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8 pages, 2217 KiB

Open AccessEditorial

Risk Management Technologies for Deep Excavations in Water-Rich Areas

by Yixian Wang, Panpan Guo, Hang Lin and Yanlin Zhao

Water 2024, 16(2), 323; https://doi.org/10.3390/w16020323 - 18 Jan 2024

Cited by 1 | Viewed by 1297

Abstract

Deep excavations play an important role in the construction of urban infrastructures such as metro stations and high-rise buildings [...] Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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Research

Jump to: Editorial, Other

19 pages, 3085 KiB

Open AccessArticle

Study on Excavation Response of Deep Foundation Pit Supported by SMW Piles Combined with Internal Support in Soft Soil Area

by Bingxiong Tu, Jinhuo Zheng, Shuaihua Ye and Minglong Shen

Water 2023, 15(19), 3430; https://doi.org/10.3390/w15193430 - 29 Sep 2023

Cited by 6 | Viewed by 1732

Abstract

Based on a foundation pit project in Fuzhou, China, the influence of foundation pit excavation on the supporting structure and surrounding environment in a soft-soil area is studied. This study was based on actual monitoring data and investigated the variations in the supporting [...] Read more.

Based on a foundation pit project in Fuzhou, China, the influence of foundation pit excavation on the supporting structure and surrounding environment in a soft-soil area is studied. This study was based on actual monitoring data and investigated the variations in the supporting structure, surrounding constructions, and groundwater levels during excavation. The analysis of the monitoring data demonstrates the presence of pronounced ‘spatial effects’ and ‘temporal effects’ on the deformation of the support structure and surrounding structures. The deformation of the support structure and surrounding structures exhibits distinct spatial distribution characteristics at different locations along the excavation pit wall. Typically, more significant deformations are observed in the middle section of the pit wall, while deformations decrease as the distance from the pit corner decreases. The support structure’s and surrounding structures’ deformation characteristics vary during different construction stages. During the excavation phase, the rate of deformation increase in the support structure and surrounding structures is notably higher. In contrast, during the construction of the underground basement floor and the backfilling phase of the excavation pit, the rate of deformation increase in the support structure and surrounding structures is relatively lower. Throughout the entire construction period of the excavation pit, the groundwater level in the vicinity of the pit exhibits a fluctuating trend. Apart from the influence of rainfall, the overall variation in groundwater level is minimal, indicating the effective water-sealing performance of the combined Soil-Mixing Wall (SMW) support structure within the circular enclosure. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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13 pages, 4294 KiB

Open AccessArticle

Geothermal Water Exploration of the Maoyanhe Hot Spring Scenic Spot in Zhangjiajie Using the Natural Electric Field Frequency Selection Method

by Yulong Lu, Haiyang Ding, Tianchun Yang and Yang Liu

Water 2023, 15(19), 3418; https://doi.org/10.3390/w15193418 - 28 Sep 2023

Cited by 3 | Viewed by 1315

Abstract

Natural electric field frequency selection method was proposed by Chinese scholars in the 1980s on the basis of imitating the field observation method of the magnetotelluric method (MT). It can only measure the magnetotelluric field components of one or several frequencies on the [...] Read more.

Natural electric field frequency selection method was proposed by Chinese scholars in the 1980s on the basis of imitating the field observation method of the magnetotelluric method (MT). It can only measure the magnetotelluric field components of one or several frequencies on the surface to determine the existence of underground geological bodies. This method has played an important role in shallow groundwater exploration. This paper mainly discusses the application of frequency selection method in the exploration of underground hot water in the Maoyanhe Scenic spot, Zhangjiajie City, Hunan Province, in order to illustrate the effectiveness of the frequency selection method in water exploration. According to the situation of the construction site, nearly 20 geophysical prospecting survey lines of varying lengths were laid flexibly within the red line of the Maoyan River Scenic Spot. Firstly, three-frequency (170 Hz, 67 Hz and 25 Hz) measurements were carried out on each survey line to preliminarily determine the possible horizontal location of underground hot water. Secondly, in the vicinity of the low potential anomaly of the three-frequency curve, the fine measurement by using multi-frequency bipolar profile method was further carried out. The specific distribution of underground hot water was determined based on the principle of frequency domain sounding and the static effect characteristics of the electromagnetic method so as to provide a scientific basis for the drilling layout. Finally, the reliability of the frequency selection method is verified by two verification boreholes. The results indicate that the frequency selection method is one of the effective geophysical exploration methods in groundwater exploration. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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16 pages, 2608 KiB

