scholarly journals Stability Analysis of a Weathered-Basalt Soil Slope Using the Double Strength Reduction Method

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xiaoliang Liu ◽  
Xin Chen ◽  
Mei Su ◽  
Shilin Zhang ◽  
Dengfeng Lu
Keyword(s):  
Finite Element ◽  
Stability Analysis ◽  
Water Content ◽  
Heavy Rainfall ◽  
Friction Angle ◽  
Slope Instability ◽  
Soil Slope ◽  
Long Distance ◽  
Finite Element Software ◽  
Reduction Problem

Slope stability analysis of the mountain landforms in southwestern China has always been an important problem in the field of geotechnical engineering. The large landslide occurs in Jichang Town, Shuicheng County, Guizhou Province, China, on July 23, 2019, as the engineering background. Based on the nonlinear relationship between the soil water content, cohesion, and friction angle measured in laboratory tests, the finite element reduction problem of the double-strength parameters is only transformed into a reduction problem of water content. Then, based on the redevelopment platform in the ABAQUS finite element software, a user subroutine to specify predefined field variables (UFIELD) was written to numerically simulate the stability of the Jichang slope before the landslide. The results show that the Jichang slope is mainly composed of basalt-weathered red clay mixed with gravel of various particle sizes. The underlying bedrock is primarily the Permian Emeishan basalt with strong-to-weak weathering and a small amount of argillaceous siltstone. Due to the increase in water content caused by heavy rainfall, the strength of the soil decreased continuously. Once the critical stress state of the slope was exceeded, the plastic sliding block slipped at high speed over a long distance along the rock-soil layer interface, and along the way, it scraped out and carried away the original loose topsoil and gravel blocks, which finally piled up in the form of a debris flow. In addition, the attenuations of the cohesion and friction angle are different. When the water content is less than 25%, the reduction coefficient of the friction angle is greater than the cohesion, which shows that the attenuation of the friction angle is stronger than that of the cohesion. The opposite is true when the water content is greater than 25%. The new method of double-strength finite element reduction presented in this paper is reasonable and feasible and is more in line with the actual situation of weathered-basalt soil slope instability in heavy rainfall areas.

scholarly journals Development Trend and Stability Analysis of Creep Landslide With Obvious Slip Zone Under Rainfall-Taking Xinchang Xiashan Basalt Slope as an Example

2022 ◽  
Vol 9 ◽  
Author(s):  
Chunyan Bao ◽  
Lingtao Zhan ◽  
Yingjie Xia ◽  
Yongliang Huang ◽  
Zhenxing Zhao
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Stability Analysis ◽  
Soil Layer ◽  
Heavy Rain ◽  
Development Trend ◽  
Sliding Surface ◽  
Landslide Area ◽  
Finite Element Software ◽  
Sliding Zone

The creep slope is a dynamic development process, from stable deformation to instability failure. For the slope with sliding zone, it generally creeps along the sliding zone. If the sliding zone controlling the slope sliding does not have obvious displacement, and the slope has unexpected instability without warning, the harm and potential safety hazard are often much greater than the visible creep. Studying the development trend of this kind of landslide is of great significance to slope treatment and landslide early warning. Taking Xiashan village landslide in Huishan Town, Xinchang County, Zhejiang Province as an example, the landslide point was determined by numerical simulation in 2006. Generally, the landslide is a typical long-term slow deformation towards the free direction. Based on a new round of investigation and monitoring, this paper shows that there are signs of creeping on the surface of the landslide since 2003, and there is no creep on the deep sliding surface. The joint fissures in the landslide area are relatively developed, and rainfall infiltration will soften the soft rock and soil layer and greatly reduce its stability. This paper collects and arranges the rainfall data of the landslide area in recent 30 years, constructs the slope finite element model considering rainfall conditions through ANSYS finite element software, and carries out numerical simulation stability analysis. The results show that if cracks appear below or above the slope’s sliding surface, or are artificially damaged, the sliding surface may develop into weak cracks. Then, the plastic zone of penetration is offset; In the case of heavy rain, the slope can unload itself under the action of rainfall. At this time, the slope was unstable and the landslide happened suddenly.

scholarly journals Slope stability analysis in the case of probabilistic and semi-probabilistic design method

2019 ◽  
Vol 97 ◽  
pp. 04044
Author(s):  
Hubert Szabowicz
Keyword(s):  
Finite Element ◽  
Internal Friction ◽  
Design Method ◽  
Probability Distributions ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Probabilistic Modelling ◽  
Finite Element Software ◽  
Random Finite Element Method ◽  
Slope Factor

This paper addresses the issue of probabilistic and semi-probabilistic modelling of soil slopes. A slope made of cohesive-frictional soil of specific geometry was analysed as an example. Results were calculated for two methods using the Z-Soil finite element software. It has been assumed that the probability distributions of strength parameters, cohesion and internal friction angle are normal distributions with average values and coefficient of variation = 0.2. Random finite element method (RFEM) has been used for probabilistic modelling. Random fields of cohesion and internal friction angle have been generated using the Fourier series method (FSM). Monte Carlo simulation has been used to calculate the statistics of the slope factor of safety in order to determine the probability of failure. Moreover, assumed parameter distributions allowed to determine safe characteristic values used in the semi-probabilistic partial factors method. Both approaches have been compared in the article.

