西安地裂缝勘察中的地震勘探

提出了隐伏地裂缝和次级地裂缝是现今工程地震勘探的主要对象 ,并根据探槽资料给出了隐伏地裂缝潜伏的深度 ;根据地震勘探剖面提出了地裂带除主裂缝外还存在一个规模较大的次级裂缝 ,次缝位于主缝上盘 ,与主缝呈“丫”字型构造 ,在深度 30 0～ 5 0 0m处与主缝汇合 ;文中最后提供了西安地裂缝不同勘察阶段的地震勘探观测系统经验参数 ,并给出依地震勘探结果开挖探槽的验证实例。     

西安地铁四号线沿线长安地裂缝研究

采用地面调查、钻探和槽探等方法,对临潼—长安断裂带内西安地铁四号线沿线的长安地裂缝进行了研究。钻探剖面显示,在地面高程变化梯度最大处附近存在地裂缝异常,异常两侧的古土壤标志层出现明显错断。对其中一处异常进行了大型探槽开挖,探槽两侧壁剖面显示:地裂缝带由1条主缝和数条次缝组成;主缝走向平行于临潼—长安断裂,南东盘相对下降,倾向南东,与临潼—长安断裂倾向相反,倾角80°～85°;主缝错断古土壤层1.1m,相对于上升盘,地裂缝下降盘地层厚度变大。研究结果表明,长安地裂缝发育在特定的构造地貌部位,即临潼—长安断裂带内"梁洼"地貌黄土梁南侧高程变化梯度最大处附近,由构造活动引起,具有正断层性质和生长断层性质,与西安地裂缝具有相同的构造特征。     

抽水诱发的基岩潜山型地裂缝高风险区模拟预测

长期超采地下水是诱发地裂缝的重要因素之一。为了揭示由地下水开采诱发基岩潜山型地裂缝的成因机制,预测地裂缝发育的高风险区,根据无锡某一典型的工程地质剖面,采用FLAC3D接触面单元模拟地裂缝,建立了包含21个接触面单元的数值模型;分析了地下水开采过程中土体的变形特征,依据接触面的开度变化,对地裂缝的高风险区进行了预测。模拟结果表明,对于基岩面起伏、压缩层厚度不均匀的地层,地裂缝的高风险区位于基岩潜山山脊的上方。通过与现场调查结果的对比,验证了本文所提出的采用FLAC3D接触面单元预测地裂缝高风险区的方法是可行的和有效的。     

基于三维地震勘探研究地裂缝空间展布特征

 为了研究地裂缝空间展布特征和发育规律,在晋中盆地地表有地裂缝出露的区域开展三维地震勘探。地震数据采集采用端点激发束状观测系统进行,数据处理通过叠前时间偏移来提高地裂缝空间归位精度和成像效果,基于地震多属性分析特别是蚂蚁体追踪技术对地裂缝进行解释。研究区勘探面积4 km2,共解释出地裂缝20条,其中主地裂缝11条,次级地裂缝9条。地裂缝在平面上呈线条状,走向以NEE向为主,总体与晋中盆地主干断裂走向一致,构造方向性非常明显,所解释的地裂缝有的裸露于地表,有的延伸到基岩面;在剖面上地裂缝两侧地层上下错移,落差为0～40 m;在空间上主要表现为地垒构造和地堑构造两种形式。研究区地表出露的5条地裂缝,有4条在本次勘探中被验证,这表明三维地震勘探在探测地裂缝地质灾害方面是一种有效的方法。     

胶结黏土中正断层扩展的变形和孔压变化研究

基岩断层错动而引起的上覆土体变形会对地表以及地下结构物造成破坏。上覆土体的胶结特性和隐伏断层的存在,使得断层错动的变形机制更为复杂。采用滤纸技术模拟隐伏断层,通过2组离心机试验研究胶结土体中正断层裂缝的扩展机制及伴随的孔压变化规律。对土体的变形分析和孔隙水压力的监测加深了对地裂缝的认识。研究发现,正断层错动引起胶结黏土的变形机制为受弯变形。隐伏断层使得土体受弯区变小、土体破坏程度加剧。胶结黏土受弯形成的地裂缝分为张拉裂缝和剪切裂缝,这些地裂缝的发展为超孔压的消散提供了优势路径。     

