共查询到20条相似文献，搜索用时 31 毫秒
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The possibility of inferring paleoseismicity from paleomagnetic dating of speleothems, western Japan 总被引：2，自引：0，他引：2
Hayao Morinaga Takafumi Yonezawa Yasuhisa Adachi Hiroo Inokuchi Hiroya Goto Katsumi Yaskawa 《Tectonophysics》1994,230(3-4):241-248
Paleomagnetic dating of continuously growing stalagmites by comparing their paleomagnetic records with a standard record, has been applied to study the paleoseismic history of a region of western Japan. Three stalagmites (speleothems), which are assumed to have started growing since collapse of the limestone blocks on which they are formed, were collected from two limestone caves located below the Akiyoshi plateau, western Japan. From the paleomagnetic results, it is estimated that they began to grow at 6000, 2500 and 2000 yr B.P., respectively. On the assumption that their growth began immediately after their host limestone blocks fell, these three ages are interpreted to indicate the dates of past earthquakes in this region which triggered the break-off and fall of the blocks. Earthquakes are suggested because many huge collapsed limestone blocks and speleothems are observed in many caves in this region. 相似文献
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HE Keqiang Department of Civil Engineering Qingdao Institute of Architecture & Engineering Qingdao Shandong ChinaLIU ChangliInstitute of Hydrogeology Engineering Geology Chinese Academy of Geological Sciences Zhengding Hebei Chinaand WANG Sijing Institute of Geology Chinese Academy of Sciences Beijing China 《《地质学报》英文版》2001,75(3):330-335
Karst collapse, caused by natural or artificial abstraction of groundwater, has been a focus of environmentalgeological problems for its ever-increasing hazardousness. The potential erosion theory and vacuum suction erosion theory, which reveal the origin of karst collapse macroscopically, are popularly accepted. However, a mathematic prediction criterion for karst collapse cannot be established only by these two theories. From a new perspective, this paper attempts to explain the microcosmic mechanism of karst collapse on the basis of these two theories. When the shear stress surpasses the shear strength of soil, a certain point or a certain plane in the unconsolidated soil covering karst caves will fail under the mechanical effects of water and air as well as its load-pressure, and with the increase of damaged points, a breaking plane appears and the soil on karst caves is completely damaged; as a result, the karst ground collapses. On the basis of the Mohr-Coulomb failure theory and previous studies, 相似文献
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为研究炭质灰岩地区抽水致塌控制因素和影响因素,通过电法物探、地质钻探及抽水致塌试验相结合的综合手段,对兴安县石炭系下统岩关组（C1y）炭质灰岩地区的岩溶塌陷进行关联分析,建立降深水位与时间、恢复水位与时间的关系对比曲线。研究结果表明:在炭质灰岩地区进行抽水活动时,其主要补给源为小溶洞内储存水,运输通道为岩溶裂隙;该炭质灰岩地区岩溶裂隙具有不规则性,因此,在同类地层中测得的渗透系数k及影响半径R有较大差异;研究区域内抽水致塌的位置受地质构造的影响较为明显;钻井人为抽水致塌受多种因素共同作用影响,而地下水位升降为主要影响因素。 相似文献
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Time-dependent changes in the strength of repair mortar used in the loss compensation of stone 总被引：1，自引：1，他引：0
