Pore water pressure dynamics in a rock slope adjacent to a retreating valley glacier

2020 ◽  
Author(s):  
Marc Hugentobler ◽  
Simon Loew ◽  
Clément Roques
Keyword(s):  
Boundary Conditions ◽  
Pore Water ◽  
Rock Slope ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Discharge ◽  
Pressure Sensors ◽  
Swiss Alps ◽  
Special Focus ◽  
Valley Glacier

<p>Rock slope instabilities normally form through long-term strength degradation of initially stable slopes. The rate of progressive damage accumulation in the rock slope is expected to vary over time depending on the current environmental conditions. It is often assumed that glacial retreat, with its increased dynamics in the thermal and hydraulic boundary conditions in combination with mechanical ice unloading induce stresses that cause increased rock mass damage in adjacent slopes. However, direct field measurements to understand these dynamics and to quantify damage are rare.</p><p>In this contribution we present new data of a continuous borehole monitoring system installed in a stable rock slope beside the retreating glacier tongue of the Great Aletsch Glacier (Swiss Alps). Special focus lies on the pore water pressure evolution in order to better understand the origin of the presumably hydro-mechanically forced deformation measured in the study area. We compare data of two borehole pressure sensors installed at 50 m depth in the fractured crystalline rock, pressure fluctuations measured in a sink hole on the glacier close to our study site, and glacial melt water discharge measurements. These data show that the pore pressure variability in the slope is driven by annual snowmelt infiltration cycles, rainfall events, and the connection to the englacial water of the temperate valley glacier. We show that our in-situ measurements provide critical data to improve the understanding of the effects of a retreating valley glacier on the boundary conditions and eventually the stability of an adjacent rock slope.</p>

Research of Slope Stability Analysis Considering Rainfall Infiltration

2012 ◽  
Vol 204-208 ◽  
pp. 487-491
Author(s):  
Jian Hua Liu ◽  
Zhi Min Chen ◽  
Wei He
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Rock Slope ◽  
Rainfall Intensity ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Rainfall Infiltration ◽  
Safety Coefficient ◽  
Rainfall Duration ◽  
Unsaturated Seepage

Based on the saturated-unsaturated seepage theory and considering soil-hydraulic permeability coefficient characteristic curves of rock slope, the variation of suction in unsaturated region and transient saturated zone formation of rock slope were analyzed. Combined with engineering example, the strength reduction methods were adopted to analyzing the rock slope stability influence factors considering unsaturated seepage with different rainfall intensity and duration. The results show that the flow domain owing to rainfall infiltration mainly appears surface layer region of slope. The rainfall infiltration caused the groundwater level rise, the rising of transient pore water pressure and the fall of suction in unsaturated region caused the slope stability decrease. The rainfall intensity and duration have obvious influence on slope stability, and in the same rainfall duration condition, the safety coefficient of slope decreases with the accretion of rainfall intensity. With the rainfall duration increasing, the water in soil has more deep infiltration, the water content and pore water pressure was higher in the same high position, the decreasing of suction caused the safety coefficient of slope has more reduce.

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.

scholarly journals Movements, failure and climatic control of the Veslemannen rockslide, Western Norway

Landslides ◽  
2021 ◽  
Author(s):  
Lene Kristensen ◽  
Justyna Czekirda ◽  
Ivanna Penna ◽  
Bernd Etzelmüller ◽  
Pierrick Nicolet ◽  
...  
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Rock Slope ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Early Warning Systems ◽  
Western Norway ◽  
Hazard Level ◽  
Inverse Velocity Method ◽  
Inverse Velocity

AbstractOn September 5, 2019, the Veslemannen unstable rock slope (54,000 m3) in Romsdalen, Western Norway, failed catastrophically after 5 years of continuous monitoring. During this period, the rock slope weakened while the precursor movements increased progressively, in particular from 2017. Measured displacement prior to the failure was around 19 m in the upper parts of the instability and 4–5 m in the toe area. The pre-failure movements were usually associated with precipitation events, where peak velocities occurred 2–12 h after maximum precipitation. This indicates that the pore-water pressure in the sliding zones had a large influence on the slope stability. The sensitivity to rainfall increased greatly from spring to autumn suggesting a thermal control on the pore-water pressure. Transient modelling of temperatures suggests near permafrost conditions, and deep seasonal frost was certainly present. We propose that a frozen surface layer prevented water percolation to the sliding zone during spring snowmelt and early summer rainfalls. A transition from possible permafrost to a seasonal frost setting of the landslide body after 2000 was modelled, which may have affected the slope stability. Repeated rapid accelerations during late summers and autumns caused a total of 16 events of the red (high) hazard level and evacuation of the hazard zone. Threshold values for velocity were used in the risk management when increasing or decreasing hazard levels. The inverse velocity method was initially of little value. However, in the final phase before the failure, the inverse velocity method was useful for forecasting the time of failure. Risk communication was important for maintaining public trust in early-warning systems, and especially critical is the communication of the difference between issuing the red hazard level and predicting a landslide.

