考虑渗流条件下开挖面失稳离心试验研究

当土压平衡盾构穿越高水位地层（如穿越江河）时,地下水与土舱之间的高水压差会产生过大的渗透力,导致开挖面失稳。为了研究渗流条件下开挖面失稳问题,开发了一套隧道离心模型试验装置,主要包括刚性模型箱、模型盾构、开挖面伺服加载系统、水位控制系统、储水箱。针对饱和砂质粉土地层,开展了一系列不同水位高度的稳态渗流开挖面失稳模型试验。结果显示,开挖面失稳过程中随着开挖面位移的增加,有效支护压力迅速下降;在达到最小值 之后缓慢回升并趋于稳定;极限有效支护压力 与水头压力 呈线性关系。     

神东矿区地下水变化观测与分析研究

针对西部大规模高强度煤炭开采对地下水的影响,利用神东矿区约1 500 km2区域的200余个钻孔的长期观测结果,研究了超大综采工作面开采工艺对地下水系统的影响规律,地下水流场变化与基岩和含水层空间分布的关系。研究表明,超大综采工作面开采形成了地下水"汇聚带",开采对基岩和含水层厚度较薄区的地下水系统影响较大,研究区采后含水介质厚度稳定且较厚区域含水层含水厚度损失大部分在30%左右,且逐步趋于稳定。      

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复用回采巷道护巷煤柱合理宽度研究

为解决高瓦斯工作面双U型巷道布置中煤柱损失大、相邻工作面复用回采巷道维护困难的难题,综合采用理论分析、数值计算和现场试验的方法,研究得到煤柱宽度对相邻两工作面之间煤柱内复用巷道围岩应力分布和变形特征的影响规律：随着巷道一侧煤柱宽度的增加,巷道围岩垂直应力峰值向一侧移动,并逐渐远离巷道;当巷道一侧煤柱较小时,巷道以窄煤柱帮变形和顶板下沉为主,随着煤柱宽度增加,底鼓增大并成为巷道主要变形。以煤柱内应力峰值比值为指标,分析煤柱宽度与巷道稳定性的关系,并将不同宽度煤柱进行了稳定性分区。研究成果成功应用于工程实践,为类似条件下巷道布置提供依据。     

Monitoring and numerical analysis of behaviour of Miaojiaba concrete-face rockfill dam built on river gravel foundation in China

This study evaluated the behaviour of a concrete face rockfill dam (CFRD) built on river gravel foundation on the basis of in-situ measurement records and numerical analysis. The monitoring records were obtained from a detailed deformation-monitoring system. A 3D finite element analysis was performed to assess long-term dam behaviour. The behaviour of the CFRD built on river gravel foundation was analysed comprehensively. A discussion of behaviour, especially with relevance to the behaviour of dams built on stiff-foundation, was included. The effect of the river gravel foundation was analysed, and the exact mechanisms were discussed. The relative contribution of various factors on the long-term behaviour of the CFRD was also studied. In-situ measurements were compared with numerical results to discuss the capability of the numerical model to predict the dam behaviour.     

防水措施对堤坝地震液化影响的数值分析

通过基于有效应力的完全耦合动力分析方法,研究了混凝土面板坝在地震作用下的动力响应,详细地讨论了堤坝迎水面斜坡上铺设的防水毯对堤坝地震液化的影响。计算中土体采用Cyclic mobility本构模型,该模型通过在修正剑桥模型上增加应力诱导各向异性、超固结和结构性的概念及其相关发展准则,可以很好地描述可液化土体的动力特性。计算结果表明防水毯的存在可以有效降低坝体的地下水位浸润线,增加坝基的初始有效应力,从而降低坝基地震液化发生的可能性,同时坝体的变形明显减小。     

