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Effective stress concepts
Published in Buddhima Indraratna, Ana Heitor, Jayan S. Vinod, Geotechnical Problems and Solutions, 2020
Buddhima Indraratna, Ana Heitor, Jayan S. Vinod
The pore water pressure is one of the key parameters that governs the behavior of soil. The evaluation of pore water pressure is critical for two main conditions, i.e. static (no flow) and seepage (water flow). In this chapter, the focus is on the static conditions, whereas seepage is covered in Chapter 4.
Application of a model for mitigation against liquefaction occurrence
Published in Kosta Talaganov, Gunther Schmid, Computational Structural Dynamics, 2020
V. Sesov, K. Talaganov, I. Towhata, N. Harada
Large deformation of soils can be prevented by the following measures: preventing the generation of excess pore water pressure (soil densification, replacement by more stable soils);immediate dissipation of excess pore pressure (installation of drains);reduction of cyclic strain (solidification);constraint of residual strain.
Measuring hydraulic properties for unsaturated soils with unsteady method
Published in H. Rahardjo, D.G. Toll, E.C. Leong, Unsaturated Soils for Asia, 2020
T. Sugii, K. Yamada, M. Uemura
In the original instantaneous profile method, many sensors are used to measure volumetric water content and water pore pressure. Watson (1966) used RI sensors (using gamma-ray), to measure water content. Instead of RI sensor, recently, FDR (Frequency Domain Reflectometry (Topp et al. 1988)), ADR (Amplitude Domain Reflectometry (Gaskin et al. 1996)) are used for moisture measurement. Their sensors can accurately measure soil moisture easily and safely. Our method uses an ADR sensor to measure the moisture of soils, and a micro tensiometer to measure pore water pressure. To measure the amount of drainage over time, a load cell is used. In the case of sandy soils, pore water pressure is controlled by changing the elevation of the drainage tank (suction method). Figure 4 shows the experiment apparatus in this study, in which a sample cell unit that includes container filter is attached to the bottom of the sample specimen. The load cell can measure to an accuracy of 0.1g. When air pressure is necessary, air pressure is supplied from the top of the sample cell. The data logger and personal computer record the measured data of pore water pressure, volumetric water content, supplied pressure and amount of drainage over time. This study used a wire mesh filter and a glass filter.
Hill slope stability examination along Lower Tons valley, Garhwal Himalayas, India
Published in Geomatics, Natural Hazards and Risk, 2021
Ashutosh Kainthola, Vikram Sharma, Vishnu Himanshu Ratnam Pandey, Tripti Jayal, Mukesh Singh, Abhishek Srivastav, Prakash K. Singh, Prashant K. Champati Ray, Trilok Nath Singh
Large scale slope stability assessment using numerical tools coupled with GIS studies descry the ground reality prevalent in the study area. The study marks the slopes with angle 40° to be stable without considering the effect of rainfall and seismic events, as FOS value is greater than 1 except at one location (in FEM) and three locations (in FDM) out of total 33 locations considered in the present work. However, a rainfall of higher intensity or of longer duration will accumulate a significant amount of pore water pressure, reducing the effective shear strength of the slope mass, and consequently, slopes became more prone to failure. The study further investigates the stability scenario of slopes with slope angle 50°, and results of FEM and FDM indicate that 30.30% and 24.24% locations are prone to landslide events, respectively, out of 33 locations involved in the study (Figure 11). At most of the locations the FOS ascertained through finite difference tools are slightly higher than that of finite element techniques, which follows the findings of Ansari et al. (2021).
Mechanism of thawing
Published in Cogent Engineering, 2020
Amin Zeinali, Tommy Edeskär, Jan Laue
Frozen ground engineering is an important factor in design in cold region areas. When the soil is exposed to freezing temperatures, the soil moisture changes from water to ice, resulting in water volume expansion of 9%. In addition, transfer of external water (due to the suction) from deeper layers to the freezing area occurs constantly. Consequently, the soil heaves (frost heave), depending on the amount of available external water, freezing period condition, and type of the soil. During thawing, due to the released water from accumulated ice lenses, the volume of water in the soil increases. Pore water pressure increases in the soil body, which decreases the stability of the soil. Bearing capacity loss in the pavement may cause load restriction during the spring thaw period. In this paper, we focus on the thawing process in laboratory scale. We have captured the thawing process (phase changes from ice to water) by camera as well.
Dynamic behaviour of saturated sandy soil reinforced with non-woven polypropylene fibre
Published in International Journal of Geotechnical Engineering, 2018
Siavash Manafi Khajeh Pasha, Hemanta Hazarika, Hadi Bahadori, Babloo Chaudhary
Figure 4 shows time histories of the measured accelerations and base excitations of tests L1 and L2. Clear evidence which has been ascertained from past earthquakes (Yoshida 2015) shows that the amplitude of seismic waves tends to intensify due to the soft soil conditions while propagating upward to the ground surface. Rearrangement of soil particles due to the transmission of seismic motion through layers can cause rapid development of excess pore water pressure in the saturated soil. This excess pore water pressure causes a decrease in the shear strength of soil and, as a direct result, leads to decreasing acceleration while it propagates to the soil surface. Under normal conditions, the acceleration should be increased by propagating towards the ground surface, however liquefaction changes this trend.