马兰煤矿主斜井底水仓底板加固防治水方法

山西太原古交矿区马兰煤矿主斜井底水仓布置在奥陶系顶部隔水关键层内,其底板为奥陶系峰峰组灰岩,隔水层厚度4.17 m,受到底板奥灰承压含水层的严重威胁。为了消除突水隐患,在水仓底板岩石变形破坏机理模拟研究的基础上,同时考虑到研究区奥灰含水层距离近、水量大的特殊情况,探索出一种新型注浆加固方法对水仓底板进行注浆加固,并取得了良好效果。设计为一钢筋混凝土盖先覆于水仓底板上,同时用加强筋与围岩连接,之后再采用浅孔低压与深孔高压交替注浆充填的方法进行加固。此方法使水仓底板与围岩成为一个整体,对浆液起到封闭作用,使底板更加稳固。     

北京市南水北调工程水工隧洞初期支护方案研究

水工隧洞应用日趋广泛,如何确定水工隧洞初期支护方案是设计中的重点课题。以北京市南水北调配套工程南干渠工程为背景,通过现场试验确定水工隧洞支护施工配合比,然后对网喷混凝土支护及钢纤维喷射混凝土两种初期支护结构进行数值模拟研究,并结合现场监测及现场施工效果,进行浅埋水工隧洞支护方案研究。研究结果表明：采用钢纤维喷射混凝土支护与网喷混凝土支护相比,钢纤维喷射混凝土支护更能保证施工安全。研究成果对于类似隧洞设计及施工具有借鉴和参考价值。     

四论灾害系统研究的理论与实践

为了提高广西台风防减灾业务的时效性和精准度,基于自然灾害风险评估理论和方法,根据2010年广西生态遥感本底数据和社会经济空间化数据、地理信息数据,构建耦合自然生态和社会经济的台风灾害承灾体脆弱性指标体系,运用基于GIS的风险指数法,建立台风灾害承灾体脆弱性评价模型,实现了像元尺度的广西台风灾害承灾体脆弱性精细化评价。结果表明:广西台风灾害承灾体高脆弱区域主要分布在桂南、桂东南高暴露于台风灾害的建设用地和生态易损农用地、水土流失严重的裸地,占全区面积的25.9%;低脆弱区主要分布在桂东、桂东北、桂西北、桂西社会经济落后和植被覆盖度较高的山区,占全区面积的45.6%。

     

Effect of abutment modeling on the seismic response of bridge structures

Abutment behavior significantly influences the seismic response of certain bridge structures. Specifically in the case of short bridges with relatively stiff superstructures typical of highway overpasses, embankment mobilization and inelastic behavior of the soil material under high shear deformation levels dominate the response of the bridge and its column bents. This paper investigates the sensitivity of bridge seismic response with respect to three different abutment modeling approaches. The abutment modeling approaches are based on three increasing levels of complexity that attempt to capture the critical components and modes of abutment response without the need to generate continuum models of the embankment, approach, and abutment foundations. Six existing reinforced concrete bridge structures, typical of Ordinary Bridges in California, are selected for the analysis. Nonlinear models of the bridges are developed in OpenSees. Three abutment model types of increasing complexity are developed for each bridge, denoted as roller, simplified, and spring abutments. The roller model contains only single-point constraints. The spring model contains discrete representations of backfill, bearing pad, shear key, and back wall behavior. The simplified model is a compromise between the efficient roller model and the comprehensive spring model. Modal, pushover, and nonlinear dynamic time history analyses are conducted for the six bridges using the three abutment models for each bridge. Comparisons of the analysis results show major differences in mode shapes and periods, ultimate base shear strength, as well as peak displacements of the column top obtained due to dynamic excitation. The adequacy of the three abutment models used in the study to realistically represent all major resistance mechanisms and components of the abutments, including an accurate estimation of their mass, stiffness, and nonlinear hysteretic behavior, is evaluated. Recommendations for abutment modeling are made.     

光纤应变仪的研制与应用前景

光纤应变仪是利用特种光纤光栅器件或者光纤干涉技术进行高精度应变传感的仪器.常见特种光纤光栅有相移光栅和光纤光栅谐振腔,线宽均较窄,可达到0.01 pm量级甚至更窄,结合高精度解调方法,可显著提高系统的应变测量精度.     

