共查询到20条相似文献，搜索用时 31 毫秒
1.
矿物成分、特征地球化学组分对水在滑带形成中作用的指示意义:以三峡库区大型滑坡为例 总被引：5，自引：0，他引：5
弄清滑坡滑带抗剪强度降低的根本原因是滑坡形成机理研究和滑坡活动趋势预测的主要内容之一。水是滑带形成过程中导致其抗剪强度衰减的最活跃因素之一。三峡库区两个大型滑坡实例分析显示,滑带及其周围岩土矿物成分、地球化学成分的变化特征指示滑带形成与水-岩(土)物理、化学作用的方式及作用程度,从而证实矿物学、地球化学研究方法和理论是揭示滑带抗剪强度降低内在机理的有效途径之一。三峡库区黄土坡滑坡临江I#崩滑体和泄滩滑坡滑带土及其周围岩土矿物学、主量化学元素的含量变化特征指示:前者滑带形成过程中,滑带部位地下水因大气降水补给、地下水的氧化作用活跃,导致滑带土抗剪强度减低,其主要原因是其中泥灰岩碎屑的水解泥化作用、方解石溶解作用和伊利石向伊-蒙混层矿物的转化作用;后者滑带形成过程中,滑带部位地下水与外界水力联系较差、地下水的还原作用强烈,滑带部位长石化学风化、次生粘土矿物增多,可知由伊利石转化的伊-蒙混层矿物增多是导致滑带土抗剪强度衰减的主要原因。 相似文献
2.
Many gentle dip translational rock slides have taken place in the Three Gorges Reservoir, China. In order to study the mechanism of these translational rock slides, the authors use the Anlesi landslide as a typical case study to investigate in detail. Field investigations show that the slip zones of the Anlesi landslide were formed from a white mudstone in Jurassic red strata. X-ray diffraction and infrared ray analysis showed that the main mineral components of the slip zones are montmorillonite, illite, feldspar and quartz. Laboratory tests indicate that the slip zone soils are silty clay, of medium-swelling potential, the shear strength decreasing significantly as the slip zone attracts water and saturates.The main factors contributing to the Anlesi landslide are recent tectonic activity, incompetent beds, and intensive rainfall. Recent tectonic activity had caused shear failure along the incompetent beds, and joints within the sandstone. With the effect of intensive rainfall, water percolates to the incompetent beds along tectonic fissures, resulting in swelling of the soil material and high groundwater pressures within fissures in the strata. As a consequence, the Anlesi slope is prone to slide along these incompetent beds.Flac3D software was used to simulate the mechanism of the Anlesi landslide considering the rheological properties of soil and rock. The simulation results demonstrate that the stress, displacement and failure area changes with simulated creep time. The maximum displacement in the X direction reaches 7.59 m after 200-year simulated creep. Therefore, the mechanism of the Anlesi landslide can be illustrated considering the rheological properties of Jurassic red strata. 相似文献
3.
4.
柴湾滑坡是三峡库区结构复杂的大型老滑坡之一,三峡水库蓄水后,该滑坡出现明显复活迹象。本文基于滑坡结构和2007-2015年监测数据,分析了该滑坡活动对库水位变化的响应特征;采用数值模拟手段分析了库水位变化时滑体内渗流场及孔隙水压力变化特征。研究发现,该滑坡在平、剖面上分别呈现牵引式分块与浅、中层分层的缓慢活动特征;当库水位降速>0 8 m/d时,滑坡活动呈现滞后的台阶式加剧趋势;越接近地表,滑坡活动对库水位变化愈敏感。柴湾滑坡活动特征受其复杂结构控制,滑坡中前部地下水与库水密切的水力联系以及中层、深层滑体良好的渗透性决定了滑坡的分块和分层活动特征。库水位上升时透水性较强滑体内的扬压力和库水位下降时透水性较弱滑体内的动水压力是造成滑坡分块分层活动的内在动力。 相似文献
5.