Open AccessArticle

A Simplified Method for Effective Calculation of 3D Slope Reliability

by Juxiang Chen, Dayong Zhu and Yalin Zhu

Water 2023, 15(17), 3139; https://doi.org/10.3390/w15173139 - 1 Sep 2023

Viewed by 1350

Abstract

Traditional 3D slope reliability analysis methods have high computational costs and are difficult to popularize in engineering practice. Under the framework of the limit equilibrium method with 3D slip surface normal stress correction, the critical horizontal acceleration coefficient

K_{c}

, which is [...] Read more.

Traditional 3D slope reliability analysis methods have high computational costs and are difficult to popularize in engineering practice. Under the framework of the limit equilibrium method with 3D slip surface normal stress correction, the critical horizontal acceleration coefficient

K_{c}

, which is equivalent to the safety factor

F_{s}

, is selected to characterize the slope stability. The limit state function uses the difference between

K_{c}

and the known critical value

K_{c 0}

. A simplified method for calculating the reliability of 3D slope is proposed. Through two typical slope examples, the 3D reliability calculation results of six methods after coupling two limit state functions and three reliability algorithms are compared. The results show that this method is reliable and effective, and the method coupled with subset simulation (SS) is the one with good calculation accuracy and efficiency. In the case of long slopes, 2D analysis results may underestimate the probability of slope instability, and 3D reliability of the slope must be analyzed. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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30 pages, 13713 KiB

Open AccessArticle

Study on the Analysis of Pile Foundation Deformation and Control Methods during the Excavation of Deep and Thick Sludge Pits

by Dengqun Wang, Shuaihua Ye and Liangliang Xin

Water 2023, 15(17), 3121; https://doi.org/10.3390/w15173121 - 30 Aug 2023

Cited by 4 | Viewed by 2174

Abstract

This study aims to apply performance-based safety-assessment methods to the monitoring and numerical simulation of excavation engineering projects in order to comprehensively enhance engineering risk management and decision support. In this paper, a deep excavation project in Hefei with thick silty clay layers [...] Read more.

This study aims to apply performance-based safety-assessment methods to the monitoring and numerical simulation of excavation engineering projects in order to comprehensively enhance engineering risk management and decision support. In this paper, a deep excavation project in Hefei with thick silty clay layers was studied. The analysis included the surface settlement, the deformation of support structures, the vertical and horizontal displacements of pile tops, axial forces in steel braces, settlement, and the horizontal displacement of a gravity retaining wall on the south side of the excavation using field-monitoring data. A refined three-dimensional finite element model was established to further analyze the distribution of uplift displacement at the bottom of the excavation, horizontal displacement, and bending moments of piles based on simulation results. The research findings indicate that phased excavation can reduce the spatial extent of disturbance to the surrounding soil caused by excavation. Additionally, the closer the location to the excavation and the thicker the underlying silty clay layer, the faster the rate of settlement change and the greater the surface settlement. The spatial structure formed by steel braces and pile foundations effectively reduced the horizontal displacement of the engineering piles. The study’s use of field monitoring and finite element simulation provided valuable insights into the deformation of support structures and the response of the surrounding soil to excavation, confirming the rationality and applicability of the support structure in this paper. The proposed method can serve as a reference for similar complex stratum excavation design and construction. The performance-based safety assessment is introduced, and the monitoring data, numerical simulation results, and performance targets are comprehensively analyzed to provide a reliable scientific basis for engineering decision making. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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19 pages, 5068 KiB

Open AccessArticle

Monitoring Analysis of a Deep Foundation Pit with Water Supported by Cast-in-Place Pile and Internal Bracing in a Soft Soil Area of Fuzhou

by Bingxiong Tu, Jinhuo Zheng, Minglong Shen and Weilong Ni

Water 2023, 15(16), 3008; https://doi.org/10.3390/w15163008 - 21 Aug 2023

Cited by 2 | Viewed by 1971

Abstract

In addition to selecting an effective support structure to control deformation, precipitation and water stopping should also be considered when designing a support scheme for water-bearing foundation pits in soft soil areas. This paper presents a detailed description of the foundation pit support [...] Read more.

