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1.
İnan Keskin 《Environmental Earth Sciences》2013,70(4):1619-1628
Disasters caused by events such as earthquake, flooding, rock falls, landslides are often encountered. However, generally, the reasons for the destructive and devastating effects of these nature events are that settlement locations were chosen without site investigation studies, or that available studies were inadequate. Such inadequacies in the field are related to inappropriate settlement location and the resulting damage caused by rock falls. This study evaluated rockfall risk in a settlement that developed in a similar manner. The study was carried out in Bo?aziçi village of Kemah (Erzincan/Turkey), which is located in a very important tectonic zone. The study site is located on the lower sections of an area with very steep cliffs and 50–75° slopes. This cliff, which is the source of rockfalls, has a slope dip of approximately 90°. The cliff comprises 25–30 m high, fractured and cracked basaltic volcanic mass. To determine block size in the study area, scanline survey measurements and block size measurements were performed on blocks that loosened and fell from the cliff face. It was found that block sizes reached 6 m3. Rockfall analyses were performed along the selected profiles using the Rockfall V.4.0 software. Kinetic energy, bounce height, horizontal location of rock end-points, and velocity of the rocks along each section were evaluated separately for each profile. This data were used to produce distribution maps for each profile and the settlement was evaluated in terms of rockfall risk. The results indicate that the study area was at risk of future rockfalls and that it would be appropriate to relocate one part of the settlement. 相似文献
2.
3.
Failure mechanisms and triggering factors in calcareous cliffs of the Subalpine Ranges (French Alps) 总被引：3，自引：0，他引：3
In order to enhance the detection of prospective rock falls in calcareous cliffs, 25 rock falls have been described in a more detailed way than for an inventory. They are representative of middle size rock falls (10 to 100,000 m3) occurring in the French Subalpine Ranges, at an elevation between 200 m and 2000 m. Structural conditions of the rock masses, morphology of the initial cliff surface and the scar, possible failure mechanisms and processes have been studied. Typical failure configurations have been identified, based on the attitude of the failure surface, in relation to the bedding planes and the cliff surface. Irregular cliff morphology appears to be another important susceptibility factor. In most cases, the classical comparison of the average planes of the main joint sets with the average plane of the slope could not define the potentially unstable masses. Rather, those ones are due to joint planes that deviate from their mean set plane or to irregularities of the cliff surface. The proposed investigation method to detect prospective rock falls mainly consists in observing stereoscopic aerial photographs in order to look for critical configurations. Once a critical mass has been detected, its failure probability for a period of the order of one century must be evaluated (or its life expectancy). The main factor to consider for this purpose appears to be the proportion of rock bridges in the potential failure surface.
The triggering factors of rock falls in our study area have been investigated, by analysing an inventory of 46 rock falls. Statistical tests have been carried out to study the relation between rock falls and daily rainfall, freeze–thaw cycles or earthquakes. A good correlation has been obtained with freeze–thaw cycles, a slight correlation with rainfall and no correlation with earthquakes. This suggests that ice jacking could the main physical process leading to failure by causing microcrack propagation. 相似文献
4.
The 560-km-long Kerala coast is characterised by long barriers with narrow beaches and steep cliffs. Distribution of cliffs
from nine sections measuring a cumulative length of 63.5 km is evaluated in ArcGIS Software using topomaps and field survey
data. The cliff sections in the southern coast comprise both permeable and impermeable rocks, whereas those along northern
coast are comprised of either Precambrian crystalline and/or Tertiary formations. Notches, caves and even small arches are
developed in Cannanore, Dharmadam and Kadalundi cliffs, where only primary laterites are exposed to wave attack. Stacks composed
of laterite and Precambrian crystallines found in nearshore of cliffed coast indicate recession of shoreline. Mass wasting,
mudslide and mudflow type of cliff failures are common in permeable to semi-permeable rocks, whereas rotational sliding, rockfall
and toppling failure are found in hard rock cliffs. Retreat of cliff sections are induced by natural or anthropogenic activities
or both. Rate of recession vary from a few centimetres to one metre/year depending upon the nature of lithology, structures
and recession agents acting upon the cliffs. Various methods of cliff protection for e.g. hard structures—revetments, groins,
seawalls, breakwater and jetties—and soft measures—artificial reefs/marsh creation, floating breakwaters, beach nourishment,
beach scraping and vegetation planting—are suggested. 相似文献
5.
