Soft Rock Slope Research Articles

Nonlinear Analysis Method for Evaluating the Seismic Stability of Rock Slopes Considering Progressive Failure

This study investigated the applicability of a nonlinear analysis method that considers progressive failure to evaluating the stability of rock slopes, including post-earthquake residual displacement. The vibration step of the nonlinear analysis, which begins after residual displacement occurs, was found to match that of a dynamic centrifugal model test. The nonlinear analysis was concluded to be relatively conservative because it calculated a slightly larger residual displacement than that observed during the model test. A real-scale soft rock slope was analyzed, and the results showed that the proposed analysis method is useful for evaluating slope seismic stability, including post-earthquake residual displacements.

Risks during excavation work on soft rock slope

Risks during excavation work on soft rock slope

Laboratory and Centrifuge Model Tests on Influence of Swelling Rock with Drying‐Wetting Cycles on Stability of Canal Slope

This study focused on the swelling behavior of swelling rock from canal basement under multiple drying‐wetting (D‐W) cycles. A series of laboratory tests were conducted on a swelling rock, with the cracking and strength behaviors investigated. By using image‐processing technique, the crack patterns were described, and then quantitatively analyzed on the basis of the fractal dimension. The experimental data indicated that swelling ability, including cracking level, fractal dimension, and strength, decrease with increasing drying and wetting cycle. On this basis, a series of centrifuge model simulations for simulating slope failure by drying‐wetting cycles were performed, where the drying process was achieved by heat bulbs. The monitoring results suggested that a global slope failure has occurred after total cycle of 4th corresponding to 4 years. Due to the development of surface cracking, the infiltration in the slope was severe and nonuniform in space and time. Meanwhile, the failure mechanism of soft rock slope induced by D‐W was discussed.

Effects of Freezing and Thawing Cycle on Mechanical Properties and Stability of Soft Rock Slope

To explore the variation laws of mechanical parameters of soft rock and the formed slope stability, an experiment was carried out with collected soft rock material specimens and freezing and thawing cycle was designed. Meanwhile, a computational simulation analysis of the freezing-thawing slope stability was implemented. Key factors that influence the strength of frozen rock specimens were analyzed. Results showed that moisture content and the number of freezing-thawing cycles influenced mechanical parameters of soft rock significantly. With the increase of moisture content, cohesion of frozen soft rock specimens presents a quadratic function decrease and the internal friction angle shows a negative exponential decrease. The stability coefficient of soft rock material slope in seasonal freeze soil area declines continuously. With the increase of freezing and thawing cycle, both cohesion and internal friction angle of soft rock decrease exponentially. The higher the moisture content, the quicker the reduction. Such stability coefficient presents a negative exponential reduction. After three freezing and thawing cycles, the slope stability coefficient only changes slightly. Findings were finally verified by the filed database.

Stability analysis of the sliding process of the west slope in Buzhaoba Open-Pit Mine

To study the stability of the west slope in Buzhaoba Open-Pit Mine and determine the aging stability coefficient during slide mass development, the deformation band of the west slope and the slide mass structure of the 34,600 profile are obtained on the basis of hydrology, geology, and monitoring data. The residual thrust method is utilized to calculate the stability coefficients, which are 1.225 and 1.00 under sound and transfixion conditions, respectively. According to the rock damage and fragmentation and the principle of mechanical parameter degradation, the mechanical models of the slide mass development of the hard and soft rock slopes are established. An integrated model for calculating the slope stability coefficient is built considering water, vibration, and other external factors that pertain to the structural plane damage mechanism and the generating mechanism of the sliding mass. The change curve of the stability coefficient in the slide mass development is obtained from the relevant analyses, and afterwards, the stability control measures are proposed. The analysis results indicate that in the cracking stage of the hard rock, the slope stability coefficient decreases linearly with the increase in the length Lb of the hard rock crack zone. The linear slope is positively correlated to rock cohesion c. In the transfixion stage of the soft rock, the decrease speed of the stability coefficient is positively correlated to the residual strength of the soft rock. When the slope is stable, the stability coefficient is in a quadratic-linear relationship with the decreased height Δh of the side slope and in a linear relationship with anchoring force P.

Soft rock slope weathering due to rainwater.

Soft rock slope weathering due to rainwater.

