scholarly journals Distribution characteristics of seepage field and prediction of water inflow before and after tunnel construction

2018 ◽  
Vol 232 ◽  
pp. 03014
Author(s):  
Ruilang Cao ◽  
Shijie Pang ◽  
Chang Huang ◽  
Chen Chen
Keyword(s):  
Water Pressure ◽  
Three Dimensional ◽  
Soft Rock ◽  
Parallel Line ◽  
Water Inflow ◽  
Distribution Characteristics ◽  
Seepage Field ◽  
Groundwater Environment ◽  
Before And After ◽  
External Water

In the construction of a deep tunnel with rich water and soft rock, accurate evaluations of the distribution characteristics of seepage field and water inflow are important bases for predicting the stability of tunnel surrounding rock and the disturbance state of groundwater environment. This paper used the Flac3D finite difference software seepage module, based on field geological borehole, measured seepage parameters and groundwater level. A three-dimensional numerical model of geological seepage in engineering area was established. The distribution characteristics of groundwater seepage field, the variation law of seepage field before and after tunnel excavation, and the water inflow during construction period were studied. As the tunnel was excavated, the excavated surface became a drainage channel, the isoline of groundwater pressure was changed into parallel non-parallel curve set by the parallel line of the initial seepage field. The nearer the tunnel centre was, the more obvious the variation tendency of groundwater pressure was. Grouting measures were very effective for tunnel water gushing, which not only reduced water inflow, but also effectively reduced the external water pressure of lining. It was infeasible to plug water when blocking the water without grouting and only adjusting the permeability of the lining.

scholarly journals Analysis of Tunnel Water Inrush Considering the Influence of Surrounding Rock Permeability Coefficient by Excavation Disturbance and Ground Stress

2021 ◽  
Vol 11 (8) ◽  
pp. 3645
Author(s):  
Helin Fu ◽  
Pengtao An ◽  
Long Chen ◽  
Guowen Cheng ◽  
Jie Li ◽  
...  
Keyword(s):  
Permeability Coefficient ◽  
Water Pressure ◽  
Water Inrush ◽  
Surrounding Rock ◽  
Water Inflow ◽  
Calculation Error ◽  
External Water Pressure ◽  
Ground Stress ◽  
External Water ◽  
Inflow Prediction

Affected by the coupling of excavation disturbance and ground stress, the heterogeneity of surrounding rock is very common. Presently, treating the permeability coefficient as a fixed value will reduce the prediction accuracy of the water inflow and the external water pressure of the structure, leading to distortion of the prediction results. Aiming at this problem, this paper calculates and analyzes tunnel water inflow when considering the heterogeneity of permeability coefficient of surrounding rock using a theoretical analysis method, and compares with field data, and verifies the rationality of the formula. The research shows that, when the influence of excavation disturbance and ground stress on the permeability coefficient of surrounding rock is ignored, the calculated value of the external water force of the tunnel structure is too small, and the durability and stability of the tunnel are reduced, which is detrimental to the safety of the structure. Considering the heterogeneity of surrounding rock, the calculation error of water inflow can be reduced from 27.3% to 13.2%, which improves the accuracy of water inflow prediction to a certain extent.

scholarly journals Experimental Study on the Reinforcement Mechanism of Segmented Split Grouting in a Soft Filling Medium

Processes ◽  
2018 ◽  
Vol 6 (8) ◽  
pp. 131 ◽  
Author(s):  
Zhipeng Li ◽  
Shucai Li ◽  
Haojie Liu ◽  
Qingsong Zhang ◽  
Yanan Liu
Keyword(s):  
Elastic Modulus ◽  
Permeability Coefficient ◽  
Three Dimensional ◽  
Weighted Average ◽  
Quantitative Relationship ◽  
Uniaxial Compression Test ◽  
Distribution Characteristics ◽  
Reinforcement Mechanism ◽  
Before And After ◽  
Grouting Reinforcement

Subsection split grouting technology can effectively improve the grouting efficiency and homogeneity of grouting in a target reinforcement area. It is therefore necessary to clarify the reinforcement mechanism and characteristics of the soft filling medium under the condition of split grouting. A three-dimensional grouting simulation test of segmented split grouting in a soft filling medium was conducted. The distribution characteristics and thicknesses of the grouting veins were obtained under the condition of segmented grouting. The mechanical mechanism of segmented split grouting reinforcement, based on the distribution characteristics of different grouting veins, was revealed. After grouting, a uniaxial compression test and an indoor permeation test were conducted. Based on the method of the region-weighted average, the corresponding permeability coefficient and the elastic modulus of each splitting-compaction region were obtained. The quantitative relationship between the mechanical properties and the impermeability of the soft filling medium before and after grouting was established. The results revealed that three different types of veins were formed as the distance from the grouting holes increased; namely, skeleton veins, cross-grid grouting veins, and parallel dispersed grouting veins. The thicknesses of the grouting veins decreased gradually, whereas the number of grouting veins increased. Moreover, the strikes of the grouting vein exhibited increased randomness. The reinforcement effect of segmental split grouting on soft filling media was mainly confirmed by the skeleton support and compaction. The elastic modulus of the grouting reinforcement solid increased on average by a factor that was greater than 100, and the permeability coefficient decreased on average by a factor that was greater than 40 in the direction of the parallel grouting vein with the most impermeable solid. The research results may be helpful in the investigation of the split grouting reinforcement mechanism under the condition of segmented grouting.