Coastal cliff erosion is a problem in many coastal areas. However, often only very limited data are available to quantify the rates of recession for the development of coastal management strategies. In the soft flysch deposits of the Waitemata Group, Auckland, New Zealand, coastal cliffs are associated with shore platforms. Two models exist for the profile evolution of shore platforms and associated cliffs: the first suggests that an equilibrium profile develops in response to erosive processes, and this profile subsequently migrates landward; the second model suggests that the seaward margin of the shore platform is relatively static, and the profile extends landward through a combination of cliff recession and platform lowering. Physical simulations and field measurements for mudstone and limestone lithologies indicate that the second model is more likely for soft flysch deposits. A eustatic sea-level curve for the Weiti Estuary, Auckland, suggests that up to 7120 ± 70 years have been available for shore platform development since sea level reached the present seaward margins of shore platforms. Shore platform widths were measured using GPS at two sites in Waitemata Group rocks: the North Shore of Auckland; and the southern side of the Tawharanui Peninsula, North Auckland. The long-term cliff recession rates estimated from shore platform widths (1.4 ± 0.1 to 14.3 ± 0.1 mm y− 1) are consistent with the lower end of the average range of cliff top and face recession rates published for Waitemata Group rocks using different methods (11–75 mm y− 1), and in agreement with cliff base recession estimates (3.5 mm y− 1). Shore platform widths were qualitatively related to the rock mass characteristics of the associated cliffs, and therefore platform widths could provide a method of identifying regions of potential hazard. 相似文献
6.
文章选择粤北英德九龙镇典型峰林平原为研究区,在不同地貌部位调查了生态环境的岩石裸露率和土壤厚度,以及植物物种、生物量、盖度等指标,运用物种α多样性指数和Jaccard相似性系数分析了植物多样性与相似性,结果表明:（1）不同地貌部位的岩石裸露率、土层厚度差异较大,峰壁岩石裸露率显著大于峰顶、坡麓和洼地,而洼地的土层厚度显著大于峰顶、峰壁和坡麓;（2）峰顶、峰壁、坡麓和峰间洼地的群丛依次为乔栯榕-竹叶椒+檵木-纤毛鸭嘴草、乔栯榕-红背山麻杆+檵木-五节芒、黄连木-灰白毛莓-纤毛鸭嘴草和长毛八角枫-藤金合欢+粉单竹-纤毛鸭嘴草,优势种与层片结构有一定差异;（3）岩溶植物具有对环境的高度适应性,使不同地貌部位植被能够保持较高的覆盖度,但地势平缓、土层相对较厚的峰顶与峰间洼地的生物量要显著大于坡麓及峰壁;（4）岩石裸露率与土层厚度、土层厚度与生物量间都呈极显著的负相关关系;（5）峰顶与峰间洼地的物种数显著少于峰壁与坡麓,峰顶的Shannon-Wiener指数、Simpson指数和Pielou指数都显著低于其他部位,而峰壁的几项多样性指数均显著高于其他部位植被,岩溶环境地貌部位的多样性有助于提高生物多样性;（6） Jaccard相似性系数分析表明峰林空间异质性造成物种分布的差异,空间位置远近和地貌部位差异大小对物种分布影响至关重要。 相似文献
7.
B. Matasci G. M. Stock M. Jaboyedoff D. Carrea B. D. Collins A. Guérin G. Matasci L. Ravanel 《Landslides》2018,15(5):859-878
Rockfalls strongly influence the evolution of steep rocky landscapes and represent a significant hazard in mountainous areas. Defining the most probable future rockfall source areas is of primary importance for both geomorphological investigations and hazard assessment. Thus, a need exists to understand which areas of a steep cliff are more likely to be affected by a rockfall. An important analytical gap exists between regional rockfall susceptibility studies and block-specific geomechanical calculations. Here we present methods for quantifying rockfall susceptibility at the cliff scale, which is suitable for sub-regional hazard assessment (hundreds to thousands of square meters). Our methods use three-dimensional point clouds acquired by terrestrial laser scanning to quantify the fracture patterns and compute failure mechanisms for planar, wedge, and toppling failures on vertical and overhanging rock walls. As a part of this work, we developed a rockfall susceptibility index for each type of failure mechanism according to the interaction between the discontinuities and the local cliff orientation. The susceptibility for slope parallel exfoliation-type failures, which are generally hard to identify, is partly captured by planar and toppling susceptibility indexes. We tested the methods for detecting the most susceptible rockfall source areas on two famously steep landscapes, Yosemite Valley (California, USA) and the Drus in the Mont-Blanc massif (France). Our rockfall susceptibility models show good correspondence with active rockfall sources. The methods offer new tools for investigating rockfall hazard and improving our understanding of rockfall processes. 相似文献
8.
