铁路路基病害类型、机理及检测与整治技术

针对既有铁路的特点,分析了常见铁路路基病害的类型、机理;提出路基病害的检测应运用现代化检测工具,采用原位和区段测试相结合的方法;针对路基病害整治技术的复杂多样,整治具体路基病害的困难性,指出了铁路路基病害智能管理系统能较好地解决此问题。     

攀枝花机场北东角滑坡整治措施研究

攀枝花机场地形及地质条件复杂,在修建过程中实施了大量的挖填方工程,填方边坡形成的沉降变形和滑坡成为机场主要的工程病害。本文阐述了机场北东角滑坡的基本特征及成因,综合反分析演算和试验结果确定了滑动面的抗剪强度参数,并对滑坡稳定性进行了参数敏感性分析。在滑坡推力计算的基础上,对滑坡整治方案进行对比论证,从而确立了以抗滑桩、预应力锚索框架、削坡减载和地表防排水为主的综合整治措施。     

地形三维可视化在川藏公路典型路段中的应用

利用地形平面图的数据和有关区域地质资料的数字化方法实现川藏公路典型路段三维地形的显示和实时浏览,为进一步利用地理信息系统进行研究区地层岩性、地质构造和地质灾害分布的叠加分析进行地质灾害研究提供了矢量化的地形底图。川藏公路典型路段的三维地形可视化工作对于川藏铁路的选线、绕避不良地质灾害的发生和开凿铁路隧道的位置选择等将会有一定的参考价值。     

三峡工程移民迁建区灾害地质体改造与利用研究

三峡工程移民迁建区地质环境复杂 ,建设用地严重不足。如何在治理的基础上对滑坡等灾害地质体开发利用是一项风险极大 ,但具非常现实意义的课题。本文论述了预应力锚拉桩在库区大型滑坡防治中的应用成果 ,这种方法不仅能有效地控制滑坡体的稳定性 ,同时 ,也能根据移民工程要求提供适宜的建设用地 ;介绍了注浆方法对库区分布较广的以崩塌、滑坡、岩溶成因为主的崩滑堆积体的改造问题 ,它不仅可以大大降低移民迁建区地基与边坡处理的工程造价 ,也为库区灾害地质体的改造提供了范例 ;弃渣是库区极为突出的环境地质问题 ,不仅危害长江 ,也对移民迁建区构成严重威胁 ,本文介绍了巫山新城等利用加筋土技术处理弃渣 ,并大大增加建设用地的实例 ,由于该挡墙高达 5 6 m,超出了一般意义下的加筋土挡墙范畴 (通常不超过 2 0 m) ,因此出现了前缘筋带断裂和面板脱落问题 ,本文介绍了应用锚管注浆技术进行面板修复的设计 ,为复杂地质条件地区高加筋挡土墙的安全修建提供了经验.     

长江堤防工程地质信息处理模型及技术方法

长江中下游的主要防洪工程是长江干堤 ,长江堤防线路长、工程浩大、堤基工程地质水文地质条件复杂 ,涉及大量的已有地质数据和资料。今后在整治加固堤防的工程地质勘察工作中 ,还需随时进行数据的收集、存储、检索、分析、统计和维护 ,随时调用这些数据进行综合处理、编制报告和图件 ;在防汛期间可以针对堤防险工险段的险情 ,随时查询和调用有关的资料、数据或者图件 ,提供采取抢险措施决策的地质依据。这既提高了地质数据的利用价值和利用率 ,又保证了信息的准确性、完整性和共享性。因此 ,建立合理的长江堤防工程地质信息处理模型及其成熟的技术方法具有重要的意义。     

南沙群岛工程地质环境分区与质量评价

南沙群岛海区自然资源丰富,但工程地质条件复杂,地质灾害频繁。随着对该海区海洋资源的开发和其它海洋工程活动的增加,调查和研究其工程地质环境与质量评价就成为非常必要的前期工作。本文在分析了南沙群岛海区地质构造、活动断裂和火山地震活动的基础上,结合海洋水动力环境要素将南沙海区工程地质环境划分为5个区:南部陆架区、西部陆坡区、南沙海槽区、礼乐滩微陆块区、珊瑚礁隆起区,并深入分析了各分区的环境特征。     

地震CT勘探原理及其在公路隧道病害诊断中的应用

地震CT勘探是一种新的地球物理方法。具有分辨率高、可靠性强、信息量大、图象直观的特点。可以广泛地用于线路、场地、隧道、边坡等项目的工程地质勘查和病害诊断。在元磨高速公路芭蕉箐隧道的地质病害诊断中应用地震CT进行勘探,取得了良好的效果。     

