支护过程中的力学响应。结果表明:①外倾节理岩质边坡达到极限状态时,靠近坡脚的最下面一条结构面将产生贯通的塑性区;②边坡开挖将使潜在滑裂面下移,两滑裂面之间岩体剪切滑移将引起锚杆轴力增大,在靠近坡脚的新滑裂面位置处达最大;③在坡脚处设置混凝土挡墙能有效提高边坡整体稳定性,此加固措施效果较好。     

湖南岐山仁瑞寺节理边坡稳定性的细观损伤力学分析方法

 对湖南仁瑞寺岩质边坡进行地质勘查,该边坡结构面主要为X节理,一组走向为170°～265°,另一组走向为105°～125°,倾角较陡,普遍为50°～90°。通过6组实验分别确定岩块与结构面的力学参数。基于细观损伤力学理论,认为节理岩体是由岩块与微裂纹构成的各向异性材料,并利用代表性体积单元建立微裂纹的滑裂准则。通过编制相应的软件建立坡角为60°、节理倾角为52.5°和90.0°的岩质边坡计算模型,并对该边坡的稳定性进行分析。采用逐步去除约束的方式进行开挖模拟,得到边坡的塑性贯通区。通过与实际滑坡形式进行对比,模拟效果好,证明微裂纹是控制岩质边坡破坏的主要因素,对理解节理边坡的破坏机制具有重要意义。同时,该方法对于预测节理边坡破坏面的形状与位置以及复杂边坡的稳定性分析都有一定的借鉴意义。     

节理岩质边坡的光面爆破

依托于黄山至衢州高速公路两种不同的路堑节理岩质边坡,通过现场试验.合理地选择参数,研究了节理岩质边坡的光面爆破技术.试验表明,节理岩质边坡光面爆破效果良好,光面爆破应用于高速公路边坡具有保持边坡岩体稳定、平整、美观、减少超挖量和节约土地的优点,对节理岩质边坡使用光面爆破技术是可行的.     

岩质边坡破坏机制有限元数值模拟分析

岩质边坡的稳定性主要由其结构面控制，采用有限元强度折减法对岩质边坡破坏机制进行了数值模拟分析。计算表明，破坏“自然地”发生在岩体抗剪强度不能承受其受到的剪切应力的地带。分析表明，根据塑性力学破坏原理，采用有限元强度折减法有助于对岩质边坡破坏机制的理解。算例表明了此法的可行性。     

用有限元强度折减法进行节理岩质边坡稳定性分析

通过对节理岩质边坡非线性有限元模型进行强度折减，使边坡达不到稳定状态时，有限元静力计算将不收敛，此时的折减系数就是稳定安全系数。同时可得到边坡破坏时的滑动面以及破坏过程，有传统条分法无法获得节理岩质边坡的滑动面与稳定安全系数，该方法为节理岩质边坡稳定分析了开辟新的途径，通过算例表明了此法的可行性。     

利用有限元强度折减法分析岩质边坡的稳定性

基于有限元强度折减法,利用ANSYS有限元软件,对岩质边坡在地应力作用下进行了稳定性分析。选用D-P屈服准则,以边坡的位移计算不收敛及塑性区贯通作为边坡失稳判据,得到边坡的安全系数及破坏滑动面。通过与成熟的极限平衡法做比较,证明边坡稳定性安全系数是合理的,从而也说明强度折减法在岩质边坡稳定性分析中的优越性。     

节理岩体隧道的稳定分析与破坏规律探讨——隧道稳定性分析讲座之一

以往研究人员在进行节理岩体隧道稳定性分析时大都仅限于分析位移、应力、塑性区的大小及分布,不能明确看出其破裂面位置与范围,更无法得到安全系数定量标准。本文通过模型试验与数值分析方法将节理岩体隧道稳定性引入到定量分析。从强度及稳定性出发,运用有限元强度折减法分析节理岩体隧道的破坏状态及其安全系数,研究表明,节理倾角对破裂面位置影响较大,对于α=0°,破裂面对称分布于两侧;对于α=30°、45°,隧道破裂面随节理倾角变化相应旋转,分布于节理倾向的上下游;对于α≥60°,主要受自重作用,破裂面转移至洞顶及边墙脚位置,特别α=90°时,隧道在洞顶正中形成了贯通的塑性破裂面。通过安全系数结果表明,相对于匀质隧道,节理岩体隧道安全系数均存在不同程度的降低,其中倾角对安全系数影响最小,随节理间距减小、强度降低,安全系数均有所减小。     

