Displacement Of Slope Surface Research Articles

Investigations of the Effect of Artificial Rainfall on the Pore Water Pressure and Slope Surface Displacement of Loess Slopes

Investigations of the Effect of Artificial Rainfall on the Pore Water Pressure and Slope Surface Displacement of Loess Slopes

Bedrock Fractures Control Groundwater‐Driven Mountain Slope Deformations

AbstractSeasonal deformation of mountain rock slopes can be driven by groundwater infiltration and depletion. Such processes could explain our field observation in the Aletsch Valley, Switzerland, where GNSS‐derived 3D annual displacement amplitudes reach 3.4 cm. However, the physical mechanisms behind such groundwater‐driven surface displacements are not well understood. Here, we develop a fully coupled hydromechanical model to simulate the relevant processes in a valley slope embedded with numerous fractures of variable sizes. The magnitude and orientation of transient annual slope surface displacement obtained from our model are in overall agreement with the field observations. The key geological factors controlling the type and magnitude of reversible mountain slope deformations are fracture network geometry, fracture aperture, and regional stress field. We show that the heterogeneity and anisotropy of bedrock hydromechanical responses, originating from depth‐dependent variations of fracture properties, play a critical role in groundwater recharge and valley slope deformation. During recharge events, pore pressure perturbations migrate downward from the groundwater table and toward the receiving stream and the deep subsurface. This process driven by pressure diffusion and poroelastic stressing develops in the subsurface with a great reach of up to a few kilometers, called critical hydromechanical response zone, and controls surface deformation patterns. During groundwater recession, this hydromechanical response zone expands downward and ground surface displacement vectors rotate upwards. Our results suggest that slope surface deformation can inform about subsurface permeability structures and pore pressure fluctuations, which have important implications for understanding groundwater flow in fractured bedrock slopes.

Slope monitoring optimization considering three-dimensional deformation and failure characteristics using the strength reduction method: A case study

The potential deformation and failure of a slope with typical 3D shapes involve 3D characteristics, such that these factors cannot be simulated using 2D methods. If 3D characteristics are not considered in expressway slope monitoring, an excessive number of monitoring points may be arranged in the stable/safe part, whereas insufficient monitoring points may be arranged in the unstable/dangerous part. In this study, the 3D deformation and failure characteristics of the Lijiazhai slope of the Shicheng–Ji'an Expressway in Jiangxi Province, China were analyzed by 3D numerical simulations using the strength reduction method. The potential 3D slope surface displacement trends, initial position of failure, and maximum depth of potential slip surface were simulated and discussed. The deformation of Slope A was generally small. The slope ranging from the third platform to the slope top was located in Region I, where the deformation was approximately equal to zero. The deformation of Slope B was located in Region V, where the displacement generally was larger than 2 cm in the range from the first–third platforms to the slope top, and the deformation of the trailing edge exceeded 5 cm. The surface displacement monitoring points should be arranged in Region V. Monitoring was then optimized considering the 3D characteristics of the deformation and failure of a slope. Accordingly, surface and deep displacement monitoring networks were effectively arranged in the unstable/dangerous part of the slope. Results may be used as references for similar projects.

Experimental Study on the Deformation and Mechanical Properties of Bamboo Forest Slopes

In this paper, model tests on a plain soil slope and a bamboo-rooted slope under slope top loading were carried out to analyze the slope surface displacement, the change in earth pressure, and the failure mode of the slope. Furthermore, the influence of rainfall on the deformation and mechanical properties of bamboo-rooted slope sliding was studied. The results show that: (1) the failure mode of the plain soil slope was block sliding failure, while the failure mode of the bamboo-rooted slope was progressive backward failure. (2) Under the slope top load, the slope displacement shows the rule that the top of the slope was large and the foot of the slope was small. The presence of bamboo rhizomes had a negligible effect on the slope displacement, but it significantly contributed to the sliding area’s increase. (3) Compared with the plain soil slope, the earth pressure in the area of the foot of the slope under the same level of the load was elevated more obviously by the bamboo-rooted slope, which indicates that bamboo rhizomes could play a specific role in reinforcing the slope. Still, the scope of its influence was limited and mainly concentrated in the shallow soil. (4) There was a significant increase in the displacement of the bamboo-rooted slope under rainfall conditions, and the magnitude of the upward slope earth pressure was small in the process of step-by-step loading. The test results may have important guiding significance for the in-depth study of the instability law and disaster prevention in bamboo forest areas.

