含圆柱形衬砌直角域压电体的动力反平面特性

探讨了直角域附近一圆形衬砌对压电材料的反平面动力学行为的影响.通过利用镜像法对直角域情况进行等效处理到全空间中,在复数域中利用衬砌周围的边界条件构造方程求解未知系数,并通过编程进行最终的数值计算得出压电材料在衬砌周围的动应力和电场集中系数.在数值计算中,重点讨论了衬砌和基体为不同材料、衬砌和基体电极化方向相同和不同时,它们随压电材料物理系数、结构几何参数,以及入射波的频率变化的计算结果.结果表明,在SH波的作用下,压电材料在衬砌周围的动应力集中系数和电场集中系数都有一定的相似性,并且沿衬砌周围有规律的分布,然而在入射波的频率较低时二者的值相对较大,同时计算结果还与全空间衬砌下的计算结果有一定的相似性.     

地下洞室衬砌外壁形状变异性对内壁动应力集中因子峰值的影响

 采用波函数展开法及边界离散的方法给出平面SH波入射下地下衬砌洞室(衬砌内壁为圆形、外壁为任意形状)动应力集中的半解析解,利用蒙特卡罗方法随机模拟产生30组半径变异系数为0.05的衬砌外壁形状样本,通过对衬砌内壁动应力集中因子(DSCF)峰值的统计分析,研究衬砌外壁形状变异性对内壁DSCF峰值的影响。研究表明：洞室衬砌外壁形状变异性对内壁DSCF的峰值大小有重要影响,柔性衬砌情况的影响远大于刚性衬砌情况的影响。柔性衬砌和刚性衬砌样本峰值的最大值比圆形洞室峰值分别增大178.15%和31.98%;柔性衬砌和刚性衬砌样本峰值的变异系数分别可达衬砌外壁半径变异系数的9.84和2.57倍。     

含滑移界面复合式衬砌隧道地震响应边界元模拟

采用一种高精度间接边界元方法(IBEM),求解了平面P、SV波入射下“围岩-减震层-浅埋衬砌隧道”体系地震响应及动应力集中效应。引入接触-滑移界面模型,模拟复合式隧道衬砌与围岩之间接触状态。结果表明: 总体上看,随着界面滑移刚度因子增大,衬砌内壁动应力集中因子(DSCF)增大,无滑移状态下应力放大更为显著;SV波入射下,衬砌外壁DSCF则随滑移刚度因子增大而减小;P波垂直入射下,低频情况在隧道左右两端动应力集中十分显著,高频时则在隧道下部应力更为集中。另外,减震层的存在可有效降低衬砌动应力集中效应,随着入射频率增加,减震效果越好,隧道衬砌受力更为均匀;适当降低减震层弹性模量和加大减震层厚度,可取得更好的减震效果。     

凸起地形中半圆形衬砌隧道对SH波的散射解析解

根据弹性波动理论,结合分区和契合思想,利用傅里叶级数展开法,由连续性条件和自由地表边界条件,求得了凸起地形中衬砌隧道对SH波散射的解析解。通过研究半圆形山岭衬砌隧道对SH波散射的影响,得到的计算结果表明:对于软性和硬性衬砌隧道而言,凸起地形对地震波有明显的放大作用,当入射频率增大时,地表位移幅值也增大,这种现象在凸起地形范围内尤为明显;当入射频率较低时,位移幅值在凸起地形附近变化明显。与此同时,刚性衬砌表面的动应力集中现象尤为显著。除此以外,结果还表明动力反应特征主要影响因素包括入射波角度、入射波频率及衬砌材料属性等。     

