Influence of uncertainties: A focus on block volume and shape assessment for rockfall analysis

Block size and shape depend on the state of fracturing of the rock mass and,consequently,on the geometrical features of the discontinuity sets(mainly orientation,spacing,and persistence).The development of non-contact surveying techniques applied to rock mass characterization offers significant advantages in terms of data numerosity,precision,and accuracy,allowing for performing a rigorous statistical analysis of the database.This fact is particularly evident when dealing with rockfall phenomena:uncertainties in spacing and orientation data could significantly amplify the uncertainties connected with in situ block size distribution(IBSD),which represents a relation between each possible value of the volume and its probability of not being exceeded.In addition to volume,block shape can be considered as a derived parameter that suffers from uncertainties.Many attempts to model the possible trajectories of blocks considering their actual shape have been proposed,aiming to reproduce the effect on motion.The authors proposed analytical equations for calculating the expected value and variance of volume distributions,based on the geometrically correct equation for block volume in the case of three discontinuity sets.They quantify and discuss the effect of both volume and shape variability through a synthetic case study.Firstly,a fictitious rock mass with three discontinuity sets is assumed as the source of rockfall.The IBSDs obtained considering different spacing datasets are quantitatively compared,and the overall uncertainty effect is assessed,proving the correctness of the proposed equations.Then,block shape distributions are obtained and compared,confirming the variability of shapes within the same IBSD.Finally,a comparison between trajectory simulations on the synthetic slope is reported,aiming to highlight the effects of the propagation of uncertainties to block volume and shape estimation.The benefits of an approach that can quantify the uncertainties are discussed from the perspective of improving the reliability of simulations.

基于Rockfall的沟谷区高位危岩体危险性评估

为了降低高位危岩体对沟谷区建设用地威胁,以沟谷区内某商住小区为例,探讨高位危岩体危险性评估结果。通过资料收集和现场调查,采用Rockfall模型软件计算沟谷区高位危岩体对小区现状地质灾害危险性,评估了防治措施情景下的地质灾害危险性。用Rockfall模拟软件计算出沟谷区内危岩体现状和设计情景条件下的运动路径和最远威胁距离,确定建设用地红线范围内的地质灾害危险性结果。结果表明,现状条件下沟谷区建设用地红线范围内危险性中等区域面积112.15 m2,设计情景下建设用地红线范围均为危险性小的区域。

Integrated hazard assessment of rockfall incidents in the Cap Aokas Cliff Region

Rock fall accidents in mountainous cliff areas have significant consequences for human life and transportation.This study aimed to evaluate the rockfall hazard in the Cap Aokas cliff region located along the northeast coast of Algeria by identifying the key factors contributing to rockfall occurrence.We employed a combination of kinematic analysis,Matterocking method,and 3D trajectory simulations to determine zones that are susceptible to rockfall mobilization.By using a probabilistic and structural approach in conjunction with photogrammetry,we identified the controlling factors.The kinematic analysis revealed the presence of five discontinuity families,which indicated both plane and wedge failure modes.The 3D trajectory simulations demonstrated that the falling blocks followed the stream direction.We then validated the susceptibility maps generated from the analysis using aerial photos and historical rockfall events.The findings of this study enhance our understanding of rockfall phenomena and provide valuable insights for the development of effective strategies to mitigate rockfall hazards.

RockFall软件在铁路边坡危岩失稳运动路径分析中的应用

山区铁路岩质边坡坡体失稳和危岩崩塌等灾害,对线路运营安全有潜在风险。危岩体发生破坏时的运动方式受下部斜坡的物质组成、边坡坡角、危岩体几何形状、岩体性质等的影响,运动距离、运动方式及冲击能量各不相同。采用RockFall软件模拟了丰沙铁路北侧山体危岩体破坏后的运动规律,得出危岩体破坏后沿坡面的运动路径、运动速度、冲击能量等信息,可为崩塌落石防治措施选择提供合理依据。

花岗岩孤石稳定性评价及基于Rockfall的滚落模拟

广东丘陵山区广泛分布花岗岩,而花岗岩往往发育成许多球状风化体(孤石),易发生失稳滚落,对山下建构筑物以及人员安全造成威胁。本文针对广东省河源市龙川县上坪镇石湖村村委会所在地东北侧一带坡面孤石开展调查,通过分析其发育分布特征,对坡面孤石进行稳定性评价,利用Rockfall软件对孤石运动轨迹和能量曲线进行模拟,以更有效地设置拦石墙、被动防护网等拦截上部的孤石。

Investigating the performance of passageway corridor for ground reinforced embankments against rockfall