胶结黏土中正断层扩展的变形和孔压变化研究

 基岩断层错动而引起的上覆土体变形会对地表以及地下结构物造成破坏。上覆土体的胶结特性和隐伏断层的存在,使得断层错动的变形机制更为复杂。采用滤纸技术模拟隐伏断层,通过2组离心机试验研究胶结土体中正断层裂缝的扩展机制及伴随的孔压变化规律。对土体的变形分析和孔隙水压力的监测加深了对地裂缝的认识。研究发现,正断层错动引起胶结黏土的变形机制为受弯变形。隐伏断层使得土体受弯区变小、土体破坏程度加剧。胶结黏土受弯形成的地裂缝分为张拉裂缝和剪切裂缝,这些地裂缝的发展为超孔压的消散提供了优势路径。     

“y”形地裂缝场地主次裂缝地震响应差异的振动台试验

以西安地裂缝F6和F6’长安立交段"y"形地裂缝场地为背景,对"y"形地裂缝场地主次裂缝地震响应差异开展1∶15的振动台模型试验研究。试验结果表明,El Centro波激励下:1主、次地裂缝两侧的响应加速度放大系数Ki,j均随激励的增大整体上呈减小趋势,这种变化趋势在激励加速度峰值为300Gal时出现拐点;主地裂缝底部处的放大系数大于次裂缝同深度处的放大系数;主、次裂缝顶部和中部的加速度响应差异不明显。2底部加速度响应远离主、次裂缝均明显增强;激励加速度峰值≤200Gal时,中部加速度响应远离主、次裂缝均明显衰减,而顶部加速度响应远离主裂缝反而增强;主、次地裂缝加速度响应距离裂缝的衰减规律差异不明显。3主、次地裂缝顶部的下盘加速度响应均大于上盘,但底部的上盘加速度响应均大于下盘,这种上下盘效应随激励的变化趋势不明显,与主、次地裂缝的相关性也不明显。     

西安市长安地裂缝场地勘察与工程设计探讨

长安地裂缝是新近发现的地裂缝,分布在临潼—长安断裂带南盘.总体为北东走向,活动方式为南倾南降,与分布于临潼—长安断裂带北盘的西安地裂缝有相似的构造条件,但与西安地裂缝活动性有较大差异,该地裂缝活动性较弱,自晚更新世以来的地质历史时期中,未见明显活动,处于隐伏状态.文章对长安地裂缝的基本特征和成因进行了分析,对地裂缝场地勘察与工程设计进行了探讨.     

地裂缝场地的工程设计

地裂缝是地质构造和环境地质共同作用形成的,其两侧的地表沉降和主裂面的差异沉降会导致附近建筑地基下沉。距离越近下沉越大,如果建于其上,建筑很可能损坏。因此取得合理的距离是工程设计的关键。介绍西安地区地裂缝场地的设计经历和个人建议。1地裂缝的形势西安市南从大雁塔北到龙首塬,分布有七条地裂缝。均为东西走向,从地面以70°~80°角向地下延伸。倾斜面是南面在上,北面在下,见图1。图1地裂缝示意选定四个观测点,在一年中对每一个点的裂缝两侧分四次测值,发现每次都有沉降,累计沉降为12~14mm。南面距主裂缝5m以内为不均匀沉降,陡降较…     

来稿摘登

化学灌浆在船闸裂缝动水封堵中的应用湘江某船闸检修期间发现闸首部位出现数条裂缝 ,其间距 3～ 5m ,个别间距 4 0cm左右 ,裂缝走向平行岸坡 ,宽0 5～ 2mm。其中 2号裂缝横贯闸首离闸室地面至 2 5m处 ,漏水量约 4 0L min ,流速较快 ,动水压力约 0 1MPa。其余裂缝长 1～ 6m ,有渗水现象。闸首部位裂缝 7条 ,闸室部位裂缝 2条。共计裂缝长度 4 0 38m。分析裂缝成因为 :①闸首基础不均匀沉降 ;②温度变化及大体积混凝土收缩。经与甲方协商 ,决定采用丙凝灌浆堵漏。丙凝浆液材料主剂是丙烯酰胺 ,其与交联剂、促进剂发生化学反应后形成凝胶…     

Engineering-geological map of the wider Thessaloniki area,Greece

The preparation and compilation of a 1:10,000 scale engineering geological map of the wider Thessaloniki area is discussed. This map includes the range of values of the geomechanical characteristics of the 13 engineering geological units distinguished. Greater detail was available in the inhabited and industrial areas where many of the 1,300 boreholes studied had been drilled. Particular emphasis was given to the earth fill unit, which in places is up to 20 m thick. Some of the underlying Quaternary units are aquifers and severe pumping has resulted in both a lowering of the groundwater level and surface subsidence. The subsidence was most prominent in the Sindos–Kalohori–Axios River zone and required the construction of an embankment along the coast.     

