scholarly journals Analysis of the Mechanical Response of Asphalt Pavement Under Water-Stress Coupling

2021 ◽  
Author(s):  
Kun Wang ◽  
Mingjun Wu ◽  
Peng Hu ◽  
Baoqun Wang
Keyword(s):  
Shear Stress ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Asphalt Pavement ◽  
Water Pressure ◽  
Horizontal Stress ◽  
Vertical Stress ◽  
Shear Stresses ◽  
Vehicle Load ◽  
Asphalt Concrete Pavement

In order to study the mechanism of water damage of an asphalt pavement, the FLAC3D program was adopted to model and analyze the mechanical response of a saturated asphalt pavement under instantaneous vehicle load. The results show that the horizontal stress, vertical stress and shear stress of an asphalt concrete pavement increase with the increase of instantaneous load. The surfaces of asphalt pavement structural layers are most vulnerable to damage. The horizontal stress, vertical stress and shear stress decrease sharply with the instantaneous dynamic load decreasing to zero. The horizontal stress reaches maximum value at the interface between the base and the large stone porous mixture (LSPM) layer, while the maximum vertical and shear stresses occur on the surface layer of the saturated asphalt pavement. The deformation decreases almost linearly from the surface of the asphalt pavement to the subgrade, and the pore water pressure was little influenced by the transient load.

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.

Cyclic tests on high-quality undisturbed block samples of soft marine Norwegian clay

2013 ◽  
Vol 50 (4) ◽  
pp. 400-412 ◽  
Author(s):  
T. Wichtmann ◽  
K.H. Andersen ◽  
M.A. Sjursen ◽  
T. Berre
Keyword(s):  
Shear Stress ◽  
Shear Strain ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Cyclic Strength ◽  
Shear Stresses ◽  
Loading Frequency ◽  
Test Results ◽  
High Quality ◽  
Average Shear

The results of a study with undrained cyclic triaxial and direct simple shear (DSS) tests on high-quality undisturbed samples obtained from large blocks of a soft marine Norwegian clay are presented. Several tests with different average shear stresses, shear stress amplitudes, loading frequencies, and sample geometries have been performed on block samples taken from different depths. In tests with small average shear stresses, failure occurred due to large shear strain amplitudes, while large permanent shear strains were observed in tests with higher average shear stresses. Diagrams quantifying the undrained cyclic strength, permanent shear strain, shear strain amplitude, and permanent pore-water pressure dependent on average shear stress, shear stress amplitude, and number of cycles have been developed based on the test results. The undrained cyclic strength was found strongly dependent on loading frequency. Block samples from shallower depth showed a somewhat higher undrained cyclic strength. No influence of the height-to-diameter ratio of the samples (h/d = 1 and 2 were compared) could be found. A qualitative comparison of the test results with data for standard tube samples is provided.

scholarly journals Mechanical response and pore pressure generation in granular filters subjected to uniaxial cyclic loading

2018 ◽  
Vol 55 (12) ◽  
pp. 1756-1768
Author(s):  
Jahanzaib Israr ◽  
Buddhima Indraratna
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Pore Water ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Axial Strain ◽  
Water Pressure ◽  
Internal Erosion ◽  
Excess Pore Water Pressure ◽  
Excess Pore

This paper presents results from a series of piping tests carried out on a selected range of granular filters under static and cyclic loading conditions. The mechanical response of filters subjected to cyclic loading could be characterized in three distinct phases; namely, (I) pre-shakedown, (II) post-shakedown, and (III) post-critical (i.e., the occurrence of internal erosion). All the permanent geomechanical changes such, as erosion, permeability variations, and axial strain developments, took place during phases I and III, while the specimen response remained purely elastic during phase II. The post-critical occurrence of erosion incurred significant settlement that may not be tolerable for high-speed railway substructures. The analysis revealed that a cyclic load would induce excess pore-water pressure, which, in corroboration with steady seepage forces and agitation due to dynamic loading, could then cause internal erosion of fines from the specimens. The resulting excess pore pressure is a direct function of the axial strain due to cyclic densification, as well as the loading frequency and reduction in permeability. A model based on strain energy is proposed to quantify the excess pore-water pressure, and subsequently validated using current and existing test results from published studies.

scholarly journals Influence of Soil Structure on the Mechanical Response of Soft Soil

