覆盖区地球化学异常特征及甄别方法探讨

覆盖区地球化学异常是由自然和人为因素引起的，在土壤垂直剖面上元素有多种分布类型，它反映了元素在土壤中迁移、演化及人为干扰的分布特征；通过对自然和人为污染的地球化学异常源追踪和评价，为环境污染治理和地区经济可持续发展提供决策依据。     

Influences of overburden pressure and soil dilation on soil nail pull-out resistance

Soil nailing is the most popular technique for stabilizing newly formed and existing sub-standard slopes in Hong Kong because of its economic and technical advantages. The nail–soil interface shear resistance is an important parameter in design of soil nailed structures. A three-dimensional finite element model was established and used for simulating soil nail pull-out tests. The finite element model was verified by comparing simulated results with measured data. The agreement between the experimental and simulated results in terms of both average pull-out shear stress and stress variation was very good. Using this finite element model, a parametric study was carried out to study the influences of the overburden pressure and soil dilation angle on the soil nail pull-out resistance. The simulated peak pull-out resistance was not directly related to the overburden pressure, which was coincident with the observations in laboratory pull-out tests. The simulated pull-out resistance increased significantly with the increase in dilation angle of the shearing zone. This analysis indicated that the constrained dilatancy of the nail–soil interface and the soil surrounding the nail contributed a lot to the development of peak pull-out resistance.     

红层与煤系复合结构覆岩采动破坏分析及其应用

许多矿区煤层采动影响范围内的覆岩层由红层和煤层共同构成。本文研究了山东省太平煤矿东区二叠系 3号煤层覆岩破坏和防水煤柱留设的问题 ,在对上覆第四系水文地质条件分析的基础上 ,对红层和煤系复合结构覆岩的工程地质特征和破坏状况进行了分析 ,确定了合理的防水煤岩柱高度 ,并经过开采验证 ,避免了水害发生.     

黄土场地覆盖层厚度和地形条件对地震动放大效应的影响

针对黄土地区场地条件的特点分析研究了场地覆盖层厚度和地形因素对地 震动放大效应的影响规律。通过对大量实际算例的归纳统计,给出了一种定量评价场 地覆盖层厚度及地形因素影响的经验方法。为黄土地震灾害预防及减轻技术研究提 供了参考依据。     

Seismic interferometry experiment in a shallow cased borehole using a seismic vibrator source‡

We present the results of a seismic interferometry experiment in a shallow cased borehole. The experiment is an initial study for subsequent borehole seismic surveys in an instrumented well site, where we plan to test other surface/borehole seismic techniques. The purpose of this application is to improve the knowledge of the reflectivity sequence and to verify the potential of the seismic interferometry approach to retrieve high‐frequency signals in the single well geometry, overcoming the loss and attenuation effects introduced by the overburden. We used a walkaway vertical seismic profile (VSP) geometry with a seismic vibrator to generate polarized vertical and horizontal components along a surface seismic line and an array of 3C geophones cemented outside the casing. The recorded traces are processed to obtain virtual sources in the borehole and to simulate single‐well gathers with a variable source‐receiver offset in the vertical array. We compare the results obtained by processing the field data with synthetic signals calculated by numerical simulation and analyse the signal bandwidth and amplitude versus offset to evaluate near‐field effects in the virtual signals. The application provides direct and reflected signals with improved bandwidth after vibrator signal deconvolution. Clear reflections are detected in the virtual seismic sections in agreement with the geology and other surface and borehole seismic data recorded with conventional seismic exploration techniques.     

沉积盆地火成构造研究综述

岩浆活动在沉积盆地中是非常广泛的.随着油气勘探领域的扩展,对沉积盆地火成岩及相关构造的研究愈加重要.沉积盆地火成构造是指在沉积盆地中由岩浆侵入或喷发作用形成的岩浆和围岩及上覆层变形构造的总和.当前,利用三维地震数据研究岩席的几何学与侵位机制取得了重要进展,开启了沉积盆地火成构造研究的新时代.三维地震分析是沉积盆地火成构...     

上海覆盖区活断层

应用物、化探相结合的方法，首次证实了广为第四纪松散沉积层（平均厚度达２４０ｍ）所覆盖的上海地区存在着第四纪活断层，并对其基本特征和活动情况作了初步论述     

Geochemical approach to estimate the quality of water entering abandoned underground coalmines

Geochemical modeling was employed to estimate the chemistry of water infiltrating into abandoned underground flooded and unflooded coalmines of the Uniontown syncline, Fayette County, Pennsylvania. This was done to help evaluate factors governing the long-term evolution of coalmine discharge water quality in the Uniontown syncline area. The subsurface structure and lithology was delineated using borehole, mine shaft, and stratigraphic information. Hydrogeologic analyses indicated that most of the recharge to mine voids occurs in the zones of shallow overburden cover of less than 20 m in thickness. The water–rock contact period in the recharge areas of the overburden was estimated to be 5 days or greater for the flooded mines, and a day or less for the unflooded mines. Flow-through reaction-path models were applied to the topsoil and shale–sandstone lithological units identified in the recharge areas. The model predicted water entering the flooded mines at a pH of 6.65, alkalinity of 6.92 mequiv. l^–1 and a total sulfate concentration of 7.33 mM, and the unflooded mines at a pH of 6.68, alkalinity of 6.99 mequiv. l^–1 and a total sulfate concentration of 3.08 mM. The model predictions for the flooded and unflooded mines are consistent with groundwater data from the study site, indicating the usefulness of this approach in evaluating the contribution of overburden chemistry to the evolution of mine discharge quality.     

Arching within hydraulic fill stopes

Arching is a well known phenomenon, which effects stress developments which were investigated and compared using analytical and numerical solutions. Marston’s (1930) solution was extended to a generalised 3-dimensional rectangular stope and later modified for square and circular stopes for comparison with FLAC results. Aubertin et al. (2003) & Li et al. (2003) models were improved significantly by placing the backfill within narrow stopes as lifts or layers in numerical modelling where the normal stress variation with depth were found to be more realistic. The FLAC results were compared with analytical solutions which were developed by previous researchers and modified by the authors to evaluate the arching effects in backfilled placed in narrow and circular stopes. It appeared from the investigation herein that δ = 0.67 ϕ and K = K _o condition gives a very close match with the numerical model solutions obtained from FLAC. Many laboratory tests were conducted to find out friction angles for four Australian mines, which were between 30 and 49 degrees.     

超强地震作用下深厚覆盖层场地重力坝抗震安全研究

本文通过成层状地基地震动输入计算方法得到覆盖层边界自由场运动,采用粘弹性边界,考虑地基辐射阻尼效应及坝体和地基的接触非线性,针对强震区深厚覆盖层场地重力坝开展线性和非线性动力时程分析研究,结合需求能力比DCR评估其抗震性能.由线弹性动力时程分析可知,在运行基准地震OBE作用下,重力坝坝体应力均在允许范围内,其抗滑稳定安...