Influence of Root Volume, Plant Spacing, and Planting Pattern of Tap-like Tree Root System on Slope Protection Effect

Vegetation slope protection has been widely utilized as an eco-friendly approach for slope stability. Up to now, research on the slope protection effect of shrubs and herbaceous vegetation is more than those of trees, which can be attributed to the challenge of evaluating the slope protection effect of tree root systems that can be influenced by many factors, such as root morphology, root volume, plant spacing, and planting patterns. Therefore, this study takes tap-like tree root systems as the research object, constructs the corresponding root-soil composite model by using 3D printing technology, and carries out a series of physical model experiments on slopes supported by tap-like tree root systems, examining the anti-sliding force, slope surface displacement, sliding range, and slope cracks throughout the entire process of deformation and the damage to shallow slopes, to finally evaluate the effectiveness in the slope protection effect of tree root systems from multiple perspectives. The results indicate that: (1) the peak anti-sliding force of the slope supported by tree root systems correlates positively with the root volume and negatively with plant spacing generally, and the influence of tree plant spacing on the peak anti-sliding force is weaker than that of the root volume; (2) the displacement of slopes supported by tree root systems in the square planting pattern is generally less than that in the staggered planting pattern, and the displacement of slopes has a negative correlation with the root volume and a positive correlation with the plant spacing; (3) the sliding range of the slope supported by tree root systems is significantly reduced compared with that of the unsupported slope, and the tree root system can prevent the occurrence of slope surface cracks to a certain extent, which makes the sliding-body show better integrity. The above understanding enriches the study on the slope protection effect of the tree root system, reveals the influence of the tree root volume, plant spacing, and planting pattern (square distribution and staggered distribution) of the tap-like tree root system, and offers some guidance for the engineering application of tree slope protection in practice.

Multifactor Analysis of Landslide Mechanisms: A Case Study of Yongji Expressway, China

Based on deformation monitoring and stability results obtained from geological mapping, geological drilling, macrolaboratory, and microlaboratory tests, the sliding mechanism of landslide in Guzhang County of Yongji expressway was studied. The bedding slope landslide results from cutting slope along the central white mud clay slip, and by on-site investigation and deep displacement monitoring, the clay is determined as the landslide surface. Combining the experimental results and similar geotechnical engineering experience, by back-calculation, the parameters of the soft interlayer are calculated as C (5 kPa) and ϕ (8.5°). Based on X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF) test, the results are concluded that the chlorite in clay interlayer is easily water softened, excavation slope after long-term heavy rainfall chlorite clay interlayer softening. Sustained rainfall and underground water levels showed a positive correlation when the slope is sliding, and the heavy rainfall continued to accelerate slope sliding. Furthermore, the slope surface displacement and profound displacement increase quickly, and rainfall and slope displacement also showed a positive correlation.

Displacement Measurements and Numerical Analysis of Long-Term Rock Slope Deformation at Higashi-Shikagoe Limestone Quarry, Japan

The Higashi-Shikagoe limestone quarry is an open-pit mine situated in Hokkaido Prefecture, Japan, that has experienced four slope failure incidents since 1996. The rock slope behaviour has been monitored since the first failure event by measuring the rock slope surface displacement using an automated polar system. Recent measurements have revealed a gradual decrease of the distance between the beam generator and mirrors over time; however, the displacements and decrease rate differs between the centre and left- and right-hand sides of the quarry. This implies that the deformation characteristics of the rock slope and factors influencing the slope deformation differ at the centre and left- and right-hand sides of the quarry. In this study, the two-dimensional finite element method was used to identify the causes of slope deformation by investigating the effects of limestone excavation at the foot of the rock slope, the deterioration of a ∼70 m-thick clay layer at the rock slope foot wall, and shear failure owing to rainfall infiltration. The numerical results show that slope deformation on the left-hand side and centre of the quarry are induced by clay deterioration, whereas the right-hand side of the quarry is deformed owing to floor excavation and/or shear sliding. The rock slope is presently stable because the magnitude of the rate of displacement decrease is small and no acceleration is observed.