Guodong Zheng Yuhua Lang Bokuichiro Takano Motoyuki Matsuo Akihito Kuno Haruaki Tsushima 《Journal of Asian Earth Sciences》2002,20(8)
It has been often observed that black mud recently formed and accumulated in slip planes that are closely associated with a progressing landslide in Japan. Mössbauer spectroscopy revealed that the composition of Fe species in the sliding mud is different from those in the debris rock and bedrock. The sliding mud contains more ferrous iron species, which indicates a relatively stronger reducing condition within the sliding zone than within the host rocks. In addition, the composition of Fe species, the total Fe and the volume of sliding mud also change with landslide development. Therefore, detailed Fe speciation in landslide profiles can be a useful approach to understanding the progress of a landslide and may also predict future sliding as well. 相似文献
6.
在滑坡稳定性分析和设计计算中往往选用滑带土的残余强度值,但许多研究发现滑带土在稳定期会有自愈合现象发生,表现为抗剪强度的提高。对于以蠕滑为主的红层滑坡,自愈合恢复值应该在滑坡稳定性评价中予以考虑。通过对典型红层滑坡滑带土样进行“剪切―保持―剪切”试验,研究处于残余状态下的剪切面在不同法向应力、不同保持时间下的愈合情况,并进行相应的分析与讨论。试验结果表明：（1）残余状态下的土样在保持一定时间后再次剪切出现明显峰值,证明了剪切面自愈合效应存在,但是继续剪切时恢复的强度随位移快速消失;（2）随着保持时间的增长,剪切面的强度恢复值越来越大;（3）剪切面的自愈合相比法向应力更依赖于保持时间。将得到的摩擦系数值运用断层强度恢复经验公式拟合,提出不同法向应力下常数A的取值,可在滑坡安全系数计算中参考。 相似文献
7.
Ahmet Evren Erginal Beyhan Öztürk Yunus Levent Ekinci Alper Demirci 《Environmental Geology》2009,58(6):1167-1175
The nature and subsurface structure of the slip surface of a landslide was studied on the basis of geochemical analyses and
2-D electrical resistivity tomography (ERT) survey. Head scarp and lateral slip surfaces of the landslide marked by clear
slickensided shear planes were composed of the average amounts of clayey silt (32.5%) and sand (67.5%). Energy dispersive
X-ray spectroscopy (EDX) data revealed the enrichment of Si (23.24%), Fe (12.2%), Al (9.51%) and C (8.34%) in the elemental
composition of the disturbed slip surface. From X-ray diffractometry (XRD) data, six main clay types were determined, such
as Volkonskoite, Halloysite, Ferrosilite, Saponite, Illite and Nontronite. The ERT survey displayed that the landslide developed
as a reactivation on the upper part of an old landslide body. 相似文献
8.
三峡库区万州安乐寺滑坡滑带特征 总被引：1，自引：0，他引：1
安乐寺滑坡是三峡库区典型的缓倾角红层基岩滑坡, 对其滑带特征进行详细的研究有助于揭示缓倾角红层基岩滑坡的形成机制.宏观地质特征显示, 安乐寺滑坡滑带是侏罗系红层中灰白色泥岩(软弱夹层) 经挤压滑动所形成的, 擦痕指示最后一次滑动方向为100°.通过X射线衍射分析和红外光谱分析表明, 安乐寺滑坡滑带主要矿物成分为蒙脱石、伊利石、长石、石英等; 其特点是蒙脱石含量高, 并且滑动面上的蒙脱石含量高于滑带的蒙脱石含量.经扫描电镜观察, 滑带土微观结构以片状结构与定向排列结构为主; 显微擦痕发育, 并指示滑带曾发生过多次滑动.对滑带土的物理力学性质进行实验研究可知: 滑带土为中等膨胀性粉质粘土, 其抗剪强度低; 且吸水膨胀后, 抗剪强度大大降低.滑带土的这些特殊性质, 为安乐寺滑坡的滑动提供了物质基础. 相似文献
9.