Rockfall disasters can result in damages to various structures such as highways and buildings.Ground reinforced embankments(GRE) are one of the barrier types used to prevent rockfall. GRE absorb the impact energy of the hitting rock blocks by the movement of fine soil particles triggered by the penetration of the rock in the soil. In this process,stresses in the wall are distributed in both the transverse and longitudinal directions. GREs on the valley slopes can be hundreds of meters long, so such structures cause difficulty in transition to valley slope behind the embankments. Especially, access to areas such as agricultural, pasture or forest lands behind the GRE becomes a challenge. The current paper presents the design of passageways in GRE using the finite element method to provide safe corridors at several different parts within the hundreds of meters long structures. A total of 4 different passageway designs for GRE were developed. Each finite element model was subjected to rockfall with different kinetic energies of 500, 1000 and 3000kJ. The obtained results showed that 44% increase in structure volume increased the impact capacity from 500 kJ to 3000kJ.Furthermore, the critical displacement caused by rockfall impact with an energy of 3000 kJ was reduced by 31%. It was determined that the support applied with the reinforced concrete wall did not reach the desired energy absorption value due to its rigid structure, and even collapsed at 3000 kJ.

Numerical simulation on the impact characteristics between rockfalls of different shapes and gravel cushions

The shape of rockfalls significantly affects the performance of the impact cushion,which is manifested by the difference in the impact force and the penetration depth of the rockfall during the collision.In this study,we built the collision numerical model between rockfalls and cushions based on the results from previous studies,and simulated the collision process of rockfalls with four different shapes(cylindrical,cuboid,spherical,and cubic)and different cushions.Essential parameters when rockfalls impact cushions are calculated,including the maximum impact forces on the surface and bottom of the cushions and the maximum penetration depth of the rockfall.The results showed that the maximum impact force on the surface and the bottom of the cushions varies with the rockfall shapes.The maximum impact force on the cushion surface caused by cylindrical rockfall is the smallest,followed by the cuboid rockfall,the cube rockfall,and the spherical rockfall.The maximum impact force at the cushion bottom also follows this trend.However,the penetration depth of cuboid rockfall is the smallest,followed by the cylindrical rockfall,the cubic rockfall,and the spherical rockfall.The results of this study provide more extensive theoretical support for rockfall disaster prevention using gravel cushions.

川西北某拟建高速公路隧道口高位危岩特征及危险性评价

某拟建高速公路隧道口位于川西北岷江河谷地带,区内地形地貌复杂、新构造运动强烈,高位危岩极其发育,严重威胁拟建公路隧道口。本文基于无人机倾斜摄影及现场调查,采用Rockfall Analyst软件模拟落石三维运动特征。结果表明:(1)危岩区坡度较陡,岩性以砂质千枚岩为主,岩体破碎、节理裂隙发育,稳定性较差,变形破坏模式以滑移式、坠落式为主;(2)落石运动过程以自由飞落、碰撞弹跳以及贴坡运动为主,最大速率33 m/s,最大弹跳高度14.5 m,最大能量约3 100 kJ,在运动过程有大部分会落至隧道洞口上方,危险性高-极高;(3)建议清除隧道洞口上方孤石、危岩,设置锚索(杆)框格梁进行处治,隧道进口接长明洞,同时加强监测。本研究成果对川西北地区公路、铁路工程地质选线、勘察设计及防灾减灾具有一定指导和借鉴意义。

基于无人机和Rockfall Analyst的崩塌落石特征分析与运动学模拟--以察雅县崩塌落石为例

崩塌落石是高陡边坡的一种浅表部破坏方式,突发性强且随机性大,是严重的地质灾害之一。分析崩塌落石特征,并对落石进行运动学模拟对于灾害防治具有重大意义。以往的研究对于崩塌落石的运动学模拟大多基于二维模拟软件,人为控制了运动方向,具有一定的干扰性,部分独立的三维模拟软件计算时考虑的参数较多,增加了模拟难度。在调查方式上,无人机技术凭借机动灵活、工作效益高成为一种趋势。因此,文章以昌都市察雅县北西侧斜坡为研究区,结合现场调查和无人机三维倾斜摄影技术,调查分析了斜坡崩塌落石特征,通过三维模型获取了岩体结构面信息,分析了岩体稳定性;基于GIS环境下三维落石模拟软件Rockfall Analyst,根据历史崩塌轨迹采用参数反演的方法获得研究区斜坡下垫面参数,对物源区块石进行了运动轨迹、速度和弹跳高度的数值模拟。结果表明:(1)斜坡上主要存在三处物源区,岩体整体受三组主控结构面控制,不同结构面之间的组合破坏和冻融侵蚀影响下的岩体差异性分化是造成岩体失稳的主要因素;(2)通过模拟的运动轨迹确定了落石的威胁范围,弹跳高度和速度轨迹可为崩塌落石灾害防治的位置和防治措施的选择上提供地质依据。