Slope surface displacement monitoring based on a photogrammetric system

The convenience and effectiveness of monitoring methods is of great significance for slope stability evaluation. In this study, a new noncontact monitoring method based on a photogrammetric system is developed for measuring the slope surface displacement. This method monitors the slope surface displacement by using a camera and measuring plate, and a new marker design method is proposed for improving the measurement accuracy. According to the relationship between the change of the marker pixel number in the image and the relative displacement, three-dimensional displacement measurement is performed. Theoretical analysis and experimental results show that the proposed method has attractive features, such as a high precision, a low cost, simple equipment, and an easy setup.

Toppling deformation characteristics and mechanism of bank slope in Xiluodu Hydropower Station, China

Xiluodu Hydropower Station of the Jinsha River started impounding water in May 2013. In June 2013, five cracks occurred on the bank slope of the Xingguang village. By the end of 2019, the number of slope cracks has increased to 13. Based on the detailed field investigation, deformation monitoring, and drilling and adit investigation, the deformation characteristics of the Xingguang bank slope are studied. The results indicate that the Xingguang bank slope is a steep bedding toppling deformation, which is further intensified by the impoundment operation of the reservoir. Monitoring data show that the Xingguang bank slope does not deform toward the free direction, but inclines upstream, and the deformation gradually increases from the top to bottom. According to the change degree of slope surface displacement, the Xingguang bank slope can be divided into four deformation areas in the plane: intensified strong deformation area, strong deformation area, moderate deformation area, and slight deformation area. Based on the deformation degree of the rock mass, the vertical section is divided into four deformation zones: intensified strong toppling deformation zone, strong toppling deformation zone, moderate toppling deformation zone, and slight toppling deformation zone. Further study reveals that the thin-layer rock mass structure is the material basis of the bank slope toppling deformation, the landform formed by the cutting of the Jinsha River Valley provides favorable boundary conditions for the toppling deformation, and the strong unloading rebound of the rock mass is the key factor of the bank slope toppling deformation.

Research of Toppling Criterion and Analysis of Instability Evolution of Toppling Deformation Slope

Toppling failure is one of the main types of rock slope instability. Based on the Goodman-Bray toppling stability analysis model, the starting mechanism and criteria for toppling deformation are deduced. Combined with the discrete element numerical simulation method, the evolution failure mode of the toppling slope is studied, which can better reflect the basic regularity of the toppling failure, and provide support for slope engineering. In order to predict the influence of the foot displacement of the leading edge on the slope surface displacement, several monitoring points are set at the boundary of the slope and the bend of the toppling body. It is of great engineering significance and practical value to make safety early warning in time.

Field monitoring on deformation of high rock slope during highway construction: A case study in Wenzhou, China

In order to study the deformation stability of rock slope during the excavation of cutting slope and ensure the safety of rock slope during construction and operation period, this article analyzed the deformation law of a typical slope excavation by monitoring the surface deformation and the internal displacement of the rock mass. The surface deformation of the slope is monitored by setting monitoring points, and the internal deformation of the slope is monitored by installing multipoint displacement meters and inclinometers. Therefore, the relationship between slope excavation and deformation is obtained. The analysis of monitoring results shows that the slope is stable before excavation, and the displacement of the slope is gradually increased with the slope excavation. After the excavation, the displacement of each slope tends to converge. The maximum displacement in surface monitoring points is 12.30 mm, and the displacement parallels to the direction of the expressway. The maximum vertical displacement in surface monitoring points is 10.60 mm which occurred in the third step; the maximum internal displacement is 11.02 mm which mainly occurs in the weak structural plane of the rock boundary. During the excavation of the weak rock slope, the slope rock mass is prone to large displacement deformation. After the excavation, the slope surface displacement and internal displacement tend to converge in a short time.

Dynamic response and dynamic failure mode of the slope subjected to earthquake and rainfall

Rainfall and earthquakes are two of the major factors that provoke landslides. To investigate the seismic response and dynamic failure mode of the slope with tilted highly weathered layer subjected to earthquake and rainfall, two slope models with different moisture content were constructed and tested by using a large 1-g shaking table. It was observed that the acceleration amplification coefficient (AAC) in bedrock increases with increasing earthquake amplitude when the El Centro and Wenchuan acceleration amplitude are not larger than 0.33 g in two models, and the AAC in highly weathered layer decreases with increasing elevation and with increasing earthquake amplitude. The water content of the highly weathered layer can affect the dynamic response of the model. The acceleration response of model with general moisture content is weaker than that with saturated moisture content, which is the same as the displacement of slope surface. The marginal spectrum identification of dynamic damage process shows that the seismic damage occurs in the intercalated layer of the middle part slope firstly, and then it occurs in the intercalated layer of the lower part slope and in the covering layer, and finally, it occurs in the intercalated layer of upper part slope. Based on the marginal spectrum identification of dynamic damage process, the strain response, the displacement response, and the phenomenon of dynamic damage, the failure mode of the slope with tilted highly weathered layer can be concluded as the cracking–shearing–slippage and cracking–shearing–crushing.