Research on Soil-Like Slope Instability Based on FEM Strength Reduction

2013 ◽  
Vol 438-439 ◽  
pp. 1244-1248 ◽  
Author(s):  
Chun Ming Wang ◽  
Chun Yuan Liu ◽  
Mai Wu ◽  
Xin Zhao
Keyword(s):  
Finite Element ◽  
Main Idea ◽  
Strength Reduction ◽  
Slope Instability ◽  
Instability Criterion ◽  
Mountainous Area ◽  
Soil Slope ◽  
Element Analysis ◽  
The Stability ◽  
Similar Soil

In the construction of mountainous area roads, the similar soil slope is the most common slope form. During the construction, the problem we often meet is how to make the evaluation about the stability of the similar soil slope. The joints exist in the matrix rock, which make great effect on the stability of the slope. The main idea of this article is to analyze the effect of joints and the rain seeped in on the instability of the slope. To solve the problem, the finite element strength reduction theory is taken in this article, and the geotechnical finite element analysis software z_soil is chosen to make the analysis about the instability criterion and the stability in the condition the rain of the similar slope.

Stability Analysis of Mountain Slope Based on Finite Element and Discrete Element

2012 ◽  
Vol 170-173 ◽  
pp. 1087-1090
Author(s):  
Wei Bin Yuan ◽  
Cheng Min Ye ◽  
Ji Yao ◽  
Lie De Wang
Keyword(s):  
Finite Element ◽  
Stability Analysis ◽  
Slope Stability ◽  
Discrete Element Method ◽  
Discrete Element ◽  
Soil Slope ◽  
Safety Factors ◽  
Mountain Slope ◽  
The Stability ◽  
Element Method

In recent year, the foundations of the stability analysis of slope were provided by the development of finite element and discrete element method. Using finite element and discrete element method, the stability analysis of three typical slopes of shiwu thorp of Quzhou was carried out. The safety factors of slope profile were obtained. Based on the judgment criterion of slope stability，the slopes stability of shiwu thorp was judged. The results showed that the way to analyze the stability of soil slope is feasible.

Field study of rainfall infiltration into a grassed unsaturated expansive soil slope

2007 ◽  
Vol 44 (4) ◽  
pp. 392-408 ◽  
Author(s):  
Tony LT Zhan ◽  
Charles WW Ng ◽  
Del G Fredlund
Keyword(s):  
Field Study ◽  
Water Content ◽  
Pore Water ◽  
Surface Runoff ◽  
Expansive Soil ◽  
Rainfall Infiltration ◽  
Slope Instability ◽  
Simulated Rainfall ◽  
Soil Slope ◽  
Unsaturated Expansive Soil

A full-scale field study was conducted to investigate the effects of rainfall infiltration on a natural grassed expansive soil slope in China. A 16 m wide × 28 m long area was selected for instrumentation. The instrumentation included jet-filled tensiometers, moisture probes, a tipping bucket rain gauge, and a vee-notch flow meter. One artificial rainfall event amounting to about 370 mm rain depth in total was applied to the slope. The monitored results suggested that there was about a 3 day delay in the response of surface runoff, pore-water pressure, and water content to the commencement of the simulated rainfall. The depth of influence of the rainfall, depending on the elevation along the slope, ranged from 2.8 to 3.5 m. Positive pore-water pressures were measured within the influence depth, and there existed significant subsurface downslope flow at the end of the simulated rainfall, particularly near the lower part of the slope. A comparison of infiltration rates between the grassed area and a bare area nearby indicated that the presence of grass significantly increased the infiltration rate and reduced surface runoff. The cracks and fissures developed in the unsaturated expansive soil played an important role in the hydrological process.Key words: expansive soil, slope instability, infiltration, vegetation cover, grass, soil suction, water content, unsaturated soil.

Analysis on Stability of Subgrade Slope Influenced by Strength Attenuation

2011 ◽  
Vol 243-249 ◽  
pp. 4360-4365
Author(s):  
Xiao Ming Yi ◽  
Song Gen Wang ◽  
Xiu Guang Song ◽  
Hong Bo Zhang
Keyword(s):  
Finite Element ◽  
Laboratory Test ◽  
Water Content ◽  
Yellow River ◽  
Strength Degradation ◽  
Alluvial Plain ◽  
Seismic Load ◽  
Finite Element Software ◽  
Decay Pattern ◽  
The Stability

