共查询到20条相似文献，搜索用时 609 毫秒
1.
Krishna R. Reddy Hanumanth S. Kulkarni Rajiv K. Giri Milind V. Khire 《Geomechanics and Geoengineering》2017,12(2):115-136
Horizontal trenches (HTs) are constructed during the waste filling for leachate recirculation in bioreactor landfills. Leachate distribution depends on HT configuration (i.e., spacing between successive HTs), leachate injection rate, modes of injection, and hydraulic properties and MSW heterogeneity. Presently, the effects of these variables on the moisture distribution have not been studied systematically. This study provides a systematic evaluation of the effect of the HTs variables on the moisture distribution and pore fluid pressures. A two-phase flow model is used to model a bioreactor landfill having an HT leachate injection system. It quantifies the effects of the unsaturated hydraulic properties and MSW heterogeneity, trench configuration, leachate injection flux, and mode of injection on hydraulic behaviour. The results show that unsaturated hydraulic conductivity and MSW heterogeneity significantly shape the zone of influence and excess pore pressures. Under heterogeneous-anisotropic conditions, the leachate migrates more laterally and the developed pore-pressures are lower than for homogeneous MSW. A closely-spaced, multi-level, staggered HT system is found to provide uniform and adequate moisture distribution in MSW. An intermittent mode of injection that alternates between the shallow and deep trenches with a higher leachate injection flow rate is found to be effective to control the excess pore pressures. 相似文献
2.
寒区输油管道基于应变设计的极限状态研究 总被引：5，自引：4，他引：1
寒区输油管线沿线地质环境复杂,滑坡、冻胀、融沉等自然灾害会导致管道形成大差异变形量.而差异变形量所引起的应力应变行为直接影响管道的安全服役性能,严重时会使管道破坏失效.基于寒区输油管道在实际服役工况下的受力变形条件,充分考虑冻胀效应、油压效应和热应力效应对输油管道的影响,分析了不同长度、壁厚、油压条件下轴向拉伸应变的分布规律及其影响因素.基于轴向应变设计理论准则,建立了上述条件下输油管道的极限服役状态,得到了对应状态下输油管道的许应最大极限冻胀变形量.结果分析表明,采用基于应力的设计准则偏保守,采用基于轴向应变的设计准则能更多的利用管材的变形性能.可为管道的合理设计、安全评价、完整性管理提供一定的理论参考. 相似文献
3.
Li Li Jean-Sébastien Dubé Michel Aubertin 《Geotechnical and Geological Engineering》2013,31(4):1027-1039
Infrastructure rehabilitation and development are very active fields around the world. Many of these activities involve the installation of conduits buried in trenches. The analysis and design of such conduits often rely on a solution developed by Marston and his coworkers who used the basic arching theory proposed by Janssen. This solution is theoretically only valid for vertical trenches, but it has been used for trenches with different wall inclinations, which sometimes leads to non-conservative stresses. In this paper, a more general solution for the stress state in backfilled trenches is developed based on the approach adopted by Marston and his coworkers. The effects of wall inclination and of a surcharge on top of the backfill are introduced in the analytical solution. Numerical modeling is performed and the results are used to adjust some components of the equations, leading to a more general solution. The good correlation between the vertical stress distributions given by the proposed solution and additional numerical simulations indicates that this new solution is representative of the stress state in backfilled trenches, and can thus be used for the design of infrastructure rehabilitation and development. 相似文献
4.
基于Biot饱和多孔介质U-W格式动力控制方程,采用Galerkin法和Fourier变换,推导了饱和土体2.5维有限元方程及黏弹性人工边界,建立了饱和土地基中空沟分析模型,并在波数域中进行求解,通过快速Fourier变换（FFT）进行波数展开,获得三维空间域中结果。算例分析了移动荷载作用下均质饱和土地基、分层饱和土地基、上覆单相弹性层饱和土地基3种饱和土地基模型中空沟的隔振效果。结果表明：饱和土地基中空沟的隔振效果不仅与空沟自身深度有关,还与地基中成层土体的分界面以及土体参数有关,波在不同土体分界面上的透射和反射会影响空沟的隔振效果;饱和土地基中上覆单相弹性层厚度对空沟的隔振效果影响显著,随着上覆单相弹性层厚度的增加,饱和土地基中空沟的隔振效果变好。 相似文献
5.
