探地雷达在隧道衬砌混凝土质量检测中的应用

简要介绍了应用探地雷达对隧道衬砌混凝土质量进行检测的方法、原理及其实际应用效果。测试结果表明,探地雷达能及时、快速地发现衬砌混凝土的质量问题,为工程质检和评价提供依据,是一种能很好地对衬砌混凝土的质量进行检测的无损检测方法。     

湘中芭蕉冲金矿土壤地球化学特征及找矿前景分析北大核心CSCD

湘中芭蕉冲金矿区为低山丘陵地球化学景观区,位于羌塘-扬子-华南板块东北缘,区内已查明4个工业矿体,矿体受断裂构造控制。本文以该矿为基础进行湖南省中低山丘陵景观区土壤地球化学找矿研究,以供同行参考。在该区完成土壤地球化学测量30 km,采集土壤样品1435件,样品采集深度在30~40 cm,部分采集深度为40~50 cm,成分均为土壤B层。利用多元统计学方法,对Au、Ag、Pb、Zn、As、Sb、Hg七种元素进行R聚类分析、因子分析及地球化学参数统计,确定Au、Ag为主成矿元素,Pb、As为找矿指示元素,运用衬值异常推断了隐伏构造位置,圈定单元素异常39处,综合异常区6处。通过地质工程查证,证明了衬值异常推测的含金构造的存在,发现芭蕉冲F_(2)含金构造和工业矿体,实现该区域的找矿突破。     

浅析某基坑工程及其对相邻建筑物的影响

通过工程实例,探讨了深基坑工程在设计、施工过程中存在的问题。通过工程测量的方法,对基坑变形以及相邻建筑物的位移进行了监测,并根据这些监测数据对基坑失效的原因以及对相邻建筑物的影响进行了分析。对基坑以及相邻建筑物的安全提出了建议。     

基于监控量测的公路隧道二次衬砌受力分担比例

依托垫江至邻水高速公路铜锣山及明月山隧道,对公路隧道二次衬砌受力分担比例进行研究。通过围岩压力实测值与普氏理论、太沙基理论和公路隧道设计规范深埋围岩压力公式计算值进行对比,结果表明: Ⅲ级、Ⅳ级和Ⅴ级围岩压力计算值比较符合实测情况。通过对围岩压力、初期支护与二次衬砌的接触压力现场量测数据进行分析,得出Ⅲ级( 深埋) 、Ⅳ级( 深埋) 、Ⅴ级( 深埋) 和Ⅴ 级( 浅埋) 围岩二次衬砌受力分担比例分别为29. 20%、35. 28%、41. 38% 及32. 17%。研究成果对于公路隧道结构设计有着理论指导作用。     

基于褶皱几何参数统计规律的渗漏量评估方法

褶皱网络中褶皱的空间分布是水力通性分析及渗漏量评估的基础。褶皱的空间分布规律尚待研究。基于一个典型场地的场底褶皱网络,利用K-S检验方法分析了褶皱几何参数服从的概率分布类型,统计得到了褶皱几何参数相应的统计参数。提出了基于褶皱几何参数的统计规律随机生成褶皱网络,并对随机褶皱网络进行渗漏量评估,然后从随机分析得到的渗漏量中选择特征值来表征场地的渗漏量的方法。通过案例分析,研究了该方法的应用。结果表明：对典型场底褶皱网络的统计分析为确定类似场地中褶皱几何参数的概率分布类型和统计参数具有重要的参考价值。由随机生成的褶皱网络得到的渗漏量样本的均值可以作为特征值,用来保守地评估场地内实际的渗漏量。基于案例分析,在对褶皱几何参数统计规律积累了丰富的经验后,可以实现对待建场地的设计不再需要获取整个场地的航拍图像,从而为有褶皱场地渗漏量评估提供了新思路。     

川西南某水电站库水渗漏评价的灰域模拟

基于灰色系统理论,采用灰色取值法代替量化分析中的确定性条件与参数,提出了水库渗漏评价的灰域模拟方法。结合金沙江某巨型水电站库水渗漏问题进行了实例分析,结果表明地下水流动系统灰域模拟是大型水库选址、勘探、水库渗漏评价以及水库运行后长观孔布置等工作的有效工具     