Repair mortar and mixture of repair mortar with porous limestone sand aggregate were tested under laboratory conditions. Water absorption properties and micro-fabric analyses with a combination of strength tests were applied to assess the durability and compatibility of repair mortar with porous limestone. Uniaxial compressive strength and flexural strength were measured after 3, 7, 14, 28 and 90 days of casting. Durability was tested by comparing strength test results of samples kept air dry, water saturated, dried in drying chamber, freeze–thaw and non-standardized freeze–thaw cycles. The results indicate that with time various trends in strength were observed. In general, limestone aggregate content decreases more the compressive strength more than the flexural strength of the mortar. Standardized freeze–thaw tests of saturated samples caused a rapid material loss after 25 cycles, while freeze–thaw tests of undersaturated samples demonstrated that even after 100 cycles the test specimens still have a significant strength. Water-saturated samples that contain 50% of limestone aggregate have a 50% loss of strength in comparison with saturated repair mortar, while air-dry and water-saturated repair mortar has a minor strength difference after 90 days. The use of smaller amounts of porous limestone aggregate in repair mortar allow the preparation of repairs that are compatible with the monuments of Central Europe that were constructed from porous limestone. 相似文献
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岩溶塌陷的类型、成因机制及防治途径──兼论武汉市岩溶塌陷勘查工作要点 总被引：8，自引：0，他引：8
按岩溶塌陷的类型, 对其成因机制作了分析。在此基础上, 提出了武汉市岩溶塌陷勘查与防治工作要点。 相似文献
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岩溶地面塌陷是岩溶发育地区常见的地质灾害类型。岩溶塌陷对基础设施和人民生命财产安全构成极大威胁。文章以贵港市北环新村岩溶地面塌陷灾害为例,采用地质分析与颗粒流离散元数值模拟相结合的方法,研究岩溶塌陷成因与致灾规律。结果表明:本次塌陷是由多类因素共同导致,主要包括地质环境、地下水位波动与管道渗漏及工程建设活动等;白云岩、灰岩差异性风化所形成的粉砂质土极易诱发土洞与岩溶塌陷灾害;塌陷灾害可分为土洞形成阶段、土洞发展阶段和土洞塌陷阶段,其土洞规模、形状及影响存在显著差别;土洞形成发展过程中,地表沉降量从塌陷中心向四周逐渐减小,存在明显的沉降敏感区,塌坑边缘的竖向临空面存在拉应力作用,极易再次诱发塌陷。研究成果可为岩溶地面塌陷灾害防控与预警提供一定的理论参考。 相似文献
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武汉地区浅层岩溶发育特征与岩溶塌陷灾害防治 总被引：6，自引：5，他引：1
运用综合分析和数学统计的方法,较为深入地研究了武汉地区浅层岩溶的发育特征。武汉地区存在6个走向 NWW-SEE、各自相对独立的碳酸盐岩条带。根据上覆盖层工程地质性能的差异,划分出5种岩溶地质结构类型。武汉地区浅层岩溶主要类型有溶隙、落水洞及小型溶洞等,钻孔遇洞率46.0%-50.1%,线岩溶率5.93%-6.00%。浅层岩溶带中,1/3的溶洞洞高小于0.6 m,50%小于1.0 m,90%小于3.0 m。1/3的溶洞顶板在基岩面以下2.5 m 以内,50%在4.5 m 以内,90%在12.5 m 以内。溶洞充填物主要是黏土,含有灰岩碎块石。全充填溶洞占70.8%,未充填溶洞约占1/5,半充填溶洞不到8%。全充填溶洞顶板在基岩面以下平均埋深5.13 m,半充填5.71 m,无充填7.69 m,且具有全充填和半充填溶洞埋深较小、无充填溶洞埋深较大的特点,反映出溶洞充填方式是自上而下充填,充填物主要来源于上部覆盖层。武汉地区浅层岩溶为上部“垂直渗流岩溶带”地下水垂直渗流作用下的产物。根据岩溶发育程度的差异,基岩面以下浅部碳酸盐岩在垂直方向上可分为上部强岩溶和下部弱岩溶两个带;岩溶塌陷灾害平面上可划分出高、中、低3个危险性区,各区防治原则不同。高危险区是岩溶塌陷灾害防治的重点,防治的基本原则是阻止上覆粉细砂的流失;中等危险区的防治原则是保护中部老黏土层或红层的完整性;低危险区应注意远城区土洞存在的可能性。各危险区治理应以岩溶地质结构为基础,在防治原则指导下制定相应的防治措施。此外,工程建设中应合理选择和利用弱岩溶带。 相似文献
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广州市白云区夏茅村岩溶塌陷地质灾害严重,塌陷区内地质环境条件极其复杂,隐伏灰岩岩溶土洞发育强烈,溶洞、土洞规模较大,且发育多层溶洞,溶洞间相互连通,岩溶塌陷区基岩面起伏较大,高程变化剧烈,第四系覆盖层厚度较大,底部粉质黏土层土洞发育,土体中规模巨大的土洞是产生岩溶地面塌陷的基础条件。基岩断裂构造带及其影响带范围内,岩石破碎,形成导水断层,存在地下水迳流通道,沿断裂带地下水循环活跃,溶蚀强烈,形成岩溶强发育带,为岩溶塌陷的发生提供了良好的动力条件。区内楼房基础施工扰动了地下水和土洞间的平衡状态从而成为了地面塌陷发生的诱发因素。运用7项地质环境条件指标和5项经济人口指标分别定性评估岩溶地面塌陷的易发度和易损度,并将二者叠加进行地质灾害风险评估。研究结果表明,夏茅村潜在地质灾害风险大,只有严格控制地下水动力条件,才能避免再次发生岩溶地面塌陷。 相似文献
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Bearing capacity of rock over mined cavities in Nottingham 总被引：1，自引：0，他引：1
A significant geohazard is created in Nottingham, UK, by hundreds of man-made caves cut in the weak sandstone beneath the city centre. Stability of the caves has been assessed by a single full-scale loading test, by numerical modelling with FLAC and by physical modelling in plaster. For typical caves 4 m wide, bearing capacity of the rock roof rises from 2 MPa where it is 1 m thick to 8 MPa where 3 m thick. Stability decreases over wider caves and where the loading pad edge is over the edge of the cave. Numerical modelling of a very wide cave revealed the failure mechanisms and also showed that an internal support wall increased roof bearing capacity by 50%. Local building regulations that require 3-5 m of rock cover over the sandstone caves appear to be conservative. In stronger rocks, including karstic limestone, a guideline that cover thickness exceeds 70% of the cave width appears to be appropriate. 相似文献
