scholarly journals Stress in an Elastic Bedrock Hump Due to Glacier Flow

1977 ◽  
Vol 18 (78) ◽  
pp. 67-75 ◽  
Author(s):  
L. W. Morland ◽  
E. M. Morris
Keyword(s):  
Stress Field ◽  
Applied Load ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Normal Pressure ◽  
Cohesive Stress ◽  
Coulomb Failure ◽  
Gravity Effects ◽  
Coulomb Failure Criterion ◽  
Glacier Flow

Abstract The stress field in an isotropic elastic hump representing a typical bedrock feature is obtained for plane strain conditions. Gravity effects are included and the applied load is a normal pressure distribution deduced from an idealized model of glacier flow. A Coulomb failure criterion is applied, including the effective stress change due to pore-water pressure, and stresses on the predicted failure planes determined for different pressure amplitudes and relative gravity contributions. The latter make little difference to the maximum “failure stress" but influence the regions where such stress levels occur. Levels of cohesive stress required to inhibit Coulomb failure are obtained, and are low in general, implying that coherent rock in the adopted hump profile, subject to the model pressure, would not fail. That is, this profile is stable unless jointing introduces an easier failure mechanism.

scholarly journals Stress in an Elastic Bedrock Hump Due to Glacier Flow

1977 ◽  
Vol 18 (78) ◽  
pp. 67-75 ◽  
Author(s):  
L. W. Morland ◽  
E. M. Morris
Keyword(s):  
Stress Field ◽  
Applied Load ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Normal Pressure ◽  
Cohesive Stress ◽  
Coulomb Failure ◽  
Gravity Effects ◽  
Coulomb Failure Criterion ◽  
Glacier Flow

AbstractThe stress field in an isotropic elastic hump representing a typical bedrock feature is obtained for plane strain conditions. Gravity effects are included and the applied load is a normal pressure distribution deduced from an idealized model of glacier flow. A Coulomb failure criterion is applied, including the effective stress change due to pore-water pressure, and stresses on the predicted failure planes determined for different pressure amplitudes and relative gravity contributions. The latter make little difference to the maximum “failure stress" but influence the regions where such stress levels occur. Levels of cohesive stress required to inhibit Coulomb failure are obtained, and are low in general, implying that coherent rock in the adopted hump profile, subject to the model pressure, would not fail. That is, this profile is stable unless jointing introduces an easier failure mechanism.

scholarly journals ANALYSIS OF DEEP STRESS FIELD USING WELL LOG AND WELLBORE BREAKOUT DATA: A CASE STUDY IN CRETACEOUS OIL RESERVOIR, SOUTHWEST IRAN

2018 ◽  
Vol 44 (4) ◽  
pp. 113-128
Author(s):  
Mohammad Abdideh ◽  
Sina Alisamir
Keyword(s):  
Neural Network ◽  
Stress Field ◽  
Failure Criterion ◽  
Drill String ◽  
Oil Reservoir ◽  
Injection Test ◽  
Study Results ◽  
Coulomb Failure ◽  
Stress Profiles ◽  
Coulomb Failure Criterion

To identify the wellbore instability of Bangestan oil reservoir in the southwestern Iran, the direction and magnitude of stresses were determined using two different methods in this study. Results of injection test and analysis of wellbore breakouts were used to verify the accuracy of the stress profiles. In this study the Bartoon method, which using the breakout angle and strength of rock, was used. In addition, the ability of artificial neural network to estimate the elastic parameters of rock and stress field was used. The output of the neural network represents a high accuracy in the estimation of the desired parameters. In addition, the Mohr-Coulomb failure criterion was used to verify stress profiles. Estimated stresses show relative compliance with the results of injection test and Barton method. The required minimum mud pressure for preventing shear failures was calculated by using the Mohr-Coulomb failure criterion and the estimated stress profiles. The results showed a good compliance with failures which have been identified in the caliper and image logs. However, a number of noncompliance is observed in some depth. This is due to the concentration of fractures, collisions between the drill string and the wellbore wall, as well as swab and surge pressures. The stress mode is normal and strike-slip in some depth based on the estimated stress profiles. According to direction of breakouts which is clearly visible in the caliper and image logs, the minimum and maximum horizontal stresses directions were NW-SE and NE-SW, respectively. Thses directions were consistent with the direction of regional stresses in the Zagros belt.