爆炸地震波作用下深埋圆形隧道的动力响应分析

 深地下结构在爆炸地震波作用下的动力响应是防护工程设计和评估的重要问题,发展适应深部特点的快速计算方法具有重要意义。采用集中质量方法将圆形隧道离散为有限自由度体系,并将爆炸地震波的作用看作一系列作用在集中质量上的动力,利用局部变形理论将围岩的弹性抗力简化为弹性链杆,采用矩阵力法考虑结构在各种内力作用下产生的自身变形和弹性半空间的变形,并据此建立结构动力方程矩阵。通过对结构动力方程的求解,可以得到结构的动力集中系数和结构内力、弯矩、位移等参数。采用所提出的方法计算一个算例,分析围岩等级、荷载作用位置、正压作用时间以及入射波角度等因素对隧道衬砌结构动力响应的影响。     

隧道设置减震层减震机制研究

 通过Fourier-Bessel函数展开法,推导平面SV波垂直入射下半无限弹性介质中圆形双层衬砌结构、围岩–减震层–衬砌洞室的动应力集中系数级数解,分析入射波频率、减震层弹性模量和厚度对动应力集中系数的影响,并结合数值模拟分析结果对比,深入研究减震层减震机制。研究结果表明：入射频率对衬砌动应力集中系数有显著影响,减震层对低频波具有较好的减震效果;由于减震层剪切模量低,围岩和隧道可以剪切变形,从而减小了作用在衬砌外部的法向作用力,降低了衬砌内侧最大动应力集中系数,但围岩和衬砌外侧切向应力增大;随着减震层与围岩弹性模量之比减小,减震层厚度增大,二次衬砌动应力集中系数变小,减震层与围岩的弹性模量比宜低于1/10～1/20,和减震层弹性模量对应,存在一个最优的减震层厚度值。以一公路隧道为背景,开展隧道减震层结构大型振动台试验研究,结果表明：隧道衬砌设置减震层后,可以显著降低衬砌内力,减小衬砌裂缝的数量。     

基于非局部Biot理论下饱和土中深埋圆柱形衬砌对平面弹性波的散射

基于Biot饱和多孔介质理论和非局部弹性理论,构建了非局部Biot运动方程及本构方程。利用波函数展开法及饱和土与衬砌边界连续条件和衬砌内边界自由边界条件,求解了饱和土体中圆柱形衬砌对平面波散射问题的解析解。并通过将该解退化为单相介质中及经典Biot理论下衬砌对平面P波散射稳态解,验证了计算结果的正确性。研究结果表明,衬砌内边界及外边界动应力集中因子均随非局部因子的增大而减小;隧道内边界动应力集中因子分布曲线随非局部因子的减小而扩大;当入射波频率大于0.045 MHz时,饱和土中空隙尺寸及空隙动力的影响将不可忽略;非局部因子一定时,衬砌外径与内径比越大则衬砌内边界动应力集中因子越大,且当衬砌较薄时,衬砌内边界动应力集中因子可能产生负值。     

复杂环境下倾倒式危岩体的动力稳定性分析

 危岩作为我国主要的地质灾害之一,对其进行合理的稳定性评价与校核对当地具有重要的生命安全意义和经济价值。目前,国内规范对倾倒式危岩体的动力稳定性分析中,所考虑的水平地震作用并未包含裂隙中水体对危岩体的间接作用。基于弹性力学的基本假定和流体力学的相关理论,推导P波在固液分界面的透射与反射系数,求出液体中透射P波对危岩体的动水压力,并从能量的角度验证公式推导的正确性。根据透射系数的表达式分别探讨固体介质的弹性模量、密度、泊松比以及入射角度对透射系数的影响规律,并定性分析其对倾倒式危岩体稳定系数的影响。最后,结合重庆万州区太白岩南坡的倾倒式危岩体,探讨不同降雨强度和地震动强度下倾倒式危岩体稳定系数的变化规律。对比天然和暴雨工况下,动水压力对倾倒式危岩体稳定系数的影响,结果表明：考虑动水压力会明显减小倾倒式危岩体的稳定系数,在暴雨工况下更为明显。进而提出在对倾倒式危岩体进行复杂环境下的动力稳定性校核时应该考虑动水压力的作用。     

Imperfect bonding effect on dynamic response of a non-circular lined tunnel subjected to shear waves

Combining the wave function expansion method and conformal transformation method, the dynamic stress around a non-circular tunnel with imperfect interface subjected to anti-plane shear waves is derived. The non-circular tunnel is mapped into an annular region, and the analytic solutions of stress and displacement solutions are expanded in terms of wave functions. By introducing the spring-type interface model, the coefficients are determined by satisfying the imperfect bonding conditions around the concrete lining. The distribution of tangential stresses on the imperfect interface is graphically illustrated, and the interacting effect of imperfect interface and incident wavelength is discussed in detail. The imperfect interface is revealed as a key factor dominating the seismic responses of a tunnel.     