In addition to selecting an effective support structure to control deformation, precipitation and water stopping should also be considered when designing a support scheme for water-bearing foundation pits in soft soil areas. This paper presents a detailed description of the foundation pit support scheme, the precipitation and water-stopping scheme, and the monitoring scheme of the foundation pit project of Taijiang Square in Fuzhou. During the construction of the foundation pit, the monitoring data of 12 items such as the deep horizontal displacement of the enclosure pile, the horizontal displacement at the top of the foundation pit, the settlement at the top of the foundation pit, the axial force of the internal bracing, and the axial force of the enclosure pile were obtained through 12 months of monitoring. The analysis of the monitoring data for each item led to the following two main findings. The first finding is that, during the construction of the pit, the monitoring values of the 12 monitoring items did not exceed the alarm values, which proves that the support scheme of the cast-in-place pile enclosure structure and internal bracing can meet the design requirements of deep foundation pits in soft soil areas. The second finding is that tube-well dewatering is an effective way to lower the groundwater level in water-containing deep foundation pits in soft soil areas, and double-wheel deep-mixing water-stopping curtain walls can effectively control the infiltration of groundwater outside the water-containing deep foundation pits in soft soil areas. This foundation pit project is representative, and it provides a good reference case for the design of water-bearing deep foundation pit projects in soft soil areas. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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25 pages, 13277 KiB

Open AccessArticle

Risk Reduction Measures and Monitoring Analysis of Deep Foundation Pit with Water in a Metro Station in Hefei

by Dengqun Wang, Shuaihua Ye and Jun Zhang

Water 2023, 15(16), 3007; https://doi.org/10.3390/w15163007 - 21 Aug 2023

Cited by 2 | Viewed by 1769

Abstract

The construction of an urban metro will inevitably involve deep excavation. Risk assessment before deep excavation, risk reduction measures, and real-time monitoring during excavation can effectively ensure the safety of deep excavation. Taking the deep excavation pit of Lingbi Road Station of Hefei [...] Read more.

The construction of an urban metro will inevitably involve deep excavation. Risk assessment before deep excavation, risk reduction measures, and real-time monitoring during excavation can effectively ensure the safety of deep excavation. Taking the deep excavation pit of Lingbi Road Station of Hefei Rail Transit Line 8 as the research object, this paper first analyses and evaluates the self-risk, groundwater risk, and surrounding environmental risk of the deep excavation pit, and gives the corresponding measures to reduce the risk of the deep excavation pit. Then, the monitoring content of the excavation process is determined according to the environment of the excavation, the hydrogeological conditions, and the type of supporting structure, and the monitoring scheme is designed. Finally, the entire excavation process is monitored in real time. By analyzing the monitoring data of 13 projects, such as horizontal displacement of the wall top, axial support force, groundwater level, etc., it is found that the monitoring values of 13 projects do not exceed the control value. This proves that the composite internal bracing structure of the underground diaphragm wall is suitable for deep foundation pit support in the Hefei area, as the selection of the water-bearing deep foundation pit support structure, the value of the support structure parameters, and the design of the foundation pit dewatering scheme are all reasonable. The study of this paper also serves as a case reference for the support design of water-bearing deep excavation of subway station in Hefei area. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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17 pages, 3518 KiB

Open AccessArticle

Influences of Underwater Shield Tunnelling on River Embankment Seepage Stability Considering Various Overburden Thickness

by Wenyu Shu, Jingjing Ma, Ningning Geng, Yang Xiang, Shiyu Ma, Xian Li, Fang Tong and Shisheng Fang

Water 2023, 15(13), 2346; https://doi.org/10.3390/w15132346 - 25 Jun 2023

Viewed by 1645

Abstract

Underwater shield tunneling will disturb the soil near the river, especially in water-rich soft ground. This may cause a groundwater infiltration hydraulic gradient to exceed the critical value, leading to calamities, such as unexpected flooding or submerged erosion. To ensure the security of [...] Read more.

