西南某水电站中缓倾裂隙特征及发育模式分析

本文在大量的裂隙调查基础上,总结分析了西南某水电站坝址区中缓倾裂隙的地质特征,阐释了中缓倾裂隙的形成机制和发育模式。通过统计分析,结果表明:(1)岩坡中缓倾裂隙总体与岸坡大体平行,是河谷下切伴生的岸坡应力分异和卸荷回弹形成的表生压致拉裂破裂体系; (2)岸坡的形成是河谷多期次下切的结果,河谷下切坡度变陡,后期形成的中缓倾裂隙亦相对早期宽缓河谷形成的中缓倾裂隙倾角增大,河谷侧向偏移致使凸岸坡体更有利于保存早期裂隙,因此凸岸坡体中上部多见中倾裂隙与缓倾裂隙同时存在现象; (3)峡谷的形成总体是间歇性快速下切,相对稳定阶段岸坡形成表生中缓倾裂隙,快速下切期间以河谷垂向卸荷为主,由此形成与间歇性快速下切各阶段相对应的裂隙密集区和裂隙稀疏区的间断分布。     

Incrementally non‐linear plasticity applied to rock joint modelling

Rock joint constitutive modelling is discussed through two new rock joint constitutive relations and a discrete numerical model. Regarding the constitutive relations, we emphasise the number of ‘tensorial zones’, that is, domains of constitutive incremental linearity; they involve four zones for the first (called ‘quadrilinear’) and an infinite number for the second one (called ‘incrementally nonlinear’). Using these formulations, a large class of loading paths can be considered. Hardening through shearing and relations between the normal and tangential directions of the joint (e.g., dilatancy) can be described. Their predictive abilities are checked. Plastic features are included even if the relations are defined outside the elasto‐plastic formalism. These relations obey, hence, the physical evidence as the plastic limit criterion and flow rule. The flow rule is nonassociated, and the corresponding link with the nonsymmetry of the constitutive matrix is examined. Comparisons between the two relations and the discrete numerical model, that is, a direct numerical simulation, which is fundamentally different, also are discussed within the context of infilled rock joints. Copyright © 2011 John Wiley & Sons, Ltd.     

小直径钢管灌注排桩在边坡抢险工程应用探讨

我国是一个多山的国家,地形复杂,地质条件多样,每年汛期地质灾害发生频繁,易诱发滑坡、崩塌、泥石流等灾害,对国民经济建设、人员安全构成了巨大威胁。由于灾害发生正值主汛期,该类边坡的处治均为抢险工程,工期要求紧。小直径钢管灌注排桩具有施工速度快、开挖量小、对边坡扰动小的优点,特别适合对工期要求紧的抢险工程。本文以西南某公路挡墙病害抢险处治工程为例,分析了边坡挡墙变形机制,通过采用小直径钢管灌注排桩的处治方案,提高了挡墙的抗倾覆能力,有效解决了挡墙基础承载力不足及大规模开挖基坑引发边坡二次滑塌等次生灾害问题,可为类似工程提供参考和借鉴。     

Cross-bedding related anisotropy and its interplay with various boundary conditions in the formation and orientation of joints in an aeolian sandstone

