Rock Slope Failures Research Articles

Interpretation, age and significance of a relict paraglacial and periglacial boulder-dominated landform assemblage in Alnesdalen, Romsdalsalpane, southern Norway

A boulder-dominated landform assemblage in an alpine setting in Norway is described, interpreted and dated using a combination of Schmidt-hammer exposure-age dating (SHD) and cosmogenic 10Be surface-exposure dating. The origin and formation of these features is determined from their morphology, topographic setting and age. Three main components of the assemblage are recognized. First a ~300 m long and ~160 m wide, tongue-shaped rock-slope failure with a SHD age of 11.49 ± 0.82–12.96 ± 0.86 ka is identified on the basis of its planform, thickness, ‘runout distance’ and association with a fractured backing scarp. This is interpreted as a relict paraglacial landform triggered by deglaciation. Second, a 400-m long unequivocal pronival (protalus) rampart with an SHD age of 6.95 ± 0.97–8.35 ± 1.21 ka is identified on the basis of its narrow ridge form aligned close to the foot of an extensive talus slope. Although formation of the rampart probably commenced with deglaciation, the younger SHD ages indicate formation at a diminishing rate through the Holocene. Third, a ~550 m by ~150 m lobate component with transverse ridges, longitudinal and transverse depressions and enclosed pits, previously identified as a rock glacier, is dated to 11.33 ± 0.83–13.33 ± 0.90 ka with the Schmidt hammer and between 13.3 ± 2.0–14.7 ± 2.0 ka with 10Be. This third component may also be a product of rock-slope failure but attribution to rock-glacier creep associated with either interstitial ice (permafrost) or buried glacier ice during the Allerød Interstadial – Younger Dryas Stadial, and to which one or more rock-slope failures contributed debris, cannot be rejected. The advantages and limitations of compiling such evidence for identifying, differentiating and classifying apparently similar boulder-dominated colluvial landforms are exemplified.

Modeling the entire progressive failure process of rock slopes using a strength-based criterion

To simulate the entire process of the progressive failure of rock slopes, a series of techniques are incorporated into the original NMM (numerical manifold method). To reflect the stress concentration near the crack tip, the Williams' displacement series is adopted to enrich the global displacement function of the NMM. Furthermore, the most recently proposed strength-based LT criterion, which can account for tensile cracks, tensile-shear cracks and compressive-shear cracks, is adopted to determine the crack propagation direction and length. Three typical numerical examples, including a Mode-I crack problem, a Mode-II crack problem and a Brazilian disc problem are adopted to verify the numerical model. The numerical results indicate that the numerical model is capable of accurately simulating the Mode-I crack propagation problem, the mode-II crack propagation problem and the failure process of Brazilian disc. Furthermore, the numerical model is adopted to investigate the entire progressive failure process of two rock slopes. The corresponding results indicate that the numerical model can not only simulate the propagation and coalescence of multiple cracks in rock masses but also the opening/sliding of rock blocks along discontinuities. The proposed numerical model warrants further investigation.

Chronology and Geomorphological Activity of the Akdag Rock Avalanche (SW Turkey)

Large rock-slope failures are among the primary geohazards in high mountain areas. These rock avalanches and rockslides constitute most of the world’s largest landslide deposits. This study focuses on the formation and geomorphological activity of the Akdag landslide complex located on the southern slope of Mount Akdag, SW Turkey. We employed detailed mapping in the field, spatial and morphometric analysis using GIS and remote sensing technologies, and surface exposure dating with cosmogenic 36Cl to reconstruct the chronology of the landslide complex. For the analysis of cosmogenic 36Cl, we collected 18 surface samples from calcareous boulders within the landslide deposit. Our field mapping shows that the Akdag rock avalanche is a large and active slope failure developed between carbonates and flysch. The rock-avalanche deposits cover an area of 9.8 km2 and together with the primary and secondary slope failures which form the landslide complex, cover an area of 15 km2. The Akdag rock avalanche is one of the largest (3×108 m3) known bedrock landslides in Turkey. Cosmogenic 36Cl exposure ages indicate that the main collapse occurred at 8.3 ± 1.4 ka (2), followed by secondary failures. We dated one of the latter to 1.1 ± 0.2 ka (2). Based on field evidence, we surmise that increased water discharge in the springs along the carbonate-flysch contact zone played a key role in the Early Holocene failure.