基于波场等效的节理面刚度参数取值研究

节理岩体中的节理面往往有一定厚度,如果采用无厚度的线性节理模型分析,其刚度参数的确定非常困难。通过分析弹性波穿过节理面时的波场效应,建立了基于节理后振动强度相等的波场等效法,用于确定带厚度节理的刚度参数,并分析了各因素对弹性波在节理上传播的影响。结果表明:线性节理面的刚度参数是节理岩体的固有属性,与外界荷载无关,采用波场等效法计算刚度参数可行;在弹性波范围内,这种等效参数与入射波频率、入射角等因素关系不大。该方法可用于有厚度节理面动强度参数的确定与分析,完善现有的节理面刚度取值方法。     

Interaction of shotcrete with rock and rock bolts—A numerical study

The shotcrete–rock interaction is very complex and is influenced by a number of factors. The influence of the following factors was investigated by a series of numerical analyses: the surface roughness of the opening, the rock strength and Young's modulus, the discontinuities, the extent and properties of the excavated disturbed zone, the mechanical properties of the interface between shotcrete and rock, and the thickness of the shotcrete lining and the rock bolts. The study was carried out as a sensitivity analysis. The results showed that the rock strength and the surface roughness had significant impact on the number of failures at the rock–shotcrete interface and in the shotcrete lining. Furthermore, the behaviour of the lining is sensitive to small amplitudes of the surface roughness. In all the cases investigated, a high interface strength was favourable. The results indicate that if a thick shotcrete lining is dependent on the bond strength. The benefit of using a thicker lining can be doubtful. The analyses showed that for an uneven surface the extent of the EDZ had a minor effect on the behaviour of the shotcrete lining. Furthermore, if rock bolts were installed at the apex of the protrusion instead of at the depression, the number of failures decreased both at the interface and in the lining.     

A further study of P-wave attenuation across parallel fractures with linear deformational behaviour

When a wave propagates through fractured rock masses, it is greatly attenuated (and slowed) due to the presence of fractures. In the situation where dynamic responses are induced by a far field explosion or vibration, the magnitude of the stress wave is generally too small to mobilize nonlinear deformation of the fractures, so linear deformational behaviour is adopted in studying wave attenuation. Cai and Zhao [Effects of multiple parallel fractures on apparent wave attenuation in rock masses. Int J Rock Mech Min Sci 2000;37(4): 661–82.] used the method of characteristics to study P-wave attenuation across linear deformational fractures by considering interfracture wave reflections. However, the frequency characteristic of the incident wave (a one-cycle sinusoidal wave) was overlooked in their previous study. The present study treats the incident wave as the sum of a series of harmonic waves in the frequency domain. Results and wave phenomena in the previous study are improved and better understood. When the incident wavelength is substantially greater than fracture spacing, an equivalent medium method is developed to explain the wave phenomena in such a situation. In addition, the uncertainty of back analyzing fractured structures and the effects of wave frequency are examined. These results are in accordance with conclusions in the field of geophysics.     

Stochastic seismic wave interaction with a rock joint having Coulomb-slip behavior

Seismic wave interaction with a slippery rock joint with an arbitrary impinging angle is analytically studied based on the conservation of momentum on the wave fronts. Based on the displacement discontinuity method, the wave propagation equations are derived for incident P- and S-waves. By comparison, the calculated transmission and reflection coefficients for normal incident waves are the same as the existing results, which proves the wave propagation equation obtained in the paper is correct. The wave propagation derived in the context can be applied to incident waves with different waveforms. Stochastic seismic waves are then used to analyze the seismic wave interaction with the slippery rock joint, where the stochastic seismic waves are generated from frequency spectra. The parametric studies are carried out to investigate the effect of type, intensity and impinging angle of the incident seismic waves on the wave propagation across the slippery rock joint.     

