Theoretical prediction of rutting in flexible pavement subgrades

1992 ◽  
Vol 29 (5) ◽  
pp. 765-778 ◽  
Author(s):  
D. V. Ramsamooj ◽  
R. Piper
Keyword(s):  
Pore Water ◽  
Critical State ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Permanent Deformation ◽  
Flexible Pavement ◽  
Load Test ◽  
Model Parameters ◽  
Silty Clay ◽  
Rate Of Development

The theoretical model for predicting the cyclic response of soils is extended to handle the generation and dissipation of pore-water pressures and to predict the rutting of the subgrade of a flexible pavement. The model utilizes multiyield surfaces and the concepts of critical state mechanics to predict the permanent deformation of the subgrade under vehicular loading. The theoretical solution also considers the effects of the drainage characteristics of the subgrade soil on the rate of development of the permanent deformation. Experimental verification of the model concepts are presented for a drained cyclic load test on Ottawa sand and for undrained cyclic loading on Newfield clay using published experimental data. An illustrative example is given for the prediction of rutting in a silty clay subgrade. The model parameters for the silty clay are obtained from triaxial and consolidation tests. These parameters are then put into a computer program that determines the rut depth, pore-water pressure, and the ratio of the vertical deformation and the rut depth as functions of the number of vehicular loads for a flexible pavement for various conditions of drainage ranging from undrained to fully drained. The role of the coefficient of consolidation of the subgrade in controlling the rate of development of the rut depth is highlighted. Key words : critical state soil mechanics, multiyield surfaces, rutting, silty clay subgrade, drainage, vehicular loading.

scholarly journals Numerical Simulation of Seepage and Deformation in Excavation of a Deep Foundation Pit under Water-Rich Fractured Intrusive Rock

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Changfeng Yuan ◽  
Zhenhui Hu ◽  
Zhen Zhu ◽  
Zijin Yuan ◽  
Yanxiang Fan ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Inrush ◽  
Risk Level ◽  
Silty Clay ◽  
Deep Foundation ◽  
Foundation Pit ◽  
Deep Foundation Pit

Water is one of the major risk sources in the excavation of deep-large foundation pits in a water-rich area. The presence of intrusive broken diorite porphyrite in the stratum aggravates the risk level of deep foundation pits. Based on a geological survey report and design documents of parameter information, MIDAS/GTS software was used to perform the numerical simulation of an engineering example of a deep foundation pit project of ultradeep and water-rich intrusion into the broken rock station of subway line 4 in a city. The simulation results show the characteristics of seepage path evolution, seepage aggregation areas and points, and the effect of seepage on the deformation of a deep foundation pit during the whole construction of this deep foundation pit. The results show that with the precipitation-excavation of the deep foundation pit, the pore water pressure at the bottom of the foundation pit follows a distribution of three “concave” shapes. High-permeability pressure zones are found around the foundation pit, intruding broken diorite porphyrite zones, and middle coarse sand zones. With further excavation of the foundation pit, the seepage pressure in the middle part of the foundation pit gradually decreases, and the two “concave” distributions in the middle gradually merge together. After excavation to the bottom of the pit, the pore water pressure at the bottom is distributed in two asymmetrical “concave” shapes, and the maximum peak of pore water pressure is found at the intrusion of fractured porphyrites prone to water inrush. The four corners of the foundation pit are prone to form seepage accumulation zones; therefore, suffosion and piping zones are formed. The surface settlement caused by excavation is found to be the largest along the longitudinal axis of the deep foundation pit, whereas the largest deformation is found near the foundation pit side in the horizontal axis direction of the foundation pit. With the excavation of the deep foundation pit, the diaphragm wall converges to the foundation pit with the maximum deformation reaching about 25 mm. After the first precipitation-excavation of the deep foundation pit to the silty clay and the bottom of the pit with the largest uplift, with further precipitation-excavation of the deep foundation pit, the uplift at the bottom of the deep foundation pit changes only slightly.

scholarly journals Pore water pressure responses of saturated sand and clay under undrained cyclic shearing

2021 ◽  
Author(s):  
An ◽  
Hiroshi ◽  
Nhan ◽  
Nhan ◽  
Tien ◽  
...  
Keyword(s):  
Shear Strain ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Silty Clay ◽  
Shear Tests ◽  
Sand Liquefaction ◽  
Cyclic Shear ◽  
Wide Range ◽  
Number Of Cycles

