The 17 February 2006 rock slide-debris avalanche at Guinsaugon Philippines: a synthesis

The paper presents a synthesis of the key findings of the conference and workshop convened to consider the causes of and lessons to be learned from the disastrous rockslide-debris avalanche on 17 February 2006 in southern Leyte, Philippines. Some 1,221 people died and the barangay of Guinsagon was buried. The geology, historical seismicity, progressive disintegration of the rock mass, development of smectite layers and the continuous development and movement of shears within the Philippine Fault Zone combine in the steep rugged terrain to produce massive landslides, of which the 15 million m³ Guinsaugon event was the latest. The relevance of recent heavy rain and an almost synchronous seismic event are considered but it is concluded that the movement was the result of progressive failures and tectonic weakening while the landslide hazard was increased by the presence of rice paddy fields in the valley bottom. An anecdotal time to failure curve is presented, based on eyewitness accounts and observations of instability. Attention is drawn to the importance of both the education and training of the local people in the recognition of signs of potential movement and a reporting management system. Such simple measures could save lives and empower local communities to take some ownership of their level of landslide risk.     

The 17 February 2006 Guinsaugon rock slide-debris avalanche, Southern Leyte, Philippines: deposit characteristics and failure mechanism

The Guinsaugon rock slide-debris avalanche was the most catastrophic single landslide event in Philippine history, with 14–18 M m³ of debris instantly burying an entire village. Hummocky topography, pressure ridges and other internal structures suggest that the landslide deposit was emplaced as a debris avalanche and debris flow. Susceptibility to planar and wedge failures as well as to toppling due to rock discontinuities were demonstrated using kinematic analysis and SMR. Limit equilibrium analysis on planar failures yielded factors of safety ranging from 0.8 to 1.5. The study showed that pore pressure on discontinuities had a more significant effect on the slope stability than seismicity. For wedge failures, there is a sudden drop in the factor of safety at pore water pressures of 258–306 kPa. At the site, the pore water pressure may have been as high as 490 kPa. The possibility of such a landslide event in the future is discussed.      

Ambient noise and ERT data provide insights into the structure of co-seismic rock avalanche deposits in Sichuan (China)

Bulletin of Engineering Geology and the Environment - The post-seismic history of the 2008 Mw7.9 Wenchuan earthquake shows that marginally stable deposits of large co-seismic landslide dams can...     

西藏野生花卉

金黄脆蒴报春Primula strunosa报春花科多年生草本,海拔3300～4100米。     

Two-scale modeling of jointed rock masses

Numerical modeling of the mechanical behavior of jointed rock masses is a difficult task as the discontinuities not only require special modeling consideration, but also require different treatments depending upon the scale of problem involved. A framework is proposed here that is based upon a meshed based partition of unity method, also known as the numerical manifold method. Specifically, the discontinuities posed by joints or faults are divided into two groups. The primary discontinuity set is the one with a wider spacing and dominates the kinematics of the system. It is modeled explicitly as physical discontinuities. The secondary discontinuity set, characterized by high density and small spacing, is modeled as an equivalent continuum by incorporating joint compliance and strength characteristics. Following the presentation of the formulation, two examples are also provided at the end to highlight the ease with which the proposed approach may be used in mechanical analysis of a complex jointed rock system.     

中国西藏的人居发展

自2001年夏天，在进藏工作的三年时间里，笔者曾多次沿着雅鲁藏布江而下，翻越米拉、加查和卡若拉等诸多山口，越过了怒江、年楚河、尼阳河、狮泉河等众多河流，穿过了荒无人烟的广袤的无人区，考察了西藏历史上称为卫、藏、底和康区的40几个县，行程2万多公里，对西藏住房问题做了比较深入的调查研究。在考察的路上，不管是散落在高山峡谷的农牧民房舍，还是集中于城镇街区居民住宅，都给我留下终生难忘的印象，并向我传递着一个强烈的信息，西藏人民的居住条件和人居环境正在发生着历史性的深刻变化，西藏人民过着自由、安详和幸福的生活．     

高速远程滑坡裹气流态化动力学特性实验研究

 为定量化揭示高速远程滑坡在裹入气流作用下的动力学特性,以高速远程滑坡裹气流态化运动特性实验成果为基础,运用自行设计的水平圆环式旋转剪切流变装置,开展一系列环剪实验,获取碎屑流在不同裹入气流作用下的动态抗剪强度参数。结果表明：(1) 碎屑流运动过程中,气体的裹入,可起到明显的减阻作用;(2) 在碎屑流的整个运动过程中,随着时间的推移,碎屑流与环盖间剪切力并非一恒定值,而是呈现出忽高忽低的波动性演化特征;(3) 随着碎屑流受剪时间的增长,碎屑流与环盖间剪切力值整体呈略微增长的趋势,且剪切速率越大,该趋势越明显。     

西藏冈底斯西段松多复式岩体锆石U-Pb定年及地球化学特征

冈底斯岩浆岩带的岩石成因和动力学过程对于揭示新特提斯洋俯冲、印度-亚洲大陆碰撞和之后的高原隆升具有重要意义.通过对松多区岩体地球化学和锆石LA-ICP-MS U-Pb定年研究,结果表明:二长花岗斑岩锆石206 Pb/238 U年龄为(44.5±1.6) Ma(95％置信度,n=18,MSWD=1.5),黑云二长花岗斑岩...     