山东安丘地区软土震陷及地震产生的土层构造新启示

通过地震调查、土工试验和14C测年,从沂沭断裂地震带安丘地区的全新世中—晚期湖沼相软土中,识别出了软土震陷灾害现象和地震产生的软土沉陷向斜褶曲、小尺度同震断层、狭缩–膨胀构造和震裂缝等共生土层变形构造,其中,软土沉陷向斜是直接反应震陷灾害的纵向土层变形。小尺度同震断层是地震产生的小断层,发育在沉陷向斜之下,其垂向延长0.5~1.8 m。沉陷向斜随着同震断层的产生而初现;又紧随断层向深部延伸而向下发展。地震振动使饱和软土发生触变,土质点从沉陷向斜的转折端向两翼发生流动,在此过程中,附加地震应力不断作用,结果形成了窄而深的沉陷向斜。软土震陷最大深度为1.08 m,平均震陷深度为0.68 m。推断当时的地震烈度达到Ⅷ度、震级超过M6。测得淤泥质土的14C年龄为3901±33a B.P.,该地震事件约发生公元前19世纪。同震断层是形成震陷的重要诱导因素,这为认识软土震陷的形成机理提供了新资料;也为防治或减轻软土震陷的危害提出了新启示。因此,应重视软土下伏土层可能产生同震断层的隐患。     

Application of environmental isotope to groundwater study of the Qinling Railway tunnel

A comparison of isotopic data of groundwater with those of surface water and rainfall indicates that groundwater in the Qinling Railway tunnel, which is the longest single-track tunnel under construction in China, originates from precipitation. However, measurements of deuterium and oxygen-18 in the fissure water in the adjacent drift have shown that these two isotopes are obviously depleted relative to the spring water in the area. This permits the groundwater being classified into two types: shallow weathering fissure water and deep structural fissure water, both with different features of circulation, and makes it possible to determine mixing ratios of the water inflows into the drift. The reason for the deep water depletion in the two heavy isotopes with respect to the shallow water is believed to be the difference of their recharge elevations, above 2200 m and below 1800 m for the deep and shallow water, respectively. Unlike the deep water, with slow motion and a circulation depth of over 1000 m, the shallow water is in an active circulation zone and moves usually in a depth of 40–50m. Calculation of isotope mass balance indicates that the relative contribution of the shallow water to the inflow at main locations or in sections of the drift ranges between 25.1% and 67.3%, indicating that the shallow water is also a significant component of the water inflow.     

Characteristics and trends of land subsidence in Tanggu, Tianjin, China

Land subsidence in the Tanggu area is directly related to withdrawal of shallow groundwater within a depth of 300 m. The main strata responsible for the subsidence are at a depth of between 136 and 300 m. The contribution to subsidence made by the clayey soils is different from that of the sandy soils, as the former is related to the seasonal dropping of the water table while the latter is associated with annual changes. In addition, while there is a clear correlation between the accumulative groundwater extraction and the accumulative subsidence, this linear relationship is not obvious between annual extraction and annual subsidence. A case study in Tanggu, Tianjin, is presented in order to demonstrate a proposed computational model to predict land subsidence – the Optimization Model for Land Subsidence (OMLS). Electronic Publication     

青海托拉海冲洪积扇区水文地质及水质分析

研究区位于沙松乌拉山前托拉海冲洪积扇区,区内沉积了厚度较大的第四系松散沉积物,其岩性主要为卵砾石、砂砾石及砂层。含水层厚度大于50 m,为赋存地下水提供了良好的空间场所。该区因降水稀少,蒸发量大,松散岩类孔隙水主要接受托拉海河水的下渗补给,主要河水补给来源于托拉海东沟、西沟,其中托拉海西沟年平均流量较小。洪积扇中前部地区地下水位埋深一般为20~65 m,水量较丰富,水质较好。     

西安市地面沉降与地下水位动态监测信息管理系统应用研究

西安地面沉降是抽汲地下水诱发的城市环境地质问题。西安市地面沉降与地下水位动态监测信息管理系统紧密结合地面沉降与地下水监测的业务流程,利用计算机技术、数据库技术、GIS技术等,在网络化的计算机软硬件基础上,实现地面沉降与地下水位动态监测的科学化和自动化管理、模拟预测和可视化分析。本文概述了西安市地面沉降与地下水动态监测信息管理系统的设计和建立,着重阐述了系统的应用效果和发展展望等。为科学开发和合理利用地下水资源、有效地预防地面沉降及地裂缝的发展和政府决策提供了科学依据。     