2018 ◽  
Vol 38 ◽  
pp. 03027
Author(s):  
Bin Bin Xu
Keyword(s):  
Yield Stress ◽  
Pore Water ◽  
Soil Structure ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Before And After ◽  
Strain Relationship ◽  
Consolidation Behavior

Usually the natural sedimentary soils possess structure more or less, which makes their mechanical response much different from the fully remolded soils. In this paper, the influence of soil structure on the mechanical response such as compressibility, shear, permeability is literately reviewed. It is found that the compressibility and consolidation behavior of structured and remolded soils can be divided clearly before or after the structural yield stress. The stress-strain relationship can be divided into two segments before and after the structural yield stress. Before the yield stress, the curve is elevating and after the yield stress the curve is decreasing. The increasing rate of pore water pressure increases after the soil reached yield stress.

Earthquake-induced deformation analyses of the Upper San Fernando Dam under the 1971 San Fernando Earthquake

2001 ◽  
Vol 38 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Guoxi Wu
Keyword(s):  
Finite Element ◽  
Pore Water ◽  
Effective Stress ◽  
Pore Water Pressure ◽  
Ground Deformation ◽  
Water Pressure ◽  
Soil Liquefaction ◽  
Shear Stresses ◽  
Cyclic Shear ◽  
San Fernando

A nonlinear effective stress finite element approach for dynamic analysis of soil structure is described in the paper. Major features of this approach include the use of a third parameter in the two-parameter hyperbolic stress-strain model, a modified expression for unloading–reloading modulus in the Martin–Finn–Seed pore-water pressure model, and an additional pore-water pressure model based on cyclic shear stress. The additional pore-water pressure model uses the equivalent number of uniform cyclic shear stresses for the assessment of pore-water pressure. Dynamic analyses were then conducted to simulate the seismically induced soil liquefaction and ground deformation of the Upper San Fernando Dam under the 1971 San Fernando Earthquake. The analyses were conducted using the finite element computer program VERSAT. The computed zones of liquefaction and deformation are compared with the measured response and with results obtained by others.Key words: effective stress method, finite element analysis, Upper San Fernando Dam, earthquake deformation, VERSAT.

scholarly journals FUNCTION OF INTERCEPTION, EVAPOTRANSPIRATION AND ROOT REINFORCEMENT OF PLANT ON SLOPE STABILIZATION

2020 ◽  
Vol 15 (1) ◽  
pp. 19-26
Author(s):  
Euthalia Hanggari Sittadewi
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Tree Canopy ◽  
Shear Stresses ◽  
Slope Stabilization ◽  
Root Reinforcement ◽  
Soil Shear Strength ◽  
Positive Effect

The ability of plants to carry out the functions of interception, evapotranspiration and root reinforcement provides an effective and contributes to an increase in slope stability. Canopy has a role in the process of interception related to the reduction of amount the infiltrated water and the rapid fulfilment of soil moisture. Through the evapotranspiration mechanism, plants can reduce pore water pressure in the soil so that the trigger force for landslides can be reduced and the soil will be more stable. The roots mechanically strengthen the soil, through the transfer of shear stresses in the soil into tensile resistance in the roots. Roots also bind soil particles and increase surface roughness, thereby reducing the process of soil displacement or erosion. There is a positive relationship between the density of the tree canopy with the value of rainfall interception, evapotranspiration with a decrease in pore water pressure in the soil and the ability of root anchoring and binding with an increase in soil shear strength, indicating that the function of interception, evapotranspiration and strengthening of plant roots have a positive effect on increasing slope stability. Plants selection that considers the level of interception, the rate of evapotranspiration and root reinforcement by adjusting environmental and slopes conditions will determine the success of slope stabilization efforts by vegetative methods.Keywords : interception, evapotranspiration, root reinforcement, slope stabilization.

scholarly journals Empirical Studies of Ice Sliding

1979 ◽  
Vol 23 (89) ◽  
pp. 157-170 ◽  
Author(s):  
W. F. Budd ◽  
P. L. Keage ◽  
N. A. Blundy
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Sliding Friction ◽  
Normal Load ◽  
Water Pressure ◽  
Empirical Studies ◽  
Shear Stresses ◽  
Friction Characteristic ◽  
Wide Range ◽  
Static Shear