Previous research revealed that the cross-bedding related anisotropy in Jurassic aeolian Aztec Sandstone cropping out in the Valley of Fire State Park, Nevada, affects the orientation of compaction bands, also known as anti-cracks or closing mode structures. We hypothesize that cross-bedding should have a similar influence on the orientation of the opening mode joints within the same rock at the same location. To test this hypothesis, we investigated the relationship between the orientation of cross-beds and the orientation of different categories of joint sets including cross-bed package confined joints and joint zones in the Aztec Sandstone. The field data show that the cross-bed package confined joints occur at high-angle to bedding and trend roughly parallel to the dip direction of the cross-beds. In comparison, the roughly N–S trending joint zones appear not to be influenced by the cross-beds in any significant way but frequently truncate against the dune boundaries.To characterize the anisotropy due to cross-bedding in the Aztec Sandstone, we measured the P-wave velocities parallel and perpendicular to bedding from 11 samples and determined an average P-wave anisotropy to be slightly larger than 13%. From these results, a model based on the generalized Hooke's law for anisotropic materials is used to analyze deformation of cross-bedded sandstone as a transversely isotropic material. In the analysis, the dip angle of cross-beds is assumed to be constant and the strike orientation varying from 0° to 359° in the east (x), north (y), and up (z) coordinate system. We find qualitative agreement between most of the model results and the observed field relations between cross-beds and the corresponding joint sets. The results also suggest that uniaxial extension (ε_zz > ε_xx = ε_yy = 0) and axisymmetric extension (ε_xx = ε_yy < ε_zz and ε_xx = ε_yy > ε_zz) would amplify the influence of cross-bedding associated anisotropy on the joint orientation whereas a triaxial extension (ε_xx > ε_yy > ε_zz) would mitigate this influence. We suggest that the potential implication of different categories of joint sets (i.e., cross-bed package confined joints and joint zones) forming in response to the variation of the boundary conditions (axisymmetric extension and triaxial extension, respectively) and the interplay with the rock anisotropy is significant. These results have important implications for fluid flow through aeolian sandstones in reservoirs and aquifers.     

Quasi‐static analysis of elastic behavior for some systems having higher fracture densities

Elastic behavior of geomechanical systems with interacting (but not intersecting) fractures is treated using generalizations of the Backus and the Schoenberg–Muir methods for analyzing layered systems whose layers are intrinsically anisotropic due to locally aligned fractures. By permitting the axis of symmetry of the locally anisotropic compliance matrix for individual layers to differ from that of the layering direction, we derive analytical formulas for interacting fractured regions with arbitrary orientations to each other. This procedure provides a systematic tool for studying how contiguous, but not yet intersecting, fractured domains interact, and provides a direct (though approximate) means of predicting when and how such interactions lead to more dramatic weakening effects and ultimately to failure of these complicated systems. The method permits decomposition of the system elastic behavior into specific eigenmodes that can all be analyzed, and provides a better understanding about which of these specific modes are expected to be most important to the evolving failure process. Copyright © 2009 John Wiley & Sons, Ltd.     

钢管混凝土短柱隔震装置的试验与隔震结构仿真分析

本文阐述了钢管混凝土短柱装置的工作原理,给出了装置的构造,对隔震装置的试验结果进行了详细分析,并对传统结构模型与隔震结构模型的对比实验作了仿真计算与分析．从计算结果可知,钢管混凝土基底隔震装置具有良好的隔震性能和推广使用价值。     

