Increase In Water Pressure Research Articles

Study on the dynamic pore water pressure model of centerline tailings sand based on dynamic triaxial tests

The increase of pore water pressure under a dynamic load is an important reason for the vibration liquefaction of saturated sand. Therefore, studying the dynamic pore water pressure model of tailings sand plays an important role in the seismic liquefaction analysis of tailings ponds. In this paper, the dynamic pore water pressure development characteristics of tailings fine sand and tailings silt in a tailings pond with the centerline method are studied by dynamic triaxial tests. The research results show that the liquefaction dynamic pore pressure ratio of tailings fine sand shows a trend of "rising–smooth–rising" with increasing vibration frequency ratio, and the liquefaction dynamic pore-pressure ratio of tailings silt shows an approximate linear and stable increasing trend. According to the development law of dynamic pore pressure, a new tailings sand pore pressure stress model is proposed in this paper, and the fitting effect is compared with four different pore pressure models, which verifies the applicability of the new model to predict the growth of dynamic pore pressure in tailings and silt.

Application of Mobile-Based Augmented Reality Technology Concepts in Interactive Learning Systems for Liquefaction Phenomena for the Deaf

One of the natural disasters currently happening in Indonesia is an earthquake. An earthquake is a condition where the earth shakes due to volcanic activity and collisions due to the movement of the earth's plates. Earthquake activity causes many problems. One of them is liquefaction. Liquefaction is an event that indicates a loss of soil shear strength due to an increase in pore water pressure. This occurs because the earthquake load occurs so quickly and briefly. Liquefaction is an illustration of the effect of an earthquake so that the soil layer loses its strength. The public rarely knows the phenomenon of earthquakes and liquefaction. Not many people know how the process of the movement of the earth is the forerunner of earthquakes, especially people with hearing impairments. They could only feel an earthquake. Therefore, there is a need for education that can be conveyed to the public. Educational techniques in the virtual form will be a special attraction for people, especially people who are deaf or hard of hearing. Augmented Reality (AR) technology is a technology where virtual objects and real objects are combined. The AR is used to create virtual and interactive learning media. This study produced an application as a learning media that utilizes AR technology with the Marker Based Tracking method. The technology was developed using the MDLC (Multimedia Development Life Cycle) method for the learning media to be more interactive. The results of the tests concluded that the application could be used as an interactive learning medium to increase knowledge about earthquakes and the effects of liquefaction on the community.

Numerical investigation of variable-mass seepage mechanism of broken rock mass in faults

The continuous migration and loss of small particles in fractured rock mass with water flow is the main cause of water inrush in fault zones. In this study, a fluid–solid coupling model for fault zone was established to study the complex coupling between the groundwater seepage and migration of broken rock mass, and reveal the mechanism of erosion-induced water inrush. The rock skeleton and broken rock mass in the fault zone were modelled by large skeleton particles and small filling particles, respectively, in 3D particle flow software while the fluid flow through the fault was modelled by the built-in computational fluid dynamics module. The numerical results show that: (1) with the increase of water pressure, the loss of filling particles increases continuously, and the whole seepage process can be divided into three stages: slow seepage, abrupt seepage and steady seepage, (2) the mass loss, porosity and permeability first increase slowly, then increase rapidly, and finally tend to be stable, (3) higher fine particle content are more likely to cause structural instability due to mass loss, thus increases the risk of water inrush and mud outburst.

The study of newly established approaches to control soil liquefaction: An overview

As a result, continuous decrease in effective stress and increase in pore water pressure, liquefaction that is triggered by earthquakes can harm the foundation of existing building and other structures and cause large financial losses. Numerous earlier studies looked into ways to control sand liquefaction while lowering costs, negative effects on the ecology, and other related problems. Recent advances in Materials science and interdisciplinary methods have made novel materials readily available that can be used to increase liquefaction resistance and enable other liquefaction prevention techniques. studies into the recently studies into the recently technologies are examined in this work in order to bring up some crucial issues and inspire additional study and discussion. To have a firm understanding of the development of liquefaction resistance, The review first looked at and discussed the qualities of the recently created approaches, the efficiency of the mitigation mechanism, potential control difficulties. The relevance and homogeneity in soil together varying sizes, as well as potential disruption to surrounding structures, are then explored. Additionally, a brief description of the probable cost and length of the site construction mitigation measures is provided. The reader will thoroughly comprehend the liquefaction mitigation research trend after reading this review; they will also be able to further investigate new approaches and techniques that may be efficient, simple to implement on-site, inexpensive, environmentally amiable, and extremely durable. This research suggests long-term in-depth studies on quantitative cost evaluation, length time, and mitigation effectiveness.