为研究空沟对高速列车引起地基振动的隔振效果,在已有研究基础上改进出一种新的解析研究模型。模型中首次运用了饱和半空间模型来研究地基上隔振沟对高速列车的隔振效果;隔振沟则通过在饱和半空间土体上设置3个合适宽度、截面为矩形的弹性层来模拟;中间矩形弹性层为路堤,路堤上方放置了枕木与轨道。枕木与轨道分别通过纵向异性Kirchhoff薄板与Euler梁来模拟,饱和土地基采用Biot多孔饱和介质理论来描述。控制方程通过傅立叶变换与傅立叶级数展开,在变换域中进行求解。研究表明,随着列车运行速度的提高,空沟的隔振效果明显提高;饱和土体固-液相的耦合作用对隔振沟的隔振效果的影响明显,尤其当列车运行速度超过土体表面Rayleigh波速时,随着土体渗透系数的增加,空沟隔振效果显著降低。此外,列车运行速度超过土体表面波速时,饱和土地基上空沟的隔振效果明显优于相应单相弹性地基上空沟的隔振效果。 相似文献
6.
The stabilisation of deep landslides is still a challenge for geotechnical engineers, mainly due to the high cost of structural control works that generally lead engineers to opt for drain systems. Unfortunately there are operative difficulties affecting excavation of deep drain trenches in soils dislocated by landslides (especially as regards the provisional support of the excavation walls). Small- and medium-diameter wells are a valid alternative in deep landslides, being less expensive than large-diameter wells equipped with horizontal pipes and simpler to construct than deep trenches. However, no technical procedures for their proper design are reported in the literature: design criteria commonly used in practice are derived from pumping problems and are largely inadequate, being based on Dupuit’s hypothesis that presumes stream lines to be horizontal. This paper presents numerical solutions obtained from three-dimensional seepage and consolidation analyses of a slope drained by small- and medium-diameter wells, arranged according to various positions, showing that the efficiency of the well system decreases as the depth of the landslide slip surface increases. Comparison is also made between well systems and deep trenches occupying the same draining volume in the landslide body, showing that the former attains much greater efficiency than the latter. Non-dimensional abaci for the square grid of wells (which is the most effective arrangement) are reported herein to be used for practical purposes.
相似文献7.
根据Biot波动理论,采用复变函数与多级坐标法,求解了P波作用下饱和土体中地下输流管道的波动散射方程,分析了管道中流体介质性质、入射波角度及管道埋深等对地下输流管道周边动应力集中系数及孔压集中系数分布的影响。计算结果表明：在低频弹性波入射时,管道周边动应力集中系数及孔压集中系数分布相对均匀,而随入射频率的增加,其分布变得复杂化,但其峰值有所减小;中低频波入射作用下,管道内为水、石油介质时,动应力集中系数和孔压集中系数较空气介质时小,而在高频波作用时情况相反;对于管道内流体介质为水时,随着入射角度的变化,应力集中分布也沿一定角度的方向发生转动,入射波自管道下方垂直入射时,管道周边动应力集中系数峰值相对较大;随埋深的增加,动应力集中系数和孔压集中系数均呈震荡减小的趋势。 相似文献
8.
应力状态改变对土压力影响的分析 总被引：1，自引：0，他引：1
对基坑开挖引起地基土应力状态以及地下水状态改变给土压力计算带来的影响进行了深入的分析,提出了应采用侧压减少试验和卸荷试验方法确定的强度指标来计算主、被动土压力等计算方法. 相似文献
9.
Current analytical methodologies for the evaluation of soil pressures on laterally displaced pipelines, as in the case of differential (e.g. fault-induced) permanent ground movements, allow the use of sand fill material properties under the condition that the size of the trench is adequate so that the failure surface develops fully within the sand fill (i.e. “free field” response). The accuracy of this assumption is investigated in this paper by means of numerical analyses, which employ a number of advanced features, such as pipe-backfill interface elements, large strain formulation and mesh rezoning. Following verification against well-documented experimental data, the analyses investigate: (a) the shape and size of the failure mechanism, as well as, (b) the potential trench effects on soil pressures and pipeline strains in the case of a strike-slip fault rupture. It is shown that for small embedment depths soil failure extends to the ground surface, in the form of a general shear failure mechanism, while for larger depths it becomes progressively localized and surrounds the pipeline. It is also shown that, for most cases of pipeline diameter and embedment depth, common trench dimensions cannot contain the “free field” failure surface dimensions. Finally, analyses for limited trench dimensions, reveal that the ultimate soil pressure increases exponentially with decreasing trench width, leading to high bending strains in pipelines subjected to differential lateral ground displacements. 相似文献
10.
三明移动通讯大楼基坑降水设计方案比较分析 总被引：1，自引：0，他引：1
通过对两种不同基坑降水的设计方案进行分析对比,阐述了降水技术要求,预防周边建筑物不均匀沉降的防治措施,从而提高工程设计的经济效益和社会效益。 相似文献
11.