A 36-Year Record of Rock Avalanches in the Saint Elias Mountains of Alaska, With Implications for Future Hazards

Glacial retreat and mountain-permafrost degradation resulting from rising global temperatures have the potential to impact the frequency and magnitude of landslides in glaciated environments. Several recent events, including the 2015 Taan Fiord rock avalanche, which triggered a tsunami with one of the highest wave runups ever recorded, have called attention to the hazards posed by landslides in regions like southern Alaska. In the Saint Elias Mountains, the presence of weak sedimentary and metamorphic rocks and active uplift resulting from the collision of the Yakutat and North American tectonic plates create landslide-prone conditions. To differentiate between the typical frequency of landsliding resulting from the geologic and tectonic setting of this region, and landslide processes that may be accelerated due to changes in climate, we used Landsat imagery to create an inventory of rock avalanches in a 3700 km2 area of the Saint Elias Mountains. During the period from 1984-2019, we identified 220 rock avalanches with a mean recurrence interval of 60 days. We compared our landslide inventory with a catalog of M ≥ 4 earthquakes to identify potential coseismic events, but only found three possible earthquake-triggered rock avalanches. We observed a distinct temporal cluster of 41 rock avalanches from 2013 through 2016 that correlated with above average air temperatures (including the three warmest years on record in Alaska, 2014-2016); this cluster was similar to a temporal cluster of recent rock avalanches in nearby Glacier Bay National Park and Preserve. The majority of rock avalanches initiated from bedrock ridges in probable permafrost zones, suggesting that ice loss due to permafrost degradation, as opposed to glacial thinning, could be a dominant factor contributing to rock-slope failures in the high elevation areas of the Saint Elias Mountains. Although earthquake-triggered landslides have episodically occurred in southern Alaska, evidence from our study suggests that area-normalized rates of non-coseismic rock avalanches were greater during the period from 1964 to 2019, and that the frequency of these events will continue to increase as the climate continues to warm. These findings highlight the need for hazard assessments in Alaska that address changes in landslide patterns related to climate change.

The year after an extraordinary sedimentation event in a regulated Alpine river: The impact on benthic macroinvertebrate communities

AbstractOn August 2017, a massive rock slope failure triggered an extreme sedimentation event in a regulated Alpine river. Consequently, high sediment load affected the river for about 1 month, with sediment concentration peaking up to several hundred g/L, and overall sediment yield of 0.4–0.8 Mm3. The availability of sound pre‐event data concerning benthic macroinvertebrate assemblages gave us the opportunity to assess the impact of this unusually severe sediment disturbance through before/after comparison. Within 1 month from the event, all the monitored communities displayed low density, richness and diversity, with minimum values never recorded before, particularly at the most upstream investigated reach, and where riverbed aggradation was comparatively larger. Persisting riverbed alteration was also identified as a major determinant justifying the slow recovery observed during the year after the event. Overall, the high resilience of some taxa, suited to a baseline unnatural condition, allowed the fast recolonization of the investigated river reaches. However, the recovery of other taxa, more sensitive to sediment pressure, was slow or did not occur during the monitored year.