The dynamic characteristics of saturated remolded loess under cyclic load

Due to the joint development characteristic and macropore structure of loess, it is easy to cause structure collapse under earthquake or artificial vibration. The study on the loess disaster effect and its mechanism under earthquake action is insufficient due to its complexity. Hence, to study the deformation and mechanical properties more accurately, the dynamic characteristics of saturated remolded loess under cyclic dynamic load were tested using a GDS dynamic triaxial instrument in this paper. The test results show that strain and pore water pressure increase gradually at different rates with the development of vibration, and there is an obvious inflection point in the time-history curve of both. When the number of vibrations (N) exceeds this point, the strain increases rapidly, and pore water pressure tends to be stable. Under the action of large amplitude and low-frequency dynamic load, the strain and pore water pressure increase rapidly with fewer vibrations and the deviator stress (q) decreases rapidly, while the sample achieves damage faster with the increase of amplitude. During the application of a dynamic load, the effective stress (p) gradually decreases and its rate of change slows down. Finally, when the saturated remolded loess is subjected to a constant-amplitude dynamic load, the combination of large amplitude and low frequency leads to the failure of the sample in the shortest time.

Towards a predictive model of the shear strength behaviour of fibre reinforced clay

Randomly distributed fibres can be a potential reinforcement material to improve the shear strength of soils. However, gaps remain in experimental research and predictive modelling of the shear strength of fibre reinforced high plasticity clays. In light of this, a series of consolidated undrained triaxial tests were carried out to investigate the shear strength behaviour of London Clay reinforced with 0.3% to 0.9% polypropylene fibre by dry weight of soil. The effects of fibre length and confining pressure were also considered. The results indicated that fibres significantly improve the shear strength of soil. The shear strength improvement increases with the fibre length, but decreases with increasing confining pressure at test scale. The addition of fibres also leads to the increase in the pore water pressure of soil. Using these and other experimental results, a predictive model was developed based on the concept of equivalent confining stress. The model is able to describe the deviator stress-strain and pore water pressure-strain relationship of fibre reinforced clay and can be used efficiently to predict the shear strength of fibre reinforced clay subjected to different confining pressures.

Behaviour of Axial Bearing Pile under Liquefaction Condition Based on Empirical and 3D Numerical Simulation

The liquefaction phenomenon affects to bearing capacity losses of building foundations. When liquefaction occurs in loose sandy soils, the pore water pressure increases, and the effective soil stress decreases significantly. This study deals with the bored pile foundation of Kretek 2 bridge, which is located in an area with high vulnerability to liquefaction. The study aimed to estimate the axial load-bearing capacity of the foundation of Kretek 2 bridge under liquefaction conditions. This study compares the results of calculations using empirical approaches with 3D numerical simulation modeling using MIDAS GTS NX. The results of the empirical calculations show a reduction in the axial bearing capacity of the foundation under liquefaction conditions of 2.88-8.16% and 2.63-7.23% for the approach of Reese and Wright 1977 and O’Neill and Reese 1989, respectively. While using 3D numerical modeling, although there was a decrease in skin resistance, there was no significant decrease in the total bearing capacity, and it was still above the design load (3632.563456.02 kN). Based on these results, the bearing capacity of the installed Kretek 2 Bridge foundation is still capable of receiving loads during static and liquefaction states.