地理信息系统GIS支持下的城市地质环境评价

以 GIS为支撑工具 ,对城市地质环境空间数据库的建立方法、城市建设用地类型的初步划分及城市建设用地与地质环境的协调性评价模型作了分析 ,并选取典型实例进行剖析 ,结果表明 GIS是城市地质环境研究的有效工具。     

当前国际环境地质工程(环境岩土工程)研究的热点领域及其相关技术

当前环境地质工程(或称环境岩土工程)(EnvironmentalGeotechnology)国际学术讨论会的频繁召开, 反映了世界各国对解决环境问题的迫切愿望, 预示着一个世纪性的环境地质工程研究热潮已经到来。结合我国的国情分析这些会议所研讨的内容, 将有助于提高对当前环境地质工程热点研究领域的认识, 从而在解决国家所面临的环境问题及经济社会可持续发展中发挥应有的作用。本文是作者对当前国际环境地质工程(环境岩土工程)研究热点领域及其相关技术的集成。由于环境问题的广泛性, 对于国内的传统环境工程地质和地质灾害内容不加重复, 但它们同样重要。     

长江三峡工程库区巴东新城址环境工程地质预测

巴东县城新址是长江三峡工程库区移民城镇环境工程地质问题较突出的场址之一, 主要环境工程地质问题是古滑坡的失稳和库岸再造。在查清地质环境条件的基础上, 本文着重进行了黄土坡古滑坡、赵树岭古滑坡等古滑坡的稳定性预测, 并根据实测的有关参数, 采用图解法预测库岸再造宽度。在此基础上, 根据影响该区城市开发建设的主要的地质环境要素, 建立隶属函数, 采用模糊综合评判模型及算法, 给出巴东县城新址区的城市开发建设的环境地质分区评价。     

横观各向同性液体饱和多孔介质中平面波的传播

基于孔隙介质的Ｂｉｏｔ理论１，研究了横观各向同性液体饱和多孔介质中平面波的传播特性。首先导出了波传播的特征方程并给出了其解析解，结果显示：有４种不同波速的平面体波传播；第一准纵波，第二准纵波，准横波和反平面横波。文中给出了波速和衰减的解析表达式，数值计算了频散曲线和衰减曲线，并讨论了各类准体波位移之间的耦合关系。     

Characteristic analysis for stress wave propagation in transversely isotropic fluid-saturated porous media

According to generalized characteristic theory, a characteristic analysis for stress wave propagation in transversely isotropic fluid-saturated porous media was performed. The characteristic differential equations and compatibility relations along bicharacteristics were deduced and the analytical expressions for wave surfaces were obtained. The characteristic and shapes of the velocity surfaces and wave surfaces in the transversely isotropic fluid-saturated porous media were discussed in detail. The results also show that the characteristic equations for stress waves in pure solids are particular cases of the characteristic equations for fluid-saturated porous media.     

Attenuated Wave Field in Fluid-Saturated Porous Medium with Excitations of Multiple Sources

This research addresses the investigation of an elastic wave field in a homogeneous and isotropic porous medium which is fully saturated by a Newtonian viscous fluid. A new methodology is developed for describing the wave field in the medium excited by multiple energy sources. To quantify the relative displacements between the fluid and solid of the medium, the governing equations of the elastic wave propagation are derived in the form of displacements specially. The velocities and attenuation of the waves are considered as functions of viscosity and frequency. Making use of the Hankel function and the moving-coordinate method, a model of the wave motion with multiple cylindrical wave sources is built. Making use of the model established in this research, the relative displacement between the fluid and the solid can be quantified, and the wave field in the porous media can then be determined with the given energy sources. Numerical simulations of cylindrical waves from multiple energy sources propagating in the porous medium saturated by viscous fluid are performed for demonstrating the practicability of the model developed.     

Singularities on wave fronts of slow waves in anisotropic fluid-saturated porous media

Energy focusing is found on the wave fronts of slow waves, which is a new propagation characteristic for slow waves in fluid-saturated porous materials. The material parameters, as well as the propagation directions, are chosen as the control parameters. Combined with the two axial variables, the influence of the anisotropy of the solid skeleton and pore fluid parameters on the propagation characteristic of slow waves in anisotropic fluid-saturated porous materials is discussed. The correspondence between the focusing on the wave fronts and the contours of zero Gaussian curvature on the slowness surface is explored. The development of the focusing patterns is investigated and the distinct trends in the energy flux focusing structures are revealed. This is helpful in further understanding the roles of the pore fluid in the damage of the fluid-saturated porous media.     

