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1.
This paper presents the numerical and experimental investigation of a dam foundation. The site consists of granite and especially
weathered granite. Numerical and analytical analyses have been conducted to evaluate suitability of the granite for a dam
foundation. Mohr–Coulomb failure criterion has been used to calculate the compressive strength of the rock mass. Finite element
implementation of Mohr–Coulomb criterion has been used for deformation and settlement analysis. Packer testing and in-situ
estimation of rock mass deformability using the Goodman jack have been performed. The results of the evaluations show that
very small normal and differential settlements can be expected in structural regions due to dam construction, and the compacted
concrete dam can safely be constructed on either the competent granite or the weathered granite. However, the dam foundation
on the weathered granite has high conductivity potential problems for the reservoir. 相似文献
2.
The purpose of this paper is to present a review of peat landslide events in Ireland since 2003, when two significant events
occurred. Since 2003, there have been at least 13 such events. Several of these events included more than one slide. It is
also likely that there have been unrecorded slides. It seems that there is an increasing incidence of such events, but they
seem to occur in clusters with intervening quiet periods. These clusters coincide with periods of intense rainfall. For many
slides, at least two causal factors can be identified. Primarily these comprised intense rainfall but human activities such
as road construction and peat cutting also contributed to the slides. Detailed geotechnical testing of the peat, including
laboratory direct simple shear tests (DSS), is reported for two of the slides. Back-analysis of these two failures suggests
that the mobilised strength of the material in the failure surface is similar to that measured in the DSS tests. However,
conventional geotechnical analyses need to be treated with caution as they fail to account for the complex interactions in
the sliding surface and in particular the lubricating role of water. 相似文献
3.
Weathering characterization for landslides modeling in granitoid rock masses of the Capo Vaticano promontory (Calabria,Italy) 总被引：1，自引：1，他引：0
This work focuses on developing multidisciplinary researches concerning weathering profiles related to landscape evolution of the Capo Vaticano promontory on the Calabria Tyrrhenian side (southern Italy). In this area, the tectonic uplift, occurred at least since Pleistocene, together with the Mediterranean climatic conditions, is the main cause of deep weathering and denudation processes. The latter occurred on the outcropping rocks of the crystalline-metamorphic basement, made up of weathered granitoids, in turn belonging to the Monte Poro granitoid complex (intermediate to felsic plutonic rocks covered by Cenozoic sedimentary successions). Field observations coupled to borehole explorations, geophysical surveys, and minero-petrographical analyses allowed the characterization of the granitoid outcrops typical of the studied area in terms of kind and degree of slope instability. This characterization was based on suitable correlations verified between several factors as weathering degree, elastic properties of rocks, and discontinuity features. Weathering profiles are mainly composed by rock masses varying from completely weathered rock with corestones of highly weathered rock (classes IV–V) to slightly weathered rocks (class II). The weathered rocks are involved in several landslide typologies such as debris flow (frequency 48.5%), translational slide (frequency 33.3%), and minor rock fall and rotational slide (frequency 9%). The achieved data allowed the establishment of a general correlation between weathering degree and type of slope instability. Debris flow-type instabilities are predominant on the steeper slopes, involving very poor rock masses ascribed to the shallowest portions of the weathering class IV. Translational slides are less widespread than the previous ones and often involve a mixture of soil and highly weathered rocks. Rotational slides are more frequently close to the top of the slopes, where the thicknesses of more weathered rocks increase, and involve mainly rock masses belonging to the weathering classes IV and V. Rock falls mostly occur on the vertical escarpments of the road cuts and are controlled by the characteristics of the main discontinuities. The assessment of rock mass rating and slope mass rating, based on the application of the discontinuity data, allowed respectively an evaluation of the quality of rock masses and of the susceptibility of rock slopes to failure. The comparison between the last one and the real stability conditions along the cut slopes shows a good correspondence. Finally, the geological strength index system was also applied for the estimation of rock mass properties. The achieved results give a worthy support for a better understanding of the relationship between the distribution of landslides and the geological features related to different weathering degrees. Therefore, they can provide a reliable tool to evaluate the potential stability conditions of the rock slopes in the studied area and a general reference framework for the study of weathering processes in other regions with similar geological features. 相似文献
4.