饱和半空间中隧道衬砌对平面SV波的散射IBIEM求解

基于Biot两相介质理论,采用一种高精度的间接边界积分方程法(IBIEM),研究了平面SV波在饱和半空间中隧道衬砌周围散射的基本规律,并给出了不同参数下地表位移幅值、衬砌动应力集中因子及表面孔隙水压分布图和相应的频谱结果。数值分析表明:饱和半空间隧道衬砌对SV波的散射特征取决于围岩介质孔隙率、入射波的频率和角度、隧道埋深等因素;隧道外壁透水状态对地表位移和隧道应力影响不大;不同角度SV波入射下,隧道应力集中部位有很大差别,且随半空间介质孔隙率增大,应力集中越发显著;衬砌外壁孔隙水压峰值可达到入射波应力幅值的4倍,且30°斜入射下幅值明显大于0°垂直入射情况;衬砌上方附近不同点位位移频谱特征差异显著,斜入射情况位移放大效应明显;随埋深增大,地表位移幅值和衬砌表面动应力谱振荡更为剧烈,但幅值会有所降低。另外,按波速比等效的单相介质模型可以近似计算SV波入射下隧道–饱和围岩的位移场和应力场。     

山岭隧道受震损害类型与原因之案例研究

 以1999年台湾集集地震造成完工通车仅1 a的三义壹号铁路隧道损害为例,应用隧道受震数值分析成果及相关研究,探讨隧道受震损害的原因。研究成果显示,受震损害区段皆落于埋深接近0.25倍岩体波长的范围内,即隧道埋深与岩体特性的组合强化震波受地表自由面反射与隧道散射的效应,导致衬砌受震引起应力大幅增加而造成破坏。而衬砌损害可归纳为4种类型：纵向裂缝、环向裂缝或环向施工缝错动、环状剥落以及斜向裂缝与剥落。分析隧道施工地质记录及震后检测结果显示,衬砌纵向裂缝主要受地盘深处上传的S波垂直方向或45?入射导致衬砌轴力与弯矩受震增加而影响。环向裂缝或环向施工缝错动则受到水平方向P波造成的张力破坏以及乐夫波造成衬砌应力增加的影响。环状剥落系隧道承受较显著的水平方向应力下,S波45?入射导致衬砌应力增量以及避车洞开口结构配置的影响。而斜向裂缝则受S波通过软硬地盘互层的应变差异以及隧道衬砌结构刚度特性所致。研究成果表明隧道受震损害原因与影响因素,可为山岭隧道耐震分析与设计提供参考。     

高地震烈度区岩体地下洞室动力响应分析

 考虑地震荷载特征及地下洞室的特点,利用动力时程分析法,对金沙江两家人水电站地下厂房洞室进行地震动力响应分析。研究自然地震波作用下,有无衬砌工况下的厂房洞室相对位移、点安全系数变化趋势,分析地震波穿越地下洞室时位移变化规律及厂房洞室衬砌抗震效果。结果发现：地震波传播除了受介质、结构面分布的影响外,还受岩体洞室面的影响,洞室自由面附近岩体的振动强度被放大;地下洞室断面质点最大相对位移、点安全系数波动规律与地震波谱相似;地下洞室壁及F4断层未出现较大永久性位移,处于弹性可恢复范围;施加衬砌后洞室的振动强度降低,洞室围岩刚度增大,其所承受的地震荷载亦随之增大,而位移减小,支护后洞室最大相对位移及永久性位移比无支护工况下分别平均下降10.88%和29.20%,洞室衬砌抗震效果良好。研究结果可为类似工程问题提供参考。     