Rock slope monitoring using drone based multispectral and thermal images

Nowadays, remote sensing compact sensors able to be attached to Unmanned Aerial Vehicle (UAV) platform, which suitable in monitoring and mapping the slope feature at large area. Therefore, this study presents the use of remote sensing compact sensors from visible spectrum (400 nm – 700 nm), Near-Infrared spectrum (700 nm – 1300 nm) and infrared thermography spectrum (1300 nm – 15000nm), respectively in order to produce an efficient technique for monitoring the stability of rock slope. Then, the stability of rock slope is being analyse using vegetation index such as Normalized Difference Vegetation Index (NDVI), water index with emphasizing to the Normalized Difference Water Index (NDWI) for different land type features and radiometry temperature extracted using thermography image. NDVI has been used in analysing the healthiness of vegetation and the healthier vegetation tends to have a stronger root which useful in stabilizing the slope. Meanwhile, the NDWI has the ability to detect the presence of water on the rock slope surface. In addition, the higher index of NDWI indicates the presence of water where at the higher index NDWI potentially be less stable as the water seeps through the crack line of the rock surface. For thermography, by acquiring the thermal data of the rock slope surface, it allows to analyze the damage due to weathering effect. As a summary, this technique is significant to be used as initial indicator to investigate the rock slope failure based on low cost technique and quick data information.

Study on the Influence of Anchorage Angle on the Anchorage Effect of Soft-Hard Interbedded Toppling Deformed Rock Mass

The toppling deformation of a rock mass is an important form of rock slope failure that often occurs during the excavation process of anti-dip rock slopes. The toppling deformation is very important for controlling slope deformation, determining reasonable anchorage support modes and ensuring the effectiveness of support measures during construction and operation. In this paper, an indoor test was designed and an indoor test model was developed according to engineering practice and the analogy method to study the influence of the anchorage angle and find the most suitable anchoring method for a soft-hard interbedded toppling deformed rock mass. The effect of different anchorage angles on the anchorage effect of toppled deformation slopes was studied by indoor tests. The number of cracks, the number of broken fractures, the average depth of broken fractures, the number of toppling-bending slabs, and the average bending angle of the model were determined through the tests. According to the comprehensive results of the test analysis and analytic hierarchy process, an anchorage angle of 45° is optimal. The results obtained by the test analysis and the analytic hierarchy process were consistent. The test and analysis results have a guiding significance for engineering applications and help to select the best anchorage angle and anchorage mode for actual soft-hard interbedded toppling deformation slopes.

Bouldery deposits along the Kherlen fault, Central Khentey, Mongolia: implications for paleoseismology

The assumed Jargalant rockslide is located in Khentey Upland of Mongolia, an area undergoing active tectonic deformation and seismogenic activity but where geomorphic research that connects rock slope failure and long-term paleoseismic events has yet to be conducted. We present the first reconnaissance study on this topic, which demonstrates the possibility of cosmogenic 10Be dating of landslide-induced bouldery deposits to date the timing of the assumed seismic events. We performed integrated geomorphic analysis (geomorphic mapping, topographic profile analysis, and surface trenching) and 10Be surface exposure dating (boulder and bedrock scar) to document the recurrence interval of the assumed paleoseismic events by determining the recurrence of rock slope failures in Jargalant River valley. We identified four geomorphic surfaces and units identified based on their morphology, the distribution of quartzite boulders, and their ages. The geomorphic units are as follows: (1) outburst flood fan (S1), (2) remnant landslide-dam deposit (S2), (3) surviving rockslide body (S3), and landslide scar (S4). Bedrock quartzite outcrops only in the assumed headscarp, while most of the upland is composed of schist. The average 10Be age of quartzite boulders of S1 to S3 is 283.4, 138.8, and 48.4 ka, respectively, and that of the landslide scar (inner and outer edge) are 44.5 and 193.5 ka. Based on the morphology, depositional characteristics, quartzite provenance, and separated and clustered 10Be exposure age, we hypothesize that at least three catastrophic rock slope failures could occur at 283 ka, 138 ka, and 48 ka, likely being triggered by earthquakes associated with active Kherlen fault.

