椭圆空洞对盾构隧道地震易损性曲线影响研究

采用增量动力分析方法,探究水平向地震下地层空洞对盾构隧道地震响应特征的影响规律。针对管片损伤及周边地层应力,选择弯矩比作为性能评价指标,峰值加速度(PGA)及峰值速度(PGV)作为衡量地震强度指标(IM),阐明椭圆形空洞对管片抗震性能的影响,得到隧道结构的地震易损性曲线。研究表明：椭圆空洞加大了浅埋盾构隧道的地震破坏概率;PGA与PGV均可作为IM并获得相应的隧道易损性曲线;使用弯矩比作为破坏指标,PGV作为地震动指标,其对应的易损性曲线对地层变异性更敏感。研究结论可为潜在空洞发育区防震方案的制定提供参考。     

深层碳酸盐岩储层溶洞围岩应力分布研究

以冀中凹陷任北奥陶系碳酸盐岩储层为例,基于油田测井资料及岩石力学实验确定了研究区岩石力学参数,对目标储层典型的长椭圆形孤立落水溶洞围岩应力进行了数值模拟,并根据第三强度理论研究了围岩破坏情况。研究结果表明,（1）溶洞在上覆岩层压力和侧向压力的共同作用下,长椭圆形溶洞围岩的应力集中效应带为9倍的半径范围;（2）长椭圆形溶洞围岩应力以压应力为主,主要集中分布在洞顶和洞底;（3）溶洞填充性对其围岩主应力差及破坏范围影响很大。当填充压力小于0.1 MPa时,溶洞围岩主应力差及破坏区域范围随填充压力的增大而增大;而当填充压力大于0.1 MPa时,溶洞围岩主应力差及破坏区域范围随填充压力的增大均呈减小的趋势。      

乌东德水电站大坝防渗帷幕成幕影响地质因素分析及处理措施

灌浆工程为地下隐蔽工程,其地质条件约束着实际的现场施工工艺,且不同地质条件对应不同的岩石属性,并将直接影响着防渗帷幕的优化设计,同时地质条件分析不足也将给整个灌浆工程带来很多不确定的风险。目前,地质条件预测在隧洞开挖过程中的研究较充分,但在灌浆工程中地质因素的研究较少。本文以乌东德水电站大坝防渗帷幕工程为例,分析了对防渗帷幕成幕有影响的岩溶、角砾岩、断层、岩层走向与帷幕走向大角度相交及长大结构面等地质因素,并针对不同地质因素的特点,提出了采取浓浆回填、灌浆孔加密加深、灌浆压力及浆材动态调整等处理措施,为帷幕灌浆工程优化提供了必要支持。     

天然气水合物开采过程甲烷气泄漏海床基高密度电阻率法监测效果模拟与分析

为实现天然气水合物开采过程沉积物内甲烷气泄漏过程有效监测,设计了一种海床基原位电学监测方法。为界定该方法对不同模式泄露甲烷气的探测能力,以南海神狐海域天然气水合物试采区为研究区,构建相应地质及电阻率模型,模拟利用设计电学系统对其进行监测,计算得到不同采集参数的电阻率剖面,并对其进行对比分析。研究结果表明：海水层会在探测剖面上某深度区间内形成层状低阻异常带,对该深度区间有效电信号形成压制。将该异常带顶界深度定义为系统有效探测深度后,发现该深度受电极距直接影响,10 m极距偶极装置有效探测深度约为50 m。电学探测剖面对有效探测深度内分布的层状和团状甲烷气聚集区、慢速甲烷气泄露区、沿断层泄露的甲烷气区具有良好反映能力,数据处理得到的相对电阻率剖面与电学探测剖面相比能更好地反映甲烷气聚集区边界。该监测方法能够实时监测含气区空间变化。     

泥蚶(Tegillarca granosa)重组铁蛋白富集重金属离子的特性及化学传感器的研究

利用泥蚶(Tegillarca granosa)铁蛋白原核表达工程菌获得的重组铁蛋白,通过圆二色光谱分析蛋白二级结构,扫描电镜和电感耦合等离子质谱研究重组铁蛋白富集Fe~(2+)、Mn~(2+)、Cd~(2+)、Cr~(3+)、Hg~(2+)、Pb~(2+)和As~(3+)等7种重金属离子的特性,同时探索利用重组铁蛋白修饰丝网印刷电极,设计和制备重组铁蛋白检测Pb~(2+)和Cd~(2+)浓度的电化学生物传感器。结果表明复性成功的铁蛋白多为完整的?-螺旋结构,而复性不成功的蛋白聚集体则多为无规卷曲。重组铁蛋白的直径和形态与富集的离子种类有关。泥蚶铁蛋白对单一金属离子Fe~(2+)和Mn~(2+)的富集凸显优势。对两种混合金属离子的富集大多表现为竞争关系。但重组铁蛋白对Hg~(2+)和As~(3+)混合组的富集量明显高于单一金属离子组的富集量,对Hg~(2+)和As~(3+)混合组的富集表现出协同促进作用。重组铁蛋白传感器对Pb~(2+)和Cd~(2+)溶液的最低检测限为10μg/L。     

Target Deployment and Retrieval Using JIAOLONG Manned Submersible in the Depth of 6600 m in Mariana Trench