On June 14 2008, an Iwate–Miyagi inland earthquake that had a magnitude of 7.2 hit the eastern foot of the Ohu Mountains in
Tohoku district, Japan. The seismic peak ground acceleration was greater than 1,000 gal in the Aratozawa Dam area. The earthquake
triggered a massive landslide at the upper reach of the dam. The landslide had the sediment volume of over 67 million cubic
meters and is considered the largest catastrophic landslide in Japan during the last 100 years. This report presents a summary
of our findings pertinent to the landslide’s activities based on our field investigations that started the day after the landslide.
This report covers: (1) details of the land deformations caused by the landslide, (2) geological background pertinent to landslide
development, and (3) estimation of the slip surface and the other physical properties of the landslide based on the analysis
of the boring core specimens and landform features. The landslide is roughly divided into two sections, a lower and an upper
half. The lower half moved almost simultaneously as one massive block of 700 m long, 800 m wide, and 70–80 m thick. The slip
surface had developed on the very fine sand of the alternate layer of fine-grained sandstone and siltstone. The slickensided
slip surface has a gradient of only 2°. This feature indicates that the type of the landslide movement is considered to be
a block glide. The landslide body is nearly identical to the topography of the landslide area that was developed about 50,000 years ago. This shows the possibility that the landslide was reactivated. The upper half consists of two large ridges and the broad
debris field and is 600 m long, 900 m wide, and 70–100 m thick. The maximum height of the main scarp is over 150 m. 相似文献
10.
11.
位于四川茂县南新镇的周场坪滑坡是一大型古滑坡,曾于1982年发生大规模快速复活,目前滑体半堰塞岷江。野外地质调查表明,周场坪滑坡在平面上呈不规则长舌形,长约850 m,滑体前后缘高差约350 m;在剖面上发育3级滑动,钻探揭露滑带埋深以50~70 m为主,推测潜在失稳滑坡体积为1 500×10 4~2 000×10 4 m 3。周场坪滑坡在平面上分为4个变形区,在滑体中后部和前缘坡脚发育大量拉裂缝与下错陡坎,拉裂缝宽度以0.2~3.0 m为主,陡坎下错高度2~10 m。在野外调查和钻探分析的基础上,对该滑坡开展了地表位移(GNSS)、深部蠕滑变形(钻孔测斜仪)和雨量等监测。监测分析表明,目前周场坪滑坡后缘变形速率达0.80 m/a,中部和前缘分别为0.69 m/a和0.51 m/a,呈推移式滑动变形,整体向NW310°方向滑动;地表位移速率在监测期内基本在1~3 mm/d之间波动,波动主要受降雨量影响,且略滞后于降雨量;滑移加速度基本在0~6 mm/d 2范围波动。ZK2钻孔测斜仪监测数据表明,滑坡在80 m深度内主要沿2层滑带蠕滑,其中浅层滑带埋深在22 m左右,深层滑带埋深在46 m左右,滑移速率在0~5 mm/d范围波动。综合研究认为,周场坪滑坡目前处于缓慢变形的深层蠕滑中,其变形速率受降雨和河流侵蚀等因素的影响,在极端内、外动力条件下,可能会加速滑动,并再次整体复活,造成堵塞岷江等危害。 相似文献
12.
Four Quaternary volcanic ash zones in the southern Norwegian Sea have been investigated in core P57-7 from the Iceland Plateau. Both the geochemical composition and morphological variation of each ash layer have been studied. The four volcanic ash zones appear in the light oxygen isotope stages 1, 5, 7 and 11. The ash zones are composed of transparent platy grains, light brown transparent grains, brown blocky and black blocky grains and white/transparent pumice, and each zone shows a distinct stratigraphic evolution. The geochemical results show a mixture of basaltic and silicic grains in each ash zone, and that each zone contains grains from more than one eruption. The geochemical investigations strongly suggest that all the ashes are derived from Iceland. The youngest ash zone includes two layers, which based on their geochemical composition and stratigraphic position are correlated with the 14C-dated Vedde Ash (10 600 yr BP) and Saksunarvatn Ash (9 100 yr BP). Possible sources on Iceland for these layers are discussed. 相似文献
13.