Impact resistance performance and optimization of the sand-EPE composite cushion in rock sheds

Rock sheds are widely used to prevent rockfall disasters along roads in mountainous areas.To improve the capacity of rock sheds for resisting rockfall impact,a sand and expandable polyethylene(EPE)composite cushion was proposed.A series of model experiments of rockfall impact on rock sheds were conducted,and the buried depth of the EPE foam board in the sand layer was considered.The impact load and dynamic response of the rock shed were investigated.The results show that the maximum impact load and dynamic response of the rock shed roof are all significantly less than those of the sand cushion.Moreover,as the distance between the EPE foam board and rock shed roof decreases,the maximum rockfall impact force and impact pressure gradually decrease,and the maximum displacement,acceleration and strain of the rock shed first decrease and then change little.In addition,the vibration acceleration and vertical displacement of the rock shed roof decrease from the centre to the edge and decrease faster along the longitudinal direction than that along the transverse direction.In conclusion,the buffering effect of the sand-EPE composite cushion is better than that of the pure sand cushion,and the EPE foam board at a depth of 1/3 the thickness of the sand layer is appropriate.

Discontinuity development patterns and the challenges for 3D discrete fracture network modeling on complicated exposed rock surfaces

Natural slopes usually display complicated exposed rock surfaces that are characterized by complex and substantial terrain undulation and ubiquitous undesirable phenomena such as vegetation cover and rockfalls.This study presents a systematic outcrop research of fracture pattern variations in a complicated rock slope,and the qualitative and quantitative study of the complex phenomena impact on threedimensional(3D)discrete fracture network(DFN)modeling.As the studies of the outcrop fracture pattern have been so far focused on local variations,thus,we put forward a statistical analysis of global variations.The entire outcrop is partitioned into several subzones,and the subzone-scale variability of fracture geometric properties is analyzed(including the orientation,the density,and the trace length).The results reveal significant variations in fracture characteristics(such as the concentrative degree,the average orientation,the density,and the trace length)among different subzones.Moreover,the density of fracture sets,which is approximately parallel to the slope surface,exhibits a notably higher value compared to other fracture sets across all subzones.To improve the accuracy of the DFN modeling,the effects of three common phenomena resulting from vegetation and rockfalls are qualitatively analyzed and the corresponding quantitative data processing solutions are proposed.Subsequently,the 3D fracture geometric parameters are determined for different areas of the high-steep rock slope in terms of the subzone dimensions.The results show significant variations in the same set of 3D fracture parameters across different regions with density differing by up to tenfold and mean trace length exhibiting differences of 3e4 times.The study results present precise geological structural information,improve modeling accuracy,and provide practical solutions for addressing complex outcrop issues.

危岩崩塌运动轨迹特征的Rockfall数值模拟研究

运用Rockfall数值模拟软件,对危岩体的稳定性进行了分析,通过设定危岩体的法向恢复系数、切向恢复系数和动摩擦系数等参数,绘制出危岩体的运动轨迹、能量分布和弹跳高度数值模拟图,为指导防护体系的结构设计、确保防治效果提供了依据。

Coupled DEM-FDM analyses of the effects of falling rock’s shape and impact angle on response of granular cushion and rock shed

Rock shed is an effective protection measure against rockfall.To investigate the influences of falling rock’s shape and impact angle on the impact effect of the cushioned rock shed,a modeling approach for a rock shed with a cushion layer using PFC-FLAC.The granular cushion is modeled as an aggregate of discrete non-cohesion particles,while the concrete plate and the beam are modeled as zones.The falling rock with different sphericities and impact angles is modeled as a rigid assembly.The numerical model is validated by comparing the simulation results with experimental and numerical results from previous literature.This model is applied to analyze the effects of rock shape and impact angle on the dynamic interaction effects between falling rock and cushioned rock shed,including the impact force,transmitted bottom force,penetration depth,and plate deflection.The numerical results show that the variation in the falling rock’s shape has different effects on the falling rock with different impact angles.These findings could support rock shed design by revealing the limitations of the assumptions in the past research,which may result in unsafe rock sheds for some rockfall cases.