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徐州岩溶塌陷时空分布规律及成因分析 总被引：6，自引：4，他引：2
文章通过对以往岩溶地面塌陷勘查工作成果进行系统梳理,揭示了徐州地区裸露型岩溶和覆盖型岩溶的分布规律及历史上岩溶塌陷的时空分布特征,发现塌陷的分布具有明显的规律性:(1)塌陷受废黄河断裂带控制,离废黄河断裂带越近岩溶发育越强烈,离废黄河断裂带较远的部位岩溶发育明显减弱;(2)塌陷主要分布于浅部岩溶强烈发育地段的奥陶系灰岩中,少数分布于寒武系灰岩之中;(3)塌陷集中分布在古河道形成的,砂性土单层结构地段,少数分布在砂性土-黏性土双层结构地段;(4)塌陷全部位于岩溶水开采降落漏斗内。结合岩溶塌陷的时间与地下水的动态活动过程之间的关系,全面分析地面塌陷形成的原因,提出了古河道与废黄河断裂带的重叠部位为岩溶地面塌陷发生的有利部位,但最终发生地面塌陷则是人类工程活动过程引起岩溶水位剧烈波动——大幅、快速下降的结果。该研究成果可为徐州市今后进一步防治岩溶塌陷地质灾害提供地质科学依据,有重要的实用价值。 相似文献
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This paper describes seismic velocity tomography applied to the investigation and assessment of karst collapse hazards to facilitate accurate characterization of geological conditions of karst sinkhole formation. In the survey areas of Xiamao, Guangzhou, China, and Huangchi, Foshan, China, seismic velocity tomography was used to explore the structures of rock and soil associated with karst collapse. The results show that sand intercalated with clay or clay intercalated with soft soil dominates the cover of these two areas. The overburden is 20–33 m thick and underlain by Carboniferous limestone. In the limestone, there are well-developed karst caves and cracks as well as highly fluctuating bedrock surfaces. The seismic velocities are less than 2500 m/s in the cover, 2500–4500 m/s in the karst fracture zones and caves of Xiamao, and 1500–2000 m/s in the Huangchi collapse area. The karst fracture zones, relief of bedrock surfaces, and variations of soil thicknesses revealed by seismic velocity tomography are well constrained and in agreement with those in the drilling borehole profiles. This paper demonstrates that seismic velocity tomography can delineate anomalies of rock and soil with the advantages of speed, intuitive images, and high resolution. 相似文献
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矿坑排水与岩溶地面塌陷的关系 总被引：5，自引：5，他引：0
浙江省某岩溶矿区南部洼地先后发生6处地面塌陷,引发了当地居民的恐慌。矿区排水是唯一地下水开采活动,为分析塌陷区与矿区之间的水力联系,遂在研究区全面布置地下水监测系统。通过对比分析观测水位、矿坑排水量及当地降雨量数据,探讨地面塌陷与矿区排水之间的关系及其潜在成因。研究表明,研究区岩溶地下水动态变化整体保持一致,受降雨、矿坑排水等综合因素影响。北部矿区和南部洼地存在岩溶连通管道,两者在雨季水力联系微弱、旱季水力联系密切。经长期径流潜蚀作用,〖JP2〗导致区内地面塌陷区灰岩顶板岩溶发育处上覆土层出现土洞,当矿区排水量急剧增大时,南部洼地岩溶水位大幅度下降,使得土洞中出现负压、上覆土层所受浮托力降低、孔隙水与岩溶水补排关系改变,在多种效应共同作用下,土洞最终形成地面塌陷。 相似文献
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L. E. Zuffianò M. Polemio R. Laviano G. De Giorgio M. Pallara P. P. Limoni F. Santaloia 《Environmental Earth Sciences》2018,77(13):517
Hypogenic caves, developed by sulphuric acid speleogenesis, are known all over the world among which the Santa Cesarea Terme caves have been included. They are four submerged caves, located along a coastal carbonate sector in Southern Italy and hosting the outflow of coastal springs of thermal mixed waters (from 21 to 33 °C). These waters derive from the mixing of three water end members: the fresh pure groundwater of a wide karstic aquifer, the deep sulphur thermal water and the seawater. This cave system represents an almost unique case of hypogenic sea caves in carbonate environment. The thermal mixed waters have a different effect on the surrounding rocks of the caves, influencing the sulphuric acid speleogenetic process within the whole cave system. To understand the complex and overlapping natural processes acting on the