Failure Mechanism of a Rainfall-Triggered Landslide in Clay Slopes

In December 2013, a portion of a large and deep ancient landslide on the southern slope of the Montescaglioso town (Basilicata, Southern Italy) was abruptly reactivated, as a consequence of exceptional rainfall events, causing relevant damages to structures and infrastructures. The sliding surface is supposed to be located within a thick deposit of Pleistocene stiff clays overlain by dislocated blocks of calcarenites and cemented conglomerates. This paper discusses the research carried out to investigate the failure mechanism that occurred during the landslide event and the factors that controlled the reactivation. To this purpose, geological and geomorphological analyses were first proposed, followed by a back-analysis of the landslide process, performed via limit equilibrium calculations implementing time-dependent pore water pressure distributions derived from transient seepage finite element analyses. Furthermore, the overall landslide mechanism was investigated through a three-dimensional finite element analysis, built using the monitoring campaign carried out in the post-failure stage and calibrated according to the in situ failure mechanism evidence. Both the limit equilibrium and finite element analyses provide results in good agreement with the geomorphological evidence, further allowing us to recognize the effects of rainfall infiltration in the increase of pore water pressure along the sliding surface and the variation of the stress–strain state leading to failure occurrence.

Vertical Capillary Barriers and Wick Drains to Mitigate the Rain-induced Slope Failures: Numerical Analysis

Slope failures are catastrophic when they suddenly occur in human habitats. The stability of slopes gradually diminishes with heavy rainfall due to the increase in pore water pressure; subsequently, the shear strength of the slope soil decreases. The effect of rainwater on the instability of slopes was studied in this research with respect to factor of safety values. Accordingly, finite element analysis and limit equilibrium analysis were conducted using a 2D model of a soil slope in SEEP/W and SLOPE/W programs to observe the responses of the slope soil profile under heavy rainfall. Movement of the wetting front and the fluctuation of the groundwater table were studied to develop a drainage mechanism, thereby to control the effect of infiltrated rainwater on slope failure. A conceptual method was introduced in this study by developing a numerical model with an effective drainage system which consists of vertical capillary barriers with combination of horizontal wick drains in a cascade manner in the slope. This method exhibited high stability of the slopes even with continuous rainfall for number of days, therefore, applicable as a sustainable prevention method of slope failures.

Sustainable or Not for Water Consumption after Implementing CCS in China’s Coal-Fired Power Plants for Achieving 2 °C Target

The shortage of urban water caused by CCS retrofitting over coal-fired power plants has become an emerging issue, especially in China where water resources are scarce. In this study, we quantified the impact of CCS retrofitting on water resources and analyzed the increased water pressures due to CCS retrofits in 234 cities of China. We identified 54 cities with 165 power plants that would face water pressure due to CCS retrofitting for achieving 2 °C targets. The results show that the average water withdrawal and water consumption of power plants in 234 cities would increase by 1.63 times and 1.49 times, respectively, involving 480 million people in China. The ratio of freshwater withdrawal to available water (WTA) and the ratio of freshwater consumption to available water (CTA) at the city-level increased by 0.2 and 0.06 under 2 °C constraints respectively, involving a population of 84 million people. Moreover, CO2-EWR technology does not provide relief from urban water stress. This paper assesses the water demand for carbon capture technologies and provides a basis for siting future large-scale deployment of carbon capture technologies in China.

Study on the Safety Thickness of Rock Strata for Outburst Prevention in Deep Tunnel Based on Numerical Modeling and Backpropagation Neural Network

Water inrush and mud inrush pose a serious threat to safe construction in underground engineering, but it is very difficult to determine the safe distance of outburst prevention rock mass. Based on deep-buried tunnel engineering, this paper proposes a method to determine the safe distance from water inrush disaster between the tunnel and the fault fracture zone. This method combines numerical modeling and backpropagation (BP) neural network. By means of numerical simulation, the internal influence law of the water pressure, lateral pressure coefficient, fault fracture zone width, and tunnel burial depth on the surrounding rock is analyzed. The evolution law of the minimum safe strata thickness under a single variable and the correlation degree between minimum safe strata thickness and various disaster factors are revealed. Based on the BP neural network analysis of the simulation results and the measured data of Wulaofeng Tunnel, the calculated values of safe strata thicknesses of fault fracture zone (F10) were determined. The results show that the thickness of the safe rock strata increases with increasing water pressure, lateral pressure coefficient, fault fracture zone width, and tunnel burial depth. The minimum safe thickness of F10 of the tunnel ranges from 7.1 m to 7.4 m, and 10 m is reserved in the actual project. The calculated results are consistent with the reserved thickness value in the construction. This conclusion can provide a reference for similar projects.

