scholarly journals Post-Evaluation of Slope-Cutting on Loess Slopes Under Long-Term Rainfall Based on Model Test

2021 ◽  
Author(s):  
Guodong Liu ◽  
Shiqiang Xu ◽  
Zhijun Zhou ◽  
Tao Li
Keyword(s):  
Model Test ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Sensors ◽  
In Situ Stress ◽  
Shaanxi Province ◽  
Wetting Front ◽  
Loess Slope ◽  
Post Evaluation ◽  
Steady Stage

Abstract Failures of treated slope occurring in China are at a consistently increasing rate, leaving the huge number of treated loess slopes calling for post-evaluation, however, no mature technique is in place. Depended on an loess slope in Shaanxi province treated by slope-cutting, indoor geotechnical and model tests were conducted, revealing the rainwater infiltration characteristics and pressure varying characteristics inside the slope, the results of which were then adopted to perform the post-evaluation of the treated slope. The results showed that the rainwater scouring effect on the loess slope surface attenuates gradually, and enters a steady stage after the first year of rainfall. The rainwater preferentially penetrates the platforms with gradually attenuating rates, however the wetting front can not be deemed as the boundary between the saturated and unsaturated areas, as the most parts of the model slope were indicated unsaturated by the pore water pressure sensors. Caused by the in-situ stress release, the soil pressures don’t increase but decrease sharply at the start of the rainfall. The displacements mainly occurs in the first two years of rainfall, following by steady periods. The model test results and investigation results were then used to conduct the post-evaluation of the prototype slope, which formed a post-evaluation frame relevant to other slope post-evaluations.

A suitable methodology for assessing impacts of successive rainfalls infiltration on road slope stability

2013 ◽  
Vol 184 (1-2) ◽  
pp. 171-181
Author(s):  
Hugues Georges Rameau ◽  
Claude Prepetit ◽  
Jean-Claude Verbrugge
Keyword(s):  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Rainfall Simulation ◽  
Wetting Front ◽  
Rainfall Events ◽  
Simulation Techniques ◽  
Apparent Cohesion ◽  
National Road ◽  
The Relationship

Abstract Water precipitation in road slopes, pavements, and shoulders may cause disturbances such as erosion, increase of the water table level, decrease of the carriageway bearing capacity, and so on. Roads are normally equiped with drainage systems that are sized and implemented in accordance with the rules of art. These equipments are used for the collection and quick evacuation of water precipitation estimated on the basis of the return period that is taken into account. Despite that, rainwater can still infiltrate unprotected cut or fill slopes, and pavements for repeated and intense rainfalls, which may cause a raise in pore-water pressure and a decrease of the factor of safety of road slopes. Using laboratory rainfall simulation techniques, infiltration measurements were made on intact samples to determine with respect to soil properties, how cumulative rainfalls cause decrease in apparent cohesion and lead to slope failure. This paper focuses on describing the relationship between the rainfall characteristics, the changes in soil water profile, and the changes in apparent cohesion for sandy clay samples collected on the national road RN3 located in Haiti. For a set of consecutive rainfall events at around an interval of 24 hours, the results prove that when wetting front depth approaches 2 meters or more, the risk of landslide is proportionally high in a soil with apparent cohesion (Ca) initially high and an effective cohesion (c′) relatively low.

scholarly journals Mechanical Mechanism of Hydraulic Fracturing Effect Caused by Water Inrush in Tunnel Excavation by Blasting

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Quan Zhang ◽  
Jiong Wang ◽  
Longfei Feng
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Inrush ◽  
In Situ Stress ◽  
Confined Water ◽  
Shear Damage ◽  
Splitting Factor ◽  
Blasting Excavation

When the deep tunnel is excavated, the pressure of the confined water is relatively high, causing the water inrush to have a hydraulic fracturing effect. The method of theoretical analysis was adopted to study this effect. A mechanical model for fracturing water inrush under blasting excavation conditions was established. The water inrush under this condition is the result of the combined action of static load (water pressure and in situ stress) and dynamic load (explosive stress wave). According to whether the normal stress on the hydraulic crack surface was tensile stress or compressive stress, two types of water inrush were proposed: water inrush caused by tensile-shear damage and water inrush caused by compression-shear damage. These two types of critical water pressures were calculated separately. The relationship between critical water pressure, in situ stress, and blasting disturbance load was given, and a pore water pressure splitting factor was introduced in the calculation process. The theoretically obtained critical water pressure had been verified in the case of water inrush in a deep-buried tunnel. The established theory can guide field practice well.

scholarly journals Laboratory Experiment and Numerical Analysis on the Precursory Hydraulic Process of Rainfall-Induced Slope Failure

