A Three-Dimensional Analysis of the Total and Effective Stresses in Submerged Backfilled Stopes

The determination of the stress state in backfilled stopes is an important step for assessing the behaviour of mine openings and for designing barricades. Most previous analyses have considered only the 2D case (plane strain condition) and neglected the effect of pore water pressure. In this paper, a three-dimensional solution is proposed for totally or partly submerged backfill. The new solution gives the normal stresses along the vertical and horizontal axes, with the effect of a surface load on the backfill. The solution is validated using laboratory experimental results taken from the literature. The good agreement obtained between the proposed analytical solution and laboratory test results indicates that this new solution provides a realistic evaluation for both the total and effective stresses in vertical backfilled stopes.     

加筋砂土作用在挡土墙上的土压力研究

以土的塑性极限分析理论和拱体理论为基础，结合挡土墙的长高比，提出了墙后砂土的两种三维破坏模式，并把两种模式与加筋相结合，求出了在加筋水平间距Sx和竖向间距Sx下作用在墙上主动土压力的上限解和设计的加筋长度。最后通过实例验证了本文的理论。     

滨海地区吹填土地基加固处理差异性分析

滨海地区的围海造陆工程,多以海中泥沙直接吹填至造陆区域。由于吹填土质不均,在加固过程中,易引起吹填土地基沉降、孔隙水压力、土体强度等指标变化的差异性。文中分析了造成这种差异性的原因以及土体指标变化的规律性,并针对这种情况,提出了处理的建议。     

孔隙水压力量测的延迟效应分析

从理论上考虑，用压力传感器量测土中变化的孔隙水压力会存在延迟效应，本文阐明了延迟效应的机理，并以饱和土孔压消散试验为例进行了深入的分析，研究表明，延迟效应的主要影响因素是体积压缩系数和传感器敏感元件的刚度因数，从计算结果看出，除硬粘性土外，延迟效应对孔压量测结果影响甚小。     

钻孔和巷铜周围流体压力变化对围岩变形及应力状态的影响

钻孔、巷硐周围流体压力的分布和变化对围岩变形和应力状态有着显著影响。但这是一个涉及多个变量、多种响应的动态耦合过程，尚无法用解析法解算。孔硐周围的流体压力的动态变化又难以实现物理模拟。以钻孔排放瓦斯为例，通过数值模拟，结合宏观观测结果和微观机制的分析，对其规律和一些工程现象与措施的机理作了初步分析。     

Measurement and Analysis of Pore Water Pressure in Large Caverns and Shafts in a Hydro-electric Project

With an objective to understand the behaviour of pore water pressure around large underground openings, piezometers were installed in the rock around the desanding chambers, surge shaft, its drainage galleries, and the transformer cavern of a large hydro-electric project. The monitored data indicated that the pore water pressure was insignificant in the rock surrounding the desanding chambers prior to lining. On completion of the concrete lining of the chambers, the maximum pore water pressure was about 50 kPa as the flow of water was restricted. When one of the desanding chambers was charged with water, the piezometers around it indicated an excessive increase in the pore water pressure due to seepage of water from the chamber. Thus the piezometer readings were useful in taking appropriate remedial measures. In the surge shaft, higher values of pore water pressure were recorded on the hill side of the shaft as compared to the valley side. In one of the drainage galleries, the pore water pressure gradually increased to 450 kPa, which was released by drilling relief holes in the area. In the other drainage gallery, no significant change in the pore water was recorded. In the transformer cavern, the recorded pore water pressures were within 20 kPa.     

Analytical analysis of hydraulic effect of vegetation on shallow slope stability with different root architectures

A parametric study is performed to investigate hydraulic effect of vegetation on shallow slope stability with different root architectures in an infinite slope. Calculated results show during the first one hour of rainfall (181 mm/day), the exponential root architecture has higher ability to maintain shallow slope stability than the parabolic one. Under light rainfall (i.e., 20 mm/day) for 24 h, hydraulic effect of vegetation is more important inside root zone than outside root zone, while it is the opposite for rainfall intensities of 181 and 394 mm/day over the same duration. Parabolic rooted slope is more sensitive to rainfall pattern than bare one.     