Research of Lower Bound Method for Wedge Slope Subjected to Pore Water Pressure and Earthquake Force

2013 ◽  
Vol 444-445 ◽  
pp. 951-955
Author(s):  
Ze Li ◽  
Zhi Lin Liang
Keyword(s):  
Lower Bound ◽  
Pore Water ◽  
Rock Slope ◽  
Programming Model ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Earthquake Force ◽  
Plastic Limit Analysis ◽  
Structural Surface ◽  
Lower Bound Theory

Based on the lower bound theory for the plastic limit analysis, rock slope is divided into rigid block and structural surface. And the mathematical programming model which takes the safety factor as the objective function is established for the calculation of slope stability. This model has to meet the balance equations of the blocks, the Mohr-Coulomb yield conditions and the boundary conditions of slope. In the end, a classic model of rock slope on consideration of the pore water pressure and earthquake force is analyzed, and its lower bound solution is worked out. This result is compared to the result worked out by limiting equilibrium to test the validity and correctness of the method and procedure used in this paper.

scholarly journals Application of Miniature FBG-MEMS Pressure Sensor in Penetration Process of Jacked Pile

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 876
Author(s):  
Xueying Liu ◽  
Yonghong Wang ◽  
Mingyi Zhang
Keyword(s):  
Fiber Bragg Grating ◽  
Pore Water ◽  
Radial Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Sensors ◽  
Bragg Grating ◽  
Engineering Practice ◽  
Lateral Resistance ◽  
Soil Foundation

In order to study the penetration mechanism of jacked piles in viscous soil foundation, the stress variation law of the pile–soil interface was obtained by installing silicon piezoresistive earth pressure and pore water pressure sensors, and fiber Bragg grating (FBG) sensors in a model pile body, and the penetration characteristics of jacked piles in homogeneous viscous soil were defined. The test results show that: Fiber Bragg grating and silicon piezoresistive sensing technology can better meet the requirements of testing the characteristics of jacked pile in viscous soil. The ratio of pile lateral resistance to pile end resistance varies when pile is jacked in homogeneous viscous soil. In the early stage of pile jacking, the ratio of pile lateral resistance is small, and in the later stage of pile jacking, the ratio of pile lateral resistance increases, but the ratio of pile end resistance is still higher than that of pile lateral resistance. The ratio of the effective stress to the total radial stress is high, and the variation law of the two is consistent with the depth. The total radial stress, pore water pressure, and effective radial stress all exhibit the degradation phenomenon, and the degradation degree decreases gradually with the increase in penetration depth at the same depth. The ratio of excess pore water pressure to overburden weight decreases with the increase in depth, and the maximum value is 87%. The research results can provide a reference for the engineering practice of jacked pile in viscous soil foundation.

Soil compressibility in transient unsaturated seepage analyses

2014 ◽  
Vol 51 (8) ◽  
pp. 858-868 ◽  
Author(s):  
Timothy D. Stark ◽  
Navid H. Jafari ◽  
Aaron L. Leopold ◽  
Thomas L. Brandon
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Storm Event ◽  
Soil Compressibility ◽  
Transient Seepage ◽  
Seepage Analyses ◽  
Unsaturated Seepage

Most levee underseepage and uplift analyses are based on steady-state seepage and can yield conservative results. Although computations are simpler and steady-state seepage parameters are easier to determine and readily available, transient unsaturated seepage analyses are more representative of levee seepage conditions because boundary conditions acting on the levee or floodwall and saturation change with time, which induce pore-water pressure and seepage changes with time in the embankment and foundation strata. In addition, these boundary conditions, e.g., flood surge or storm event, are rapid such that steady-state conditions may not have time to develop in the embankment and some foundation materials. Transient seepage analyses using a floodwall case study indicate that as soil compressibility of the underseepage layer decreases, rapid landside pore-water pressures increase and can approach steady-state values. The transient results also indicate that uplift factors of safety during the flood event are about 22% higher than those at steady state. The effect of soil compressibility can delay or accelerate the onset of uplift water pressure increase from the initial steady-state conditions.

TIME TO THE END OF PRIMARY CONSOLIDATION (EOP) OF SOFT CLAYEY SOILS: CONCERNING THE EFFECT OF ATTERBERG’S LIMIT AND CYCLIC LOADING HISTORY

2019 ◽  
Vol 128 (2B) ◽  
pp. 29-41
Author(s):  
Trần Thanh Nhàn
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Clayey Soils ◽  
Loading History ◽  
Cyclic Shear ◽  
Wide Range ◽  
Primary Consolidation ◽  
Time Required

In order to observe the end of primary consolidation (EOP) of cohesive soils with and without subjecting to cyclic loading, reconstituted specimens of clayey soils at various Atterberg’s limits were used for oedometer test at different loading increments and undrained cyclic shear test followed by drainage with various cyclic shear directions and a wide range of shear strain amplitudes. The pore water pressure and settlement of the soils were measured with time and the time to EOP was then determined by different methods. It is shown from observed results that the time to EOP determined by 3-t method agrees well with the time required for full dissipation of the pore water pressure and being considerably larger than those determined by Log Time method. These observations were then further evaluated in connection with effects of the Atterberg’s limit and the cyclic loading history.

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