A relationship between displacement and tilting angle of the slope surface in shallow landslides

Tilt sensors with low cost and simple installation were developed for slope monitoring, but there is limited evidence to testify that the tilting angle of slope surface can be considered as an important indication of landslides, similar as the displacement of slope surface. In this study, the relationship between displacement and tilting angle of the slope surface in shallow landslides was investigated by the laboratory tests under different testing condition and field tests in which the slope failure was induced by applying artificial rainfall. A linear relationship between the displacement and tilting angle of slope surface was detected, and the equation for this linear relationship was also proposed in this study. Furthermore, the results also indicated that the linear relationship between the displacement and tilting angle of slope surface is independent of triggering factors of slope failure, materials of slopes, as well as the slopes sizes.

The effect of bermuda grass root morphology on the displacement of slope

During recent years, with the drastic development of highway, lots of slopes are produced which cause the increase of geological disasters including soil erosion on the slope and shallow sliding surface, it makes significant impact on the ecological environment. Adopting ecological protection technique of plant slope protection not only can prevent geological disasters, but also benefit the protection of ecological environment. In the paper, bermuda grass, as one kind of ordinary slope protection plants, was chosen as specimen, and the root-soil composite was regarded as organic system which consists of soil and root system; the effect of root morphology on displacement of slope surface under the function of rain erosion and slope runoff erosion was studied and analyzed by using nonlinearity finite calculation method. The result indicates Bermuda grass root system can defense the rain erosion of slope surface soil, restrain the soil displacement and prevent water and soil erosion of slope.

FULL-SCALE MODEL TEST FOR PREDICTING COLLAPSE USING INVERSE OF VELOCITY OF SLOPE SURFACE DURING EXCAVATION

Predicting the onset of slope failure or rock falls is important for occupational safety because they kill approximately ten to 20 workers every year in Japan. Approximately half of such victims are from slope failure during slope excavation and construction. In order to predict the time of slope failure during an excavation, a full-scale model slope was built, and the displacement of the slope surface was monitored during slope excavation. The surface displacement rapidly increased with the elapsed time after the excavation, and the relationship between the displacement and elapsed time included an exponential function just before collapse. Based on the results, by computing the inverse of the velocity of the slope surface displacement obtained in ten-second intervals, a warning signal can be provided five min before collapse.

Dynamic Response Differences Between Bedding and Counter-Tilt Rock Slopes with Intercalated Weak Layers

Bedding and counter-tilt rock slope with intercalated weak layers are common geological bodies in west China, the dynamic response research will guide the anti-seismic reinforcement of bedding and counter-tilt rock slope with intercalated weak layer effectively. Two test models of bedding rock slope with intercalated weak layer and counter-tilt rock slope with intercalated weak layer, which are in the same size, have been designed and developed. A large scale shaking table test has been performed to analyze the dynamic response difference of bedding and counter-tilt rock slope with intercalated weak layer. The study results show that the acceleration amplification coefficient inside the bedding slope is smaller than that inside the counter-tilt rock slope; at the middle and upper parts of the slope body (relative height > 0.4), the acceleration amplification coefficient at bedding rock slope surface is larger than that of counter-tilt rock slope. At the lower part of the slope (relative height le 0.4), the acceleration amplification coefficient at bedding rock slope surface is close to that of counter-tilt rock slope. The slope surface displacement of both bedding and counter-tilt rock slopes increases with increasing input seismic wave amplitude. The slope surface displacement of the bedding rock is larger than that of counter-tilt rock slope. The seismic stability of counter-tilt rock slope is stronger than bedding rock slope. The dynamic failure form of bedding rock slope mainly includes vertical tension crack at back edge, bedding sliding along intercalated weak layer and rock collapse at slope crest; whereas the dynamic failure form of counter-tilt slope mainly includes intersection of horizontal and vertical cracks on slope surface, extrusion of intercalated weak layer and shattering of slope crest.