An analytical solution for the nonlinear distribution of effective and total stresses in vertical backfilled stopes

The increasing use of backfill in underground mines requires a proper evaluation of the stress state in and around the filled openings. This is, however, a relatively complex issue due, in part, to the large contrast in strength and stiffness between the backfill material and surrounding rock mass. In recent years, it has been shown that arching theory, based on limit equilibrium analysis, can be used to estimate the stress distribution in backfilled stopes. Nonetheless, many simplifications are involved in such analytical solutions and this affects the precision and significance of the calculated results. In this paper, a previously developed solution is enhanced by introducing the combined effects of non-uniform vertical stress distribution and positive pore water pressure. This leads to a more representative analytical solution, as demonstrated by successful comparisons with numerical simulations. The results indicate that the proposed solution can be used to estimate the effective and total stress state in submerged or partially submerged backfilled stopes with a simple geometry.     

Study on Swell Pressure Stress of Bentonite in Geosynthetic Clay Liners

1 Introduction Bentonite is a valuable industrial material, which is composed mainly of montmorillonite. Due to many particular characteristics such as strong water sorbility, dilatability, stickiness, high ion-exchangeable capacity, Bentonite has been used widely in many fields of application, including petroleum, metallurgy and chemical industry, textile industry, medical application, construction, mining, agriculture, environment (Koch, 2002; Wang and Wu, 2002; Wagner and Schnatmeyer, 20…     

On the solutions of modeling a slug test performed in a two-zone confined aquifer

The slug test is a popular field method for estimating aquifer parameters. As a finite-thickness skin is present at a wellbore, the result of test-data analysis may represent average hydraulic properties of the skin and formation zones. Moench and Hsieh (Int. Assoc. of Hydrogeology, The IAH 17th International Congress on Hydrology of Rocks of Low Permeability, Int. Assoc. of Hydrogeology. Tucson, Arizona, 7–12 January) provided the Laplace-domain solution for a confined aquifer with a finite-thickness skin that satisfies the governing equations, boundary conditions, and continuity requirements at the interface of the skin and formation zones. Two new formulae presented here relate the modified zero-order Bessel functions of the first and second kinds to their first and second derivatives. Their solution is evaluated using the modified Crump approach for the Laplace inversion. The numerical values obtained by the modified Crump approach are compared with others based on finite-element modeling. The results indicate that the values based on finite-element modeling exhibit poor accuracy, attributed to errors in the mass balance equation and interface condition in their mathematical model.

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Resumen Los ensayos slug o tipo pulso son métodos populares de campo para estimar parámetros de acuíferos. Debido a que en los sondeos existe una membrana de espesor finito, el resultado del análisis de los datos del ensayo pueden representar las propiedades hidráulicas promedio de las zonas de la formación y dicha membrana. Moench AF y Hsieh PA (Asociación Internacional de Hidrogeólogos, 7–12 Enero 1985) Análisis de datos de prueba slug en un pozo con membrana de espesor finito. 17 Congreso Internacional de la Asociación Internacional de Hidrogeólogos sobre Hidrología de Rocas de Baja Permeabilidad. Asociación Internacional de Hidrogeólogos. Tucson, Arizona. 7–12 Enero. han aportado la solución en el ámbito de Laplace para un acuífero confinado con una membrana de espesor finito que satisface los requerimientos de las ecuaciones dominantes, las condiciones restrictivas, y de continuidad en la interfase de las zonas de formación y membrana. Las dos nuevas fórmulas que se presentan aquí relacionan las funciones modificadas Bessel de orden cero de la primera y segunda clase con su primera y segunda derivadas. Se evalúa su solución usando el enfoque modificado de Crump para la inversión Laplace. Los valores numéricos obtenidos mediante el enfoque modificado de Crump se comparan con otros valores numéricos basados en modelos de elementos finitos. Los resultados indican que los valores basados en el modelo de elementos finitos presentan poca precisión, que se atribuye a errores en la ecuación de balance de masa y a las condiciones de interfase en su modelo matemático.