scholarly journals Experimental Investigation of Effects of Vibration upon Elastic and Cohesive Properties of Beds of Wet Sand

1995 ◽  
Vol 2 (5) ◽  
pp. 383-392 ◽  
Author(s):  
S. Alsop ◽  
A. J. Matchett ◽  
J. M. Coulthard
Keyword(s):  
Critical State ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Critical State Model ◽  
State Model ◽  
Cohesive Stress ◽  
Factors Affecting ◽  
Sample Shape ◽  
Particulate Solids ◽  
Percent Moisture

The transmission of sinusoidal vibrations through beds of cohesive particulate solids was measured. Results were interpreted in terms of a critical state model to predict the elastic swelling constant k, and the cohesive stress C. Factorial experimental design was used to identify significant parameters. Factors that affect k include percent moisture, bulk density, sample size, sample shape, the presence of a supporting membrane, and loading order. Factors that affect C include percent moisture and particle size distribution. Factors affecting k were interpreted in terms of their effects upon bed structure and factors affecting C in terms of an equivalent pore water pressure due to capillary and liquid bridge effects. The critical state model was modified to incorporate general relationships between axial and radial strains.

scholarly journals A model of glacial tectonics, applied to the ice­pushed ridges in the Central Netherlands

1985 ◽  
Vol 34 ◽  
pp. 55-74 ◽  
Author(s):  
Dick F. M. van der Wateren
Keyword(s):  
Shear Stress ◽  
The Netherlands ◽  
Stress Field ◽  
Sliding Friction ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Large Degree ◽  
Shear Stresses ◽  
Thrust Sheets ◽  
Basal Shear

During a detailed structural geological and geomorphological survey of ice-pushed ridges around the Gel­derse Vallei (centre of the Netherlands) several questions arose about the origin of these landforms. The Gelderse Vallei is a Saalian glacial basin filled with younger sediments, 40 km long and up to 20 km wide, running NNW-SSE. Thrust sheets which build up the ice-pushed ridges on either side of the valley were transported away from the centre of the basin. They are up to 25 m thick and are pushed to a level about 100 m above the decollement. The thrust sheets, mainly consisting of coarse sand layers, moved as rigid masses, while only the finegrained basal layers deformed by heterogeneous simple shear. Pore water pressure plays an important role by greatly reducing the sliding friction in the decollement layer. Once a glacial thrust sheet is formed, the weight of the upward moving frontal part (the toe) offers a resistance to movement, which can not be overcome by the basal shear stress of the glacier alone. Basal shear stresses in most glaciers are in the order of 0.1 MPa (1 bar) and appear to be incapable of lifting a toe of the size found in most ice-pushed ridges in the Netherlands. The article presents a model of a system ice lobe - substratum, which is to a large degree controlled by gravitational forces. The dilemma may be solved by the concept of the gradient stress field under the marginal area of an ice lobe. This concept was first formulated by Rotnicki (1976). Because ice thickness decreases towards the margin, the substratum is subjected to a decreasing load in the same direction. If the increments of stress difference under a slab of ice in the marginal zone are summed, a gradient stress is arrived at which is di­rected towards the ice edge. An estimate of the forces involved in the static equilibrium around the glacier margin indicates that the contribution by the gradient stress field is sufficient to move the toe. In the model proposed in the article, the energy to move and imbicate glacial thrust sheets around the margins of an ice lobe, is supplied by the continuous flow of ice into the ice lobe. The dimensions of ice­pushed ridges are thus to a high degree functions of the thickness of the ice lobe or icecap. The Gelderse Vallei ice lobe will have been at least 250 m thick to be able to form the ridges. The basal shear stress contributes less to the tectonic transport, the larger the thrust sheets and the high­er the ice-pushed ridges.

scholarly journals Numerical analysis of earthquake response of an ultra-high earth-rockfill dam

2013 ◽  
Vol 1 (3) ◽  
pp. 2319-2351 ◽  
Author(s):  
W. X. Dong ◽  
W. J. Xu ◽  
Y. Z. Yu ◽  
H. Lv
Keyword(s):  
Numerical Analysis ◽  
Stress Field ◽  
Seismic Analysis ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Dynamic Responses ◽  
Economic Damage ◽  
Earth Dams ◽  
Nonlinear Method ◽  
Rockfill Dam