Friction and degradation of rock joint surfaces under shear loads

The morpho‐mechanical behaviour of one artificial granite joint with hammered surfaces, one artificial regularly undulated joint and one natural schist joint was studied. The hammered granite joints underwent 5 cycles of direct shear under 3 normal stress levels ranging between 0.3 and 4 MPa. The regularly undulated joint underwent 10 cycles of shear under 6 normal stress levels ranging between 0.5 and 5 MPa and the natural schist replicas underwent a monotonics shear under 5 normal stress levels ranging between 0.4 and 2.4 MPa. These direct shear tests were performed using a new computer‐controlled 3D‐shear apparatus. To characterize the morphology evolution of the sheared joints, a laser sensor profilometer was used to perform surface data measurements prior to and after each shear test. Based on a new characterization of joint surface roughness viewed as a combination of primary and secondary roughness and termed by the joint surface roughness, SR_s, one parameter termed ‘joint surface degradation’, D_w, has been defined to quantify the degradation of the sheared joints. Examinations of SR_s and D_w prior to and after shearing indicate that the hammered surfaces are more damaged than the two other surfaces. The peak strength of hammered joint with zero‐dilatancy, therefore, significantly differs from the classical formulation of dilatant joint strength. An attempt has been made to model the peak strength of hammered joint surfaces and dilatant joints with regard to their surface degradation in the course of shearing and two peak strength criteria are proposed. Input parameters are initial morphology and initial surface roughness. For the hammered surfaces, the degradation mechanism is dominant over the phenomenon of dilatancy, whereas for a dilatant joint both mechanisms are present. A comparison between the proposed models and the experimental results indicates a relatively good agreement. In particular, compared to the well‐known shear strength criteria of Ladanyi and Archambault or Saeb, these classical criteria significantly underestimate and overestimate the observed peak strength, respectively, under low and high normal stress levels. In addition and based on our experimental investigations, we put forward a model to predict the evolution of joint morphology and the degree of degradation during the course of shearing. Degradations of the artificial undulated joint and the natural schist joint enable us to verify the proposed model with a relatively good agreement. Finally, the model of Ladanyi and Archambault dealing with the proportion of total joint area sheared through asperities, a_s, once again, tends to underestimate the observed degradation. Copyright © 2001 John Wiley & Sons, Ltd.     

可膨胀管技术实验方法与仿真分析

可膨胀管技术是钻井工程领域的一项新兴技术,应用该技术可以简化井身结构,降低钻探成本。论述了该技术研究现状和地面实验的一种方法,并且利用非线性有限元技术对膨胀过程进行了仿真分析,得到了有效数据。     

Timing of brittle faulting and thermal events,Sydney region: association with the early stages of extension of East Gondwana

Structural studies in the Sydney region have revealed the presence of vertical to near-vertical, north-northeast-striking faults that are manifest as joint swarms and highly brecciated zones in which gouge of varying thickness is developed. Strike-slip movement accompanied by minor dip-slip, normal movement occurred on these faults. Timing of movement on these faults by K–Ar dating of illite and illite–smectite in fractions extracted from fault gouges, was attempted. These dates were compared with dates obtained from the host-rocks. K–Ar ages determined from the 2–10 μm to <0.1 μm fractions produced from the gouge and host-rocks, range from 159.5 ± 3.2 to 106.6 ± 2.1 Ma (n = 26). In <0.5 μm fractions extracted from the gouges that are less contaminated by detrital phases, K–Ar ages vary from 138 ± 4.4 to 106.5 ± 2.1 Ma (mean 121 Ma; n = 6) which are similar to ages obtained from host-rocks in the Sydney region. The similarity in age between the host rocks and gouge suggests that the K–Ar system has been reset. The resetting is attributed to a thermal event at ca 120 Ma related to the underplating of felsic intrusions associated with early stages of breakup of East Gondwana. Subsequent to this event, dykes of Early Eocene age (K–Ar whole-rock: 51.0 ± 1.1 Ma) exploited north-northeast-striking faults and subsequently developed brecciated margins. These observations and the fact that gouge formed before the thermal event suggests that movement took place on north-northeast-striking faults prior to 120 Ma and after 51 Ma.     

方钢管混凝土框架抗震性能试验研究与非线性有限元分析

为研究采用穿芯高强螺栓-端板节点的方钢管混凝土柱-钢梁平面框架的抗震性能,制作了3榀方钢管混凝土框架试件,通过低周反复荷载试验,研究了框架的抗震性能,分析了轴压比、梁柱线刚度比对框架抗震性能的影响.在考虑几何、材料及接触非线性的基础上,采用有限元软件ABAQUS 6.10对试验框架进行了低周反复荷载作用下的精细化数值模拟.与试验结果的比较表明,数值分析结果与试验结果吻合较好,具有较好的精度,可用于方钢管混凝土框架的分析.基于数值分析结果,剖析了框架梁柱连接节点、柱脚等关键受力部位的应力发展过程,明确了框架的受力机理和破坏机制.