不等长工作面台阶区域覆岩运动诱冲机制及防治

针对阳城煤矿不等长工作面台阶区域发生冲击地压灾害问题,基于工作面特殊布置方式及覆岩赋存特征,采用理论分析、数值模拟和现场实测等方法,分析了台阶区域覆岩结构运动特征和围岩应力演化规律,研究了台阶区域冲击地压诱发机制。研究结果表明：1304工作面台阶区域覆岩经历了“OX-S-C”型较为复杂的结构演变,覆岩空间结构由OX向S型转换时,顶板岩层大面积破断下沉,在台阶区域形成多个悬臂梁结构,越往高位,悬臂梁长度越大;受覆岩运动和采动应力场叠加影响,煤岩体形成高应力集中区,在顶板岩层动载冲击作用下,煤岩体弹性应变能突然释放,诱发冲击地压。采用COMSOL软件对不同卸压钻孔参数下煤体应变能分布特征进行模拟研究,优化了台阶区域卸压钻孔参数。根据模拟结果,随着钻孔孔径、孔深增大及间距减小钻孔卸压效果越明显,考虑工程实际,确定孔径为150 mm、孔深为30 m、间距为1 m为合理有效的卸压钻孔参数,并应用于1302工作面台阶区域的冲击地压防治,取得了较好的防冲效果。     

Comparison of 2D versus 3D modeling approaches for the analysis of the concrete faced rock‐fill Cokal Dam

This paper's primary purpose is to compare the 2D and 3D analysis methodologies in investigating the performance of a concrete faced rock‐fill dams under dynamic loading conditions. The state of stress on the face plate was obtained in both cases using a total strain based crack model to predict the spreading of cracks on the plate and the corresponding crack widths. Results of the 2D and 3D analyses agree well. Although significantly more demanding, 3D analyses have the advantage of predicting the following: (i) the opening of the vertical construction joints; (ii) the cracking at the valley sides; and (iii) the crushing of the plate during the seismic action. During the earthquake loading, the cracking predicted at the base of the face plate after the impounding spread significantly towards the crest of the dam; however, the crack widths are obtained relatively small. Crushing of the face plates at the construction joints is the primary cause of the large scale cracking predicted on the face plate for high intensity earthquakes. Earthquake induced permanent deformation of the fill increases the compressive stresses on the face plate, thereby reducing the minute cracking on the plate. However, this effect also leads to significant increases in the residual openings at the construction joints and at the plinth level. Copyright © 2013 John Wiley & Sons, Ltd.     

DÉTERMINATION DU DÉBIT DES PUITS INCOMPLETS DE NAPPES LIBRES FONCÉS EN TERRAIN ISOTROPE ET ANISOTROPE

ABSTRACT

In this paper, the author relies on Darcy's law and on an hypothesis formulated from experimental considerations to establish a semi-empirical formula for the calculation of the discharge of partially penetrating wells of free aquifer sunk in isotropic soils.

This relatively simple relation applied to 27 cases studied under an experimental design or numerical computations, reveals itself to have an unexpected accuracy.

Starting from previous formula, the author establishes another one for partially penetrating wells bored in anisotropic soils.     

Tracking of facial deformations in multi-image sequences with elimination of rigid motion of the head

The paper deals with measurement of human facial deformations from synchronized image sequences taken with multiple calibrated cameras from different viewpoints. SIFT (Scale Invariant Feature Transform) keypoints are utilized as image feature points in the first place to determine spatial and temporal correspondences between images. If no temporal match is found for an image point by keypoint matching, then the tracking of the point is switched to least squares matching provided the point has one or more spatial corresponding points in the other views of the previous frame. For this purpose, a new method based on affine multi-image least squares matching is proposed where multiple spatial and temporal template images are simultaneously matched against each search image and part of the spatial template images also change during adjustment. A new method based on analyzing temporal changes in the image coordinates of the tracked points in multiple views is then presented for detecting the 3-D points which move only rigidly between consecutive frames. These points are used to eliminate the effect of rigid motion of the head and to obtain the changes in the 3-D points and in the corresponding image points due to pure deformation of the face. The methods are thoroughly tested with three multi-image sequences of four cameras including also quite large changes of facial deformations. The test results prove that the proposed affine multi-image least squares matching yields better results than another method using only fixed templates of the previous frame. The elimination of the effect of rigid motion works well and the points where the face is deforming can be correctly detected and the true deformation estimated. A method based on a novel adaptive threshold is also proposed for automated extraction and tracking of circular targets on a moving calibration object.