非均质地基中平面应变隧道开挖面稳定上限分析

非均质是软黏土地基中比较普遍的现象,而目前隧道开挖面稳定研究中比较成熟的理论主要是针对均质土体。因此,从塑性极限分析上限法的基本原理出发,采用平面应变隧道刚体平动破坏模式(多块体上限法),考虑软黏土地基的非均质性,推导了平面应变隧道极限支护压力关于隧道埋深、土体重度及土体强度的上限公式。通过与其他方法的比较分析,证明了极限分析方法在隧道开挖面稳定性方面的可行性;利用该方法的计算结果详细探讨了隧道开挖面稳定的影响因素;而且由计算结果可知,地基土的非均质性在影响隧道开挖面极限支护压力的同时,也影响着隧道开挖破坏面的位置和形状,为工程实践提供重要的理论依据。     

Determination of arsenic concentration and distribution in the Floridan Aquifer System

Here we report on the different sampling strategies for almost seven years of sampling rocks/sediments for the determination of As within the Intermediate Aquifer System (IAS) and upper Floridan Aquifer System (FAS), a very large and productive limestone aquifer spanning from Georgia into Florida. In the FAS, As contamination has become a recurring problem during aquifer storage and recovery (ASR), particularly in central and south Florida.To investigate these phenomena, samples from solid drill cores and rock cuttings were collected from the Hawthorn Group, Suwannee Limestone, Ocala Limestone and Avon Park Formation. Samples were taken along drill cores and rock cuttings (referred to as ‘interval’ samples) or from particular drill core sections and rock cuttings (referred to as ‘targeted’ samples) likely to contain elevated concentrations of As as indicated by the presence of pyrite, hydrous ferric oxide, organic matter, clay minerals, fracture surfaces, and high permeable (moldic) zones.Arsenic was present in all of the stratigraphic units at low concentrations, close to the global average for As in limestone of 2.6 mg/kg. The highest As concentration was 69 mg/kg. In all units, however, the average bulk As concentration in the targeted samples was substantially higher than that in the interval samples. Based on direct spot measurements by electron microprobe and indirect calculations, pyrite was identified as the main source of As in the FAS. Concentrations in pyrite ranged from less than 100 mg/kg to more than 11,000 mg/kg. Because pyrite is heterogeneously distributed, both vertically and horizontally in the sampled stratigraphic units, the same was observed for the distribution of As. However, As concentrations generally decreased with depth, i.e., highest As values in the Hawthorn Group and lowest As values in the Ocala Limestone and Avon Park Formation. Compared to pyrite, other trace minerals contained much less As.The average As concentrations of the two types of sample media (solid cores and rock cuttings) were quite similar. These results indicate that if simply the average bulk rock As concentration of a geologic unit is the desired outcome of an investigation, either interval or targeted sampling of rock cuttings, seems to be sufficient. This is particularly important when time and money are a factor. This approach could work equally well for any other trace element. Structural sedimentary information, such as fractures, etc., is likely lost, however, when sampling rock cuttings. Thus, if this information is required, solid core samples need to be collected by hollow core diamond drilling.     

砂卵石地层中防渗墙槽壁稳定性影响因素研究

地下连续墙或防渗墙施工中槽孔的开挖是极其重要的分项工程,泥浆护壁条件下槽壁的稳定性影响因素很多．应用ABAQUS有限元软件,考虑泥浆的渗透,模拟计算不同密度的泥浆以及泥浆分层后槽壁的位移,对槽壁的稳定性进行分析．经对槽壁位移值的分析得到泥浆密度增大槽壁的位移随之减小以及减小的幅度,随着泥浆的沉淀,槽壁位移增大．研究可为...     

四川马尔康日部地区地貌及地质特征对工程选址的影响

工程区周边地貌特征不但是判识新构造运动的重要标志,而且对河谷发育及区域稳定性评价是十分重要的.对拟建的大渡河巴拉水电站的河谷阶地以及水电站的上、中、下坝区域内的现存地貌和第四系进行了详细的调查,从研究当地地貌和河谷地貌特征、河流阶地及第四系河床沉积物入手,分析当地地质作用发育史及其主要影响因素.     

四川达县杨柳垭滑坡特征与稳定性分析

达县杨柳垭滑坡直接威胁到杨柳垭变电站的安全运行和云内华川厂职工生命财产安全,并将严重影响数个乡镇近百万人及工矿企业的正常供电,直接经济损失将达到数亿元.因此,尽快开展此处地质灾害勘查与治理工作十分必要.勘查采用了工程地质测绘、钻探、坑槽探及室内试验等手段,查明了滑坡形成机制、变形特征等,进行了稳定性和推力计算,满足了施...     

陆地水体参数的卫星遥感反演研究进展

以江河、湖泊与湿地等形式存在的陆地水体对气候变化和人类生产生活有着重要影响,准确掌握陆地水体参数的变化对全面理解地球水循环及有效管理水资源等具有重大意义,卫星遥感技术的迅速发展为陆地水体的动态监测带来广阔前景.围绕陆地水体的重要物理参数,回顾了基于卫星遥感来提取水域面积的光学遥感法、雷达遥感法和水域面积-水位关系法,获...     

清江水布垭库区南潭村滑坡特征及其稳定性

南潭村滑坡位于湖北巴东县水布垭镇南潭村,是发育于原斜坡表层及部分浅层风化基岩中的沿岩土接触面或软弱结构面发生滑移的岩土混合质滑坡。本文结合南潭村滑坡的地质环境资料和现场勘察结果,介绍了滑坡的形态特征、结构特征和变形特征,从地质条件、降雨和人类工程活动等三个方面分析了滑坡的形成原因和影响因素,并采用剩余推力法对滑坡的稳定性进行了定量计算。通过对滑坡进行综合评价,提出了排水系统、减载反压、改变种植方式和变形监测等综合防治建议,为滑坡灾害的研究和治理提供借鉴。     

瓦屋山水电站厂房区红层岩体古滑坡稳定性研究

红层岩体以其岩体结构的软硬相间及软弱夹层发育而在边坡稳定方面表现为"易滑地层".瓦屋山水电站厂房区边坡为顺向坡,砂岩类岩石与黏土岩类岩石呈缓倾、互层状(倾角10°～20°)产出.构造与表生改造作用下,在这两类软硬相间的岩石界面上常形成分布较为连续的软弱夹层,这类岩体较易沿软弱夹层产生顺层滑动.地质历史时期,瓦屋山厂房区...     

德州市德城区地籍调查数据整理入库工作探讨

全国第二次土地调查是一项重大的国情国力调查,在此次调查中笔者负责德城区调查成果数据入库。该文基于在第二次土地调查中的工作经验,就扫描档案文件、宗地权属信息和宗地界址信息快速整理入库提出几点方法,供广大一线工作者参考。     

蓬莱阁丹崖山安全监测与分析

丹崖山边坡稳定性是关系古文物蓬莱阁安全的关键问题。丹崖山边坡高差大、断层裂隙发育、岩体卸荷深度大,地质条件十分复杂,边坡在施工期和运行期的稳定性问题特别突出。该文介绍了丹崖山岩体加固后的监测布置,并对岩体表面变形趋势、空间分布形态、加固后变形趋势进行分析,通过对多点位移计、锚杆测力计、锚索测力计、表面裂缝计及地表变形等监测结果进行综合分析,得到边坡岩体的变形规律。