林芝尼洋河谷游客接待站,西藏,中国

米瑞公路是318国道(川藏线)在林芝县分出的一条旅游公路,这条公路沿着尼洋河谷东岸蜿蜒起伏的河岸线向南延伸,在通往雅鲁藏布江大峡谷的20km距离内,尼洋河谷独特的地貌一览无余。公路沿线的达则村被选为这条观光线路的起点,达则村的可建设用地所剩无多,因此村口的一     

Investigation and characteristic analysis of a high-position rockslide avalanche in Fangshan District,Beijing, China

Bulletin of Engineering Geology and the Environment - At 8:30 a.m., on August 11, 2018, a high-position rockslide avalanche was reported in Da’anshan village, Fangshan district, Beijing,...     

Testing and modeling of cyclically loaded rock anchors

The Norwegian Public Roads Administration(NPRA) is planning for an upgrade of the E39 highway route at the westcoast of Norway. Fixed links shall replace ferries at seven fjord crossings. Wide spans and large depths at the crossings combined with challenging subsea topography and environmental loads call for an extension of existing practice. A variety of bridge concepts are evaluated in the feasibility study. The structures will experience significant loads from deadweight, traffic and environment. Anchoring of these forces is thus one of the challenges met in the project. Large-size subsea rock anchors are considered a viable alternative. These can be used for anchoring of floating structures but also with the purpose of increasing capacity of fixed structures. This paper presents first a thorough study of factors affecting rock anchor bond capacity. Laboratory testing of rock anchors subjected to cyclic loading is thereafter presented. Finally, the paper presents a model predicting the capacity of a rock anchor segment, in terms of a ribbed bar, subjected to a cyclic load history. The research assumes a failure mode occurring in the interface between the rock anchor and the surrounding grout. The constitutive behavior of the bonding interface is investigated for anchors subjected to cyclic one-way tensile loads. The model utilizes the static bond capacity curve as a basis, defining the ultimate bond sbuand the slip s1 at τ_(bu). A limited number of input parameters are required to apply the model. The model defines the bond-slip behavior with the belonging rock anchor capacity depending on the cyclic load level(τ_(max) cy/τ_(bu)), the cyclic load ratio(R= τ_(min) cy/τ_(max) cy), and the number of load cycles(N). The constitutive model is intended to model short anchor lengths representing an incremental length of a complete rock anchor.     

Analogy between grid-based modeling of landslide and avalanche using GIS with surface flow analysis

Bulletin of Engineering Geology and the Environment - Mountainous areas with steep slopes are vulnerable to landslide and often to avalanche according to the climate condition. In the rainy season,...     

Characteristics and dynamic analysis of the February 2021 long-runout disaster chain triggered by massive rock and ice avalanche at Chamoli,Indian Himalaya

A massive rock and ice avalanche occurred on the western slope of the Ronti Gad valley in the northern part of Chamoli, Indian Himalaya, on 7 February 7, 2021. The avalanche on the high mountain slope at an elevation of 5600 m above sea level triggered a long runout disaster chain, including rock mass avalanche, debris avalanche, and flood. The disaster chain had a horizontal travel distance of larger than 17,600 m and an elevation difference of 4300 m. In this study, the disaster characteristics and dynamic process were analyzed by multitemporal satellite imagery. The results show that the massive rock and ice avalanche was caused by four large expanding discontinuity planes. The disaster chain was divided into five zones by satellite images and field observation, including source zone, transition zone, dynamic entrainment zone, flow deposition zone, and flood zone. The entrainment effect and melting water were recognized as the main causes of the long-runout distance. Based on the seismic wave records and field videos, the time progress of the disaster was analyzed and the velocity of frontal debris at different stages was calculated. The total analyzed disaster duration was 1247 s, and the frontal debris velocity colliding with the second hydropower station was approximately 23 m/s. This study also carried out the numerical simulation of the disaster by rapid mass movement simulation (RAMMS). The numerical results reproduced the dynamic process of the debris avalanche, and the mechanism of long-runout avalanche was further verified by parametric study. Furthermore, this study discussed the potential causes of disaster and flood and the roles of satellite images and seismic networks in the monitoring and early-warning.     

