Effect of rock mass permeability and rock fracture leak-off coefficient on the pore water pressure distribution in a fractured slope

With the increase in shaft depth, the problem of cracks and leakage in single-layer concrete lining in porous water-rich stable rock strata has become increasingly clear, in which case the mechanism of fracturing in shaft lining remains unclear. Considering that the increase in pore water pressure can cause rock mass expansion, this paper presents the concept of hydraulic expansion coefficient. First, a cubic model containing spherical pores is established for studying hydraulic expansion, and the ANSYS numerical simulation, a finite element numerical method, was used for calculating the volume change of the model under the pore water pressure. By means of the multivariate nonlinear regression method, the regression equation of the hydraulic expansion coefficient is obtained. Second, based on the hydraulic expansion effect on the rock mass, an interaction model of pore water pressure–porous rock–shaft lining is established and further solved. Consequently, the mechanism of fracturing in shaft lining caused by high-pressure pore water is revealed. The results show that the hydraulic expansion effect on the surrounding rock increases with its porosity and decreases with its elastic modulus and Poisson’s ratio; the surrounding rock expansion caused by the change in pore water pressure can result in the outer edge of the lining peeling off from the surrounding rock and tensile fracturing at the inner edge. Therefore, the results have a considerable guiding significance for designing shaft lining through porous water-rich rock strata.

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Effect of Wetting-Drying Cycle on the Deformation and Seepage Behaviors of Rock Masses around a Tunnel

Geofluids ◽

10.1155/2020/4237163 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Qingzhen Guo ◽

Haijian Su ◽

Hongwen Jing ◽

Wenxin Zhu

Keyword(s):

Rock Mass ◽

Principal Stress ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Water Inrush ◽

Surrounding Rock ◽

Tunnel Excavation ◽

Cycle Number ◽

Simulation Results

Water inrush caused by the wetting-drying cycle is a difficult problem in tunnel excavation. To investigate the effect of the wetting-drying cycle on the stability of the tunnel surrounding rock, physical experiments and numerical simulations regarding the process of tunnel excavation with different wetting-drying cycle numbers were performed in this study. The evolutions of stress, displacement, and pore water pressure were analyzed. With the increase in cycle number, the pore water pressure, vertical stress, and top-bottom approach of the tunnel surrounding rock increase gradually. And the increasing process could be divided into three stages: slightly increasing stage, slowly increasing stage, and sharply increasing stage, respectively. The failure process of the surrounding rock under the wetting-drying cycle gradually occurs from the roof to side wall, while the baseplate changes slightly. The simulation results showed that the maximum principal stress in the surrounding rock mass of the tunnel increases, while the minimum principal stress decreases. Furthermore, the displacement of the rock mass decreases gradually with the increasing distance from the tunnel surface. By comparing the simulation results with the experimental results, well consistency is shown. The results in this study can provide helpful references for the safe excavation and scientific design of a tunnel under the wetting-drying cycle.

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Laboratory study on response of underwater cohesive sediment to columnar vibration source

Water Quality Research Journal ◽

10.2166/wcc.2018.199 ◽

2018 ◽

Vol 54 (3) ◽

pp. 193-202

Author(s):

Peng Zhao ◽

Feier Chen ◽

Guoliang Yu

Keyword(s):

Pressure Distribution ◽

Experimental Observation ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Near Field ◽

Mechanical Vibration ◽

Cohesive Sediment ◽

Vibration Source ◽

Soil Pressure

Abstract This paper investigates the responses of cohesive sediment to mechanical vibration by experimental observation, containing: (1) the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration to the vibration source; (2) the soil pressure distribution in the near field centered in an artificial columnar vibration source. Under the mechanical vibration with a frequency of 200 Hz and an amplitude of 1.15 mm, the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration of underwater viscous sediment were measured in the sediment of four different depositing conditions. Results of the dynamic soil pressure, dynamic pore water pressure and dynamic acceleration of underwater viscous sediment in the near field responding to artificial vibration source are exhibited and discussed. It is found that, excited by the sinusoidal vibrator, the soil pressure presents a response of statistical sinusoidal fluctuation with the same frequency to the vibration source. In the sediment of lower initial yield stresses, the soil pressure distribution distinctly tends to firstly increase and then decrease with distance. The amplitude of the soil pressure is attenuated exponentially with distance.