China''s 7000 m manned submersible JIAOLONG carried out an exploration cruise at the Mariana Trench from June to July 2016. The submersible completed nine manned dives on the north and south area of the Mariana Trench from the depth of 5500 to 6700 m, to investigate the geological, biological and chemical characteristics in the hadal area. During the cruise, JIAOLONG deployed a gas-tight serial sampler to collect the water near the sea bottom regularly. Five days later, the sub located the sampler in another dive and retrieved it successfully from the same location, which is the first time that scientists and engineers finished the high accuracy in-situ deployment and retrieval using a manned submersible with Ultra-Short Base Line (USBL) positioning system at the depth more than 6600 m. In this task, we used not only the USBL system of the manned submersible but also a compound strategy, including five position marks, the sea floor terrain, the depth contour, and the heading of the sub. This paper introduces the compound strategy of the target deployment and retrieval with the practical diving experience of JIAOLONG, and provides a promising technique for other underwater vehicles such as manned submersible or Remote Operated Vehicle (ROV) under similar conditions.     

挠力河流域耕地水分盈亏时空变化特征及趋势模拟

为揭示挠力河流域耕地资源水分盈亏态势,以遥感影像、DEM数据和气象台站数据为基本信息源,基于遥感和GIS技术,对流域1990-2014年间耕地水分盈亏时空变化特征进行研究,并运用情景模拟技术模拟未来水分盈亏态势。结果表明：24 a间流域耕地面积增长放缓,1990-2002年水田急剧增加,旱地轻微上升,2002-2014年水田增长速度急剧下降,旱地面积减小;耕地水分盈亏程度变化明显,各等级耕地空间分布差异大,1990-2002年以中度和重度缺水变化为主,基本不存在严重缺水区,2002-2014年,轻度缺水区面积变化最大,重度缺水区缓慢下降。正常缺水是3期面积最大的缺水等级;模拟显示未来流域水分亏缺态势将更加严峻,高MPLD指数区分布更为集中,局部高水分亏缺区面积会进一步扩大,除轻度缺水区逐渐减少外,其余4种类型缺水区均保持增加,其中重度缺水区将大量增加。该研究结果可为挠力河流域农田灌溉方案的制定提供借鉴和参考。     

Polyaxial stress-dependent permeability of a three-dimensional fractured rock layer

A study about the influence of polyaxial (true-triaxial) stresses on the permeability of a three-dimensional (3D) fractured rock layer is presented. The 3D fracture system is constructed by extruding a two-dimensional (2D) outcrop pattern of a limestone bed that exhibits a ladder structure consisting of a “through-going” joint set abutted by later-stage short fractures. Geomechanical behaviour of the 3D fractured rock in response to in-situ stresses is modelled by the finite-discrete element method, which can capture the deformation of matrix blocks, variation of stress fields, reactivation of pre-existing rough fractures and propagation of new cracks. A series of numerical simulations is designed to load the fractured rock using various polyaxial in-situ stresses and the stress-dependent flow properties are further calculated. The fractured layer tends to exhibit stronger flow localisation and higher equivalent permeability as the far-field stress ratio is increased and the stress field is rotated such that fractures are preferentially oriented for shearing. The shear dilation of pre-existing fractures has dominant effects on flow localisation in the system, while the propagation of new fractures has minor impacts. The role of the overburden stress suggests that the conventional 2D analysis that neglects the effect of the out-of-plane stress (perpendicular to the bedding interface) may provide indicative approximations but not fully capture the polyaxial stress-dependent fracture network behaviour. The results of this study have important implications for understanding the heterogeneous flow of geological fluids (e.g. groundwater, petroleum) in subsurface and upscaling permeability for large-scale assessments.     

Laboratory investigation and simulation of breakthrough curves in karst conduits with pools

A series of laboratory experiments are performed under various hydrological conditions to analyze the effect of pools in pipes on breakthrough curves (BTCs). The BTCs are generated after instantaneous injections of NaCl tracer solution. In order to test the feasibility of reproducing the BTCs and obtain transport parameters, three modeling approaches have been applied: the equilibrium model, the linear graphical method and the two-region nonequilibrium model. The investigation results show that pools induce tailing of the BTCs, and the shapes of BTCs depend on pool geometries and hydrological conditions. The simulations reveal that the two-region nonequilibrium model yields the best fits to experimental BTCs because the model can describe the transient storage in pools by the partition coefficient and the mass transfer coefficient. The model parameters indicate that pools produce high dispersion. The increased tailing occurs mainly because the partition coefficient decreases, as the number of pools increases. When comparing the tracer BTCs obtained using the two types of pools with the same size, the more appreciable BTC tails that occur for symmetrical pools likely result mainly from the less intense exchange between the water in the pools and the water in the pipe, because the partition coefficients for the two types of pools are virtually identical. Dispersivity values decrease as flow rates increase; however, the trend in dispersion is not clear. The reduced tailing is attributed to a decrease in immobile water with increasing flow rate. It provides evidence for hydrodynamically controlled tailing effects.     

Mapping groundwater renewability using age data in the Baiyang alluvial fan,NW China

Hydrogeology Journal - Groundwater age has been used to map renewability of water resources within four groups: strong, partial, and rare renewability, and non-renewable. The Baiyang alluvial fan...