Underwater shield tunneling will disturb the soil near the river, especially in water-rich soft ground. This may cause a groundwater infiltration hydraulic gradient to exceed the critical value, leading to calamities, such as unexpected flooding or submerged erosion. To ensure the security of construction and the stability of river embankment seepage, it is crucial to assess the safety of the underwater tunnel cover thickness. A shield tunnel project under a river in Hefei is used as an example. The numerical model established by the finite element method is used for calculating and analyzing the changes in the groundwater flow field and the stability state of embankment seepage induced by underwater shield tunneling under different overburden thickness conditions. The results show that the construction disturbance of the shield tunnel through the river is increased, the internal force environment of the embankment slope is destroyed, and the maximum seepage hydraulic gradient is increased. In the case study, the embankment keeps in a stable state of seepage when the cover thickness of the shield tunnel has 2.9 times its outer diameter. The findings of this study can serve as a scientific guide to assure seepage stability in an underwater shield tunneling project and to stop river embankment erosion. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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13 pages, 4811 KiB

Open AccessArticle

Detection of Landfill Leachate Leakage Based on ERT and OCTEM

by Yulong Lu, Jialuo Tao, Chuanghua Cao, Hanlin Liu, Yang Liu and Zhengbin Ge

Water 2023, 15(9), 1778; https://doi.org/10.3390/w15091778 - 5 May 2023

Cited by 4 | Viewed by 2595

Abstract

Leakage in the impervious layer of a domestic waste landfill seriously pollutes the soil and groundwater. Therefore, it is necessary to carry out rapid nondestructive leakage location detection. In this research, the electrical resistivity tomography (ERT) method and the opposing-coils transient electromagnetic method [...] Read more.

Leakage in the impervious layer of a domestic waste landfill seriously pollutes the soil and groundwater. Therefore, it is necessary to carry out rapid nondestructive leakage location detection. In this research, the electrical resistivity tomography (ERT) method and the opposing-coils transient electromagnetic method (OCTEM) were used to detect the leakage location. The inversion sections of both methods showed a clear low–middle–high resistivity spectrum in the longitudinal direction that could be used to speculate the distribution pattern of the upper waste body layer, the bottom impermeable layer, and the lower limestone layer. The leakage area was identified in Zone B of the landfill on the basis of inversion results and drilling verification results. The results indicate that OCTEM and ERT were both sensitive to leakage detection. However, OCTEM had higher longitudinal resolution and more refined inversion results, resulting in more effective delineation for the location of the damage and leakage of the impervious landfill layer, thereby providing a new technical basis for landfill leakage detection. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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26 pages, 6461 KiB

Open AccessArticle

Application and Automatic Monitoring and Analysis of Hybrid Support Structure in Ultra-DEEP Foundation Pit Engineering in the Lanzhou Area under Complex Environmental Conditions

by Jian Wu, Shuaihua Ye, Zhiquan Wang and Dong Yang

Water 2023, 15(7), 1335; https://doi.org/10.3390/w15071335 - 28 Mar 2023

Cited by 12 | Viewed by 2653

Abstract

This paper takes the deep foundation pit project of Lanzhou Hospital of Traditional Chinese Medicine as the background. The design and construction of the foundation pit is relatively difficult due to the complex environment around the pit, the dense surrounding buildings, the complex [...] Read more.

This paper takes the deep foundation pit project of Lanzhou Hospital of Traditional Chinese Medicine as the background. The design and construction of the foundation pit is relatively difficult due to the complex environment around the pit, the dense surrounding buildings, the complex underground soil layer and the influence of groundwater on the pit. In order to detect problems in the construction process, the pit was monitored in real time through an automated monitoring system for the whole process of excavation and backfilling of the pit. The analysis of the actual monitoring data shows that: (i) the support scheme of bored pile + prestressed anchor cable support combined with concrete corner bracing can meet the design of this type of foundation pit without causing disturbance to the surrounding buildings; (ii) combined with the actual case of the influence of groundwater on the excavation process of the foundation pit, it proves that the real-time measurement by the robot can timely detect the safety hazards caused by external factors during the construction process of the foundation pit. The project is a very important one for deep pits and complex pits. This project provides a good reference case for deep foundation pits and foundation pit projects in complex environments. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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15 pages, 6050 KiB

Open AccessArticle

Mining Leachates Effect on the Hydraulic Performance of Geosynthetic Clay Liners under Different Temperatures

by Yang Liu, Xinxin Li, Yuanzhuo Tu and Yulong Lu

Water 2023, 15(6), 1132; https://doi.org/10.3390/w15061132 - 15 Mar 2023

Cited by 9 | Viewed by 2007

Abstract

Geosynthetic clay liners (GCLs) are often used as anti-seepage systems in landfills and at the bottom of tailing ponds. The anti-seepage performance of GCL will change under different temperatures. In this study, bentonite was mixed with test solutions at different temperatures to measure [...] Read more.