J. T. Hutton Dianne S. Lindsay C. R. Twidale 《Australian Journal of Earth Sciences》2013,60(1-2):37-50
Black Hill is a boulder‐strewn residual of norite standing 45 m above the Murray Plains about 80 km northeast of Adelaide. Between the boulders, the crystalline rock has weathered to a dark‐brown terra rossa‐rendzina soil with calcite, illite, kaolin, and hematite as the principal secondary minerals. At one site on the smooth lower slopes of the outcrop, the material above the norite consists of partially weathered granular fragments with considerable dolomite and some calcite in nodular form. Below the surface, the rock has been weathered along joints to produce the clay mineral nontronite, and between each corestone and this plastic clay there is a zone of laminated but essentially unaltered rock 10–25 cm thick. Pieces of amorphous silica occur sporadically in some joints and on the surface. The dark‐brown soil appears to be related to the present environment but the nontronite in the joint weathering, the dolomite, and the amorphous silica are all consistent with the norite having been inundated, possibly during the Miocene marine transgression. Calculations based on the retention of elements such as aluminium, potassium, titanium, and iron have been used to predict quantitatively the amount of certain minerals such as quartz, calcite, and dolomite introduced to the weathering profiles. 相似文献
5.
Use of backpropagation neural network for landslide monitoring: a case study in the higher Himalaya 总被引：7，自引：0，他引：7
Static and dynamic rock slope stability analyses were performed using a numerical discontinuum modelling technique for a 700-m high rock slope in western Norway. The rock slope has been investigated by the Geological Survey of Norway (NGU), which has been carrying out rock slide studies for the county Møre and Romsdal in western Norway. The purpose of numerical modelling was to estimate the volume of the rock mass that could potentially slide under static and dynamic forces. This estimation was required to assess the run-up heights (tsunami) in a fjord that could potentially be caused by the rockslide. Three cases have been simulated for predicting the behaviour of the rock slope. First, an initial static loading is applied in the numerical model to simulate the prevailing rock mass conditions at the site. Second, saturated and weathered joint conditions are modelled by reducing the residual friction angle along the discontinuities of the rock mass. In doing so, the model simulates the effect of degradation of discontinuities in the rock slope. Third, a dynamic loading, based on peak ground accelerations expected in the area, is applied to simulate dynamic earthquake conditions.
These numerical studies have provided some useful insights into the deformation mechanisms in the rock slope. Both sliding and rotation of blocks start to occur once the residual friction angle along the discontinuities is reduced and when the region is shaken by a strong earthquake. The results indicate that, due to variations in the inclination of discontinuities, the entire slope does not become unstable and that down-slope sliding and rotation of blocks occur mainly on the top layers of the slope. Within the range of parameter values considered for this study, it is unlikely that the whole rock slope can be destabilised. The study provides an illustration of how the geo-mechanical properties of a rock mass can be integrated in a discontinuum rock slope model, which is used for predicting the behaviour of the slope under existing environmental and earthquake conditions. This model has helped not only to better understand the dynamics of the rockslide but also to estimate the potential rock volume that can become unstable when subjected to static and dynamic loads. 相似文献
6.
SEAN J. FITZSIMONS ERIC A. COLHOUN GUUS VAN DE GEER ROBERT S. HILL 《Boreas: An International Journal of Quaternary Research》1990,19(1):1-15
Interpretation of weathered glacial and interglacial deposits in the lower King Valley suggests that the Early Pleistocene Thureau Formation is conformably overlain by the Regency Formation. Pollen analysis of the Regency Formation provides evidence of a new climatic stage, the Regency Interglacial. The interglacial deposit consists of humified peat overlain by drifted wood and leaves. The pollen analysis shows a transition from montane scrub rainforest to lowland temperate rainforest dominated by Lagarostrobos franklinii, Nothofagus cunninghamii and Phyllocladus aspleniifolius. Trace quantities of the species Quintinia psi-latispora and Gothanipollis perplexus , now both extinct in Tasmania, were also recorded. On the basis of intense chemical weathering and correlation with sediments that have a reversed magnetization the weathered glacial deposits of the Thureau Formation are thought to be older than 730,000 B.P. The eroded interglacial deposit rests on the weathered deposits and is buried by outwash gravels of the David Formation, which was deposited during an ice advance of the Middle Pleistocene Henty Glaciation (c. 150,000 B.P.). Comparison of the Regency site with a site 2 km to the south at Baxter Rivulet shows that the unconformity between the interglacial deposit and the overlying outwash gravel represents the erosion of the evidence for the Middle Pleistocene Moore Glaciation. 相似文献
7.