The water content in the subgrade changes easily as the variation of the environment water, which causes the strength attenuation of the subgrade. It is harmful to the stability of subgrade slope. Strength decay pattern of silt soil in yellow river alluvial plain is studied through the laboratory test. And then the finite element software GEO-SLOPE is used to calculate coefficient of stability under different conditions. Results show strength indexes of silt soil are maximum in the optimal water content, and the change of the water content would cause strength attenuation. The stability of subgrade slope decreases as the strength degradation, while the evolution is different, which is semi-parabolic in the lower subgrade but rectilinear in the higher subgrade. Seismic load leads to stress concentrate at the slope, combined with the strength attenuation the landslide is easily to take place.

scholarly journals Three-dimensional stability analysis of an urban slope located in João Monlevade, Brazil

2019 ◽  
Vol 8 (11) ◽  
pp. e168111449
Author(s):  
Fernanda Cristina Pereira ◽  
Flavia Laís Dias Oliveira ◽  
Laís Emily de Assis ◽  
Tatiana Barreto dos Santos
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Dimensional Stability ◽  
Factor Of Safety ◽  
Three Dimensional ◽  
Friction Angle ◽  
City Council ◽  
Residual Soil ◽  
Soil Slope ◽  
Clayey Silt

Geotechnical stability analysis of slopes is an important tool for decision making in civil projects.  Use of three-dimensional software for analysis of soil slope stability has increased in recent years. Rocscience Inc. created Slide3 software in 2017. Slide3 is a software that allows geotechnical engineers to calculate the factor of safety of complex 3D slope stability geometries that 2D models cannot fully simulate. In this context, this paper presents a three-dimensional stability analysis of a slope located in an urban area at city of João Monlevade, Minas Gerais, Brazil. The slope was selected due to the instability history in rainfall periods. Topography of the area was provided by the city council. Young and mature residual soils were identified in the studied slope. Young residual soil was physically classified as clay without gravels and presents in natura values of cohesion and friction angle, equal to 32 KPa and 23.97º, respectively. Mature residual soil was physically classified as clayey silt without gravels and presents in natura values of cohesion and friction angle, equal to 19 KPa and 23.30º, respectively. The factor of safety of the soil slope was equal 0.977, considering the slope saturated. The factor of safety of the drained slope was equal to 1.415. Generalized limit equilibrium (GLE) method was used in this equilibrium-limit analysis.  The results stability analysis of the slope was coherent, once previous instability occurs in a period that was identified above average rainfall.

scholarly journals Influence of water content on the shear strength parameters of clayey soil in relation to stability analysis of a hillside in Brno region

2013 ◽  
Vol 61 (6) ◽  
pp. 1583-1588 ◽  
Author(s):  
Kristýna Bláhová ◽  
Lenka Ševelová ◽  
Pavla Pilařová
Keyword(s):  
Shear Strength ◽  
Stability Analysis ◽  
Water Content ◽  
Clayey Soil ◽  
Friction Angle ◽  
Dry Density ◽  
Stability Analyses ◽  
Influence Of Water ◽  
Moisture Conditions ◽  
Processing Stability

Shear strength of soils is highly affected by moisture conditions (i.e. water content), especially if the soil contains clay materials. Usually the laboratory specimen, which are used to determine shear strength of soil are prepared at water content and dry density same as in the field conditions, without respect to the fact, that the conditions in the future might not remain the same. For the purpose of this study soil specimen were compacted and the optimum moisture content was identified. After compaction soil was tested at the dry side of optimum water content at w = 9 %, 10 % and 11 %. Parameters of shear strength were obtained and used for stability analysis with software GEOSLOPE/W 2012. According to referenced literature, it was expected for the shear strength of the soil to decrease with increasing water content. This hypothesis was not proven for clayey soil from Brno region. Development of values of friction angle and cohesion exhibited anomalous behaviour and such development was found also for values of Factor of safety (FOS) obtained from stability analyses. Results proved the necessity of taking moisture conditions into account, when processing stability analyses, in order to achieve reliable and safe constructions.

scholarly journals The Complex Monolithic Movement for the Brick-wooden Building in Deformation Analysis and Reinforcement

2016 ◽  
Vol 10 (1) ◽  
pp. 884-890
Author(s):  
Shan Ren-liang ◽  
Zhang Xiao-nan ◽  
Lu Man ◽  
Zhao Hong-yu
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Internal Force ◽  
Henan Province ◽  
Deformation Analysis ◽  
Long Distance ◽  
Finite Element Software ◽  
Building Foundation ◽  
Curved Track ◽  
Long Distance Movement

This paper first analyzes the reasons of complex monolithic movement of a brick-wooden building in Henan province in China. The building foundation integral underpinning technique and curved-track moving technique which combine the track sharing-monolithic movement method and efficient long distance movement method were put forward. These methods use the anchor static pile, in order to guarantee the safety of the building for complex monolithic movement. The analysis of the internal force and deformation of underpinning structure was calculated by finite element software SAP2000. A practice case showed that the internal force of the underpinning structure is less than the bearing capacity, which proved the efficiency of the proposed method.

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