In this study, changes in the pore water pressure were observed for saturated specimens of a loose fined-grain sand (Nam O sand) and a soft silty clay (Hue clay) subjected to undrained cyclic shearing with different testing conditions. The cyclic shear tests were run for relatively wide range of shear strain amplitude (g = 0.05%-2%), different cycle numbers (n = 10, 50, 150 and 200) and various shear directions (uni-direction and two-direction with phase difference of q = 0o, 45o and 90o). It is indicated from the experimental results that under the same cyclic shearing condition, the pore water pressure accumulation in Hue clay is at a slower rate, suggesting a higher cyclic shear resistance of Hue clay than that of Nam O sand. Liquefaction is reached easily in nominally 50% relative density specimens of Nam O sand when g ³ 0.4%, meanwhile soft specimen of Hue clay is not liquefied regardless of the cyclic shearing conditions used in this study. The threshold number of cycles for the pore water pressure generation generally decreases with g meanwhile, the threshold cumulative shear strain for such a property mostly approaches 0.1%. In addition, by using this new strain path parameter, it becomes more advantageous when evaluating the pore water pressure accumulation in Nam O sand and Hue clay subjected to undrained uni-directional and two-directional cyclic shears.

Investigation on the Effects of Freeze-Thaw Action on the Pore Water Pressure Variations of Soils

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Lianhai Zhang ◽  
Wei Ma ◽  
Chengsong Yang
Keyword(s):  
Pore Water ◽  
Soil Type ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Great Influence ◽  
Frozen Soil ◽  
Silty Clay ◽  
Freeze Thaw ◽  
Soil Microstructure ◽  
Thaw Cycle

Freeze-thaw action changes soil microstructure and thus has a great influence on physical and mechanical properties of soils, which is closely correlated to pore water pressure (PWP). Herein, the PWPs of sandy soil and silty clay were measured in laboratory during freeze-thaw cycles (FTC). Experimental results showed that PWP was influenced by temperature, freeze-thaw history (i.e., number of freeze-thaw cycle), soil type and others. The PWP experienced a periodical change as temperatures periodically changes during the FTC testing, the PWP decreased during freezing and increased during thawing. Soil type has a slight influence on the variation of PWP, both in character and extent. A theoretical analysis of PWP in frozen soil was given to explain the PWP changes. In addition, the PWP depression during freezing was a major driving force for water migration. The PWP variations are highly relevant to the changes in soil microstructure such as soil particle (grain size composition and mineral composition), pore structure, and particle arrangement, which will be the focus of further research.

scholarly journals Integrating local pore water pressure monitoring in territorial early warning systems for weather-induced landslides

Landslides ◽  
2021 ◽  
Author(s):  
Gaetano Pecoraro ◽  
Michele Calvello
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Model Performance ◽  
Early Warning Systems ◽  
Model Parameters ◽  
Pressure Measurements ◽  
Warning Systems ◽  
Warning Model ◽  
Statistical Indicators

AbstractA methodology designed to integrate widespread meteorological monitoring and pore water pressure measurements is proposed. The procedure is tested in 30 hydrological basins highly susceptible to weather-induced landslides in Norway. The following data are used: a catalog of 125 weather-induced landslides in soils registered between January 2013 and June 2017, widespread meteorological monitoring data employed in a territorial warning model, and pore water pressure measurements retrieved from boreholes installed for a variety of geotechnical projects. The territorial warning model is initially applied to identify the warning events and the correspondent warning level in the test areas over the analysis period. Afterwards, a method for assessing the territorial warning events by analyzing the trends of the monitored pore water pressures is proposed. Finally, an augmented territorial warning model is calibrated and validated using statistical indicators widely adopted in literature. The analysis of the results reveals a satisfactory correspondence between days with landslides and the warning levels provided by the augmented territorial warning model. A final comparison between the results of the model calibration and the model validation highlighted the consistency of the model performance, once the three model parameters are adequately set.