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Elastic-Plastic Numerical Analysis of Tunnel Stability Based on the Closest Point Projection Method Considering the Effect of Water Pressure

Mathematical Problems in Engineering ◽

10.1155/2016/2569345 ◽

2016 ◽

Vol 2016 ◽

pp. 1-12 ◽

Cited By ~ 2

Author(s):

Zhan-ping Song ◽

Ten-tian Yang ◽

An-nan Jiang

Keyword(s):

Rock Mass ◽

Numerical Analysis ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Surrounding Rock ◽

Tunnel Stability ◽

Elastic Plastic ◽

Closest Point Projection ◽

Point Projection

To study the tunnel stability at various static water pressures and determine the mechanical properties and deformation behavior of surrounding rock, a modified effective stress formula was introduced into a numerical integration algorithm of elastic-plastic constitutive equation, that is, closest point projection method (CPPM). Taking the effects of water pressure and seepage into account, a CPPM-based formula was derived and a CPPM algorithm based on Drucker-Prager yield criterion considering the effect of pore water pressure was provided. On this basis, a CPPM-based elastic-plastic numerical analysis program considering pore water pressure was developed, which can be applied in the engineering of tunnels and other underground structures. The algorithm can accurately take the effects of groundwater on stability of surrounding rock mass into account and it can show the more pronounced effect of pore water pressure on stress, deformation, and the plastic zone in a tunnel. The stability of water flooding in Fusong tunnel was systematically analyzed using the developed program. The analysis results showed that the existence of groundwater seepage under tunnel construction will give rise to stress redistribution in the surrounding rock mass. Pore water pressure has a significant effect on the surrounding rock mass.

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Pore Water Pressure Distribution and Dissipation During Thaw Consolidation

Transport in Porous Media ◽

10.1007/s11242-016-0782-z ◽

2016 ◽

Vol 116 (2) ◽

pp. 435-451 ◽

Cited By ~ 5

Author(s):

Xiaoliang Yao ◽

Jilin Qi ◽

Mengxin Liu ◽

Fan Yu

Keyword(s):

Pressure Distribution ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Thaw Consolidation

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The Risk of Liquefaction Associated with Water Head Fluctuation in the Low-lying Area of Tokyo

Journal of Civil Engineering and Construction ◽

10.32732/jcec.2019.8.2.41 ◽

2019 ◽

Vol 8 (2) ◽

pp. 41-47

Author(s):

Tomohide Takeyama ◽

Kazuya Honda ◽

Atsushi Iizuka

Keyword(s):

Pressure Distribution ◽

Pore Water ◽

Seismic Analysis ◽

Pore Water Pressure ◽

Water Pressure ◽

Ground Level ◽

Flood Damage ◽

Tokyo Bay ◽

Ground Settlement ◽

Groundwater Head

In the wide area of the eastern part of Tokyo, the ground level is less than mean sea level. This area is more vulnerable to disasters than other areas. If large flood damage such as storm surge should occur in this area, the disaster would be a long-term catastrophe. On the coast of Tokyo Bay, countermeasures have been taken by tide embankments and floodgates. However, considering the damage scale when it occurs, an analysis in this area is very important. In this area, ground settlement occurred and groundwater head dropped because groundwater excessively withdrew by the industrial purpose during the period of economic growth. Currently, the groundwater head recovers and the ground settlement has been subsided. However, due to the groundwater head fluctuation, pore water pressure distribution had been different from hydrostatic pressure distribution. Therefore, in the analysis in this area, it is necessary to consider past groundwater head fluctuation. In this research, the ground settlement and the distribution of pore water pressure are simulated from groundwater level fluctuation over the past 100 years. Then, we conducted the seismic analysis by input the distribution of effective stress calculating from the simulated ground water pressure. The sites analyzed in this research are Tokyo Sea Life Park at the mouth of Arakawa River.

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