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Joon-Young Park ◽  
Young-Suk Song
Keyword(s):  
Numerical Modeling ◽  
Laboratory Test ◽  
Water Content ◽  
Pore Water ◽  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Volumetric Water Content ◽  
Wetting Front ◽  
Artificial Rainfall

A combined analysis involving a laboratory test and numerical modeling was performed to investigate the hydraulic processes leading to slope failure during rainfall. Through a laboratory landslide test in which artificial rainfall was applied to a homogeneous sandy slope, the timing and configurations of multiple slides were identified. In addition, volumetric water content was measured in real time through the use of monitoring sensors. The measured volumetric water content data were then used to validate the relevance of the numerical modeling results. The validated numerical modeling of the laboratory-scale slope failures provided insight into the hydraulic conditions that trigger landslides. According to the numerical modeling results, the miniaturized slope in the laboratory test was saturated in a manner so that the wetting front initially progresses downward and then the accumulated rainwater at the toe of the slope creates a water table that advances toward the crest. Furthermore, each of the five sequential failures that occurred during this experiment created slip surfaces where the pore-water pressure had achieved full saturation and an excessive pore-water pressure state. The findings of this study are expected to help understand the hydraulic prerequisites of landslide phenomena.

scholarly journals An appraisal of end conditions in advanced monotonic and cyclic triaxial testing on a range of geomaterials

2019 ◽  
Vol 92 ◽  
pp. 02007
Author(s):  
Ken Vinck ◽  
Tingfa Liu ◽  
Emil Ushev ◽  
Richard J. Jardine
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Sensors ◽  
Local Strain ◽  
Triaxial Tests ◽  
Triaxial Testing ◽  
Cyclic Triaxial ◽  
Cyclic Triaxial Tests ◽  
End Conditions

Compressing samples between rigid platens, as in triaxial testing, induce non-uniform specimen stress, strain and pore water distributions. Although well recognised historically, the effects of such platen restraints are often disregarded or overlooked when performing or interpreting monotonic and cyclic experiments. This paper presents an updated appraisal of end conditions based on laboratory experiments run on sand, glacial till, intact and puttified chalk as part of offshore piling research projects. Monotonic and cyclic triaxial tests are reported that incorporated local strain and pore pressure sensors and a range of platen configurations. New insights are reported regarding the small-to-large behaviour and undrained cyclic pore water pressure measurement.

Analysis of the Effect of Stopping Dewatering on Group Piles Foundation

2011 ◽  
Vol 250-253 ◽  
pp. 1348-1355
Author(s):  
Jun Fa Zhang ◽  
Lei Tao ◽  
Jian Jun Wen ◽  
Wen Xiang Liu
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Groundwater Table ◽  
Shaanxi Province ◽  
Analysis Program ◽  
In Situ Testing ◽  
Building Foundation ◽  
Abnormal Phenomenon ◽  
Group Piles

After the construction of building foundation with high groundwater table was finished, stopping dewatering of pit could create some effect on the force of foundation. In this paper, equivalent temperature-changed method was brought forward to simulate the influence of stopping dewatering which could conveniently use current structural analysis program to simulate the change of pore water pressure in soil. And based on ANSYS program, this method was applied in the project of Telecom Network Management Center in Shaanxi Province. Numerical results indicate that the effect of stopping dewatering on pile-raft system is significant, and some ‘abnormal phenomenon’ in In-Situ Testing is reasonably explained.

scholarly journals Reservoir Landslide Physical Modelling under Ice-Snow Melting and Reservoir Water Combined Action

2020 ◽  
Vol 2020 ◽  
pp. 1-21
Author(s):  
Tongqiang Xiong ◽  
Jianlin Li ◽  
Lehua Wang ◽  
Huafeng Deng ◽  
Xiaoliang Xu
Keyword(s):  
Failure Mode ◽  
Model Test ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Snow Melting ◽  
Reservoir Water ◽  
Infiltration Process ◽  
Deformation And Failure ◽  
Snow Water ◽  
Combined Action

Extreme ice-snow melting in winter affects the infiltration process of snow water on the slope surface significantly and plays an important role in the deformation stability of landslide. Variation in pore water pressure is regarded as an essential factor of landslide instability induced by snow water. In order to figure out the internal relationship between the infiltration process of snow water and the failure mode of deformation and instability of the accumulation landslide, the response law and deformation and failure mode of pore water pressure and soil pressure of landslide accumulation under different ice-snow melting conditions are deeply studied based on the indoor large-scale landslide model test. We have studied the physical model test under the combined action of reservoir water and ice-snow melting. It reveals the seepage erosion deformation and failure mechanism. It undoubtedly provides references of great importance for the geological hazard governance of bank slope in the Three Gorges Reservoir Area.

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