Test Study of Pore Water Pressure during Dynamic Compaction at the Subgrade of Highway in the Yellow River Flood Area

2011 ◽  
Vol 374-377 ◽  
pp. 436-439
Author(s):  
Kai Yao ◽  
Zhan Yong Yao ◽  
Xiu Guang Song ◽  
Qing Sen Shang
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Yellow River ◽  
Water Pressure ◽  
Dynamic Compaction ◽  
The Yellow River ◽  
Silty Clay ◽  
Excess Pore Water Pressure ◽  
River Flood ◽  
Excess Pore

The Yellow River flood area mainly consisted of silt and silty clay. Water level observing holes and pore water pressure gauges were embedded in the test section. The observation results showed that: The pore water pressure of 3m and 5m grew slowly at the beginning. With the increase of ramming strike and the total ramming strike energy, the fourth hit pore water pressure mutated and then grew slowly. The pore water pressure of 7m and 9m grew slowly all the time. Because of the well point dewatering, the excess pore water pressure dissipated very soon. 70~75% of the excess pore water pressure of the first pass dissipated 3 hours after ramming strike, then the excess pore water pressure dissipated slowly. The excess pore water pressure of 3m and 5m grew significantly, so the effective reinforcing depth of dynamic compaction was 5m.

scholarly journals Effect of Rainfall Pattern and Crack on the Stability of a Red Bed Slope: A Case Study in Yunnan Province

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Zhenping Zhang ◽  
Xiaodong Fu ◽  
Qian Sheng ◽  
Dawei Yin ◽  
Yongqiang Zhou ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Pore Water ◽  
Yunnan Province ◽  
Pore Water Pressure ◽  
Limit Equilibrium ◽  
Water Pressure ◽  
Small Scale ◽  
Silty Clay ◽  
The Stability ◽  
Red Bed

Red bed slopes in the southwest of China are associated with a grant number of geological hazards, such as landslides, mud-rock flows, and rock blocks falling, which are vital problems in geotechnical engineering. The damage can be induced or triggered due to a series of human and environmental activities, such as excavation, concentrated or long-term rainfall, earthquake, and fluctuation of groundwater level. According to the field observations and geological exploration results, a small-scale landslide was observed on January 10, 2016, after excavation along XiaoMo highway in Yunnan Province. A numerical model in actual size using GeoStudio software based on this typical red bed engineering slope was established in this study. Back analyses and laboratory tests were used to obtain the mechanical parameters of the geomaterial inside the slope. The historic rainfall data of Mengla County from July to September in 2016 was utilized as the flux boundary in analyzing the seepage variation features and the stability of the engineering slope in the rainy season. One major tension crack was set in the shallow region of the silty clay according to the geology survey to perform the disturbance of excavation on the geomorphology of the slope. Attempts were made to establish the anisotropic permeability of the crack induced by the complex fillings, and differences in the hydraulic response between the cracking and completed slope during the rainfall process were discussed. The result shows that the factor of safety of the slope without crack before the rainfall is 1.076, and the slope is considered in the state of the critical limit equilibrium, which is in accordance with the previous state of the slope under real conditions. The pore water pressure variations of the monitor points in the shallow region of the completed slope present close compliance with the rainfall intensity subjected to different rainfall patterns, which also controls the distribution of the plastic zone in the slope after rainfall. The comparisons in the seepage field and plastic zone between the cracking and completed slope reveal that the crack can shorten the infiltration path effectively, and the higher the permeability coefficient in the vertical direction is, the larger the pore water pressure increasing zone is and the higher the underground water level is, which should be paid more attention in highway constructions.

A conceptual model for clay soils subjected to negative pore-water pressures

1995 ◽  
Vol 32 (5) ◽  
pp. 905-912 ◽  
Author(s):  
E.J. Murray ◽  
J.D. Geddes
Keyword(s):  
Conceptual Model ◽  
Pore Water ◽  
Volume Change ◽  
Critical State ◽  
Pore Water Pressure ◽  
Soil Mechanics ◽  
Water Pressure ◽  
Complex Problem ◽  
Clay Soils ◽  
Pore Water Pressures

Understanding and predicting the volume change behaviour of soils subjected to negative pore-water pressures presents a complex problem that requires a sound theoretical model matched to experimental evidence. A complete model must cover both saturated and unsaturated behaviour and relate stress levels to pore-water pressures and volume changes. A conceptual model for clay soils is presented which employs the principles of critical state soil mechanics. In developing the model, consideration is given to negative pore-water pressures arising as a result of the independent response to reductions in water content and reductions in confining stresses. In this way the limits of the conceptual model are defined. Key words : suction, negative pore-water pressure, volume change, unsaturated soil, critical state.

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