岩体软弱夹层的弹性模量动力测试方法

 针对岩体软弱夹层的力学参数具有渐变性,假设软弱夹层的损伤度按照二次曲线规律变化,建立应力波在软弱夹层的传播模型,研究应力波的波形变化规律,提出软弱夹层弹性模量的动力测试方法。现场试验研究表明：当采用波形变化系数量化入射侧的计算波形和实测波形差异时,随着软弱夹层峰值损伤度增加,波形变化系数先减小后再增加,波形变化系数为最小值时,入射侧的计算波形和实测波形非常接近;随着子波主频增加,软弱夹层的动态弹性模量近似成线性增加,通过线性拟合求得了软弱夹层的静态峰值弹性模量为0.74 GPa;基于变形相等原则计算得本次试验的软弱夹层的等效动态弹性模量为4.24 GPa,采用波速法测试得夹层动态弹性模量为4.70 GPa,波速法测试结果与等效动态弹性模量相近,表明该方法测试结果合理。     

减震层减震原理及跨断层隧道减震技术振动台试验研究

通过波函数展开法给出平面SV波入射下深埋圆形隧道"围岩—减震层—初期支护—二次衬砌"减震结构的动力响应解析近似解,分析了减震层厚度、弹性模量对衬砌结构动应力集中系数的影响,并开展了跨断层隧道抗减震研究大型振动台模型试验,通过分析跨断层及其设置减震层后隧道衬砌动力响应特性和破坏形态,得到以下有益结论:减震层与围岩弹性模量比越低,减震层厚度越大,衬砌动应力集中系数越小;减震层与围岩弹性模量的最优减震比在1/10~1/20,最优减震层厚度不宜大于0.2 m;跨断层破碎带隧道设置减震层可以明显降低跨断层衬砌结构加速度峰值和衬砌动应变幅值;断层处隧道衬砌裂缝分布数量多、复杂,多集中于拱脚、拱肩,并分布有剪切错动引起的环向裂缝,设置减震层后,断层处隧道衬砌裂缝明显减少,衬砌受力得到明显改善;断层处地表出现了平行断层方向为主的的贯通裂缝和大量斜裂缝,说明断层处以剪切破坏为主,设置减震层后,地表裂缝明显减少。     

A waveform modification method for testing dynamic properties of rock under high temperature

In this study,a waveform modification method was proposed using a self-designed heating device combined with the split Hopkinson pressure bar(SHPB) technique for determination of dynamic behaviors of rock at high temperature.Firstly,the temperature gradient distribution on the incident bar was measured according to the variation of elastic modulus of the bar with temperature,and the relationship between the longitudinal wave velocity and temperature of the bar was obtained based on onedimensional stress wave theory.The incident bar with a temperature gradient was divided into a series of microelements,and then the transmission coefficient of the whole incident bar was obtained.Finally,the stress wave was modified by the transmission coefficient from 25℃ to 600℃.This method was used to study the dynamic properties of rock at high temperature,which not only preserves a classical SHPB device,but also effectively ensures the accuracy of the experimental results.A dynamic Brazilian disc experiment was carried out to explore the influences of loading rate and temperature on dynamic tensile strength of sandstone at high temperature using the proposed waveform modification method.     

Simulation of viscoelastic behavior of defected rock by using numerical manifold method

Numerical simulations of longitudinal wave propagation in a rock bar with microcracks are conducted by using the numerical manifold method which has great advantages in the simulation of discontinuities. Firstly, validation of the numerical manifold method is carried out by simulations of a longitudinal stress wave propagating through intact and cracked rock bars. The behavior of the stress wave traveling in a one-dimensional rock bar with randomly distributed microcracks is subsequently studied. It is revealed that the highly defected rock bar has significant viscoelasticity to the stress wave propagation. Wave attenuation as well as time delay is affected by the length, quantity, specific stiffness of the distributed microcracks as well as the incident stress wave frequency. The storage and loss moduli of the defected rock are also affected by the microcrack properties; however, they are independent of incident stress wave frequency.