In this paper a detailed engineering geological assessment of rock masses and support design studies at Garmi Chay dam site, has been carried out. This project is located in the northwest of Iran and will be used for flow control and water storage. The diversion tunnel of the dam has a diameter of 5.5 m and a length of 420 m and will be driven in slightly to highly weathered micaschist and trachy andesite rock units. The geological studies include field and laboratory investigations that based on the results; for more exact investigation, tunnel alignment was divided into three geotechnical zones. These zones consist mainly of highly weathered gray micaschists, dark red trachy andesites and slightly weathered gray micaschists, respectively. Then, for every zone, support capacity of rock masses was evaluated by means of empirical and numerical methods. The rock mass classification systems (RMR, Q, GSI, RSR, SRC and RMi), the convergence–confinement method and a 2D finite element computer software, Phase2 were used for empirical and numerical method, respectively. According to the results acquired from these methods some stability problems were expected in the tunnel especially in highly weathered micaschist zone, so that in practice two big collapses occurred. Because of high weathering, low constants of rock masses and their soil-like behavior, the stability analysis by analytical method does not give illogical results in lightly weathered micaschist zone. The support system, suggested by empirical method, was applied and its performance was evaluated by means of numerical modeling. After installation the support suggested by Phase2 program, the thickness of plastic zone and deformations around the tunnel decreased significantly. Consequently the agreement of these methods with each other was resulted and using combination of them was recommended for more reliable support design. 相似文献
8.
岩体与岩石的力学强度之间既有内在联系又存在明显的差异,场地岩石力学指标对于评价场地岩体的力学特性至关重要。以三门核电场地为研究对象,在室内岩石力学试验的基础上,结合野外地质调查,综合考虑岩体结构特征和应力分布状态等因素的影响,引入定量描述岩体结构特征和风化程度的地质强度指标（GSI）,采用Hoek Brown强度准则估计岩体力学参数,同时与岩体地质力学分类法（RMR）计算得到的岩体力学参数进行对比分析。基于GSI的Hoek-Brown法得到的中等风化凝灰质砂岩、微风化凝灰质砂岩和微风化安山玄武岩岩体的c值分别为4.03、6.20、6.10 MPa,φ值分别为31.96°、34.37°和33.87°。基于RMR评分的Hoek-Brown法得到的c值分别为4.42、6.44、7.24 MPa,φ值分别为28.92°、32.43°和34.51°。研究结果表明,采用Hoek-Brown准则确定的核电场地岩体力学强度指标比较合理,得到的岩体力学指标可以作为核电站基础设计的重要依据。 相似文献
9.
Finite element modeling approach to assess the stability of debris and rock slopes: a case study from the Indian Himalayas 总被引：4，自引：2，他引：2
Landslides and slope failures are recurrent phenomena in the Indian Himalayas. The study area comprises the hill slopes along a road stretch of 1.5 km at a distance of 9 km from Pipalkoti on Chamoli–Badrinath highway (NH-58) in the Garhwal Himalayas, India. Based on the field survey, contour map, and the hillshade, the study area has been divided into different zones. Three different zones/slopes in this study area including one potential debris slide, one stable debris slope, and one potential rock slide have been undertaken for investigation and modeling. Field mapping, data collection related to slope features and soil/rock sample collection, and discontinuity mapping for all the slopes have been carried out in field. Soil samples have been tested in the laboratory to determine the physico-mechanical properties. These properties along with some material properties from the literature have been used as input parameters for the numerical simulation. To investigate the failure process in the debris/rock slides as well as stable debris slope, the slopes were modeled as a continuum using 2D finite element plain strain approach. Shear strength reduction analysis was performed to determine the critical strength reduction factor. The computed deformations and the stress distributions, along the failure surface, have been compared with the field observations and found to be in good agreement. The analysis results indicated rock/debris slide slopes to be highly unstable. The debris slide modeling depicted failures both above and below road levels as observed in field. The rock slide modeling could depict the exact pattern of failure involving 3 sets of discontinuities simultaneously as observed in real-field scenario which is a major limitation in case of limit equilibrium analysis. The field-observed stable slope comes to be stable through FE analysis also. Based on these analyses, landslide hazard assessment of the study area could be done. 相似文献
10.