AbstractAn experimental programme has been carried out for studying temperate-ice sliding over rock surfaces with a wide range of roughnesses, for normal and shear stresses comparable to those expected under real ice masses. The limiting static shear stress for acceleration has been found to be directly proportional to the normal load giving a constant limiting coefficient of static friction characteristic of the surface. For a constant applied normal stress N and shear stress τb, well below the limiting static shear, a steady velocity Vb results which increases approximately proportionally to τb and decreases with increasing N and the roughness of the surface. For high normal stress the velocity becomes approximately proportional to the shear stress cubed and inversely proportional to the normal stress. As the shear stress increases acceleration sets in, which, for different roughness and normal loads, tends to occur for a constant value of the product τbVb. For some surfaces at high normal loads this acceleration was retarded by erosion. For constant-applied-velocity tests a steady shear stress resulted, which tended to become constant with high velocities, and which increased with increasing normal stress but with a reduced coefficient of sliding friction. The relevance of the results to the sliding of real ice masses is discussed with particular reference to the importance of the effect of the relative normal stress, above basal water pressure, to the sliding rate.

scholarly journals Study on Dynamic Response Characteristics of Saturated Asphalt Pavement under Multi-Field Coupling

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 959 ◽  
Author(s):  
Yazhen Sun ◽  
Rui Guo ◽  
Lin Gao ◽  
Jinchang Wang ◽  
Xiaochen Wang ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Asphalt Pavement ◽  
Water Pressure ◽  
Moving Load ◽  
Transverse Stress ◽  
Middle Point ◽  
Mechanical Coupling ◽  
Temperature Load

To study the dynamic response of saturated asphalt pavement under moving load and temperature load, 3-D finite element models for asphalt pavements with hydro-mechanical coupling and thermal-hydro-mechanical coupling were built based on the porous media theory and Biot theory. First, the asphalt pavement structure was considered as an ideal saturated fluid–solid biphasic porous medium. Following this, the spatial distribution and the change law of the pore-water pressure with time, the transverse stress, and the vertical displacement response of the asphalt pavement under different speeds, loading times, and temperatures were investigated. The simulation results show that both the curves of the effective stress and the pore-water pressure versus the external loads have similar patterns. The damage of the asphalt membrane is mainly caused by the cyclic effect of positive and negative pore-water pressure. Moreover, the peak value of pore-water pressure is affected by the loading rate and the loading time, and both have positive exponential effects on the pore-water pressure. In addition, the transverse stress of the upper layer pavement is deeply affected by the temperature load, which is more likely to cause as transverse crack in the pavement, resulting in the formation of temperature cracks on the road surface. The vertical stress at the middle point in the upper layer of the saturated asphalt pavement, under the action of the temperature load and the driving load, shows a single peak.

scholarly journals Effect of Clogging on the Permeability of Porous Asphalt Pavement

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Yaolu Ma ◽  
Xianhua Chen ◽  
Yanfen Geng ◽  
Xinlan Zhang
Keyword(s):  
Pore Water ◽  
Evaluation Method ◽  
Pore Water Pressure ◽  
Asphalt Pavement ◽  
Water Pressure ◽  
Asphalt Pavements ◽  
Porous Asphalt ◽  
Capacity Coefficient ◽  
Drainage Capacity ◽  
High Level

The purpose of this paper is to report on the drainage of porous asphalt pavement evaluation method suited for use in analyzing clogging effect. To preliminarily reveal the decrease in permeability caused by clogging of permeable asphalt pavement, an innovative device was proposed to evaluate the anisotropy of permeability influenced by clogging, and the maximum drainage capacity without surface ponding can be obtained when the supplied water was controlled. Then, finite element models for asphalt pavements with hydromechanical coupling were proposed based on porous media theory and Biot’s theory. The variation in pore water pressure was simulated by considering the decrease in voids and the increase in clogging grains. The results indicate that the internally retained water should not be ignored because the semiconnected voids were filled with water rapidly at the beginning of permeability tests. To avoid surface ponding, the drainage capacity coefficient (DCC) can be used to evaluate the maximum drainage capacity (MDC) influenced by clogging. Moreover, the pore water pressure increased due to the reduction in voids and a high level of clogging. In addition, the peak value of pore water pressure is also affected by the upper-layer height of the pavement. Under the action of clogging and driving load, a reasonable thickness of the upper layer and a drainage evaluation should be considered to improve road safety.

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