Since 1980 the main goal of geochemical investigations in Lithuania has been the estimation of technogene changes of microelements in the earth's surface sediments. For this purpose the geochemical mapping at various scales has been employed: at regional scale (1:2,500,000-1:500,000), at large scale (1:50,000-1:25,000), and at local scales 1:10,000-1:1000. The most important tasks are to determine and to establish the geochemical background for technogene changes in the topsoil layer and in the water reservoir bottom sediments. When mapping the zones of increased technogenical load the increase of concentration for most microelements in soils (ground) and in water reservoirs were established. Zn, Pb, Cu, Sn. Ag, Cr and Ni are the main elements-pollutants of these zones, concentrations of which exceed the background values from a few up to a dozen times. In certain cases their concentrations and the concentrations of specific elements, such as Sb, Bi. Ce, La, exceed thousands times the background value. At such zones the danger of pollution is increased due to the occurrence of mobile and potentially mobile toxic elements. During the soil mapping within the towns and factories not only the concentration of elements and the associations of elements-pollutants have been ascertained, but also the approximate contamination dangerous for biota -the total index of contamination (Zs) — has been calculated. The additional index that shows dangerous pollution is the maximum permissible by general sanitary concentration of chemical elements in soil (MPLCs) used in Lithuania. At some extremely contaminated zones (Zs > 128) the migration forms of toxic elements were determined by AAS-ES (gradual extraction using reagents of various acidity). The geochemical mapping data are used for the land-use, for the selection of geochemical monitoring polygons, hydrochemical. ecomedical and other investigations. 相似文献
14.
基于对高桥乡窑厂坪滑坡进行的钻孔勘探、水文调查以及滑坡体的变形破坏特征分析,查明该滑坡为岩质滑坡。通过滑坡体的变形破坏迹象、运动特征,将滑坡划分为Ⅰ(剧滑区)、Ⅱ(沉陷下错解体变形区)、Ⅲ(拉裂破坏变形区)、Ⅳ(拉裂沉陷变形区)、Ⅴ(滑覆区)5个区,并判别窑厂坪滑坡开始发育时具有推移式的特点,变形启动后则逐渐转变成以牵引式为主的变形破坏模式。 相似文献
15.
金鸡岭滑坡在暴雨后发生明显变形,通过现场勘察、钻探、物探、深部位移监测以及水平位移监测得出初步结论。为进一步查明该滑坡成因机制,通过解译现有勘察监测资料,结合Midas-GTS软件分析不同工况下滑坡的渗流场、位移场、稳定性计算,综合评价其成因机制。结果如下：（1）物探解译得出金鸡岭滑坡为岩土混合、含水滑坡,滑动面位于T2b1泥灰岩和T2b2泥岩分界线;（2）深部位移监测揭示该滑坡为浅表层土体在发生滑移,滑动面与物探解译得出的滑动面位置一致;（3）水平位移监测表明浅表分布的后梆滑坡和潘家岭滑坡变形速率较快,变形强烈;（4）数值模拟结果显示金鸡岭滑坡在现状工况下处于基本稳定状态;在排干地下水工况下处于基本稳定状态;在暴雨工况下处于欠稳定状态,可能产生整体滑移,其上的潘家岭滑坡及后梆滑坡产生土体次级滑移。（5）金鸡岭滑坡的地形地貌、地质构造、地层岩性、为滑坡的形成和发展提供了物源和场地条件,暴雨和人类工程活动作为诱发因素,进一步加剧滑坡变形。该研究成果将为三峡库区类似滑坡的成因机制与稳定性分析提供理论依据,对后期防治措施具有重要指导意义。 相似文献
16.