Evaluation of crustal deformation and associated strong motions induced by the 2022 Paktika earthquake,Afghanistan

The 2022 Paktika earthquake(moment magnitude:6.2) occurred on June 22,2022,near the border between the Khost and Paktika Provinces of Afghanistan,causing heavy damage and casualties in Paktika Province.This study evaluated the crustal deformation and associated strong motions induced by the Paktika earthquake.Crustal deformations were determined using the Differential Interferometric Synthetic Aperture Radar(DInSAR) technique and three-dimensional finite element method(3DFEM) and the results were compared.The permanent ground displacements obtained from the DInSAR and 3D-FEM analyses were similar in terms of amplitude and areal distribution.Strong motions were estimated using the 3D-FEM with and without considering regional topography.The estimations of maximum ground acceleration,velocity,and permanent ground deformations were compared among each other as well as with those inferred from failures of some simple structures in the Spera and Gayan districts.The inferred maximum ground acceleration and velocity from the failed adobe structures were more than 300 Gal and 50 cm/s,respectively,nearly consistent with the estimates obtained using empirical methods.The empirical method yielded a maximum ground acceleration of 347 Gal,whereas the maximum ground velocity was approximately50 cm/s.In light of these findings,some surface expressions of crustal deformations and strong ground motions,such as failures of soil and rock slopes and rockfalls,have been presented.The rock slope failures in the epicentral area were consistent with those observed during various earthquakes in Afghanistan and worldwide.

新疆温宿县天山大峡谷景区崩塌危岩体破坏机制及运动学特征分析

新疆温宿县天山大峡谷景区峡谷两侧崩塌灾害较发育,滚石崩落至峡谷内将威胁过往车辆和游客。崩塌灾害受多种因素影响,具极大的随机性,故探究崩塌危岩体运动学特征参数的强弱对当地崩塌灾害防治至关重要。本文选取1号峡谷入口西侧典型崩塌危岩体为研究对象,在现场调查基础上分析崩塌灾害的形成机制,结合监测数据对现状危岩体稳定性进行分析,利用Rockfall软件对危岩体的崩落运动特征进行预测。结果表明:现状危岩体基本处于稳定状态,预测危岩体发生崩落后会与坡脚堆积体坡面或峡谷地表发生剧烈碰撞并产生强烈反弹,在碰撞瞬间落石的动能和速度均达到峰值,发生碰撞后因能量损耗导致动能和运动速度逐渐降低。预测发生崩塌破坏后落石最大反弹高度为2.44 m,最大平移速度15.51 m/s,最大动能1365.16 J,最大影响范围11.68 m。研究结果对该区域危岩体影响范围的确定及崩塌灾害的防治提供重要参考,对峡谷内其他崩塌危岩体研究具指导意义。

基于PFC^3D和Rockfall的中武山危岩体数值模拟研究

基于颗粒流PFC^3D理论及方法,结合无人机高精度航拍影像数据,对中武山危岩体失稳过程进行数值模拟方法研究。通过PFC^3D构建三维地质模型进行崩塌模拟,计算得出危岩体的运动路径。在模拟的运动路径中选取6个运动剖面,采用Rockfall软件进行二维运动过程计算,得出腾跃高度、冲击能量、岩块速度等计算结果。中武山危岩体模拟结果表明,PFC^3D三维运动模型结合Rockfall软件的数值模拟方法,可较好地模拟危岩体的失稳运动过程。研究方法相比以往研究具有更好的可视化特性,研究得到的相关参数可为后续灾害防治工作提供参考,进而可提出有针对性的治理措施。研究结果对防灾减灾工程具有重要的现实意义。

基于无人机与Rockfall的危岩体结构特征识别与运动规律模拟

赤水红层地区高陡边坡危岩体具有位置险峻、隐蔽性强等特点,致使危岩体的识别成为困扰工程建设的巨大难题。针对研究区危岩体调查难以开展的问题,利用无人机倾斜摄影技术,获取带有空间地理坐标的照片。运用Agisoft PhotoScan软件构建了唐家屋基边坡高清数字地表模型(DSM),利用三点不共线可确定一个平面的原理,在模型中提取结构面空间点云坐标,计算出结构面产状,并对危岩体的结构特征进行提取,确定了4处典型危岩体。基于三维模型对危岩体的体积进行了测量,通过定性分析得知,危岩体处于欠稳定状态。利用Rockfall软件对4个危岩体的崩落运动特征进行模拟,发现危岩体发生崩塌破坏后滚石会对坡脚房屋和公路造成破坏。研究结果对高陡边坡危岩体的勘察、稳定性评价及影响范围确定有重要参考价值。