特长深埋隧道基岩裂隙水探测与应用研究

基岩裂隙水的富集对隧道施工安全及建成后的运营管理造成严重威胁。对基岩裂隙水的赋存情况进行准确及时的预测,可有效降低隧道地质灾害的发生几率,确保隧道施工安全。依托宜巴高速公路郑家垭隧道,结合掌子面YK129+843处涌水情况,研究了岩体赋存裂隙水情况下深度偏移图、反射层提取图以及岩体物性图中岩石参数曲线的变化趋势。研究表明TSP超前地质预报方法对基岩裂隙水赋存情况的探测结果比较准确,对类似地质条件下的超前地质预报工作具有一定的借鉴意义。     

浅埋厚煤层条带充填保水开采分析研究

我国西北地区浅埋厚煤层开采对地表及潜水层造成严重破坏,而充填开采是减小地表破坏以及实现保水开采的有效途径。为研究浅埋厚煤层条带充填保水开采的安全性,以哈拉沟煤矿为研究对象,建立了“边界煤柱+条带充填体+覆岩”的力学模型,采用相似试验与现场实测相结合的方法,在周期来压步距、地表下沉及台阶裂缝等方面进行对比分析,得出了较为准确的基岩裂缝角及直接顶初次垮落步距,并通过对隔水层的稳定性分析,确定了条带充填开采的充填宽度为38 m,充填间隔为16 m。根据土工试验得到黄土层的相关力学参数,确定了下行裂缝的发育深度。结果表明:条带充填开采引起的下行裂缝未影响到主关键层,有效隔水岩组厚度满足相关规程要求,可实现安全保水开采。     

Recovery from groundwater extraction in a small catchment area with crystalline bedrock and thin soil cover in Sweden

An experiment has been in progress since 1997 in a small catchment area (28,000 m(2)) with crystalline bedrock and thin soil cover to study the conceivable impact on groundwater conditions of tunneling and the use of groundwater. The impact on hydrology and hydrochemistry from intensive extraction of groundwater at a depth of 50 m in the bedrock has been studied at Lake G?rdsj?n in Sweden. The catchment area was first monitored under pristine conditions, followed by four and a half years of extraction and then a recovery phase. The geological conditions result in a low buffer capacity and high sensitivity to acidification. During the period of extraction, the surface runoff decreased by approximately 50% compared to a nearby reference area. The groundwater extraction caused increased fluctuation in groundwater levels in a wetland, which in turn caused oxidation of reduced sulfur to sulfate. The sulfate concentrations increased almost 100-fold in some instances, causing a lowering of the pH by one unit in shallow groundwater. Since extraction of the groundwater was discontinued, the pH has gradually risen and the sulfate concentrations have decreased. However, the concentration of sulfate in groundwater in the wetland has remained stable at approximately double the pre-experiment levels. Magnesium concentrations were lower after the experiment, caused by exhaustion of the magnesium pool in the wetland through acidification. The extraction of water from the bedrock shortened the retention times and increased the recharge of groundwater in the bedrock. After extraction was terminated, the groundwater levels in the boreholes recovered within a month to levels similar to those before extraction. The hydrochemistry of the bedrock groundwater, which was strongly affected by the hydrochemistry of shallow groundwater during the experiment, has also gradually begun to regain its pre-extraction signature. However, the surface runoff has remained low during the first 2 years of recovery, at about 60% of the volume compared to the unaffected catchment area. This could be explained by delayed recovery in resaturation of the shallow rock that was unsaturated during the experiment.     

地铁车站拱盖法施工沉降监测分析及控制对策

青岛地铁3号线中山公园站位于土岩复合地层中,采用拱盖法施工,车站开挖最深约27.24 m,上层为第四系强风化花岗岩,下部为中微风化花岗岩、花岗斑岩。局部强风化厚度大,中、微风化岩面局部较陡峭,岩层接触部位易失稳。为使开挖工程顺利进行,对开挖过程地表沉降进行监测分析。结果表明:采用拱盖法施工时,导洞掌子面施工至监测断面前方20 m左右时开始出现沉降;随着掌子面与监测断面距离的减少,沉降速率不断增加;掌子面下穿监测断面时,一般沉降量为7～15 mm;穿过监测断面5～10 m时,监测点沉降速率达到最大;穿过监测断面10 m后,沉降速率开始下降;穿过监测断面20 m后,大部分监测点趋于稳定。为保证支护起到良好的控制地表沉降的作用,初期支护应在开挖后立即施作,并尽早闭合。此外,左、右导洞在开挖过程中会相互产生较大的沉降影响,监测发现左、右导洞开挖间距在2.5倍洞径左右为宜。通过监测分析,提出一系列控制对策,实践证明,这些措施是可行且有效的。