金沙江上游沃达滑坡自1985年开始出现变形,现今地表宏观变形迹象明显,存在进一步失稳滑动和堵江的风险。采用遥感解译、地面调查、工程地质钻探和综合监测等方法,分析了沃达滑坡空间结构和复活变形特征,阐明了滑坡潜在复活失稳模式,并采用经验公式计算分析了滑坡堵江危险性。结果表明:沃达滑坡为一特大型滑坡,体积约28.81×106 m3,推测其在晚更新世之前发生过大规模滑动;滑坡堆积体目前整体处于蠕滑变形阶段,局部处于加速变形阶段;复活变形范围主要集中在中前部,且呈现向后渐进变形破坏特征,复活区右侧变形比左侧强烈。滑坡存在浅层和深层两级滑面,平均埋深分别约15.0,25.5 m,相应地可能出现两种潜在失稳模式:滑坡强变形区沿浅层滑带滑动失稳时,形成的堵江堰塞坝高度约87.2 m;滑坡整体沿深层滑带滑动失稳时,形成的堵江堰塞坝高度约129.2 m。沃达滑坡存在形成滑坡-堵江-溃决-洪水链式灾害的危险性,建议进一步加强滑坡监测,针对性开展排水、加固等防治工程。 相似文献
17.
刘家湾滑坡位于青川东河口红光乡刘家湾,为汶川地震触发的特大型岩质山体滑坡。野外调查结果表明,该滑坡堆积体与一般汶川地震滑坡运动堆积体迥异的是滑体在沿碳质板岩与白云岩划分带破坏溃滑后,滑源区又沿白云岩风化卸荷带触发了二次溃滑,形成二级堆积平台的形态且以不同岩性区分,在岩性划分带及风化卸荷带呈现出明显的动力破坏特性。通过对该滑坡堆积体进行岩体物理力学试验及波速测试研究表明,该滑坡由白云岩、碳质板岩及千枚岩组成的内硬外软岩质边坡具有明显的量化差异特性,强震条件下差异岩性组合边坡岩层接触面的动力突变效应耦合凸出地形是导致该边坡破坏的主要因素。近一步研究显示该滑坡运动可大致分山体震裂阶段、地质分界面应力突变阶段、高速溃滑阶段、碎屑流堆积阶段、二次溃滑堆积5个动力过程。 相似文献
18.
Weathering intensity changes due to climatic variability across tectonically stable portions of continental crust can generate a thick and extensive weathered cover, resulting in regolith-dominated terrains (RDTs). Mineral exploration in RDTs is challenging because of the lack of bedrock outcrop, and the difficulty of linking surface regolith geochemistry to the geology at depth. Complex weathering obscures the expression of the basement geochemistry in the regolith, and therefore the footprints of mineral systems are difficult to detect. The southeast of the Yilgarn Craton and the Albany–Fraser Orogen (AFO) in the south of Western Australia is an RDT that extends along the coastline and the Eucla basin.This study proposes a landscape evolution model of the AFO, driven by transgression–regression sea-level changes that resulted in the formation of numerous islands and development of estuarine zones. This model contrasts with the river system-dominated landscape evolution present in the Yilgarn Craton. This difference has significant implications for mineral exploration and geochemical interpretation of the regolith in this region.Weathering profiles developed “on inland” and “on island” are thicker and more mature than those developed in sea-inundated areas. Even if in the Yilgarn Craton local areas display reworking of weathering profiles and other complexities from Permian, non-marine Tertiary sediments and Quaternary fluvial and aeolian sediments, at a regional scale, if vertical geochemical mobility of elements has occurred, “on inland” and “on island” are more reliable for understanding geochemical anomaly-basement relationships, whereas the “marine inundated” areas require a more detailed investigation, because of the role of marine reworking of weathering profiles and possible mixture of sediments from different provenances.Landscape changes from the topographically high, dissected Yilgarn environment with thick saprolite development and uneven basement topography, to the nearly flat regions dominated by sand dunes and thin saprolite development at the coastline. These regions are the result of the erosional and depositional effects of successive sea-level transgression–regression cycles. Within this framework, the following four different regolith settings have been identified in a progressive change from Yilgarn Craton environments to the modern coastline: (1) Albany; (2) Kalgoorlie–Norseman; (3) Esperance; and (4) Neale.Mapping the palaeocoastlines, islands and estuarine zones, as well as the region of influence of marine limestones and sediments, can significantly improve the understanding of how surface geochemistry relates to the landscape, and how it links with the geology at depth, and therefore, how it may reflect the presence of mineral systems. Understanding the difference in the landscape evolution between the AFO and Yilgarn Craton is essential to properly calibrate mineral exploration protocols in both regions. 相似文献
19.