Interaction between tunnel and unstable slope – Influence of time-dependent behavior of a tunnel excavation in a deep-seated gravitational slope deformation

A back analysis of old tunnels in an unstable slope context leads to consider several situations of tunnel entering a slope: cross-cutting tunnel to the slope, oblique tunnel to the slope, or shallow tunnel parallel to the slope. Identified pathologies of structures vary depending on these situations. In the context of a shallow tunnel, the tunnel excavation leads to a slope destabilization due to a more or less important deconfinement of the surrounding massif. Construction techniques influence, on one hand, slope surface displacement acceleration, on the other hand, structural damages in the tunnel lining. Nevertheless, the interaction between tunnel and unstable slope depends on the distance between the slope surface and the tunnel lining plot according to the tunnel diameter (D) and on the geological, geomorphological, hydrological and seismic contexts of the slope. This research focuses on different mechanisms of slope instability in a glacial unloading context, especially in creeping contexts, and on damages affecting the structure of tunnels parallel to the slope. Through numerical simulations, the influence of the construction techniques was studied; so was the choice of the tunnel situation, more or less away from the slope surface. Mainly the delay time before tunnel structure implementation) on the damage lining processes, the interaction between tunnel and slope surface displacements and their time evolution have been taken into account for the most critical tunnel situation in the slope. The different situations of tunnel in the slope permit to set in evidence the safety distance from the slope in the context of a slow glacial unloading mechanism.

Numerical Analysis of Geocell Protective Slope Stability

Geocell protective slope is a kind of important ecological protection form, which is widely used in the geotechnical engineering field. Based on the finite element software ABAQUS, and combining with protective slope body’s mechanics performance in shallow soil, the finite element model of geocell slope protection is established under the conditions of rainfall seepage, and then we simulate the shallow and the overall stability of slope in rainfall seepage cases. The results show that the safety factor of slope body increased by about 14% when using geocell slope protection and it reduces the displacement of slope surface effectively, it prolongs the destruction time of the slope under the condition of continuous reduction of soil shear strength, and it further helps reducing the collapse or part of slope sliding of slope disasters.

Numerical Analysis of Geocell Protective Slope Stability

Geocell protective slope is a kind of important ecological protection form, which is widely used in the geotechnical engineering field. Based on the finite element software ABAQUS, and combining with protective slope bodys mechanics performance in shallow soil, the finite element model of geocell slope protection is established under the conditions of rainfall seepage, and then we simulate the shallow and the overall stability of slope in rainfall seepage cases. The results show that the safety factor of slope body increased by about 14% when using geocell slope protection and it reduces the displacement of slope surface effectively, it prolongs the destruction time of the slope under the condition of continuous reduction of soil shear strength, and it further helps reducing the collapse or part of slope sliding of slope disasters.

Deep-seated failure propagation in a fractured rock slope over 10,000 years: The La Clapière slope, the south-eastern French Alps

The “La Clapière” area (Tinée valley, Alpes Maritimes, France) is a typical large, complex, unstable rock slope affected by Deep Seated Gravitational Slope Deformations (DGSD) with tension cracks, scarps, and a 60 × 10 6 m 3 rock slide at the slope foot that is currently active. The slope surface displacements since 10 ka were estimated from 10Be ages of slope gravitational features and from morpho-structural analyses. It appears that tensile cracks with a strike perpendicular to the main orientation of the slope were first triggered by the gravitational reactivation of pre-existing tectonic faults in the slope. A progressive shearing of the cracks then occurred until the failure of a large rock mass at the foot of the slope. By comparing apertures, variations and changes in direction between cracks of different ages, three phases of slope surface displacement were identified: 1) an initial slow slope deformation, spreading from the foot to the top, characterized by an average displacement rate of 4 mm yr − 1 , from 10–5.6 ka BP; 2) an increase in the average displacement rate from 13 to 30 mm yr − 1 from the foot to the middle of the slope, until 3.6 ka BP; and 3) development of a large failure at the foot of the slope with fast displacement rates exceeding 80 mm yr − 1 for the last 50 years. The main finding of this study is that such a large fractured slope destabilization had a very slow displacement rate for thousands of years but was followed by a recent acceleration. The results obtained agree with several previous studies, indicating that in-situ monitoring of creep of a fractured rock slope may be useful for predicting the time and place of a rapid failure.