Abstract. Failure of high earth dams under earthquake may cause disastrous economic damage and loss of lives. It is necessary to conduct seismic safety assessment, and numerical analysis is an effective way. Solid-fluid interaction has a significant influence on the dynamic responses of geotechnical materials, which should be considered in the seismic analysis of earth dams. The initial stress field needed for dynamic computation is often obtained from postulation, without considering the effects of early construction and reservoir impounding. In this study, coupled static analyses are conducted to simulate the construction and impounding of an ultra-high earth rockfill dam in China. Then based on the initial static stress field, dynamic response of the dam is studied with fully coupled nonlinear method. Results show that excess pore water pressure accumulates gradually with earthquake and the maximum value occurs at the bottom of core. Acceleration amplification reaches the maximum at the crest as a result of whiplash effect. Horizontal and vertical permanent displacements both reach the maximum values at the dam crest.

Analysis of Fast Drained and Consolidated Mechanism of Soft Soil under Excessive Pore Water Pressure

2012 ◽  
Vol 170-173 ◽  
pp. 909-913
Author(s):  
Qing He Huang ◽  
Yan Hong Zou
Keyword(s):  
Pore Water ◽  
Applied Load ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Drainage Channel ◽  
Seepage Velocity ◽  
Stress Increase ◽  
Horizontal Drainage ◽  
Speed Up

Fast drained and consolidated mechanism of soft soil under excessive pore water pressure generate excessive pore water pressure in the soft soil through the addition of vertical and horizontal drainage channel as well as the applied load, because the drainage path is significantly reduced, the seepage velocity speed up and water excreted rapidly under the excessive pore water pressure, also, the effective stress increase rapidly between the soil particles and accelerate consolidation of soft soil so as to improve the strength of soft soil.

scholarly journals GEODYNAMICS

GEODYNAMICS ◽  
2007 ◽  
Vol 1(6)2007 (1(6)) ◽  
pp. 85-94
Author(s):  
V. V. Furman ◽  
◽  
M. M. Khomiak ◽  
L.N. Khomyak ◽  
◽  
...  
Keyword(s):  
Lateral Displacement ◽  
Water Pressure ◽  
Contact Friction ◽  
Finite Element Models ◽  
Coulomb Failure ◽  
Quasistatic Process ◽  
Coulomb Failure Criterion ◽  
The Right ◽  
Orogenic Belts

We investigate a role of the contact friction in thrusting within the framework of the critical taper theory and according to geological settings for orogenic belts including the Ukrainian Carpathians (in Early Cretaceous time). Finite element models are used to simulate tectonic compression of sedimentary rocks by submerged stage and take into account frictional slipping on the detachment horizon. We assume a simple wedge geometry (rectangular layer 60 km long, 1.5 km thick and 2.5 km deep), plane strain state, quasistatic process and use elastic constitutive relation. Mechanical loads include gravity, water pressure on top and lateral displacement (up to 0.5 km) from the left, whereas the right side is fixed. Numerical results show specific features of the inhomogeneous stress fields for small (0.01-0.5), middle (0.5-0.64), large (0.64—0.8) and overlarge (0.8-1.15) friction coefficients. The magnitude of the tangential contact stress controls the front between sliding and sticking zones. Stress trajectories enable to predict thrust structures using Mohr-Coulomb failure criterion.

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.

Conjectures, Hypotheses, and Theories of Drumlin Formation (In memory of Stanislaw Baranowski)

1981 ◽  
Vol 27 (97) ◽  
pp. 503-505 ◽  
Author(s):  
Ian J. Smalley
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Stress Level ◽  
Critical Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Glacial Till ◽  
Forming Process ◽  
Stress Levels

AbstractRecent investigations have shown that various factors may affect the shear strength of glacial till and that these factors may be involved in the drumlin-forming process. The presence of frozen till in the deforming zone, variation in pore-water pressure in the till, and the occurrence of random patches of dense stony-till texture have been considered. The occurrence of dense stony till may relate to the dilatancy hypothesis and can be considered a likely drumlin-forming factor within the region of critical stress levels. The up-glacier stress level now appears to be the more important, and to provide a sharper division between drumlin-forming and non-drumlin-forming conditions.

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