In this study, the retention of Ca and other metals (Pb, Cu, Fe, Zn and Mn) in the Oostriku peat bog (central Estonia) was modelled. Equilibrium sorption of metals on amorphous ferric oxyhydroxide and solid organic matter was simulated at steady-state. Ferric oxyhydroxide formation and possible precipitation of other metals (Mn, Pb and Cu) in the peat was also assessed. Evolution of metal sorption fronts along a peat profile over time was simulated with a dynamic model to test if metal–metal competition effects could cause Pb and Cu to sorb at higher amounts in the uppermost peat than in the lower peat, as observed in the field. The predicted sorbed amounts of metals were compared with those previously observed in the peat. In general, good agreement between both batch and dynamic model results and the independent observations at the Oostriku peat site was obtained. This suggests that the relatively simple model approach employed here might be generally useful for assessing other peat sites and similar applications. 相似文献
11.
Amar Deep Regmi Kohki Yoshida Megh Raj Dhital Biswajeet Pradhan 《Environmental Earth Sciences》2014,71(6):2711-2727
Sangrumba landslide is one of the largest and the most active landslides in Nepal Himalaya. Geologically the landslide belongs to the Higher Himalaya and consists of Pre-Cambrian biotite–garnet and sillimanite gneiss with some quartzite. The present paper aims at describing various degrees of rock weathering and their effect in Sangrumba landslide. Field study followed by mineralogical, geochemical and geotechnical analyses of the collected rock and soil samples from the landslide zone were used in characterizing weathering degree. The gneisses are intensely weathered while quartzite is unweathered. Petrographical and X-ray diffraction analyses showed that the rocks in the landslide zone had undergone weathering process with the formation of different types of clay minerals as kaolinite, vermiculite, smectite and chlorite. This was further confirmed by the Scan Electron Microscope and Energy Dispersive X-ray analyses. These clay minerals drastically reduced the rock strength facilitating the extensive failure of the Sangrumba landslide. The major and trace element composition of the rock and soil samples was calculated from the XRF analyses. The geochemical analyses and weathering indexes of rocks showed that they are significantly weathered and had a major influence in the formation of the Sangrumba landslide. In addition, mechanical strength measurement of rock/soil showed that the strength drastically decreases as the weathering intensity increases. Rainfall followed by the rock type are the most dominant parameters influencing the weathering process which leads to the formation of large landslide as the present one. These findings can be used in other areas with similar geological and topographical conditions. 相似文献
12.
跨海峡海底隧道风化槽围岩力学特性研究 总被引：1，自引：0，他引：1
厦门海底隧道工程是我国建设的第一条海底公路隧道。隧道在建设过程中穿越F1～F4 四条断层破碎带,破碎带处洞体围岩软弱、破碎,岩石主要为风化破碎类花岗岩,该类岩石尤其是强风化花岗岩强度低,压缩性高,自稳和自承能力差,给隧道衬砌结构的设计和施工工艺的选择带来一系列特殊的问题。通过对风化破碎类花岗岩（主要包括微风化花岗岩和强风化花岗岩）试样进行一系列的室内试验,重点研究风化槽花岗岩的力学行为。强风化花岗岩三轴压缩试验及流变试验表明：强风化花岗岩强度低、变形大、弹性模量低,在达到峰值后,有明显的塑性流动,通过Mohr-Coulomb准则得到强风化花岗岩的摩擦角 约为31°,黏聚力约为0.1 MPa,且该岩石具有明显的流变特征。在流变试验的基础上,建立适合风化槽围岩特点的流变力学模型。其研究成果为海底隧道风化槽隧道围岩注浆加固和衬砌设计提供可靠依据和技术支撑。 相似文献
13.