Geosynthetic clay liners (GCLs) are often used as anti-seepage systems in landfills and at the bottom of tailing ponds. The anti-seepage performance of GCL will change under different temperatures. In this study, bentonite was mixed with test solutions at different temperatures to measure the basic performance indexes of bentonite components and analyze the permeability. The composition and micro-structure of bentonite at different temperatures were analyzed by X-ray diffraction, X-ray fluorescence spectrum, and SEM, and the change rule of permeability property with the mine leachates at different temperatures was understood by combining the macro-measured parameters with the microscopic analysis results. The research results indicate that the fluid loss of two bentonites increased with the increasing temperature due to the inhibition of ion exchange between bentonite and mixture by the increased temperature. The swelling index of the bentonite increased at high temperatures. The micro-structure analysis showed the increase of the pore size attributed to high temperature, and the uneven distribution of the pore size resulted in the increase of the intrinsic permeability. The study would provide the reference for the application of GCL in mining. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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22 pages, 10868 KiB

Open AccessFeature PaperArticle

Failure Characteristics of the Water-Resisting Coal Pillar under Stress-Seepage Coupling and Determination of Reasonable Coal Pillar Width

by Quanhui Liu, Yuanbo Xue, Dan Ma and Qiang Li

Water 2023, 15(5), 1002; https://doi.org/10.3390/w15051002 - 6 Mar 2023

Cited by 9 | Viewed by 2089 | Correction

Abstract

Groundwater inrush hazard has always been a great threat to the construction of vertical shafts in coal mines. Generally, the failure of the water-resisting coal pillar under coupled stress-seepage conditions around the vertical shaft is the main reason for the generation of the [...] Read more.

Groundwater inrush hazard has always been a great threat to the construction of vertical shafts in coal mines. Generally, the failure of the water-resisting coal pillar under coupled stress-seepage conditions around the vertical shaft is the main reason for the generation of the water inrush channel. In order to understand the mechanical behaviors of the water-resisting coal pillar, the strength of typical coal affected by the size and water content was investigated, and the stress sensitivity of permeability was investigated by a stress-seepage coupling test. The stress field and deformation of the water-resisting coal pillar were investigated by numerical simulation, the stability of the water-resisting coal pillars with different widths was evaluated, and the reasonable width of the coal pillars under coupled stress-seepage condition was determined. Results show that the water content and coal pillar width have a great influence on the mechanical characteristics of coal samples. Under the conditions of lower water content and larger coal sample width, the coal sample presents higher strength, smaller axial deformation, smaller permeability and porosity, and weak sensitivity to stress. The simulation results show that the boundary of the main roadway at the end of the coal pillar is dominated by tensile stress, and fractures can significantly contribute to the destruction of coal pillars. With the increase in the width of the water-resisting coal pillar, the internal damage variable, maximum tensile stress, porosity, and average water flow velocity of the coal pillar decrease, which reduces the risk of water inrush and improves the safety of the water-resisting coal pillar. An evaluation model of the reasonable width of the water-resisting coal pillar under the stress-seepage coupling was proposed, and the model was verified by the shear slip law and experimental results. This study provides theoretical and experimental guidance for the risk management of groundwater inrush disaster during the construction of vertical shafts in coal mines. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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13 pages, 6356 KiB

Open AccessArticle

Impact of the Boreholes on the Surrounding Ground

by Sudip Shakya, Koki Nakao, Shuichi Kuwahara and Shinya Inazumi

Water 2023, 15(1), 188; https://doi.org/10.3390/w15010188 - 2 Jan 2023

Cited by 3 | Viewed by 3083

Abstract

The infrastructures that were constructed decades ago do not meet the present structural benchmark, and they need to be demolished. In order to reclaim these lands, the existing pile foundations must be removed; otherwise, the land will lose its value. Since the piles [...] Read more.