Q2饱和黄土隧洞围岩变形特征研究

Q₂饱和黄土含水率高,强度低、变形大。饱和黄土隧洞围岩变形破坏一直是工程界关心和亟待解决的问题。利用隧洞围岩收敛变形、二次应力场监控量测与数值分析,获取隧洞围岩动态综合信息,研究在一次支护条件下,隧洞围岩的收敛变形和应力变化特征。结果显示,隧洞围岩收敛变形和应力在最初的10~15天呈线性快速增长趋势。后期,收敛变形随时间呈非线性增加,受一次衬砌的限制,其变形在隧洞开挖30~40天后渐趋于稳定,但应力持续增加,反映Q₂饱和黄土隧洞围岩具有显著的时效特性。为避免隧洞围岩压力过大,造成隧洞围岩及支护破坏,建议在开挖后30~40天施作二次衬砌。     

Quantification of groundwater recharge in the city of Nottingham, UK

 Groundwater is an important and valuable resource for water supply to cities. In order to make full and wise use of the asset value, a clear understanding of the quantities and sources of urban groundwater recharge is needed. The water supply and disposal network is often an important source of recharge to urban groundwater through leakage from water mains and sewers. An approach to establishing the spatial and temporal amounts of the three urban recharge sources (precipitation, mains and sewers) is developed and illustrated using the Nottingham (UK) urban aquifer. A calibrated groundwater flow model is supplemented by calibrated solute balances for three conservative species (Cl, SO₄ and total N), thus providing four lines of evidence to use in the recharge estimation. Nottingham is located on a Triassic sandstone aquifer with average precipitation of 700 mm/year. Using the models, current urban recharge is estimated to be 211 mm/year, of which 138 mm/year (±40%) is from mains leakage and 10 mm/year (±100%) is from sewer leakage. The wide confidence intervals result from the scarcity of historical field data and the long turnover time in this high volume aquifer, and should be significantly lower for many other aquifer systems. Received: 1 December 1997 · Accepted: 14 September 1998     

Flow exchange between the deep and shallow groundwaters in the Sbeϊtla synclinal basin (Tunisia): an isotopic approach

Stable (¹⁸O, ² H) and radiogenic (³H, ¹⁴C) isotopes of water have been used to constrain the source, origin, age, migration pathway and mixing processes in the Sbeïtla (Tunisia) system. The system is composed of an upper unconfined Middle Miocene aquifer with a variable thickness from 10–300 m, an intermediate confined/unconfined Lower Miocene aquifer about 100 m thick and a deeper confined Lower Cretaceous aquifer about 150 m thick separated by a thin clay layer. A total of 53 groundwater samples from the three aquifers and spring samples were collected during February and March 2000 and isotopically analysed using conventional methods. The stable isotopes composition of waters establishes that the deep groundwater (depleted as compared to present corresponding local rainfall) is ancient water recharged probably during the late Pleistocene and the early Holocene periods. The relatively recent water in the superficial aquifer is composed of mixed waters resulting presumably from upward leakage from the deeper groundwater. The radiogenic (³H, ¹⁴C) isotopes data confirm that the recent water, with a tritium content between 6.5 and 19 TU, represents post-nuclear recharge and the ancient groundwater with low carbon-14 contents between 7 and 26 pmC infiltrated between 8,000 to 20,000 years ago. When used in conjunction with the stable isotopes data, the mixing process can be clearly identified, especially in the Sbeïtla sill area. Groundwater of the upper aquifer exhibits isotopic signatures of both the old and recent waters. By using isotopic mass balance, the computed contribution of the deep groundwater in recharging the upper aquifer is up to 94%.     

济南岩溶地区小岭重点渗漏带补源试验

为了解济南趵突泉泉域重点渗漏带下伏可溶性岩补源渗漏特征、影响因素及对泉水的影响,以小岭重点渗漏带为研究对象,采用野外调查、地球物理勘探、钻探、补源试验、模型评估等方法,分析小岭重点渗漏带下伏可溶性岩石岩性、厚度、岩溶发育情况、影响因素及补源渗漏量,评估补源效果。结果表明：小岭重点渗漏带下伏岩层为炒米店组,岩性主要为中厚层微晶灰岩、薄层状灰岩、泥质条带灰岩,厚度自东向西从7.6 m向56.3 m增厚,岩溶发育较弱,受千佛山断裂影响,发育规模大的断裂带两侧岩溶越发育,岩溶发育带越宽,补源渗漏能力越强。在钻孔补源条件下,小岭重点渗漏带断裂两侧精准补源地段炒米店组地层补源渗漏量为20 023 m³·d⁻¹。在综合考虑其他补源措施的情况下枯水期补源量为15 000 m³·d⁻¹、补源时长1个月对泉水的影响值为2 cm。