Analysis of test results of composite specimens modeling rock

Formulas permitting evaluation of the representative nature of familiar tests with composite specimens are derived using the asymptotic method of averaging differential equations. It is demonstrated that to obtain effective values of the compression modulus, there is no need to increase the number of elements in the model, nor have adequate knowledge of the compression modulus of the element and the compression modulus (or stiffness) of a crack. The technique employed to apply the asymptotic method of averaging - an effective means of investigating a broad class of rocks - is briefly described.In Memory of Professor S. B. UkhovTranslated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, pp. 2–7, November–December, 2004.     

Monitoring and engineering geology analysis of the Zhangmu landslide in Tibet,China

The Zhangmu landslide is a large ancient landslide located on the China–Nepal border. Many local slope failure events occurred at this site in the past, posing a direct threat to people and property. One hundred borehole logs (total drilling length of almost 5500 m) were collected to investigate the inner structure of the landslide. Electron spin resonance (ESR) dating and width measurement of annual tree rings were used to determine the reactivation time of different parts of the landslide. A bromide tracer experiment and measurements of the distribution of borehole groundwater were combined to analyze the flow field in the study area. The alluvial stratum in the study area indicates a long-term stable deposition environment. Based on the distribution of the alluvium stratum, we identified the area least prone to landslide damage. Both the surface and underground deformation characteristics were analyzed based on displacement monitoring data from 2006, 2011, and 2013. Combining the monitoring result with the lithology and precipitation, we found that landslide reactivation is closely related to precipitation, suggesting that the reactivation began in the old shear zone.     

Numerical modeling of discontinuous rock slopes utilizing the 3DDGM (three-dimensional discontinuity geometrical modeling) method

The geometry of discontinuities in a rock mass is one of the most important influences on the behavior and characteristics of that rock mass. The geometry of discontinuities largely determines the stability of the rock mass, as well as appropriate methods for reinforcing and stabilizing that mass. This study introduces the 3DDGM (three-dimensional discontinuity geometrical modeling) method, which is based on the 3DGM (three-dimensional geometrical modeling) algorithm that was developed using the Mathematica software package. The 3DDGM method provides essential input data for the stability analysis of a discontinuous rock mass using block stability assessment techniques or block modeling codes. The 3DDGM method developed in the present work was designed to model discontinuities in rock masses and to provide accurate values for discontinuity parameters (i.e., location, spacing, separation, system, orientation, etc.). This algorithm was developed to increase the accuracy of the discontinuity model based on the Heliot algorithm. The 3DDGM algorithm was tested by applying it to a real case, the sloping discontinuous rock mass at the phase 7 gas flare site in the South Pars Gas Complex in Assalouyeh, Iran, and the algorithm was successful in providing a three-dimensional model of the discontinuities in the rock mass at the site.     

Simulating dynamic processes and hypermobility mechanisms of the Wenjiagou rock avalanche triggered by the 2008 Wenchuan earthquake using discrete element modelling

The discrete element method is well suited for simulating the cracks and subsequent large displacements of catastrophic landslides or rock avalanches, and is therefore a useful tool for analysing their complicated dynamic processes and hypermobility mechanisms. In this study, particle flow code was used to investigate the dynamic processes and hypermobility mechanisms of the Wenjiagou rock avalanche triggered by the 2008 Wenchuan earthquake. Characterization of the avalanche dynamics was achieved using a model comprising four stages: failure rupture, projectile motion, granular debris flow, and debris mass accumulation. The results show that collision on the valley floor was the main factor causing the fragmentation of the Wenjiagou rock avalanche. The upper and front edge of the landslide body were the most likely to move over a long distance. The results also show that friction was the main source of energy dissipation during the entirety of the avalanche movement. The high gravitational potential energy of the avalanche was the basis of the high mobility. In addition, because of their effects on energy dissipation, the low basal friction coefficient, favourable block movement, and topographical conditions played key roles in the rapid, long-runout Wenjiagou avalanche process.     

Numerical modeling of coupled thermo-mechanical response of a rock pillar

Understanding the rock mass response to excavation and thermal loading and improving the capability of the numerical models for simulating the progressive failure process of brittle rocks are important for safety assessment and optimization design of nuclear waste repositories.The international cooperative DECOVALEX-2011 project provides a platform for development,validation and comparison of numerical models,in which the sp pillar stability experiment（APSE） was selected as the modeling target for Task B.This paper presents the modeling results of Wuhan University（WHU） team for stages 1 and 2 of Task B by using a coupled thermo-mechanical model within the framework of continuum mechanics.The rock mass response to excavation is modeled with linear elastic,elastoplastic and brittle-plastic models,while the response to heating is modeled with a coupled thermo-elastic model.The capabilities and limitations of the model for representation of the thermo-mechanical responses of the rock pillar are discussed by comparing the modeling results with experimental observations.The results may provide a helpful reference for the stability and safety assessment of the hard granite host rock in China＇s Beishan preselected area for high-level radioactive waste disposal.