Stability analysis of flawed rock slope by using virtual-bond-based general particles dynamics

General particle dynamics code (GPD) with a virtual bond model is adopted to investigate the stability of rock slopes subjected to gravity. The natural discontinuities are represented by straight flaws in the numerical model. The failure process of rock samples containing three pre-existing and four pre-existing flaws subjected to uniaxial compression is simulated. The numerical failure processes of rock samples are in good agreement with the experimental observations as well as the complete stress–strain curves. Moreover, six en-echelon flaw arrays including collinear flaw array, en-echelon flaw array with bridge angle of 90°, en-echelon flaw array with bridge angle more than 90°, en-echelon flaw array with bridge angle less than 90°, multiple rows of en-echelon flaws with doubly periodic rectangular array, multiple rows of en-echelon flaws with diamond-shaped array in rock slope are studied. The crack initiation, propagation and coalescence process in rock slopes with six en-echelon flaw arrays subjected to gravity are analyzed. Two crack initiation modes including primary crack and secondary crack are found as well as nine crack coalescence modes. The stress distributions as well as displacement fields are investigated during the crack evolution. The gravity increase method is implemented into the VB-GPD to obtain the safety factor of rock slopes. The proposed method was then verified by the case study of the Xingluokeng mine in China. The results indicate a good accordance between simulation and field monitoring. This study reveals that the proposed method can tackle flawed rock slope failure problems.

Assessing the Stability of Rock Slopes with Respect to Block-Flexure Toppling Failure Using a Force-Transfer Model and Genetic Algorithm

Block-flexure toppling is the commonest type of failure in anti-dip bedding rock slopes. In this work, a new model called the force-transfer model (FTM) for this kind of failure is proposed, which is based on cantilever beams and limit equilibrium theory. A genetic algorithm (GA) was further employed to predict the safety factor and failure surface of the rock slope. A centrifuge test was also conducted to check the feasibility of using the combined FTM–GA method to model block-flexure toppling failure. The centrifugal results showed that a complex failure surface was produced in a slope undergoing block-flexure toppling. The failure surface is stepped and has a step height approximately equal to the spacing of the cross joints. Comparing these results with the theoretical ones shows that it is eminently feasible to use the FTM–GA method to analyze the stability of slopes liable to undergo block-flexure toppling failure. Moreover, the safety factor (i.e., failure load in the centrifugal test) and failure surface of the slope can be accurately determined using the new method. The newly proposed method can, therefore, be used as a theoretical tool for evaluating and designing anti-dip bedding rock slopes.

The Anomalously Old Bush Stream Rock Avalanche and Its Implications for Landslide Inventories in Dynamic Landscapes

Previous dating of rock slope failures in most glaciated mountain chains has revealed almost exclusively young, mostly Holocene ages. In this study, a rock avalanche in the glaciated Rangitata Basin in Canterbury, New Zealand is mapped, described, and dated, revealing a pre-Holocene age of failure. The geomorphology and characteristics of the rock avalanche, named here as the Bush Stream Rock Avalanche, were assessed from field mapping and photogrammetric analyses. To assess the age of the rock avalanche, in-situ cosmogenic 10Be exposure dating was applied to boulders on the deposit. The geomorphological mapping shows that the morphology of the head scarp and deposit of the rock avalanche are distinct from the surrounding landscape, much of which appears to be glacial in origin. The rock avalanche travelled about 4 km, with a volume of 50-100 M m3, and appears to have temporarily blocked Bush Stream. The dated boulders suggest an age of 15-20 ka, making it the oldest reported alpine rock avalanche in New Zealand, and one of the oldest worldwide. Deep depressions, possibly kettle holes, in the deposit are indicative of runout over a glacier (or associated dead ice), but any glacier present at the time must have been small and probably decaying. The excellent preservation was likely favoured by a small catchment located on the dry lee side of the Two Thumb Range which dampened glacial and fluvial activity. The study confirms that rock avalanches were being produced in the Southern Alps early in the deglaciation, but that evidence for them likely exists only in the rare environments that have conditions favourable for preservation. Preservation potential in most of the Southern Alps is low, with older deposits readily buried or eroded by New Zealand’s high rates of erosion, aggradation, and dynamic processes. Unless methods can be developed to identify missing older events, we are hampered in our ability to understand the frequency, and therefore causes, of large slope failures in the Southern Alps and in other highly dynamic alpine landscapes.