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Résumé Le slug-test représente une méthode populaire de terrain pour estimer les paramètres d’un aquifère. Du fait de la présence d’une couche à l’épaisseur limitée sur un site de forages, le résultat de l’analyse des données du test pourrait représenté le terrain mais aussi cette couche. Moench AF et Hsieh PA (Association Internationale d’Hydrogéologie, 7–12 Jan 1985) Analyses de données de slug test dans un puits présentant une couche d’épaisseur finie. 17ème congrès international de l’AIH sur l’Hydrologie des roches de faible perméabilité, Association Internationale d’Hydrogéologie. Tucson, Arizona, 7–12 Jan. apportent une solution du domaine de Laplace pour un aquifère confiné avec une épaisseur limitée qui satisfait l’équation en question, les conditions aux limites, et les besoins de continuité à l’interface de la couche et de l’encaissant. Deux nouvelles formules présentées dans cet article met en relation les fonctions de Bessel modifiées d’ordre zéro du premier et second type, avec leur dérivées première et deuxième. Leurs solutions sont évaluées en utilisant une approche de Crump modifiée pour l’inversion de Laplace. Les valeurs numériques obtenues avec l’approche de Crump sont comparées avec d’autres approches utilisant les modèles aux éléments finis. Les résultats indiquent que les valeurs basées sur les modèles aux éléments finis montrent une faible précision, du fait d’erreurs dans le bilan hydrologique et les conditions aux limites dans le modèle.

     

钻孔压水试验水压式栓塞排水泄压问题研究

压水试验水压式栓塞较其他类型栓塞可靠、灵活,但一直存在试验结束后排水泄压难题,使该类型栓塞使用局限于浅孔及地下水位高的钻孔。本文对该问题进行了研究,提出了解决方案,设计了新型水压式栓塞结构。解决了一直以来水压式栓塞的排水泄压难题,突破了试验孔深限制,使水压式栓塞能得到广泛应用。介绍了该新型水压式栓塞的结构和工作原理以及工程应用效果。     

地壳的应力状态、构造附加静压力和岩石矿床形成深度的研究

本文对深度计算公式：D=P/d（式中D为深度,P为压力,d为密度）的应用提出质疑。该公式源自一个流体力学原理,即描述静流体中压力与深度关系的帕斯卡原理,所以只适用于流体。如果物质是一种固体,而不是液体或气体,它可以承受剪应力或差应力,则这一公式就不能应用。所有岩石,从出露地表深至核幔边界,都是固体。当外力作用于固体单元上时,固体的应力场存在两部分：均应力和差应力,不论外力是构造力还是重力。而当外力作用于液态物质时,在这个液体应力场中则总是只有均应力而无差应力。地应力测量结果表明,作用于垂直截面上的水平应力通常大于作用于水平截面上的垂直应力,而且越靠近造山带或剪切带,水平应力越大,显示构造力在地壳应力场中起某种主导作用。事实上推动板块运动的力主要是水平的,而非垂直的。地壳中某处的总静压力至少由两部分合成：由构造引起的压力和由重力引起的压力,前者称构造附加静压力。合理计算成岩成矿深度的方法,应该是从总压力中减去构造附加静压力,再除以岩石比重,即D=（P-Pt）/d,式中Pt为构造附加静压力。     

水利水电工程钻探绳索取心钻进中压水试验研究

在水利水电钻探中要充分发挥绳索取心钻进的优势,压水试验和绳索取心的有机结合是必须解决的重要问题,分析对比了全孔钻进双栓塞压水试验方案和不提大钻压水试验方案的优缺点,得出不提大钻压水试验方案能够很好的解决绳索取心应用到水利水电钻探中的适应性问题。     

上海软土的初始应力状态的影响研究

在K_0固结不排水三轴试验和各向等压固结不排水三轴试验的基础上,探讨初始应力状态对上海软土的强度和变形的影响规律,从而得出一些有益的结论,可供进一步的研究参考。     

蒸馏水中蒙脱石晶层间膨胀压力理论研究

蒙脱石颗粒周围的溶液浓度对其膨胀性有较大影响,传统的双电层模型可以对电解质环境下蒙脱石的膨胀特性做出较好的模拟,但并不适于蒸馏水的情况。针对膨润土在蒸馏水或纯水中已有的膨胀特性试验,本文在前人的研究基础上详细推导了蒸馏水中蒙脱石晶层间的膨胀压力模型,并给出一种简便算法。运用此算法可以避免非线性方程的求解,从而可以较方便的将膨胀力和晶层间距联系起来。     