Study on the Aperture Evolution Law and Seepage Mechanism of 3D Rough Structure Plane under the Shear–Seepage Coupling Test

In order to study the mechanical characteristics and seepage mechanism of the structural plane under the action of seepage water pressure, the shear–seepage coupling test was carried out. It was found that with an increase in seepage water pressure, the peak shear strength, and shear stiffness of the structural plane decreased, while the peak dilatancy angle, average dilatancy angle, peak shear displacement, initial flow rate, and peak flow rate increased. The profile JRC and 3D morphology parameters under different Y values increased as seepage water pressure increased, indicating that the wear degree of the structural plane decreased. The contact area, effective aperture, average aperture, and hydraulic aperture of the structural plane all increased in phase with the increase in shear displacement, and they all increased in trend with the increase in seepage water pressure. The distribution and evolution law of the structural plane aperture were analyzed by programming using scanning point cloud data and the normal displacement value of the structure plane. It was concluded that the aperture gradually increased with the increase in seepage water pressure.

Creep Characteristics and Creep Model of Coal Based on Pore Water Pressure

Anthracite in a specific area of Shanxi Province is the subject of this essay’s research. In the creep studies, different porosity intervals and pore water pressures were employed to evaluate the mechanical properties of creep under various test paths. The conventional Burges model was coupled in series with the nonlinear viscous elements and plastic elements. The key parameters in the equation are fitted, and a creep model is created to describe the nonlinear viscosity-elastic-plastic characteristics of coal under the influence of pore water pressure with varying porosities. The creep tests used varied porosity intervals, pore water pressures, and test paths to study the mechanical properties of creep. The conventional Burges model was coupled in series with the nonlinear viscous element and plastic element. To represent the nonlinear viscosity-elastic-plastic properties of coal under the effect of pore water pressure with variable porosities, the main parameters in the equation are fitted, and a creep model is developed. The results show that the porosity and strength of the coal sample are negatively correlated. In comparison to coal samples with a porosity of 5–10%, the uniaxial compressive strength of coal samples with a porosity of 10–15% and 15–20% reduced by 9.6% and 22.3%. Throughout the creep process, instantaneous strain rises with porosity, and changes in pore water pressure and porosity have an effect on instantaneous creep under low-stress loading, resulting in different creep curve starting strain values. The duration from stress loading to the accelerated creep stage in the failure stage and the time from the deceleration creep stage to the accelerated creep stage are both gradually shortened with an increase in porosity and pore water pressure. For regression analysis and parameter identification, a creep constitutive model was developed to describe the creep characteristics of coal samples with varying porosity under varying pore water pressure. The creep parameters of the new constitutive model were obtained, and they could very well reflect the creep characteristics of specimens with varying porosity intervals under the influence of pore water pressure.

An Extended Hydro-Mechanical Coupling Model Based on Smoothed Particle Hydrodynamics for Simulating Crack Propagation in Rocks under Hydraulic and Compressive Loads

A seepage model based on smoothed particle hydrodynamics (SPH) was developed for the seepage simulation of pore water in porous rock mass media. Then, the effectiveness of the seepage model was proved by a two-dimensional seepage benchmark example. Under the framework of SPH based on the total Lagrangian formula, an extended hydro-mechanical coupling model (EHM-TLF-SPH) was proposed to simulate the crack propagation and coalescence process of rock samples with prefabricated flaws under hydraulic and compressive loads. In the SPH program, the Lagrangian kernel was used to approximate the equations of motion of particles. Then, the influence of flaw water pressure on crack propagation and coalescence models of rock samples with single or two parallel prefabricated flaws was studied by two numerical examples. The simulation results agreed well with the test results, verifying the validity and accuracy of the EHM-TLF-SPH model. The results showed that with the increase in flaw water pressure, the crack initiation angle and stress of the wing crack decreased gradually. The crack initiation location of the wing crack moved to the prefabricated flaw tip, while the crack initiation location of the shear crack was far away from the prefabricated flaw tip. In addition, the influence of the permeability coefficient and flaw water pressure on the osmotic pressure was also investigated, which revealed the fracturing mechanism of hydraulic cracking engineering.