Rock slope response to strong earthquake shaking 总被引：1，自引：1，他引：0
C. Massey F. Della Pasqua C. Holden A. Kaiser L. Richards J. Wartman M. J. McSaveney G. Archibald M. Yetton L. Janku 《Landslides》2017,14(1):249-268
The 2010–2011 Canterbury earthquakes triggered many mass movements in the Port Hills including rockfalls, debris avalanches, slides and slumps, and associated cliff-top cracking. The most abundant mass movements with the highest risk to people and buildings were rockfalls and debris avalanches sourced from up to 100 m high cliffs inclined at angles >65°. Cliffs lower than 10 m in height generally remained stable during the strong shaking, with only isolated release of a few individual boulders. We used site-specific data to investigate the factors that controlled the response of the cliffs to the main earthquakes of the Canterbury sequence, adopting two-dimensional finite element seismic site response and stability modeling that was calibrated using the field observations and measurements. Observations from the assessed cliffs in response to the earthquakes show the taller cliffs experienced larger amounts of permanent cliff-top displacement and produced larger volumes of debris than the smaller cliffs. Results indicated a mean KMAX amplification ratio for all sites under study of 1.6 (range of 1.1–3.8). Field data and numerical modeling results, however, show that amplification of shaking does not necessarily increase linearly with increasing cliff height. Instead, our results show that accelerations are amplified mainly due to the impedance contrasts between the geological materials, corresponding to where strong differences in rock mass shear wave velocity exist. The resulting acceleration contrasts and rock mass strength control cliff stability. However, the amount of permanent slope displacement and volume of debris leaving the cliffs varied between the sites, due to site-specific geometry and rock mass strength. 相似文献
9.
Stability Analysis of a Rock Column in Seismic Conditions 总被引：1，自引：0，他引：1
10.
Paolo Budetta 《Natural Hazards》2011,56(1):233-250
This paper deals with a finite element stability analysis performed on a sea-cliff affected by a deep notch. The cliff is
about 200 m long with height ranging between 8 and 19 m. The notch at the cliff base is about 1 m above sea level, nearly
stretching along the entire cliff toe. Detailed geo-structural and geo-mechanical surveys were performed in situ, and rock
samples were tested in laboratory. The relevant physical and mechanical properties were used for determining rock mass strength
parameters. A finite element approach was implemented using a two-dimensional elasto-plastic finite-element stress analysis
program. The stability analysis shows that the notch causes increasing shear strains spreading from the notch end towards
the top cliff. Decreasing strength reduction factors affect the cliff as the notch reaches increased depth into the rock mass,
and when its depth is about 2 m the analysis results do not converge. At this stage, an uninterrupted shear plane develops
along which a roughly prismatic rock block can slide and then topple. 相似文献
11.
以广西柳州白莲洞遗址崖体为研究对象,经地质调查发现,白莲洞遗址崖体存在共计47处不稳定岩体,崖体岩性主要为厚层灰岩,岩溶发育且该厚层灰岩岩体节理裂隙十分发育,存在着诸多危岩体。通过野外地质调查与室内理论分析表明:白莲洞遗址崖体陡峭,灰岩厚层,层理面、构造裂隙、岩溶裂隙和卸荷裂隙发育,在持续暴雨、地震的强有力触发下导致山体松弛,变形加剧,形成了以柱状、楔形体状、块状为主的特大型危岩体,且多处于高位-特高位,从而表现出倾倒、滑移和少量坠落及其复合型的多种破坏模式;其变形破坏绝非突发,厚层块状构造、岩溶发育、坚硬灰岩夹白云岩透镜体及发育的节理裂隙是其形成的主要先天基础因素;降水的渗入、岩溶裂隙水的溶蚀及强烈的根劈作用为其主要触发因素。 相似文献
12.
Alessio Rovere Stefano Bellati Valeriano Parravicini Marco Firpo Carla Morri Carlo Nike Bianchi 《Estuaries and Coasts》2009,32(2):333-339
The existence of linkages between ecological and geomorphological processes and the influence of human activities both on
the biota and on geomorphology is well known for terrestrial environments, while it has been seldom reported for submerged
ones. A survey in the Noli-Bergeggi area (NW Mediterranean Sea) has been carried out to test the hypothesis that the harvesting
of Lithophaga lithophaga has an impact not only on the hammered rock, but also on the sediments at the cliff foot. Size and roundness of pebbles have
been measured at different stations and statistical analyses have been used to test the differences between impact and control
situations. Results show a dependence of the roundness of pebbles on the date mussel harvesting, indicating a decrease both
of the roundness index and of its variability at the cliff foot in impacted sites. Conclusions stress the biogeomorphological
nature of this activity, not limited to the present location. 相似文献
13.
