scholarly journals Experimental Study on Response Law and Failure Process of Slopes in Fully Weathered Granites Under Precipitation Infiltration

2021 ◽  
Author(s):  
Fei Tan
Keyword(s):  
Experimental Study ◽  
Physical Simulation ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Failure Process ◽  
Similarity Criterion ◽  
Weathered Granite ◽  
The Matrix ◽  
Soil Flow ◽  
Matrix Suction

Abstract To investigate the response law and failure process of slopes in fully weathered granites under precipitation infiltration, a typical fully weathered granite slope is selected for sampling in Fengkai, Guangdong. The physical simulation experimental study of rainfall-induced landslide is conducted, in which Weber criterion is used as the similarity criterion for precipitation. The research results reveal that under precipitation infiltration, the fully weathered granite slope responds quickly. Further, the water content increases sharply, and the matrix suction quickly dissipates. After dissipation, the matrix suction transforms into pore water pressure, which accelerates the deformation of the slope. The wet peak has a large infiltration depth in the slope, and the acceleration of deep part is lower than that of the shallow part. Under the action of precipitation, the fully weathered granite model undergoes four stages of failure. Firstly, gullies and cracks appear. Secondly, cracks propagate and link up. Then, the soil on the slope surface swells and ruptures. Finally, the slope slides locally until the entire slope creeps, collapses, and transforms into a "soil flow." Based on the analysis of precipitation similarity, the landslide will be triggered in fully weathered granite slope by precipitation when the precipitation intensity comes up to 155 mm/d, and the landslide occurs at an accumulated precipitation of 304 mm. Overall, the results can provide a reliable theoretical basis and abundant experimental data for the prevention, monitoring, and forecasting of geological disasters in granitic areas.

Second Canadian Geotechnical Colloquium: Appropriate concepts and technology for unsaturated soils

1979 ◽  
Vol 16 (1) ◽  
pp. 121-139 ◽  
Author(s):  
D. G. Fredlund
Keyword(s):  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Earth Pressure ◽  
Saturated Soil ◽  
Engineering Practice ◽  
The Matrix ◽  
Matrix Suction

A practical science has not been fully developed for unsaturated soils for two main reasons. First, there has been the lack of an appropriate science with a theoretical base. Second, there has been the lack of an appropriate technology to render engineering practice financially viable.This paper presents concepts that can be used to develop an appropriate engineering practice for unsaturated soils. The nature of an unsaturated soil is first described along with the accompanying stress conditions. The basic equations related to mechanical properties are then proposed. These are applied to practical problems such as earth pressure, limiting equilibrium, and volume change.An attempt is made to demonstrate the manner in which saturated soil mechanics must be extended when a soil is unsaturated. Two variables are required to describe the stress state of an unsaturated soil (e.g., (σ – ua) and (ua – uW). There is a smooth transition from the unsaturated case to the saturated case since the pore-air pressure becomes equal to the pore-water pressure as the degree of saturation approaches 100%. Therefore, the matrix suction (i.e., (ua – uW) goes to 0 and the pore-water pressure can be substituted for the pore-air pressure (i.e., (σ – uW)).The complete volumetric deformation of an unsaturated soil requires two three-dimensional constitutive surfaces. These converge to one two-dimensional relationship for a saturated soil. The shear strength for an unsaturated soil is a three-dimensional surface that reduces to the conventional Mohr–Coulomb envelope for a saturated soil.The manner of applying the volumetric deformation equations and the shear strength equation to practical problems is demonstrated. For earth pressure and limiting equilibrium problems, the unsaturated soil can be viewed as a saturated soil with an increased cohesion. The increase in cohesion is proportional to the matrix suction of the soil. For volume change problems it is necessary to have an indication of the relationship between the various soil moduli.There is a need for further experimental studies and case histories to substantiate the proposed concepts and theories.

scholarly journals The Effects of Rainfall, Soil Type and Slope on the Processes and Mechanisms of Rainfall-Induced Shallow Landslides

2021 ◽  
Vol 11 (24) ◽  
pp. 11652
Author(s):  
Yan Liu ◽  
Zhiyuan Deng ◽  
Xiekang Wang
Keyword(s):  
Water Content ◽  
Sediment Yield ◽  
Soil Type ◽  
Rainfall Intensity ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Shallow Landslides ◽  
Total Stress ◽  
The Matrix ◽  
Matrix Suction

Landslides are a serious geohazard worldwide, causing many casualties and considerable economic losses every year. Rainfall-induced shallow landslides commonly occur in mountainous regions. Many factors affect an area’s susceptibility, such as rainfall, the soil, and the slope. In this paper, the effects of rainfall intensity, rainfall pattern, slope gradient, and soil type on landslide susceptibility are studied. Variables including soil volumetric water content, matrix suction, pore water pressure, and the total stress throughout the rainfall were measured. The results show that, under the experimental conditions of this paper, no landslides occurred on a 5° slope. On a 15° slope, when the rainfall intensity was equal to or less than 80 mm/h with a 1 h duration, landslides also did not happen. With a rainfall intensity of 120 mm/h, the rainfall pattern in which the intensity gradually diminishes could not induce landslides. Compared with fine soils, coarser soils with gravels were found to be prone to landslides. As the volumetric water content rose, the matrix suction declined from the time that the level of infiltration reached the position of the matrix. The pore water pressure and the total stress both changed drastically either immediately before or after the landslide. In addition, the sediment yield depended on the above factors. Steeper slopes, stronger rainfall, and coarser soils were all found to increase the amount of sediment yield.