Experimental study on dynamic behavior of polyacrylamide-reinforced tailings.

Earthquakes are a significant factor that contributes to tailings dam failure. Generally, the seismic stability of a tailings dam can be increased by improving the dynamic properties of tailings. The dynamic properties of tailings can be improved effectively using polymers. In this study, the dynamic properties of polyacrylamide-reinforced tailings were investigated via a sequence of dynamic triaxial tests. The content of polyacrylamide in the test sample was 0.3%. Test results show that the cyclic liquefaction resistance, initial dynamic shear modulus, dynamic shear modulus, and dynamic shear modulus ratio of polyacrylamide-reinforced tailings were slightly greater than those of unreinforced tailings. The damping ratio of polyacrylamide-reinforced tailings was lower than that of unreinforced tailings when the dynamic shear strain exceeded 0.038%. The increase in the dynamic pore water pressure of polyacrylamide-reinforced tailings during cyclic loading decelerated significantly compared with that of unreinforced tailings. The revised Zeng model can effectively described the changes in dynamic pore-water pressure of unreinforced and polyacrylamide-reinforced tailings. The polyacrylamide can improve the structural stability of the tailings specimen and also improve the dynamic properties of the tailings, thereby enhancing the seismic stability of the tailings dam.

Evaluation of Liquefaction Potential based on Cone Penetration Test (CPT) and Semi-empirical Methods

The phenomenon of soil liquefaction can be an induced effect of earthquake shaking where the saturated soil loses some or all of its bearing capacity and stiffness. Likewise, the increase of water pressure in the soil pores under the seismic wave causes a decrease of the shear strength. As a result, the soil becomes liquefied and susceptible to producing permanent deformations. The phenomenon of liquefaction is generally unpredictable, and neglecting it can influence the stability of structures and infrastructure foundations. Since the 1964 Alaska and Niigata earthquakes, more research works have been conducted to assess land liquefaction vulnerability. This study is undertaken in this field, whose objective, on the one hand, is to signal the phenomenon of liquefaction in the north of Morocco as a geo-technical part known for its instability and, on the other hand, to study the semi-empirical methods to adequately evaluate the liquefaction potential while specifying the most appropriate method for our case study. Similarly, the study is based on data derived from experimental results of in-situ tests applied to the embankment crossing the valley of "Oued Gharifa" on a high-speed rail line section from KP 228+400 to KP 229+375. Moreover, this research aims to show and discuss the evaluation of liquefaction potential of the experimental results of the CPT (cone penetration test) using three semi-empirical methods, namely the Juang method, the Olsen method, and the Robertson method. In doing so, we are going to compare the application results of the three semi-empirical methods in light of evaluating the liquefaction likelihood of the studied area, taking into account the nature of the soil, the variation of the safety coefficient, and the liquefaction potential for each method as well. Doi: 10.28991/CEJ-2023-09-02-013 Full Text: PDF

Numerical modeling of high-temperature melt droplet interaction with water

Three-dimensional numerical simulations are performed for the interaction of a hot melt droplet with water. Three-phase melt-water–vapor flows are described by the Volume-of-Fluid (VOF) model implemented in OpenFOAM software. In the calculations, initially non-moving and moving melt droplets were considered. Interaction was triggered by sharp increase in water pressure, leading to collapse of the vapor film. It is shown that melt droplet motion with respect to water affects the fragmentation mechanism. For a non-moving droplet, symmetrical collapse occurs, followed by melt surface perturbation and ejection of small melt jets. The estimated diameter of vapor bubble agrees with experimental observations on single droplet steam explosions. For moving droplets, asymmetric vapor bubble collapse generates a high-speed cumulative water jet penetrating into the droplet and fragmenting it. The effect of initial droplet velocity is investigated, and comparison of melt droplet shapes and surface areas for moving and non-moving droplets is presented.