On well-posedness of the dynamic problem for an anisotropic fluid-saturated solid

It is known that a high degree of anisotropy in the constitutive behaviour of a solid may result in the loss of hyperbolicity of the dynamic equations in the form of either complex-conjugate or purely imaginary characteristic wave speeds (flutter ill-posedness and shear band formation, respectively). In the present paper we investigate the characteristic wave speeds in the dynamic problem for a transversely isotropic fluid-saturated porous solid. Three cases are considered: a dry solid and a saturated solid under locally undrained and drained conditions. It is shown that, for given constitutive parameters of the solid skeleton, the dynamic problem for a drained solid may become ill-posed due to the flutter-type loss of hyperbolicity, while the dynamic equations for a dry and an undrained solids remain hyperbolic. For a given solid skeleton, the characteristic wave speeds are strongly influenced by the pore fluid compressibility which, in turn, is extremely sensitive to the presence of a small amount of free gas.     

On dispersive propagation of surface waves in patchy saturated porous media

Frequency-dependent velocity and attenuation for Rayleigh-wave propagation along a vacuum/patchy saturated porous medium interface are investigated in the low frequency band (0.1–1000 Hz). Conventional patchy saturation models for compressional waves are extended to account for Rayleigh wave propagation along a free surface. The mesoscopic interaction of fluid and solid phases, as a dominant loss mechanism in patchy saturated media, significantly affects Rayleigh-wave propagation and attenuation. Researches on the dispersion characteristics at low frequencies with different gas fractions in patchy saturated media also demonstrate a strong correlation between the Rayleigh-wave mode and the fast compressional wave. Especially, the strongest attenuation with the maximum value of 1/Q$1/Q$ for Rayleigh waves are obtained in the frequency range of 1–200 Hz. Numerical results show that the significant dependence of velocity and attenuation on frequencies and gas fractions presents a distinctive dynamical response of Rayleigh waves in the time domain.     

Squirt-Flow in Fluid-Saturated Porous Media: Propagation of Rayleigh Waves

Propagation of attenuated waves is studied in a squirt-flow model of porous solid permeated by two different pore regimes saturated with same viscous fluid. Presence of soft compliant microcracks embedded in the grains of stiff porous rock defines the double-porosity formation. Microcracks and pores respond differently to the compressional effect of a propagating wave, which induces the squirt-flow from microcracks to pores. Elastodynamics of constituent particles in porous aggregate is represented through a single-porosity formulation, which involves the frequency-dependent complex moduli. This formulation is deduced as a special case of double-porosity formation allowing the wave-induced flow of pore-fluid. This squirt-flow model of porous solid supports the attenuated propagation of two compressional waves and one shear wave. Superposition of these body waves, subject to stress-free surface, defines the propagation of Rayleigh wave. This wave is governed by a complex irrational dispersion equation, which is solved numerically after rationalising into an algebraic equation. For existence of Rayleigh wave, a complex solution of the dispersion equation should represent a leaky wave, which decays for propagation along any direction in the semi-infinite medium. A numerical example is solved to analyse the effects of squirt-flow on phase velocity, attenuation and polarisation of the Rayleigh waves, for different combinations of parameters. Numerical results suggest the existence of an additional (second) Rayleigh wave in the squirt-flow model of dissipative porous solids.     

不可压饱和粘弹性多孔介质的变分原理及其无网格模拟

基于饱和多孔介质理论,在固相和液相微观不可压,固相骨架小变形且满足线性粘弹性积分型本构关系的假定下,建立了流体饱和粘弹性多孔介质动力响应的若干Gurtin型变分原理,包括Hu-Washizu变分原理.利用所建立的变分原理,导出了流体饱和粘弹性多孔介质动力响应无网格数值模拟的离散控制方程,此方程是一个关于时间的对称微分方程组,便于分析计算.作为数值例子,研究了流体饱和粘弹性多孔柱体的一维动力响应,数值结果揭示了流体饱和粘弹性多孔柱体中波的传播特性以及固相粘性的影响.     

A mixture theory analysis for the surface-wave propagation in an unsaturated porous medium

The mixture theory is employed to the analysis of surface-wave propagation in a porous medium saturated by two compressible and viscous fluids (liquid and gas). A linear isothermal dynamic model is implemented which takes into account the interaction between the pore fluids and the solid phase of the porous material through viscous dissipation. In such unsaturated cases, the dispersion equations of Rayleigh and Love waves are derived respectively. Two situations for the Love waves are discussed in detail: (a) an elastic layer lying over an unsaturated porous half-space and (b) an unsaturated porous layer lying over an elastic half-space. The wave analysis indicates that, to the three compressional waves discovered in the unsaturated porous medium, there also correspond three Rayleigh wave modes (R1, R2, and R3 waves) propagating along its free surface. The numerical results demonstrate a significant dependence of wave velocities and attenuation coefficients of the Rayleigh and Love waves on the saturation degree, excitation frequency and intrinsic permeability. The cut-off frequency of the high order mode of Love waves is also found to be dependent on the saturation degree.