scholarly journals Stability Analysis of Steel Lining at Pressure Diversion Tunnel Collapse Zone during Operating Period

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Ming Xiao ◽  
Chen Zhao
Keyword(s):  
Large Scale ◽  
Water Pressure ◽  
Concrete Lining ◽  
Seepage Field ◽  
Diversion Tunnel ◽  
Steel Lining ◽  
Internal Water ◽  
External Water Pressure ◽  
External Water ◽  
The Stability

At the collapse zone, the effects of the thickness of the consolidation grouting layer and the water pressure on the steel lining are vital to the stability of steel-lined pressure diversion tunnels. In this paper, a joint element and the load-sharing ratio of the consolidation layer are introduced to investigate the joint load-bearing characteristics of the steel lining and the consolidation layer and to determine a suitable consolidation layer thickness; a coupling method for simulating the hydromechanical interaction of the reinforced concrete lining is adopted to investigate the effect of internal water exosmosis on the seepage field at the collapse zone and to determine the external water pressure on the steel lining. In the case of a steel-lined pressure diversion tunnel, a numerical simulation is implemented to analyse the effect of the thickness of the consolidation layer and the distribution of the seepage field under the influence of internal water exosmosis. The results show that a 10 m thick consolidation layer and the adopted antiseepage measures ensure the stability of the steel lining at the collapse zone under internal and external water pressure. These research results provide a reference for the design of treatment measures for large-scale collapses in steel-lined pressure tunnels.

scholarly journals Assessing Redox Properties of Natural Organic Matters with regard to Electron Exchange Capacity and Redox-Active Functional Groups

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Zhiyuan Xu ◽  
Zhen Yang ◽  
Hongping Wang ◽  
Jie Jiang
Keyword(s):  
Functional Groups ◽  
Three Dimensional ◽  
Weight Fraction ◽  
Exchange Capacity ◽  
Electron Exchange ◽  
Groundwater Environment ◽  
Redox Active ◽  
Redox Capacity ◽  
Before And After ◽  
Reducing Capacity

Redox processes in groundwater play an important role in bioavailability, toxicity, and mobility of redox-active elements and contaminants. A recent study has demonstrated that low-molecular-weight fraction (LMWF) of humic substances with great number of redox-active functional groups (RAFGs) exhibits great reducing capacity. However, whether LMWF of natural organic matter (NOM) exhibits high redox capacity still remains unclear. Therefore, this study extracted Pahokee peat NOM (PPNOM) and Leonardite NOM (LNOM) from soils, and then LMWFs in these NOMs were collected using a dialysis method. Electron exchange capacities (EEC) and RAFGs of LMWF NOMs at different Eh were analyzed using a novel electrochemical method and a three-dimensional excitation emission fluorescence (3DEEM) spectroscopy. We found that the reducing capacity in LMWF PPNOM was approximately 5-6 times higher than the bulk NOM, while only 7.8% LMWF PPNOM was accounted for in the bulk NOM. An increasing in EEC (EAC + EDC, where EAC is the electron accepting capacity and EDC is the electron donating capacity) of LMWF PPNOM and LNOM with Eh reduced from −0.49 V to −0.69 V. Additionally, an obvious increase in fluorescent intensities of quinone-like fluorophores before and after being reduced LMWF LNOM is responsible for high EAC of LMWF LNOM. These findings provide a better understanding of relationship between RAFGs Eh in LMWF of NOM, further helping in predicting and protection of groundwater environment and fate of transformation and transport for redox-active contaminants in groundwater.