The effect of heterogeneities and small cavities on levee failures: The case study of the Panaro levee breach (Italy) on 6 December 2020

AbstractThis article discusses the levee failure that occurred on 6 December 2020 at Castelfranco Emilia, near Modena (Italy), showing that it cannot be explained without assuming the presence of local heterogeneities or a small cavity. The possible presence of these defects is supported by evidence derived from historical data and site observations. Fully coupled hydromechanical finite element simulations prove that the river embankment assumed without any deficiency had a sufficient level of safety for the considered event, thus it is necessary to hypothesize the presence of a local defect. The presence of a small cavity, in hydraulic communication with the river and buried at shallow depth, is assumed. This could be, for example, a new den, an old animal burrow repaired only partially, or a rotten plant root. Numerical analysis shows that the increase in water pressure within the cavity can trigger local failure of the landside slope, thus starting concentrated erosion. In highly erodible soils, this mechanism can lead very rapidly to the opening of the breach. A new analytical expression for the factor of safety of the soil wedge between the cavity and the surface is proposed. This approach is very simple and easily applicable, for example, to the assessment of levee vulnerability to animal burrows at a large scale. The results of the study are relevant for the management of water retaining structures.

Could Hydraulic Fracturing Take Place for Asphalt Core in Embankment Dams through Possible Cracks in the Core?

Hydraulic asphalt concrete is virtually impervious. Hydraulic fracturing due to the generation of pore water pressure can be generally excluded for asphalt facings and asphalt cores in embankment dams. However, when some cracks and/or large voids exist in the asphalt core in dams, hydraulic fracturing could take place during reservoir impounding. Cracks and/or large voids may be caused by either earthquake shaking, large differential settlements during construction and operation, or poor construction quality. Therefore, asphalt specimens with either cracks of different depths or large air porosity were prepared, and a model test apparatus was developed to investigate the possibility of hydraulic fracturing. Model tests were conducted on cylindrical asphalt concrete specimens of 100 mm in diameter and 180 mm in height. The top boundary of the specimens was either prevented (restrained) from moving in the vertical direction or free to move (unrestrained). The model test results for asphalt concrete with cracks under unrestraint conditions were numerically back-analysed. The model test results indicated that the cracks in the asphalt concrete under the restraint conditions could experience an “open–close” progress with increasing water pressure. That suggested that if the asphalt concrete were long, low water pressure would trigger a fracturing through the cracks. Under the unrestraint conditions, low water pressure could cause the asphalt specimens with either cracks or large air porosity to fail. The extensional strains at failure were reduced, and the reductions depended on the magnitude of the crack depth or air porosity. Suggestions are given for designing the asphalt core dams to reduce the possibility of the occurrence of cracks and/or dilations in the core, especially for dams in unfavourable geological and topographical conditions. A specialty contractor is preferable to do the asphalt core job to rule out the possibility of a weak bond between the layers and an air porosity larger than 3.0% in the core.

In-situ experimental study on hydro-borehole technology application to improve the hard coal excavating techniques in coal mine

The hydro-mining technology is considered as a promising method of bituminous coal excavation. The paper presents the results of the in-situ experimental campaign and modelling of hydro-cutting technology application. The proposed innovative technology was tested in terms of the effects of the distance between the outlet of water from the nozzle and a sidewall, pressure of the water jet, as well as the type of a nozzle on hydro-mining effectiveness. The hydro-cutting tests of coal seam performed in the Experimental Mine “Barbara” in Poland proved that the increase in water pressure in the range 20–40 MPa only slightly affects the coal face structure, while high pressure, of 80–100 MPa, has a significant impact on a coal face structure. The experimental results also showed the major effects of operating time as well as the distance of the water jet on the effectiveness of coal face mining.