Effect of lithology and structure on seismic response of steep slope in a shaking table test

Studies on landslides by the 2008 Wenchuan earthquake showed that topography was of great importance in amplifying the seismic shaking, and among other factors, lithology and slope structure controlled the spatial occurrence of slope failures. The present study carried out experiments on four rock slopes with steep angle of 60° by means of a shaking table. The recorded Wenchuan earthquake waves were scaled to excite the model slopes. Measurements from accelerometers installed on free surface of the model slope were analyzed, with much effort on timedomain acceleration responses to horizontal components of seismic shaking. It was found that the amplification factor of peak horizontal acceleration, RPHA, was increasing with elevation of each model slope, though the upper and lower halves of the slope exhibited different increasing patterns. As excitation intensity was increased, the drastic deterioration of the inner structure of each slope caused the sudden increase of RPHA in the upper slope part. In addition, the model simulating the soft rock slope produced the larger RPHA than the model simulating the hard rock slope by a maximum factor of 2.6. The layered model slope also produced the larger RPHA than the homogeneous model slope by a maximum factor of 2.7. The upper half of a slope was influenced more seriously by the effect of lithology, while the lower half was influenced more seriously by the effect of slope structure.

Numerical Simulation Study on High Dip Bedded Soft Rock Slope Stability of Surface Mine

According to the actual progress of a certain Surface Mine and based on strength reduction method, the deformation and fracture processes of the high dip bedded soft rock slope was simulated with RFPA-SRM, the stability of the slope was calculated. By analyzing the numerical simulation results, the characters of the deformation of high dip bedded soft rock slope and the landslide mode were demonstrated, which could provide a scientific basis for reasonable landslide control measures.

Approximate Theoretical Analysis on Excavation Disturbed Zone of a Soft Rock Slope in Suining-Ziyang Expressway Engineering in Southwestern China

A cutting slope model can be simplified as plane strain one, the stress field of cutting slope can be analyzed with elastic wedge body theory. By using strength criterion of slope material (Mohr-Coulomb strength criterion with safety reserve and uniaxial tensile strength criterion), the disturbed zone caused by excavation can be calculated in 3D stress state, so all the disturbed zone after each step of excavation from the top down can be searched out. The main analysis steps for judging disturbed zone are described in the paper, including the methods to calculate the stress state of cutting slope, the unloading value and the scope of disturbed zone after last step of excavation. Finally, an example in Suining-Ziyang expressway engineering is chosen to explain detailedly the analytical process with elastic wedge body theory to determine the disturbed zone.

Study of the Influence Factors of Soft Rock Slope Stability based on the Statistical Analysis

The stability of the slope influenced by numerous factors, of which many are difficult to determine, and difficult to estimate, and they are not only random but also fuzzy. Based on the structure characteristics of soft rock slope breaking the instability, the paper makes the statistic analysis of the influence factors of soft rock slope stability, obtained the three influence factors of rebound strength, side slope grade, slope SMR value, and on the basis of the obtained impact factors, this paper also puts forward some reasonable suggestions on test and theoretical research of strengthening soft rock environment effect and time effect, constantly improve the soft rock slope stability analysis method, and strengthen the mixed study of soft rock slope stability with other disciplines.

Analysis of an anti-dip landslide triggered by the 2008 Wenchuan earthquake in China

The Guantan landslide, with a total displaced mass of about 468 × 104 m3, was triggered by the 2008 Wenchuan earthquake and succeeding rainfall in Jushui Town, Sichuan Province, China. The landslide occurred on an anti-dip hard rock slope with a weak rock founding stratum of 200 m in thickness. To investigate the failure mechanism of the Guantan landslide, dynamic behaviors of hard and soft rock slopes were investigated by means of large scale shaking table tests. The laboratory models attempted to simulate the field geological conditions of the Guantan landslide. Sinusoidal waves and actual seismic waves measured from the Wenchuan Earthquake were applied on the slope models under 37 loading configurations. The experimental results indicated that deformation mainly developed at a shallow depth in the upper part of the hard rock slope and in the upper (near the crest) and lower (near the toe) parts of the soft rock slope. An equation for predicting the depth of sliding plane was proposed based on the location of the maximum horizontal acceleration. Finally, it was concluded that the failure process of the Guantan landslide occurred in three stages: (1) toppling failure caused by compression of the underlying soft rock strata, (2) formation of crushed hard rock and sliding surface in soft rock as the result of seismic shocks, particularly in the horizontal direction, and (3) aftershock rainfall accelerates the process of mass movement along the sliding plane.