围压和含水率对川西—藏东地区板岩残积土的动强度影响试验研究

受特殊地质构造条件影响,川西—藏东地区板岩、千枚岩等变质岩风化强烈,形成的残积土具有较为广泛的分布,对这一地区的变质岩残积土的动力特性开展研究,具有重要的意义。利用动三轴试验仪对川西—藏东地区板岩残积土进行分析测试,重点研究不同含水率、不同固结应力和振次下的动强度参数变化规律。结果表明,含水率和固结应力对试样动强度影响明显;在相同固结应力、固结比条件下,强度随含水率增大而减弱;在相同含水率、固结比条件下,强度随固结应力增大而增强,但都不呈正比例关系。板岩残积土的动强度指标动黏聚力随含水率的增加而明显减小,对含水率敏感性较强;动摩擦角则随含水率增加变化量较小,对含水率敏感性较低。     

柔性板桩板墙加固斜坡填方地基的土压力分配问题研究

通过对桩板墙挡土板的受力变形特征分析,指出桩间采用柔性挡土板时,作用于挡土板上的土压力相对较小。在对比分析拟化简仓法与卸荷拱法的基础上,针对当前挡土板土压力计算中存在的问题,对柔性板桩板墙加固斜坡填方地基展开试验研究,并重点研究桩前、桩后施工挡土板时墙后土压力的分布规律。通过对布置在挡土板上的位移计及预埋的土压力计进行监测,结果表明,挡土板布置在桩前时其挠曲变形及承受的土压力值较小,且桩间土拱效应更易得到发挥。挡土板上土压力自上而下多呈抛物线型分布,而作用于桩背侧的土压力分布相对复杂。通过对桩后布置挡土板的土压力分布规律进行为期21 d的监测,研究了土压力变化的时间效应。     

渤海高地饱压差油藏考虑应力敏感的产能评价方法

渤海高地饱压差油藏有着高地饱压差、储层压力变化幅度大等特点,为明确此类油藏应力敏感特性对于其储层产能的影响,论文以Q油田W组油藏为例,在岩心覆压气测渗透率实验的基础上,通过改变岩心有效应力,得出了岩心渗透率与所受有效应力的变化规律。实验表明岩心渗透率与其所受有效应力存在着乘幂式关系,将此变化规律应用于产能分析中,推导考虑应力敏感的稳态产能公式,并绘制产能图版进行对比分析。考虑应力敏感后的产能明显出现整体降低的现象,在不同的储层渗透率下,都存在一个相应的最优生产压差限,这对于渤海高地饱压差油藏合理生产制度的制定具有指导意义。     

中间主应力对垂直井井壁坍塌压力的影响

运用线弹性本构模型来分析垂直井井壁应力分布,并分别用Mohr-Coulomb准则、Drucker-Prager准则和Mogi-Coulomb准则3个强度准则来计算平谷地应力测量与监测钻孔维持井壁稳定所需的最小钻井液液柱压力。通过对比分析得出考虑中间主应力的作用,会使岩石强度得到加强,使得维持井壁稳定所需的最小液柱压力降低;3个准则得出的最小液柱压力在与深度的对应图中表现出一致的变化趋势,说明3个准则有各自的适用性;比较而言Mohr-Coulomb准则偏于保守,Drucker-Prager准则偏于危险,而Mogi-Coulomb准则要优于前两个准则。     

青藏公路沿线通信光缆埋设地段冻土工程地质条件及评价

青藏公路沿线季节冻土和多年冻土的总长度为７６０ｋｍ，根据气温冻结指数和融化指数可估算最大季节冻结深度和最大季节融化深度。根据含水量划分出５种冻土类型和５个冻胀敏感性等级。提出了光缆埋设若干选线和施工建议。