Borehole monitoring of thermo-hydro-mechanical rock slope processes adjacent to an actively retreating glacier

Most natural rock slope failures result from long-term strength degradation. It is often hypothesized that glacial retreat leads to enhanced progressive damage accumulation in adjacent rock slopes, due to mechanical unloading and changes to the thermal and hydraulic boundary conditions. However, direct observations of subsurface processes in a rock slope subject to glacial retreat are rare. In this paper, we present the design, implementation, and performance of a new borehole monitoring system installed on a rock slope in fractured crystalline rock located beside the glacier tongue of the retreating Great Aletsch Glacier (Valais, Switzerland). The three vertical, 50 m deep boreholes were instrumented to continuously monitor groundwater pressure, temperature and deformation at high resolution, in order to investigate thermo-hydro-mechanical coupled slope processes that drive progressive rock mass damage. We show that the system is capable of measuring both reversible and irreversible displacements along single fractures at magnitudes ranging between 0.001 mm to >2 mm in the studied rock slope, and that it is often possible to identify drivers of these deformation signals. The transient subsurface temperature field shows clear indications of former ice occupation in form of cold temperatures preserved at depth and superimposed annual temperature cycles penetrating down to a depth of about 17 m. The variability of the pressure head in the slope is driven by annual snowmelt infiltration cycles, rainfall events, and the assumed connection to englacial water of the temperate glacier. The new and continuously growing dataset presented here will enable us to relate the changing boundary conditions caused by glacial retreat and fatigue from daily to annual thermal and hydraulic loading cycles to progressive rock mass weakening, which may ultimately result in rock slope failure.

Experimental Study of Shear Behavior of Rock Joints under Two Types of Boundary Conditions: Constant Normal Load and Constant Normal Stiffness

Shear destruction of rock mass along weakened planes is one of the main reasons of the failure of career boards, underground workings and rock slopes. The paper deals with laboratory testing of rock joints under direct shear loading. Special test and measurement complex was created to study deformation and strength characteristics of rock joints. Test specimens were made from single slab of sandstone of homogeneous structure. Shear tests have been conducted under constant normal load (CNL) and constant normal stiffness (CNS) boundary conditions at three values of normal compressive stress: 0.5 MPa, 1.2 MPa and 1.8 MPa. The analysis of test results allowed to reveal patterns of changes of deformation-strength properties of rock joints depending on the level of normal load, boundary conditions and roughness values. The ultimate shear stress is always higher under CNS boundary condition than CNL for the same values of normal compressive stress. Shear stress practically retains constant value after reaching the ultimate stress under CNL boundary conditions and it decreases under CNS conditions. The values of ultimate shear stresses, shear modulus and the length of linear section on “shear stress–shear displacement” curve increases with increasing surface roughness at the equal levels of normal compressive stress.

Degradation of limestone exposed to drying and wetting cycles – experimental study

Degradation of rock is the deterioration of the rock forming materials and the reduction of strength and stiffness within time. It is responsible for the failure of rock slopes and landslides as the drying and wetting cycles in long-term will extensively reduce the strength of the rock and eventually end up as a soil-like material. Weathering rate is very crucial, and it is the main parameter inducing and accelerating degradation of rock. This study focuses on investigating and evaluating the effect of degradation on cored samples of limestone. Limestone was collected from the state of Perak, Malaysia and the samples were cored, trimmed and cut into 50 mm diameter and 80 mm height. A total number of 30 samples were exposed to different number of drying and wetting cycles in the laboratory. A total number of 27samples were tested using the Uniaxial compression test after 0 – 14 cycles while three samples were exposed to exactly 14 cycles to observe the reduction in weight. The results showed the strength of limestone to decrease gradually with the increment of drying and wetting cycles. Besides, samples that were continuously exposed to 14 drying and wetting cycles experienced a weight reduction of approximately 1.12%.