节理岩质边坡的块体元塑性极限分析下限法

结合块体元和塑性极限分析,并利用数学规划的方法,提出了一种新的岩石边坡稳定分析方法-块体元塑性极限分析下限法。针对节理岩体的力学特性,将岩体离散为块体–结构面组成的块体系统,假定块体为刚体;以结构面应力为未知量,根据塑性极限分析下限定理,构造了满足平衡方程、边界条件和屈服条件的静力许可应力场;建立了边坡稳定的下限法数学规划模型,并通过非线性规划方法寻求问题的下限解。最后对三个典型的算例进行分析,结果表明:采用本方法不需要逐个计算可能的滑动形式,而直接得到边坡稳定安全系数,结果同刚体极限平衡法十分接近。     

Stability charts for rock slopes based on the Hoek–Brown failure criterion

This paper uses numerical limit analysis to produce stability charts for rock slopes. These charts have been produced using the most recent version of the Hoek–Brown failure criterion. The applicability of this criterion is suited to isotropic and homogeneous intact rock, or heavily jointed rock masses. The rigorous limit analysis results were found to bracket the true slope stability number to within ±9% or better, and the difference in safety factor between bound solutions and limit equilibrium analyses using the same Hoek–Brown failure criterion is less than 4%. The accuracy of using equivalent Mohr–Coulomb parameters to estimate the stability number has also been investigated. For steep slopes, it was found that using equivalent parameters produces poor estimates of safety factors and predictions of failure surface shapes. The reason for this lies in how these equivalent parameters are estimated, which is largely to do with estimating a suitable minor principal stress range. In order to obtain better equivalent parameter solutions, this paper proposes new equations for estimating the minor principal stress for steep and gentle slopes, which can be used to determine equivalent Mohr–Coulomb parameters.     

考虑围岩非线性和剪胀特性的地下硐室极限解

以岩石非线性统一强度理论为基础,考虑了岩体的非线性软化及非关联流动特性,建立了岩体在非线性模型、理想弹塑性模型和强脆性模型下统一的极限平衡分析模式,获得了硐室的应力、变形及塑性区半径的解,这些解不但反映了硐室围岩塑性软化和剪胀特性,而且又考虑了岩石拉压强度相差较大的特点和中间主应力效应,既反映了岩石的非线性破坏特征,又可以推广到岩体及节理岩体之中去。而且,通过比较三类典型塑性模型的解答,发现当岩石软化特性不是太明显的情况下,采用理想弹塑性模型进行地下硐室的极限平衡分析是可行的,以上结论对于岩石地下硐室工程具有一定的理论及工程应用价值。     

Upper bound limit analysis of support pressures of shallow tunnels in layered jointed rock strata

With more and more large-span shallow underground projects being built in layered jointed rock strata, there is an increasing interest in the study of stability problems of such projects. The upper bound theorem of limit analysis has been found to be a valid method for analyzing such problems and it is crucial to ensure the accuracy of the failure mode when applying this method. In the present paper, for tunnels in layered jointed rock strata, 8 factors including the thickness of the weathered overburden, the states of the rock joints, and the depth of the tunnel were considered by analyzing the failure mode. By using the orthogonal array testing strategy and the distinct element method, 64 different numerical simulation models based on an actual tunnel project were simulated. The test results showed that the range of the loose zone was determined by the stretch, slippage, and fracture area of the joints. Two kinds of loose zone were obtained, i.e. the arch collapse loose zone and the caving collapse loose zone. The loose zone boundary was analyzed and fitted with linear and non-linear models; such as parabola and power function curves, respectively. The rational failure mode was studied by analyzing the recognition method, the classification, and the failure mechanism of the caving collapse loose zone. By using the liner least squares method, an empirical formula of the boundary of the caving collapse loose zone was obtained, and its boundary were divided equally with identical angles, then a kinematically admissible velocity field was established. Based on the virtual power principle and virtual work principle, the upper bound theorem of limit analysis was adopted to study the support pressures and a limit analysis model was established. A real tunnel project case was studied as an example, and the results were compared with the Terzaghi theory and the Fraldi theory, so as to demonstrate the applicability of the proposed method.     