ELSE KOLSTRUP VAGN MEJDAHL 《Boreas: An International Journal of Quaternary Research》1986,15(4):311-321
Excavations for an oil pipeline in western Jutland provided the opportunity to study geological features in the trenches. Among these were ice wedge casts, composite wedge casts, and wedges with primary infilling of eolian sand. In this paper the characteristics of three wedges with a high proportion of primary infill of eolian sand are described in some detail. Thermoluminescence (TL) dating was made on the eolian sand using 0.1–0.3 mm grains of quartz and potassium feldspar. The TL ages are: 39,000 ± 5,000, 24,000 ± 3,000, and 17,000 ± 3,000 years B.P. These ages are discussed and compared with indirect datings. Palaeoenvironmental conditions at the time of maximum cold during the upper part of the Weichselian are briefly considered. 相似文献
12.
地下连续墙槽壁稳定性分析 总被引：3，自引：0，他引：3
根据土层的物理力学性质、地下水位及护壁泥浆等进行地下连续墙槽壁稳定性分析,导出槽壁稳定性数学模型公式,并提出相应的护壁措施,防止槽壁的坍塌 。 相似文献
13.
Influence of Water Pressure on the Stress State in Stopes with Cohesionless Backfill 总被引：2，自引：2，他引：0
The rapid increase of backfill use in underground mines requires a better understanding of the interaction between the fill
material and the surrounding rock mass. This is a fairly complex issue as backfill materials are weak compared to the rock
mass. This difference in the mechanical behavior induces a stress transfer along the contact area. Previous work conducted
on backfilled trenches and mining stopes has shown that basic arching theory can be used to estimate earth pressures in narrow,
vertical openings. In this regard, most existing solutions have been developed for dry backfills. However, in many cases,
water is present in mine stopes, so its effect should be assessed. In this paper, the authors present a solution to evaluate
the stress state in submerged or partially submerged backfilled stopes. The proposed analytical solution is validated against
numerical modeling results. 相似文献
14.
基坑止水,对基坑(特别是深基坑)开挖及地下结构施工至关重要。根据多年的工程施工实践,总结和分析用于基坑开挖止水的水泥搅拌桩施工工艺流程和质量控制方面的有关问题。 相似文献
15.
The deformation of the oceanic lithosphere subducting at the junction of two trenches is studied by means of a three-dimensional finite-element analysis. Results show that the existence of a junction (i.e. a change in trend of the trench axis) yields a specific shape of the outer topographic rise. In a convex junction area—such as the Japan and Kuril trenches, the topographic bulge presents a “dome”, whereas in a concave junction area—such as the Java and Sumatra trenches, this bulge is less pronounced. These theoretical results are confirmed by the bathymetry seaward of the junctions of the Japan and Kuril trenches and of the Peru-Chile trench. Moreover, the existence of the abnormal topographic dome in front of a convex junction contributes to the creation of normal faults which help the subduction of seamounts or of other bathymetric features in such areas. 相似文献
16.
空沟是一种常用的连续隔振屏障,可以有效地降低人工振动。以位移为变量的二维格子法在波动问题计算中具有良好的适应性、高效性,兼备有限元与差分法的一些优点,应用该法针对层状地基中作用于路堤上的交通荷载引起振动的空沟竖向隔振问题进行了参数研究,分别考虑了上软下硬地基和上硬下软地基两种情况。研究结果表明：空沟宽度对隔振效果的影响较小;空沟深度与空沟的位置是影响隔振效果的关键因素,它们相互关联,其取值应综合考虑;在上述两类层状地基中,若空沟深度与上层土的厚度接近或相等均对竖向隔振不利;路堤高度越大对竖向隔振效果越不利。 相似文献
17.
L. F. Muratov Dr. 《GeoJournal》1991,23(3):207-214
The mathematical model of Raleigh convection on the rotating Earth in deepwater ocean depression is generalized for the case including the meridional temperature gradient. A steadystate thermal shear flow, in the origin of convective instability induced by this gradient has an effect contrary to the stabilizing influence of the Earth rotation. The stability of this flow has been studied with respect to the three-dimensional disturbances. Critical parameters determining the convection are calculated for the Kuril-Kamchatka and Japan trenches. The velocity components of tidal flow have been calculated using the hypothesis of Prandtl mixing way for bottom layer of trenches and the dynamic Richardson number has been calculated. It was noted that dynamic stability condition in bottom layers of the Kuril-Kamchatka and Japan trenches vary within tidal cycle. The periodical component for harmonics O1 and M2 has been calculated. 相似文献
18.