Integration of hydrogeological and geological data into a conceptual model is critical for site investigation programs, since this model is the basis for hydrogeological modeling and for engineering. In the Hungarian Radioactive Waste Disposal Investigation Program, several methods have been used to characterize the potential host rock (granite) at the Bátaapáti site for a repository for low and intermediate level radioactive waste. Hydrogeological data acquisition revealed some characteristic aspects of the site. One of the most important is the presence of extensive rock deformation zones (faults) with low hydraulic conductivity, which strongly reduce the direct hydraulic communication between adjacent blocks of rock (compartmentalization). This characteristic of the rock mass results in a mosaic-like distribution of rock compartments, each with an almost constant hydraulic head. Within the compartments, hydraulic tests have shown that transmissivity is strongly scale dependent: the larger the scale, the higher the measured transmissivity. The extensive highly transmissive zones cause very low hydraulic gradients within each block, thus the transport processes are strongly influenced by the low or average transmissivity zones and the rock matrix. 相似文献
14.
Rockfalls are common in the steep and vertical slopes of the Campania carbonate massifs and ridges, and frequently represent
the main threat to the anthropogenic environment, potentially damaging urban areas, scattered houses, roads, etc. Despite
the generally limited volumes involved, the high velocity of movement (from few to tens of metres per second) poses rockfalls
among the most dangerous natural hazards to man. Evaluating the rockfall hazard is not an easy task, due to the high number
of involved factors, and particularly to the difficulty in determining the properties of the rock mass. In this paper, we
illustrate the assessment of the rockfall hazard along a small area of the Sorrento Peninsula (Campania region, southern Italy).
Choice of the site was determined by the presence of a road heavily frequented by vehicles. In the area, we have carried out
detailed field surveys and software simulations that allow generating simple rockfall hazard maps. Over twenty measurement
stations for geo-mechanical characterization of the rock mass have been distributed along a 400-m-long slope of Mount Vico
Alvano. Following the internationally established standards for the acquisition of rock mass parameters, the main kinematics
have been recognized, and the discontinuity families leading to the different failures identified. After carrying out field
experiments by artificially releasing a number of unstable blocks on the rock cliff, the rockfall trajectories along the slope
were modelled using 2-D and 3-D programs for rockfall analysis. The results were exploited to evaluate the rockfall hazard
along the threatened element at risk. 相似文献
15.
日益严重的风化侵蚀,严重影响了莫高窟围岩的稳定性和壁画的赋存环境,成为威胁洞窟文物安全的严重隐患。为研究莫高窟北区崖体沿纵深方向的风化特征,选取莫高窟北区北侧一处崖体为试验点,采用逐层剖切的方法,沿水平方向由外向里依次取样编号。通过室内颗分试验、现场声波测试、可溶盐测试及X射线衍射测试,分析其变化规律。试验结果表明:地层颗粒组成的差异将影响崖体的抗风化能力;声波波速呈现震荡性的变化趋势;在水平深度0.7 m范围内钠长石含量相对减少,石英含量相对增加;崖体在水平深度0.4~1.0 m范围内可溶盐含量呈现递减特征;可溶盐是影响北区崖体风化的重要因素之一。综合分析各测试结果,认为1号、2号和3号探洞风化厚度分别为1.0 m、0.6 m和0.4 m。崖体风化呈现空间差异性,顶部风化最为严重,底部风化最弱。 相似文献
16.