The infrastructures that were constructed decades ago do not meet the present structural benchmark, and they need to be demolished. In order to reclaim these lands, the existing pile foundations must be removed; otherwise, the land will lose its value. Since the piles are pulled out, vacant spaces are created in the ground. This causes the surrounding ground to experience settlement, jeopardizing its stability. The degree of influence depends upon the number of boreholes, the saturated condition of the ground, the time period of the vacant condition, the presence of loading, etc. It is important to understand the scope of the probable settlement under various situations. This study focused on determining the amount of displacement and its range for three different saturated soil types under loaded and unloaded conditions using the finite element method (FEM) analysis. It was observed that stiff ground underwent maximum deformation, while soft ground experienced the maximum influence from external factors. Moreover, the presence of loading not only increased the displacement amount and range, but it also caused a change in the location of the maximum displacement. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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15 pages, 2597 KiB

Open AccessArticle

Fast Recognition on Shallow Groundwater and Anomaly Analysis Using Frequency Selection Sounding Method

by Lu Yulong, Yang Tianchun, Abdollah Taheri Tizro and Liu Yang

Water 2023, 15(1), 96; https://doi.org/10.3390/w15010096 - 28 Dec 2022

Cited by 10 | Viewed by 2557

Abstract

The validity of the frequency selection method (FSM) in shallow (<150 m) groundwater exploration was illustrated by practical applications, and the relationship between potential electrode spacing MN and groundwater depth in FSM sounding method was analyzed and preliminary theoretical research was carried out [...] Read more.

The validity of the frequency selection method (FSM) in shallow (<150 m) groundwater exploration was illustrated by practical applications, and the relationship between potential electrode spacing MN and groundwater depth in FSM sounding method was analyzed and preliminary theoretical research was carried out by a simple geologic-geophysical model of sphere. Firstly, under the combined action of horizontal alternating electric field and alternating magnetic field, a simplified geophysical model of low resistivity conductive sphere in homogeneous half space was established, and the forward calculation was performed on the FSM sounding curve. Then, the water yield of 131 wells in the application of FSM in the Rural Drinking Water Safety Project of 12th Five-Year Plan in Guangxi Province was counted. In addition, detailed tabular statistical analysis was carried out on the drilling results of 98 drilling wells, and the relationship between potential electrode spacing MN at abnormal sounding curve and actual drilling water depth was compared and studied. Theoretical analysis and practical application show that FSM has obvious effectiveness in shallow groundwater exploration, and it is an effective method to determine shallow groundwater well locations in the future. The cause of FSM anomaly is the comprehensive effect of the natural 3D alternating electromagnetic signal underground. At the same time, the practical statistics show that there is 1:1 approximation between the size of potential electrode spacing MN at the anomaly curve of the frequency selection method and the actual drilling water depth, which verifies the correctness of the theoretical simulation results. FSM could be widely used in the shallow groundwater exploration in the future, and it is an effective, non-destructive, fast, and low-cost geophysical method. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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15 pages, 3204 KiB

Open AccessFeature PaperArticle

A Machine Learning Method for Engineering Risk Identification of Goaf

by Haiping Yuan, Zhanhua Cao, Lijun Xiong, Hengzhe Li and Yixian Wang

Water 2022, 14(24), 4075; https://doi.org/10.3390/w14244075 - 13 Dec 2022

Cited by 6 | Viewed by 1691

Abstract

The risk evaluation indexes of goaf are multi-source and have complex mutual internal correlations, and there are great differences in the risk identification of goaf from different mines among the various influencing factors. This paper mainly focuses on principal component analysis (PCA) and [...] Read more.