缓慢复活型滑坡滑带土的蠕变性质与特征强度试验研究 总被引：4，自引：0，他引：4
锁儿头滑坡是甘肃省舟曲县城附近、体积约72.85×106 m3的一个巨型老滑坡。20世纪70年代末滑坡开始复活,至今一直处于缓慢活动之中,显示滑坡活动具有典型的蠕动特点。滑带力学特性是控制滑坡活动机制的关键因素之一,为了弄清该滑坡滑带物质的蠕变性质以及控制滑坡活动的强度指标,通过滑带土残余状态下的直剪蠕变试验,研究了滑坡滑带土的蠕变特性,比较了滑带长期强度和残余强度的关系。研究发现,滑带土蠕变特性与应力状态相关,滑带进入加速蠕变的临界剪应力和剪切速率均与正应力线性正相关。该滑坡应力状态指示其已具备进入加速蠕变的条件。残余状态下该滑坡滑带土的长期与残余强度基本等价,前者略大于后者,且增大量值与正应力有负相关关系。 相似文献
20.
《Chemie der Erde / Geochemistry》2021,81(4):125770
The distribution of gold in the weathering blanket at the Belikombone gold prospect in east Cameroon provides insights into gold mobility in the secondary environment and in tropical terrains worldwide. Both gridline-controlled sampling of topsoil (surface samples) and sampling of various layers in pits are used and the gold assay for each sample determined by NiS fire assay with ICP-AES finish. One hundred and thirty-two (132) surface samples and a total of 206 samples from 19 exploration pits were analyzed. The results from the topsoil samples show an anomaly with the highest Au concentration at 5.9 mgkg−1. The mineralization corridor follows a NE-SW trend. The horizons within the pits range from sap rock at the base, through saprolite, rubble layer rich in relict quartz material to a ferruginous loose layer at the top although some horizons are missing in some pits. All the layers contain gold and the highest concentration in the sap rock horizon is 3.4 mgkg−1 while the rubble layer has a gold high of 6.1 mgkg−1. The individual soil horizons show no systematic gold trends and given the presence of gold in all layers, the patterns point towards supergene dissolution and redistribution of gold. Gold enrichment within the upper horizons in the weathering blanket is attributed to sequestration by Fe oxides of chemically remobilized gold. However, the high gold content within the sap rock and saprolite layers suggests that migration of gold in the particulate form supersedes chemical gold redistribution. Particulate gold obtained by panning samples from the pits varies in shape from euhedral, elongated to irregular. Electron microprobe analysis on the grains record high contents of gold in the rim zones (90.0 to 99.8 wt%). The cores are relatively rich in Ag (12.6 to 14.2 wt%) while the rims are poor in Ag. The low Ag content in the rims is attributed to the preferential leaching of Ag. The soil pH value in this area varies between 3.6 and 7.3. Under such acidic to near neutral conditions, bisulfide and thiosulfate ions can dissolve and transport Au and Ag to be precipitated under surficial conditions creating authigenic Au haloes especially in the saprolite and sap rock layers. Such pH values together with oxidizing Eh conditions explain the solubility of gold in the area. These results are important for geochemical exploration of gold in tropical terrains, and confirm previous studies. 相似文献