Glacial conditioning and paraglacial sediment reworking in Glen Croe (the Rest and be Thankful), western Scotland

Glen Croe, located near the western edge of the Loch Lomond and Trossachs National Park, is a well-known landslide hazard site in Scotland. Debris flows have repeatedly closed the A83 Rest and be Thankful road that passes through the valley, and considerable investment has been directed towards hazard risk reduction. However, little research has focused on the former glaciation and paraglacial response that have played an important role in governing current landscape processes at the site. This paper addresses the knowledge gap by investigating the glacial processes that have shaped and conditioned Glen Croe, and pathways that have characterised subsequent paraglacial sediment transfer. The large-scale valley form results from watershed breaching and interaction between glacier erosion and paraglacial rock slope failures. The distribution of thick glacigenic sediment is conditioned by deposition at former lateral ice margins, which was influenced by topography. Sediment reworking has resulted in accumulation of debris cones and alluvial fans in the upper part of the catchment, and growth of a delta at the outlet. Spatial connectivity mapping supports an interpretation whereby upper Glen Croe is poorly connected to the valley outlet, influencing sediment storage. In contrast, slopes in the lower part of Glen Croe are well connected. Sediment distribution in Glen Croe fits within the context of glaciated valley and paraglacial landsystems, allowing an understanding of sources and transport pathways. In upland infrastructure corridors this type of information is potentially helpful for understanding how landscapes might be affected by renewed sediment reworking under altered threshold conditions.

The Time-Dependent Failure Mechanism of Rocks and Associated Application in Slope Engineering: An Explanation Based on Numerical Investigation

In this study, a numerical model for long-term deformation and progressive failure of rock slope is presented. The model accounts for both rock heterogeneity and the initiation, activation, nucleation, and coalescence of cracks in rock slope through a stochastic local stress field and local rock degradation by using an exponential softening law. The time-dependent behaviour of rocks is taken as a macroscopic consequence of damage evolution and strength degradation in microstructure. A series of demonstrative slope cases containing preexisting joints are constructed and investigated. The slope instability occurs at a particular point in time when the rock strength is reduced to a certain value. The temporal and spatial evolution of joint linkage structures is numerically obtained, which clearly shows how the local stress field and damage evolution within the joint network contribute to the fracture pattern and the long-term instability. Then, a practical slope case in jointed and layered rock formations in Yunyang city is studied. The prevailing failure phenomena of the slope, including gradual surface scaling, sliding collapses, and block falling, are numerically reproduced, with an emphasis placed on the slope failure process and development tendency. There is a good agreement on the failure mode and instability time between the numerical simulations and the field observations.

Comprehensive Method to Test the Stability of High Bedding Rock Slop Subjected to Atomized Rain

In the construction of high dams, many high rock slope failures occur due to flood discharge atomized rain. Based on the steel frame lifting technique and strength reduction materials, a comprehensive method is proposed in this paper to study the stability of high bedding rock slope subjected to atomized rain. The safety factor expression of the comprehensive method and the evaluation method for deformation instability were established according to the similarity theory of geomechanical model, failure criterion, and mutation theory. Strength reduction materials were developed to simulate the strength reduction of structural planes caused by rainfall infiltration. A typical test was carried out on the high bedding rock slope in the Baihetan Hydropower Station. The results showed that the failure modes of the bedding rock slope were of two types: sliding–fracturing and fracturing–sliding. The first slip block at the exposed place of the structural plane was sliding–fracturing. Other succeeding slip blocks were mainly of the fracturing–sliding type due to the blocking effect of the first slip block. The failure sequence of the slip blocks along the structural planes was graded into multiple levels. The slip blocks along the upper structural planes were formed first. Concrete plugs had effective reinforcement to improve the shear resistance of the structural planes and inhibit rock dislocation. Finite element method (FEM) simulation was also performed to simulate the whole process of slope failure. The FEM simulation results agreed well with the test results. This research provides an improved understanding of the physical behavior and the failure modes of high bedding rock slopes subjected to atomized rain.