Predicting external water pressure and cracking of a tunnel lining by measuring water inflow rate

2018 ◽  
Vol 71 ◽  
pp. 115-125 ◽  
Author(s):  
Yuqi Tan ◽  
John V. Smith ◽  
Chun-Qing Li ◽  
Matthew Currell ◽  
Yufei Wu
Keyword(s):  
Water Pressure ◽  
Tunnel Lining ◽  
Water Inflow ◽  
Inflow Rate ◽  
External Water Pressure ◽  
External Water

scholarly journals Three-Dimensional Numerical Investigation on the Seepage Field and Stability of Soil Slope Subjected to Snowmelt Infiltration

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2729
Author(s):  
Shengyi Cong ◽  
Liang Tang ◽  
Xianzhang Ling ◽  
Wenqiang Xing ◽  
Lin Geng ◽  
...  
Keyword(s):  
High Speed ◽  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Three Dimensional ◽  
Ground Surface ◽  
Degree Of Saturation ◽  
Seepage Field ◽  
High Speed Railway ◽  
Cutting Slope

Cutting slope failures occur frequently along the high-speed railways in Northeast China during the construction due to snowmelt infiltration. This study addresses this issue by applying a three-dimensional numerical model. The influence of the depth of accumulated snow (ds), daily temperature variation (ΔT), and freeze-thaw (F-T) cycles on the seepage field and stability of cutting slopes is discussed. The results demonstrate that water seepage due to snowmelt infiltration primarily extends through the ground surface by about 10 m. The deep-seated instability is likely to occur under a prolonged and highly accumulated infiltration, while shallow failure is associated with intense, short-duration snowmelt infiltration. The maximum degree of saturation (Sr) and pore-water pressure (PWP) values are observed at the slope toe. Increasing ds and ΔT increase the Sr and PWP due to snowmelt infiltration and thereby decreases cutting slope stability. Compared to the ds and ΔT, the F-T cycle is more likely to cause slope failure. In addition, the F-T cycle also induces the reduction of soil strength and the crack propagation. Overall, the conducted study provided useful help toward the process of safer design for cutting slope along the high-speed railway in seasonally cold regions.

Research on Effect of Grouting Circle on Seepage Field of Subsea Tunnel

2012 ◽  
Vol 204-208 ◽  
pp. 1409-1412
Author(s):  
You Wang ◽  
Xing Hua Wang ◽  
Jun Ru Chen
Keyword(s):  
Water Pressure ◽  
Jiaozhou Bay ◽  
Water Quantity ◽  
Seepage Field ◽  
Calculation Results ◽  
Free Drainage ◽  
External Water Pressure ◽  
Subsea Tunnel ◽  
External Water

According to a real project of Jiaozhou Bay subsea tunnel, the effect of grouting circle on the seepage field was discussed. The calculation results showed that the principle of "to block mainly, to emit limitedly" should be taken in the waterproofing and drainage of subsea tunnel. If the grouting circle effect was used on the condition of the same effect of water plugging, the thinner the thickness of grouting circle and the smaller permeability coefficient of grouting circle required. The role of grouting circle was that decreasing the gushing water quantity by means of blocking the seepage paths of groundwater, so as to achieve a smaller discharge could significantly reduce the external water pressure of lining. When the tunnel gushing water quantity was equal to the control discharge, it was considered as free drainage and the lining could not bear the water pressure.

scholarly journals The Hydromechanical Interplay in the Simplified Three-Dimensional Limit Equilibrium Analyses of Unsaturated Slope Stability

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 73
Author(s):  
Panagiotis Sitarenios ◽  
Francesca Casini
Keyword(s):  
Analytical Solution ◽  
Slope Stability ◽  
Slope Failure ◽  
Failure Modes ◽  
Pore Water Pressure ◽  
Limit Equilibrium ◽  
Water Pressure ◽  
Three Dimensional ◽  
Stability Limit ◽  
Smooth Transition

This paper presents a three-dimensional slope stability limit equilibrium solution for translational planar failure modes. The proposed solution uses Bishop’s average skeleton stress combined with the Mohr–Coulomb failure criterion to describe soil strength evolution under unsaturated conditions while its formulation ensures a natural and smooth transition from the unsaturated to the saturated regime and vice versa. The proposed analytical solution is evaluated by comparing its predictions with the results of the Ruedlingen slope failure experiment. The comparison suggests that, despite its relative simplicity, the analytical solution can capture the experimentally observed behaviour well and highlights the importance of considering lateral resistance together with a realistic interplay between mechanical parameters (cohesion) and hydraulic (pore water pressure) conditions.

Experimental investigation on the three-dimensional flow field from a meltblowing slot die

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 724-732
Author(s):  
Changchun Ji ◽  
Yudong Wang
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Great Influence ◽  
Distribution Characteristics ◽  
Air Velocity ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Airflow Distribution ◽  
Slot Die ◽  
Center Area

AbstractTo investigate the distribution characteristics of the three-dimensional flow field under the slot die, an online measurement of the airflow velocity was performed using a hot wire anemometer. The experimental results show that the air-slot end faces have a great influence on the airflow distribution in its vicinity. Compared with the air velocity in the center area, the velocity below the slot end face is much lower. The distribution characteristics of the three-dimensional flow field under the slot die would cause the fibers at different positions to bear inconsistent air force. The air velocity of the spinning centerline is higher than that around it, which is more conducive to fiber diameter attenuation. The violent fluctuation of the instantaneous velocity of the airflow could easily cause the meltblowing fiber to whip in the area close to the die.

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