development of these coastal caves, a multidisciplinary study has been carried out. This study has integrated all the data resulting from different methods and technologies, merging morphology, structural geology, hydrogeology, hydrogeochemistry and mineralogy. This multidisciplinary study has allowed to define the main geochemical processes acting within these caves, including the cave development and the formation of the mineral concretions. After the introduction of H2S in the thermal waters, formed by the reduction of sulphates in the sedimentary deposits crossed at depth in the offshore, the oxidation occurs within the caves, producing sulphuric acid. Favoured by upwelling deep-seated thermal flows, this acid dissolves the limestone, with condensation corrosion process that involve replacement of limestone rock with gypsum. This process has resulted to be more active and remarkable within the Gattulla Cave, one of the Santa Cesarea Terme sea caves. 相似文献
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The chemical composition of water samples was studied from different caves in Slovakia. The water samples were collected from caves of two karst regions: (1) the Demänovský Cave System (DCS), situated in the Low Tatra Mountains (Northern Slovakia), which is mainly formed of limestone and dolomites; and (2) the Slovakian Karst to the Southeast is formed of limestone. A considerable difference between water from the two regions was shown. The waters from the DCS, that were controlled by vadose water percolating through different types of host rocks, contained more Mg ions than those from the Slovakian Karst caves whereas, the concentration of SO4 was controlled by the dissolution of displacive gypsum and/or oxidation of pyrite. The distribution of NO3 in the studied samples was random, hence nitrates probably derived from few pollution sources. The total mineralization of the water was covariant with calcite and aragonite saturation indices. In general, both parameters are higher in the Slovakian Karst caves than in the DCS. It is controlled probably by differences in climatic conditions, soil and plant covers between these two regions. The main goal of this article is to characterize the major-ion water chemistry within the studied caves as well as some microelements. The results have confirmed the dominant role of the bedrock petrography in forming the general chemistry of cave waters. 相似文献
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水化学溶液下灰岩力学特性及神经网络模拟研究 总被引：3，自引：0，他引：3
基于水化学溶液浸泡的饱和灰岩三轴压缩试验结果,分析了影响灰岩变形及强度等力学特性的主要因素,认为随溶液酸碱度增加,弹性模量及峰值强度均有降低的趋势;相同pH值,Na2SO4溶液、蒸馏水和CaCl2溶液对灰岩强度的弱化程度依次降低;随着围压的增加,岩石强度逐渐增大,岩石到达峰值强度时的轴向变形也越来越大,塑性变形明显增加。考虑应力路径和化学溶液的影响,利用遗传算法优化神经网络结构,建立了进化神经网络本构模型。通过样本学习模型能较好地描述化学环境下灰岩的力学性能,5种不同化学环境下的力学试验验证了进化神经网络模型模拟结果的可靠性,该方法可以推广到化学环境下其他岩石的力学试验模拟。 相似文献
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针对龙门石窟灰岩水溶液侵蚀破坏现象,考虑石窟区的泉水、石窟渗水和雨水的化学成分,配置不同的化学溶液,研究不同化学溶液作用下龙门石窟灰岩的力学损伤特性及化学溶解行为。通过不同化学溶液侵蚀不同时间下灰岩的力学试验及分析,获得不同化学溶液侵蚀下龙门石窟灰岩强度损伤特性,建立化学溶液作用下灰岩单轴抗压强度随时间的侵蚀损伤方程。通过不同化学溶液侵蚀不同时间下灰岩溶解动力学试验及分析,研究灰岩在不同化学溶液中的溶解特性,建立化学溶液作用下灰岩侵蚀溶解动力学方程。试验分析研究表明,由于水化学溶液的溶解作用,化学溶液侵蚀下灰岩强度均有所下降。盐效应、同离子效应对灰岩溶解速率和强度的影响较大。盐效应提高灰岩溶解速率,同离子效应降低灰岩溶解速率。盐的种类和浓度均相同时,酸性越强,溶解速率越大;盐的种类和pH值相同时,盐浓度升高,灰岩溶解速率增大。研究结果将为石质文物及岩石工程的长期保护提供重要的理论基础,具有广泛的实际工程应用价值和应用前景。 相似文献
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马家沟灰岩（古）岩溶研究中的若干问题探讨 总被引：4，自引：0，他引：4
讨论了华北地区奥陶系马家沟组灰岩岩溶研究中的几个问题，包括沉积岩溶，暴露岩溶，埋藏岩溶，现代岩溶及陷落柱等，指出了沉积岩溶和暴露岩溶洞穴不能保存或保存甚少，但对后期的岩溶发育具有重要控制作用，最后，提出了今后奥陶系灰岩岩溶研究的基本思路。 相似文献
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