The Kandersteg rock avalanche (Switzerland): integrated analysis of a late Holocene catastrophic event

In this study, we focus on the Kandersteg rock avalanche in the central Bernese Alps in Switzerland. We achieved an improved understanding of the release and emplacement of the rock avalanche through a combination of detailed field mapping, remote image analysis, reconstruction of deposit and source area volumes, and runout modelling with DAN3D. Based on cosmogenic 36Cl dating of siliceous limestone boulders all across the landslide deposit, we determined an age of 3210 ± 220 years for the event. This age is markedly younger than the previously suggested age of 9600 years. An estimated 750–900 Mm3 of Cretaceous limestones, siliceous limestones (Oehrlikalk, Kieselkalk and Banderkalk formations) and Tertiary sandstones of the Doldenhorn nappe detached along pre-existing discontinuities from the northwest face of the Fisistock peak. The sliding body fragmented upon encountering the valley floor and the steep opposite valley wall. Next, the dry fragmented rock avalanche propagated northward over a substrate of fluvial sediments. As it moved, the debris became more fluid through entrainment of water and water-rich sediments, until it finally came to a halt 10 km downstream. The final volume of the deposit is estimated at 1.1 km3. Our multi-method approach allowed us to establish that the deposit stems from one colossal event at 3.2 ka and to reconstruct the processes that dominated each phase of the rock avalanche. Our research contributes significantly to understanding not only the Kandersteg event but also complex emplacement processes and mechanics of large rock slope failures.

Physical Modeling Test on Deformation and Failure of Rock Slope with New Support System

In order to explore the monitoring and control method of rock slope, indoor physical model testing of collapse control and monitoring were carried out with the example of a rock slope collapse area project in Jietai Temple in Beijing, China, as the prototype. Based on the similarity theory, in this study, a new structural support with Negative Poisson’s Ratio bolt and flexible anchored net was utilized to reinforce the rock slope. Following a graded loading sequence, the collapse failure characteristics and the overall control effect of energy absorption reinforcement measures were explored. The experimental results demonstrated that the entire process of slope collapse presented four distinct stages of failure: fracture generation, fracture propagation, partial collapse, and overall collapse. The full‐field displacement nephogram and the displacement monitoring point of the collapse area indicated that the large deformation and failure of the collapsed surrounding rock were effectively controlled, while the Negative Poisson’s Ratio bolt and the flexible anchored net had good reinforcement effects. The experimental stress record presented that the change of pressure curve was an apparent regularity in the entire process of slope collapse, which reflects the change state of internal force of surrounding rock; it includes the function of monitoring of slope collapse. It was indicated that the Negative Poisson’s Ratio bolt along with the large‐deformation flexible anchored net had good reinforcement monitoring effect on the rock slope collapse disaster.

The analysis of slippage failure of the HuangNanBei slope under dry-wet cycles in the three gorges reservoir region, China

The purpose of this paper is to study the sliding failure of the jointed rock slope caused by the degradation of rock mass mechanics under dry-wet cycles. Based on the mechanical parameters of reservoir limestone obtained under different numbers of dry-wet cycles, a discrete element approach was adopted to analyze the slippage failure mode of HuangNanBei slope in the Three Gorges Reservoir Region. The Barton-Bandis nonlinear strength criterion for discontinuities was used to improve the Mohr-Coulomb (M-C) sliding model, and the modified M-C sliding model could make the shear strength parameters of the discontinuities change with the stress state. Under the modified model, there was a tendency for disintegration between blocks in the process of slippage, which was more in line with the actual working conditions and proved the validity and necessity of this model. Furthermore, the slip rate increased with the increase of dry-wet cycles, and the increase trend had not slowed down after 30 dry-wet cycles. The cumulative displacement from 0 to 30 dry-wet cycles was obtained by changing the mechanical parameters of the discontinuities every 10 steps to simulate each dry-wet cycle. The pattern of the cumulative displacement curve was consistent with the slip curve of the 30th dry-wet cycle, which indicated that the degradation of the rock mass mechanics is irreversible. Consequently, strengthening the hydro-fluctuation belt is of great significance for disaster prevention and control in the reservoir region.