Research on Deformation Stability of Soft Rock Slope under Excavation Based on FLAC3D

In order to study deformation and stability of soft rock slope in excavation process, the deformation, plastic area distribution, and the change of safety factor of example slope based on FLAC3D software were studied in this paper. Results show that: (1) the vertical and horizontal displacement of slope gradually increase with excavation; (2) in the process of slope excavation, tension plastic zone occurs in slope surface, and shear plastic zone with connected properties gradually forms internally; (3) based on the strength reduction method and limit equilibrium method calculation, the safety factor of slope gradually reduces with excavation, and adopting the construction form of excavation with supporting meantime is very necessary.

Numerical Analyses on Progressive Failure of Slope Due to Heavy Rain with 2D and 3D FEM

ABSTRACT In the paper, based on a modified elastoplastic model with Matsuoka-Nakai failure criterion, two-dimensional (2D) and three-dimensional (3D) soil-water coupled finite element analyses are conducted to investigate a large-scale failure in a soft-rock slope due to heavy rain. Since the failure of the slope was a typical three-dimensional event, it is necessary to estimate the accuracy of 2D analysis that can be easily and commonly used in geotechnical engineering. The characteristics of slope failure, such as the development of shear strain, the deformation of ground, the propagation of shear band and the progressive failure are discussed in detail with 2D and 3D analyses. The differences between 2D and 3D analyses are carefully investigated. It is found that both 2D and 3D soil-water coupled analyses based on the modified elastoplastic model can simulate the progressive failure of a slope.

北海道常呂郡留辺蕊町金華地すべり地域における地すべりハザードマッピング

Seven ancient slide topographies in the Kanehana landslide area have been identified as concave polyhill- or concave monohill-type.The geology of this area consists primarily of the Cretaceous-Paleocene Yubetsu Group, the Upper Miocene Ikutawara and Yahagi Formations, Late Miocene-Early Pliocene rhyolite, andesite and basalt dikes, Lower Pliocene Komatsuzawa and Hakugindai Lavas, and Quaternary System. The Quaternary System consists of the Rubeshibe Formation and pumice flow, river terrace, talus, slide, alluvial fan and recent fluvial deposits. The Ikutawara and Yahagi Formations consist primarily of clastic rocks, acidic volcaniclastic rocks and rhyolite lavas. The rocks of the Ikutawara and Yahagi Formations and rhyolite and andesite dikes have been affected to various extents by hydrothermal alteration related to Late Miocene-Early Pliocene epithermal goldsilver mineralization.The hydrothermal alteration zones are divided into smectite, zeolite, propylitic, interstratified illite/smectite minerals, illite, K-feldspar, steam-heated alteration and advanced argillic alteration zones, based on the mineral assemblage of hydrothermally altered rocks. The seven ancient slides and the Kanehana-Toge slide occurred in the hydrothermal alteration zones, and were mainly related to the smectite zone.The slope instability evaluation system for slides used here is based on topography, slope geology, geologi-cal structure and the type of hydrothermal alteration according to 1: 5, 000-scale topographic and geologic mapping of the area. Using this evaluation system slope areas can be classified into four ranks ; stable hard-rock slope (class I), stable soft-rock slope (class II), potential slide area (class III) and ancient slide area (class IV). Based on the evaluation, a slide hazard map of the area was created.

LONG-TERM BEHAVIOUR OF EXCAVATED SOFT-ROCK SLOPE

LONG-TERM BEHAVIOUR OF EXCAVATED SOFT-ROCK SLOPE

Horizontal behaviour of pier foundation on a soft rock slope : Maeda, H Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10–15 April 1983V1, PC181–C184. Publ Rotterdam: A. A. Balkema, 1983

Horizontal behaviour of pier foundation on a soft rock slope : Maeda, H Proc 5th Congress of the International Society for Rock Mechanics, Melbourne, 10–15 April 1983V1, PC181–C184. Publ Rotterdam: A. A. Balkema, 1983