A brief review of the genesis of blanket peats is presented, together with detailed analyses of basal peats from northern Scotland. Particular attention is paid to local factors affecting peat growth and the problems of sampling and interpretation arising from them. Macrofossil and loss-on-ignition analyses of four peat-mineral interfaces solve many of the terminological problems of such profiles and indicate that interpretations based on field stratigraphy alone are uncertain. Pollen analyses of two profiles from contrasting microtopographic situations show well-defined vegetational change associated with early peat development. Fully organic ombrotrophic peat is present from 6805 ± 50 BP at one site, following anthropogenic burning from c . 7500 BP and partial recovery of the open birch woodland. A change from birch woodland to Calluna heath occurs at approximately the same time on a more freely drained site with much later peat development, following further burning from 4890 ± 65 BP. Anthropogenic activity is clearly associated with changes in soil and vegetation preceding peat formation, and the role of climatic factors remains equivocal. 相似文献
14.
In February 2005, a landslide of significant dimensions occurred at Bol on the Island of Brač, in Croatia. The location of
the landslide was in a geological structure of weakly bounded conglomerates lying above a flysch, in an area where numerous
slides have been previously reported. In the paper the results of a geological engineering investigation of the Bol landslide
are presented. The investigation results show that the landslide was triggered by a combination of improperly started earthworks,
an increase in air temperature in days preceding landslide that caused snow melt, and abundant rainfall, but the primary cause
of the landslide was weathering of the flysch. In other words, despite the fact that contact between the flysch and the conglomerates
slopes is in approximate correspondence with the slope of the hillside, the landslide surface was not in contact between the
conglomerates and marl, but deeper in the flysch, provoked by the penetration of the weathering front into the flysch. Numerical
modelling results were able to reproduce this mechanism by incorporating strength degradation into the weathered zone, determined
by field investigation. The results of the research can be used to predict potential slides not only in the area under study. 相似文献
15.
16.
发育完整的灰岩风化壳及其矿物学和地球化学特征 总被引：25，自引：5，他引：20
对于碳酸盐岩土覆土壤成因、尽管碳酸盐岩风化残积成土说被多数学者认同,但由于碳酸盐岩中酸不溶物含量极低,在风化成土过程中会伴随着巨大的体积缩小变化,原岩结构和半风化带无法保留,从而缺失了探索上覆土壤物质来源的重要中间环节,使得这种观点缺乏野外宏观证据的支持。最近,我们在贵州、湖南等地发现了数个以泥质灰岩和泥质白云岩为基岩的碳酸盐岩风化壳剖面,尚保留有较好的原岩结构,具有明显的风化壳分带和过渡现象。这些风化壳剖面的发现为深入研究碳酸盐岩风化成土过程提供了良好的研究场所。本文选取了较为典型的吉首泥灰岩风化壳剖面,从矿物学地球化学的角度来探讨碳酸盐岩风化壳的形成过程和发育特征,结果表明该风化壳既遵循非碳酸盐岩（主要是结晶岩类）风化壳的发育特征,也具有自己独特的地球化学演化规律。风化壳总体特点受碳酸盐中的酸不溶物矿物组合及化学成分的影响甚至控制,风化非碳酸盐风壳相似的发育特征。吉首泥灰岩风化壳剖面的发育特征和作者早先提出 的碳酸盐岩风化成土的两阶段模式是一致的,即以碳酸盐矿物大量淋失、酸不溶物逐渐堆积或残积为特征的早期阶段和残积物进一步风化成土的阶段,后一阶段的演化类似非碳酸盐岩类的风化过程。 相似文献
17.
Hallstatt Village, located in the Austrian Alps, is designated by the United Nations Educational, Scientific and Cultural Organization as part of the World Cultural Heritage Site Hallstatt–Dachstein. This region is recognized for its salt deposits that have been exploited since the Neolithic period. In former times, these salt deposits were very rare and precious. Due to unfortunate bedding conditions, mass movements have been frequent in the past and continue to affect the site today. These active and inactive mass movements were mapped geotechnically to a scale of 1:5,000 and the mineralogical and mechanical properties of the main instable soft rocks were investigated. Rock spreads, rock slides, rock falls, rock topples, earth flows and earth and debris slides are the primary types of mass movements recorded. They are most frequently observed in areas affected by mining, though they may also occur in areas where no anthropogenic influence is recognized. Evidence exists in the archaeological record that indicates prehistoric mining activities were also seriously affected by the impact of mass movements. 相似文献
18.