An Experimental Study on the Wave-Induced Topographic Change in Artificial Shallows: Focusing on the Effects of Pore-Water Pressure on Sediment Transport

2014 ◽  
Vol 56 (2) ◽  
pp. 1450008-1-1450008-21 ◽  
Author(s):  
Tomoaki Nakamura ◽  
Yuta Nezasa ◽  
Yong-Hwan Cho ◽  
Ryo Ishihara ◽  
Norimi Mizutani
Keyword(s):  
Experimental Study ◽  
Sediment Transport ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Wave Induced

Type of Slope Failure Identified from Pore Water Pressure and Moisture Content Measurements

2015 ◽  
Vol 744-746 ◽  
pp. 690-694
Author(s):  
Muhammad Rehan Hakro ◽  
Indra Sati Hamonangan Harahap
Keyword(s):  
Moisture Content ◽  
Pore Pressure ◽  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Failure Process ◽  
Small Scale ◽  
Content Increase ◽  
Sudden Increase ◽  
Model Slope

Rainfall-induced landslides occur in many parts of the world and causing a lot of the damages. For effective prediction of rainfall-induced landslides the comprehensive understanding of the failure process is necessary. Under different soil and hydrological conditions experiments were conducted to investigate and clarify the mechanism of slope failure. The failure in model slope was induced by sprinkling the rainfall on slope composed of sandy soil in small flume. Series of tests were conducted in small scale flume to better understand the failure process in sandy slopes. The moisture content was measured with advanced Imko TDR (Time Domain Reflectrometry) moisture sensors in addition to measurements of pore pressure with piezometers. The moisture content increase rapidly to reach the maximum possible water content in case of higher intensity of rainfall, and higher intensity of the rainfall causes higher erosion as compared to smaller intensity of the rainfall. The controlling factor for rainfall-induced flowslides was density of the slope, rather than intensity of the rainfall and during the flowslide the sudden increase in pore pressure was observed. Higher pore pressure was observed at the toe of the slope as compared to upper part of the slope.

Experimental Study of the Influence of the Pore Water Pressure Evolution and the Shear Band Formation on the Extraction Resistance of Submerged Anchor Plates

2018 ◽  
Author(s):  
Manuela Kanitz ◽  
Juergen Grabe
Keyword(s):  
Experimental Study ◽  
Shear Band ◽  
Pore Water ◽  
High Speed ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Offshore Structures ◽  
Shear Band Formation ◽  
Band Formation ◽  
Anchor Plates

Floating offshore structures used to generate wind energy are founded on submerged foundations such as anchor plates. Their extraction resistance is of major importance during and at the end of the lifetime cycle of these offshore structures. During their lifetime cycle, the foundation is suspended to complex loading conditions due to waves, tidal currents and wind loads. To guarantee a stable structure, the extraction resistance of the anchor plates has to be known. At the end of the lifetime cycle of the offshore structures, the extraction resistance is mainly influencing the removal of the anchor plates. This resistance is a lot higher than the sum of its self-weight and hydrostatic and earth pressure acting on the structure. With initiation of a motion of the anchor plate, the volume underneath this structure is increased leading to negative pore water pressure until inflowing pore water is filling the newly created volume. In order to investigate this effect, an extensive experimental study at model scale with a displacement-driven extraction is performed. Pore pressure measurements are carried out at various locations in the soil body and underneath the plate. The soil movement is tracked with a high-speed camera to investigate the shear band formation with the particle image velocimetry method (PIV). The experiments will be conducted considering different packing densities of the soil body and at different extraction velocities to investigate their effect on the extraction resistance of anchor plates.

scholarly journals Stability of saprolitic slopes: nature and role of field scale heterogeneities

2006 ◽  
Vol 6 (1) ◽  
pp. 89-96 ◽  
Author(s):  
A. Aydin
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Cost Effective ◽  
Field Scale ◽  
Instability Modes ◽  
Effective Manner ◽  
Ground Investigation ◽  
The Matrix ◽  
Chaotic Distribution ◽  
Horizontal Drains

Abstract. Heterogeneities in various forms and scales often control the mechanisms and locations of failure and deformation, and the factor of safety of saprolitic slopes. This paper presents a critical review of field scale heterogeneities and their roles in controlling the stability of saprolitic slopes. In particular corestones and relict joints are analysed, with emphasis on characterization and possible instability modes. Abnormal flow patterns, fast build-up and/or chaotic distribution of pore water pressure are the most common causative factors of landslides. As heterogeneities are often responsible for the occurrence of such localized abnormalities, realistic models incorporating effects of these features can help predict how and where abnormal flow/pressure patterns may develop. Potential pitfalls during ground investigation in landslide prone slopes are elucidated and effective investigation strategies to avoid these pitfalls are recommended. The uncertainties, for example, in distribution and volumetric percentage of corestones and in delineating zonal boundaries, require continuous upgrading of the engineering geological model during the construction stage of site investigations. Such uncertainties can be reduced in a cost-effective manner by recording drill penetration rates during installation of soil nails and horizontal drains. A better understanding of the interactions among the heterogeneities, the matrix and the engineering geological environment as a whole should enable the significance of discrete features in stability to be more consistently assessed, thereby providing a more rational basis for investigation and design practice in saprolitic profiles.

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