节理岩体边坡模糊稳定性分析方法研究

节理岩体边坡失稳破坏同时受控于节理与岩体抗剪强度。在对具有两组平行节理的岩体边坡失稳破坏机制研究基础上，探讨节理岩体边坡几何物理参数为模糊数情况下边坡稳定性评价的分析方法，给出节理岩体边坡模糊安全系数的计算公式，编制基于潜在滑动面自动搜索边坡模糊稳定性研究程序。算例研究成果表明，采用模糊分析方法可以对节理岩体边坡稳定性有更全面客观的了解，能为潜在不稳定边坡的稳定性评价和锚杆设计等提供重要的参考依据，避免发生由于计算参数不确定性引起的加固节理岩体边坡破坏情况。     

Methodology for tunnel and portal support design in mixed limestone, schist and phyllite conditions: a case study in Turkey

The purpose of this study is to present a methodology for tunnel and support design in mixed limestone, schist and phyllite conditions through investigating two highway tunnel case studies that are located along the Antalya–Alanya Highway in southern Turkey. The main lithologies of the project area are regularly jointed, recrystallized limestone and the weak lithologies of the schist unit (i.e., pelitic schist, calc schist, graphitic phyllite and alternations of these lithologies). A detailed geological and geotechnical study was carried out in the project area, and the tunnel ground support types and categories were determined according to the Q-system, rock mass rating method and New Austrian Tunneling Method (NATM). The shear strength parameters and geomechanical properties of the rock masses were obtained by using the geological strength index (GSI). The deformation moduli and post-failure behavior of the rock masses have been determined. Slope stability analyses were performed at the portal, side or cut slope sections. Kinematic and limit equilibrium analyses incorporating the effects of water pressure were performed for the regularly jointed failed rock slopes. Circular failure analogy was used for the slope stability analyses of irregularly jointed, highly foliated lithologies. Slope support system recommendations were made. A back analysis on a failed slope was performed. The results of the back analysis compared well with the results obtained through the GSI method. The tunnel grounds were divided into sections according to their rock mass classes. The deformations and stress concentrations around each tunnel section were investigated and the interactions of the empirical support systems with the rock masses were analyzed by using the Phase² finite element software. The regularly jointed rock masses were modeled to be anisotropic and the irregularly jointed, highly foliated and very deformable soil-like lithologies were modeled to be isotropic in the tunnel finite element analyses.     

基于高精度微震监测的特厚煤层综放面支架围岩关系

基于高精度微地震监测技术,结合岩石力学理论、矿山压力理论和现场宏观现象,对特厚煤层综放工作面的岩层运动与支架载荷关系进行了研究。研究结果表明,正常情况下,特厚煤层综放工作面的基本载荷来源于厚度大于10 m的顶煤、厚度约30 m的下位直接顶和部分厚度为20 m左右的上位直接顶;冲击载荷来源于老顶的断裂冲击,老顶在工作面前方断裂并强迫其下位岩层断裂,从而在支架上形成冲击载荷,这也是特厚煤层综放工作面设计支架支撑能力13000 kN/架但被压死的主要原因。指出了特厚煤层综放工作面支架选型的方向是:支架的基本支撑能力能够承担顶煤和部分直接顶的作用力,通过缩小支架控顶距、加大支架可缩量等措施,可减小冲击对支架的影响。