曹妃甸浅滩表层砂体插桩深度研究

曾妃甸浅滩原为古滦河三角洲,三角洲废弃后,海底表层沉积物在波浪潮流的簸选及自重应力作用下,沉积物颗粒粗化,粒度单一,且堆积紧密,工程强度较高。平台在该海医插桩时往往难以贯穿该层,其实际插桩深度较预定深度存在较大偏差。本文对此类砂体的形成机制、插桩过程中土体的压实作用对砂体强度的影响进行了分析,在对砂体力学参数做出适当调整后,运用太沙基地基极限荷载公式进行计算,得到了与实际情况较为一致的结果。     

柔度法纤维模型在方钢管混凝土柱滞回仿真中的应用

本文编制了基于二阶柔度法纤维模型梁柱单元的矩形钢管混凝土框架结构非线性分析程序,采用虚拟阶步法和改进的滞回路径追踪方法消除了其中截面切线刚度矩阵奇异时无法求逆的隐患,提高了算法的稳定性.运用此程序对矩形钢管混凝土柱进行滞回仿真,并与试验结果对比,结果表明:柔度法纤维模型梁柱单元可以有效解决框架结构的几何非线性问题和压弯耦合的材料非线性问题,使用较少的单元数量就可以得到较准确的计算结果;本文所采用的改进措施切实有效,保证了程序的稳定性.     

密肋复合墙体非线性数值分析及抗剪承载力研究

结合课题组前期的研究成果,通过对墙体中不同材料的本构模型、墙体中裂缝、多种材料的联结以及墙体边界条件的研究与探讨,运用通用有限元程序ANSYS对密肋复合墙体进行非线性有限元分析;并在试验结果与有限元模拟的基础上,依据极限平衡理论,建立起来复合墙体的斜截面抗剪极限承载力公式。理论分析与试验研究表明:复合墙体非线性有限元模型能够较好地模拟墙体内力和变形发展的全过程,描述裂缝的形成和扩展,对于实际工程和科学研究具有足够的精度;墙体斜截面抗剪承载力公式与实测值吻合较好,具有一定的精度,满足工程设计需要。     

高层隔震结构模型双向振动台试验研究

对一缩尺1∶16比例高宽比为5的橡胶垫隔震结构模型进行了双向地震动输入振动台试验研究。通过输入不同大小和类型的地震波,分析隔震上部结构和隔震支座的地震反应。试验结果表明:隔震上部结构减震效果较好;隔震支座在某些工况下,竖向可进入非线性受拉变形状态,此时的结构存在倾覆危险。试验相关数据的分析可为高层隔震结构设计理论和规范的编制提供试验依据。     

Mixing of event and pre‐event water in a shallow Entisol in sloping farmland based on isotopic and hydrometric measurements,SW China

Water percolation and flow processes in subsurface geologic media play an important role in determining the water source for plants and the transport of contaminants or nutrients, which is essential for water resource management and the development of measures for pollution mitigation. During June 2013, the dynamics of the rainwater, soil water, subsurface flows and groundwater in a shallow Entisol on sloping farmland were monitored using a hydrometric and isotopic approach. The results showed that effective mixing of rainwater and soil water occurred in hours. The rebound phenomenon of δD profiles in soils showed that most isotope‐depleted rainwater largely bypassed the soil matrix when the water saturation in the soil was high. Preferential‐flow, which was the dominant water movement pattern in the vadose zone, occurred through the whole soil profile, and infrequent piston‐flow was mainly found at 20–40 cm in depth. The interflow in the soil layer, composed of 75.2% rainwater, was only generated when the soil profile had been saturated. Underflow in the fractured mudrock was the dominant flow type in this hillslope, and outflow was dominated by base flow (groundwater flow) with a mean contribution of 76.7%. The generation mechanism of underflow was groundwater ridging, which was superimposed upon preferential‐flow composed mainly of rainwater. The quick mixing process of rainwater and soil water and the rapid movement of the mixture through preferential channels in the study soil, which shows a typical bimodal pore size distribution, can explain the prompt release of pre‐event water in subsurface flow. Water sources of subsurface flows at peak discharge could be affected by the antecedent soil water content, rain characteristics and antecedent groundwater levels. Copyright © 2016 John Wiley & Sons, Ltd.