Rockfall susceptibility has been analysed in mountain cliffs of the Cantabrian Range, North Spain. The main aim of this analysis has been to build a predictive model of rockfall activity from a low number of environmental and geological variables. The rockfall activity has been quantified in a GIS. The cartographic information used shows the spatial distribution of all the recent talus screes as well as their associated source areas in the rock-slopes. The area relation At/Ar (recent talus scree polygon/source basins) in the rock slopes has been used as the rockfall activity indicator. This relation has been validated in 50 pilot rock-slopes and compared with the relation number of recent rock fragments/source basin, obtained from field work. The environmental factors causing rockfall depend on the rock slope situation, and these are: altitude and sun radiation on the rock cliff. The geological factors considered are: lithology, relative position of the main discontinuities with respect to the topographic surface and two morphologic parameters: the roughness and slope gradient. A logistic regression analysis has been applied to a population of 442 limestone and quartzite rock cliffs. The dependent variable is the rockfall activity indicator, which allows the definition of two classes of rock cliff units: low and high activity. The independent variables are altitude, sun radiation (equinox radiation, summer solstice radiation, winter solstice radiation), slope roughness, slope gradient,anisotropy and lithology. Results suggest that it is possible tobuild a valid cartographic predictive model for rockfall activity in mountain rock cliffs from a limited number of easily obtainable variables. The method is especially applicable in massive rock slopes or in regions with uniform rock mass characteristics. 相似文献
17.
Bastien Caplain Dominique Astruc Vincent Regard Frédéric Y. Moulin 《Comptes Rendus Geoscience》2011,343(7):471-477
Wave flume experiments have been performed to investigate a sandy cliff recession under monochromatic wave forcing. We varied the wave climate through the wave energy flux F and the surf similarity parameter ξ. The various processes of the cliff erosion cycle are depicted. The sea bed evolution mostly depends on the surf similarity parameter ξ. Steep planar (ξ > 0.7), gentle planar (0.5 < ξ < 0.7) and bared (ξ < 0.5) profiles are observed. We observed different bar dynamics, including steady and unsteady self-sustained oscillating states. Then we analyze the role of the eroded material on the cliff recession rate. We show that the cliff recession rate increases with the wave energy flux. Moreover, for a given wave energy flux, it is larger for a gentle planar profile than for a bared profile. However it is similar for both a bared profile and a steep planar profile. The cliff recession rate is not a monotonic function of the cliff height as the type of bottom profile influences the wave energy at the cliff. 相似文献
18.
A rapid approach to estimate the rockfall energies and distances at the base of rock cliffs 总被引：1，自引：0，他引：1
Federica Ferrari Klaus Thoeni Anna Giacomini Cedric Lambert 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2016,10(3):179-199
This paper presents a new methodology for estimating the expected energies and first impact distances at the base of a rock cliff, subject to the geometry and properties of the cliff and the representative block being known. The method is based on a sensitivity analysis, conducted by means of kinematic simulations and carried out for a large range of input parameters and their combinations, taking into account the uncertainty associated with their estimate. The proposed approach is validated by comparing predictions to experimental data and shows great potential for a quick qualitative hazard assessment. 相似文献
19.
贵州开阳县龙井湾崩塌地质灾害评估及防治 总被引：1，自引：0，他引：1
龙井湾崩塌是磷矿开采引发和加剧的,龙井湾沟谷分布有崩塌6处。文章通过对崩塌区地质环境的勘查,阐述了该区的地质构造、岩性条件、水文地质条件及当前存在的采空区范围及特点,继而采用概率法对采空区上覆的岩体稳定性进行分析,得出了磷矿层的开采将在其上方相应的地表造成一定的变形与移动的结论,阐明了该区崩塌产生的机理,评估了崩塌体的引发和加剧对磷石膏堆场工程的危害性,提出了禁采区范围、清理危岩体(壁)等防治的工程措施。 相似文献
20.
Nicola Nocilla Aldo Evangelista Anna Scotto di Santolo 《Rock Mechanics and Rock Engineering》2009,42(5):815-833
In recent years, rock fall phenomena in Italy have received considerable attention for risk mitigation through in situ observations
and experimental data. This paper reports the study conducted at Camaldoli Hill, in the urban area of Naples, and at Monte
Pellegrino, Palermo, Italy. The rocks involved are volcanic Neapolitan yellow tuff (NYT) in the former area and dolomitic
limestone in the latter. Both rocks, even though with different strength characteristics, have shown a significant tendency
towards rock fragmentation during run out. This behavior was first investigated by comparing the volumes of removable blocks
on the cliff faces (V
0) and fallen blocks on the slopes (V
f). It was assumed that the ratio V
f/V
0 decreases with the distance (x
f) from the detachment area by an empirical law, which depends on a coefficient α, correlated with the geotechnical properties of the materials involved in the rock fall. Finally, this law was validated
by observation of well-documented natural rock falls (Palermo) and by in situ full-scale tests (Naples). From the engineering
perspective, consideration of fragmentation processes in rock fall modeling provides a means for designing low-cost mitigation
measures. 相似文献