A numerical model for wave scattering problems due to P and SV wave incidences is outlined in this paper. After verifying the present model, a general parametric study on the displacement patterns along the canyons of different shapes due to P and SV wave incidences is also performed. In order to investigate the effects of geologic conditions on ground motions, a weathered V-shaped canyon, which has different elastic moduli in the weathered layer, is also considered herein. The numerical results from this investigation demonstrated that (1) the present model is very suitable to simulate the problem of P and SV wave scattering along a natural canyon; (2) the shape of a canyon may have important effects on the displacement patterns along the canyon, so that a rectangular canyon is not appropriate to be a dam site due to its high amplification effects on incident waves; (3) the weathered layer on the surface of a canyon will significantly amplify the free field motion, especially for the case of softer weathered layer. Therefore, the excavation or grouting on a dam or a bridge abutment is not only necessary for static stability under static loads, but also beneficial to earthquake resistance because less amplification can be expected for sound rock abutments. 相似文献
19.
Mohamad Tarmizi Mohamad Zulkifley Ng Tham Fatt Wan Hasiah Abdullah John Kuna Raj S. Paramanathan Param Roslan Hashim Muhammad Aqeel Ashraf 《Central European Journal of Geosciences》2013,5(2):285-314
Petrographic studies indicate that lateral variations in the decomposition levels of peat are associated with the predominantly occurring peat macerals. Source Rock Analyzer (SRA) results indicate lateral variation in peat organic matter types from type II to III and back again to type II, occurring laterally within the top 0-m to 0.5-m layer at the basin margin to the midsection and further towards the near-center areas of the peat dome. This variation is most likely caused by a combination of factors: (a) Horizontal zonation and lateral variation of the dominant species of plant assemblages (b) Fibric (marginal) peats and hemic to sapric peats associated with type II organic matter (kerogen). Sample organic matter (coal-equivalent kerogen) typing indicates that the relative abundance of phytoclasts and palynomorphs generally supports the organic matter classification obtained by the SRA method. Lateral variations in the peat organic matter types may support the lateral vegetation variation concept. The classification of peat organic matter types (interpreted from visual analyses of palynological slides) occurring from the basin periphery to the mid-section and further towards the basin center yields organic matter of type II to type III and mixed types II to III (coal kerogen-equivalent), respectively. 相似文献
20.
Amar Deep Regmi Kohki Yoshida Hidehisa Nagata Ananta Man Singh Pradhan Biswajeet Pradhan Hamid Reza Pourghasemi 《Natural Hazards》2013,66(2):501-532
The present study was conducted along the Mugling–Narayanghat road section and its surrounding region that is most affected by landslide and related mass-movement phenomena. The main rock types in the study area are limestone, dolomite, slate, phyllite, quartzite and amphibolites of Lesser Himalaya, sandstone, mudstone and conglomerates of Siwaliks and Holocene Deposits. Due to the important role of geology and rock weathering in the instabilities, an attempt has been made to understand the relationship between these phenomena. Consequently, landslides of the road section and its surrounding region have been assessed using remote sensing, Geographical information systems and multiple field visits. A landslide inventory map was prepared and comprising 275 landslides. Nine landslides representing the whole area were selected for detailed studies. Field surveys, integrated with laboratory tests, were used as the main criteria for determining the weathering zones in the landslide area. From the overall study, it is seen that large and complex landslides are related to deep rock weathering followed by the intervention of geological structures as faults, joints and fractures. Rotational types of landslides are observed in highly weathered rocks, where the dip direction of the foliation plane together with the rock weathering plays a principle role. Shallow landslides are developed in the slope covered by residual soil or colluviums. The rock is rather fresh below these covers. Some shallow landslides (rock topples) are related to the attitude of the foliation plane and are generally observed in fresh rocks. Debris slides and debris flows occur in colluviums or residual soil-covered slopes. In few instances, they are also related to the rock fall occurring at higher slopes. The materials from the rock fall are mixed with the colluviums and other materials lying on the slope downhill and flow as debris flow. Rock falls are mainly related to the joint pattern and the slope angle. They are found in less-weathered rocks. From all these, it is concluded that the rock weathering followed by geological structures has prominent role in the rock slope instability along Mugling–Narayanghat road section and its surrounding regions. 相似文献