基于Rockfall的危岩体危险范围预测及风险评价——以九寨沟景区悬沟危岩体为例

2017年8月8日九寨沟Ms7.0级地震诱发了数以千计的崩滑地质灾害,造成景区内道路阻塞,设施损毁,严重威胁到了来往游客及景区内住民的生命财产安全。因此对景区进行地质灾害风险性评价尤为重要。本文以景区内悬沟崩塌危岩体为研究对象,通过分析危岩威胁范围、可能造成的危害程度,承灾体的抗灾能力以及流动承灾体受损情况,建立风险评价模型,将风险评价进行量化。评价结果表明,危岩带1、危岩体1为低风险。危岩带3为中等风险;危岩带2为高风险,严重威胁到了坡脚公路及来往游客的生命财产安全,要高度重视,尽快着手防护措施设计,避免造成更大的损失。

Integrated rockfall hazard and risk assessment along highways: An example for Jiuzhaigou area after the 2017 Ms 7.0 Jiuzhaigou earthquake, China

This work addresses the integrated assessment of rockfall(including landslides) hazards and risk for S301, Z120, and Z128 highways, which are important transportation corridors to the world heritage site Jiuzhai Valley National Park in Sichuan, China. The highways are severely threatened by rockfalls or landslide events after the 2017 Ms 7.0 Jiuzhaigou earthquake. Field survey(September 14-18 th, 2017, May 15-20 th, 2018, and September 9-17 th, 2018), unmanned aerial vehicle(UAV), and satellite image identified high-relief rockfalls and road construction rockfalls or landslides along the highway. Rockfall hazard is qualitatively evaluated using block count, velocity, and flying height through a 3D rockfall simulation at local and regional scales. Rockfall risk is quantitatively assessed with rockfall event probability, propagation probability, spatial probability, and vulnerability for different block volume classes. Approximately 21.5%, 20.5%, and 5.3% of the road mileage was found to be subject to an unacceptable(UA) risk class for vehicles along S301, Z120, and Z128 highways, respectively. Approximately 20.1% and 3.3% of the road mileage belong to the UA risk class for tourists along Z120 and Z128 highways, respectively. Results highlighted that high-relief rockfall events were intensively located at K50 to K55(Guanmenzi to Ganheba) and K70 to K72(Jiudaoguai to Shangsizhai Village) road mileages along S301 highway and KZ18 to KZ22(Five Flower Lake to Arrow Bamboo Lake) road mileages, KZ30(Swan Lake to Virgin Forests), and KY10.5 kilometers in Jiuzhai Valley. Rockfalls in these locations were classified under the UA risk class and medium to very high hazard index. Road construction rockfalls were located at K67(Jiuzhai Paradise) and K75–K76 kilometers along S301 highway and KZ12 to KZ14(Rhino Lake to Nuorilang Waterfall), KZ16.5 to KZ17.5(Golden Bell Lake), KY5(Lower Seasonal Lake), and KY14(Upper Seasonal Lake) kilometers along Z120 and Z128 highway in Jiuzhai Valley. Rockfalls in these areas were within a reasonable practicable risk to UA risk class and very low to medium hazard index. Finally, defensive measures, including flexible nets, concrete walls, and artificial tunnels, could be selected appropriately on the basis of the rockfall hazard index and risk class. This study revealed the integration between qualitative rockfall hazard assessment and quantitative rockfall risk assessment, which is crucial in studying rockfall prevention and mitigation.

Investigation of rockfall-prone road cut slope near Lengpui Airport,Mizoram,India

Rockfall is one of severe natural hazards that are frequently reported in northeast region of India. It carries rock block falling from the cliff with high velocities and energies which can result in damages to vehicles, disruption to transportation, injuries and fatalities. The massive rockfall event which occurred in April 2017 on the highway NH-44 A, near Lengpui Airport, blocked the traffic for 1 d, and fortunately,no casualties were reported as the event occurred in the night. This is the only highway connecting the Aizawl city to the airport and the region is highly prone to rockfall events. Hence assessment of rockfall along this highway is necessary. In the current study, rockfall hazard assessment has been carried out on three locations by rockfall hazard rating system(RHRS). During pre-failure analysis, the result shows that most hazardous slopes have RHRS score of 639. The slopes were found to be vulnerable and later on the rockfall activity occurred. Three-dimensional(3 D) stability analysis has been carried out using 3 DEC software package to analyze the failure behavior and to decide the rockfall-prone zone(unstable blocks)for slope. The total displacement of 2.24 cm and velocity of 2,25 mm/s of the failed block have been observed in the numerical analysis. Further, the rockfall vulnerable zone(unstable blocks) is considered to determine the parameters such as run-out distance, bounce height and energies of the falling rock blocks. The maximum total kinetic energy of 5047 kJ has been observed in the numerical analysis with the maximum run-out distance up to 18 m.