R. W. Van Bemmelen 《Tectonophysics》1974,22(1-2)
Blue-schists are the product of an eo-alpine metamorphic event in former trenches (foredeeps), under conditions of high confining pressures and relatively low temperatures. The metamorphic sedimentary rock sequences are generally associated with basic to ultra-basic rocks of the ophiolitic suite (and their metamorphic equivalents), both appearing in belts of partly plastically deformed, partly highly imbricated Pennine-type nappes.The metamorphism and tectonization of the foredeeps (trenches) with their sedimentary and igneous contents occurred during the overriding of major Austroalpine nappes from the concave (inner) side of the orogenic arcs. The foreland is passively subducted during this major orogenic phase (the ‘Flysch phase’ of Alpine-type orogeny).In those cases where the foreland is a continental lithosphere (such as the foreland of the Alpine belt in the Mediterranean) the subduction is less deep than in those cases where the “foreland” is formed by an oceanic lithosphere (such as in the case of the Japan arc).The geological setting of blue-schists in the Alpine system of the western Mediterranean shows that the load pressures produced by the Austroalpine nappes were generally lower than the confining pressures required by experimental data. Tectonic overpressures, produced during phases of high strain-rates which temporarily sealed off the pore fluids, may have produced the supplementary amount of confining pressure. An additional advantage of this hypothesis is, that it accounts for the occurrence of glaucophane-type metamorphism without such unusually low thermal gradients as those prognosticated by petrological experiments.Circum-Pacific blue-schist belts might be the result of deep subduction. However, the problem of rapid exhumation is then the stumbling block for the geodynamic model of plate-tectonics (Model I). The field data of observation do not confirm the expectation of this model, that subsequently dozens of kilometers of isostatic uplift occurred, exposing erosion levels from such great depths.On the other hand, the model of mantle-diapirism (Model II) suggests, that even if the trench deposits were subducted to great depths (passive subduction) upthrusting movements radiating from ‘Stockwerke’ of gravitational instability would drag up the high-P, low-T metamorphism immediately after its formation, in one and the same major phase of orogeny (flysch phase).The geological case-history of the Japan arc is analysed and its diagnostic facts are compared with the predictions (prognoses) of Model II. This verification leads to a confirmation of the functional correctness of this model of mantle-diapirism.A geodynamic analysis of the tectonic evolution and the present structural and geophysical situation of the Japanese realm leads to the conclusion that the driving forces of orogeny and seismicity are produced by stress-fields of gravitational instabilities that may occur in various structural levels (“Stockwerke”). These Stockwerke range in depth from near-surface to the top of the lower mantle, that is over a range about one thousand kilometers. This is a more complicated, but yet more realistic interpretation of the driving forces of orogeny, than the oversimplified views of plate-tectonics. 相似文献
19.
R. Siddharthan 《国际地质力学数值与分析法杂志》1987,11(2):155-170
The stability and deformation of the seafloor in response to storm wave loading is an important consideration in the design of pipelines, anchors, and offshore structures such as gravity-and pile-supported platforms. Two quite different approaches have been proposed for investigating the effects of storm waves on seafloor sands. These approaches derive from quite different considerations of soil-water interaction. In one of these approaches (exemplified by Yamamoto and Madsen) the seafloor is visualized to be a porous elastic or Coulomb-damped porous nonlinear medium. In this approach, the response of the seafloor, i.e. the displacements, stresses and porewater pressures, are computed for a given wave. The response is transient and is, therefore, related to the largest wave in the storm wave group. On the other hand, in the approach proposed by Seed and Rahman, only the development of residual porewater pressures (for estimating liquefaction potential) due to the storm wave group are considered. The effects of transient porewater pressures and stresses on the seafloor sands are ignored. The residual porewater pressures are computed using properties based on initial effective stresses through a porewater generation-dissipation model. The application of these techniques to problems of offshore structures such as pile-supported platforms has led to considerable uncertainty and confusion. In this paper, both of these approaches are combined to investigate seafloor response to a storm wave group. For typical storm wave conditions that exist in the North Sea, it appears that the inclusion of damping, inertia and anisotropic permeabilities in the study is not important relative to ocean sands. Parametric studies show that, for a given wave, the thickness and the stiffness properties of the soil deposit dictate the response of the deposit. The displacements in the deposit are, therefore, affected by the generation of residual porewater pressures. 相似文献
20.
非线性波浪作用下海底管线-海床动力响应分析 总被引：1，自引：0，他引：1
确定波浪荷载作用下海底埋置管线和海床的响应是海底管线设计中的关键问题。目前大多数研究只是考虑了管线、海床在线性推进波作用下的响应,并没有考虑管线与海床之间的相互作用效应。采用接触摩擦理论,考虑管线与海床之间的相互作用效应,基于有限元方法研究了非线性波浪作用下海底埋置管线和多孔海床相互作用问题。数值计算结果表明,在计算中如果忽略波浪非线性项,既有可能低估海底管线内应力及管线周围海床中孔隙水压力,也有可能高估海底管线内应力及管线周围海床中孔隙水压力。 相似文献