The risk evaluation indexes of goaf are multi-source and have complex mutual internal correlations, and there are great differences in the risk identification of goaf from different mines among the various influencing factors. This paper mainly focuses on principal component analysis (PCA) and the differential evolution algorithm (DE), while a multi-classification support vector machine (SVM) is adopted to classify the risks of goaf. Then, the K-fold cross-validation method is used to prevent the overfitting of selection in the model. After the analysis, nine factors affecting the risk identification of goaf in a certain area of East China were determined as the primary influencing factors, and 120 measured goafs were taken as examples for classifying the risks. More specifically, the classification results show that: (1) SVM has the useful ability of generalization, especially when solving the problems of overfitting, and it is easy to fall into the local minima under the conditions of small samples; (2) PCA is employed to realize the intelligent dimensionality reduction and denoising of multi-source impact indicators for goaf risk identification, which immensely improves the prediction accuracy and classification efficiency of the model; (3) after using the DE, the optimal solutions of the problems to be optimized are automatically obtained through the global optimization search mechanism, namely, the kernel function parameter, ‘γ’, and the penalty factor, ‘C’, of the SVM, which further verifies that the characteristics of clear logic, strong convergence, and good robustness can be found in the DE. As demonstrated, this method has the advantages of guiding significance and application value for goaf risk identification. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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14 pages, 5247 KiB

Open AccessArticle

Design and Field Monitoring of a Pile–Anchor–Brace Supporting System in a Soft Soil Area

by Lin Sun, Ke Mao, Zhengzhen Wang, Shuaihua Ye, Tiantao Su, Guoliang Dai, Guangxiang Xu and Jilong Sun

Water 2022, 14(23), 3949; https://doi.org/10.3390/w14233949 - 4 Dec 2022

Cited by 3 | Viewed by 2223

Abstract

With the continuous development of urbanization and the rapid development of science and technology, the requirements for foundation pit engineering are getting higher and higher. Foundation pit engineering is gradually developing in the direction of larger area and deeper excavation. In engineering examples, [...] Read more.

With the continuous development of urbanization and the rapid development of science and technology, the requirements for foundation pit engineering are getting higher and higher. Foundation pit engineering is gradually developing in the direction of larger area and deeper excavation. In engineering examples, the combined supporting structure of a pile–brace and pile–anchor for foundation pits is widely used, while the engineering examples supported by a pile–anchor–brace supporting system are less frequently used. Based on a super-large deep foundation pit project in Yancheng City, Jiangsu Province, China, according to the surrounding environmental conditions, the foundation pit support scheme, and on-site construction situation, the design and on-site monitoring of the pile–anchor–brace supporting system were introduced and analyzed. The results show that: (1) the deformation of the pile–anchor–brace supporting system shows an obvious spatial effect, and the horizontal displacement of the pile and soil of the long side direction is greater than the short side direction; (2) in the initial state, the deep horizontal displacement of the soil is in the form of a ‘cantilever’, but in the later stage it changed to the form of a ‘drum belly’, and both the brace and anchor cable can limit the displacement of the soil effectively; (3) the axial force of the brace develops rapidly in the initial stage, but its development tends to be gentle after the completion of the first anchor cable construction. Through on-site monitoring, it was found that the axial force of the ring brace was larger than that of the corner brace, which was larger than the opposite brace; and (4) the development trend of the axial force for the two rows of anchor cables is quite different. The average axial force of the first row of anchor cables is greater than the second row of anchor cables, and the development trend of the first row of anchor cables is steep first and then gentle, while the change trend of the second row of anchor cables is just the opposite. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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18 pages, 4813 KiB

Open AccessFeature PaperArticle

Predicting Ground Surface Settlements Induced by Deep Excavation under Embankment Surcharge Load in Flood Detention Zone

by Yixian Wang, Shi Chen, Jiye Ouyang, Jian Li, Yanlin Zhao, Hang Lin and Panpan Guo

Water 2022, 14(23), 3868; https://doi.org/10.3390/w14233868 - 27 Nov 2022

Cited by 9 | Viewed by 5159

Abstract

In this paper, a simplified prediction formula of ground settlement induced by deep foundation pit excavation is proposed, especially suitable for ground overloading near a foundation pit, such as embankment surcharge load, which is carefully considered via the means of load equivalence. The [...] Read more.

In this paper, a simplified prediction formula of ground settlement induced by deep foundation pit excavation is proposed, especially suitable for ground overloading near a foundation pit, such as embankment surcharge load, which is carefully considered via the means of load equivalence. The ground settlement induced by foundation pit excavation and embankment surcharge load is determined by the modified skewness prediction formula and the simplified Boussinesq solution, respectively, and it is assumed that no coupling effect exists between the two settlement sources. In addition, this paper improves the determination of the maximum settlement location by combining calculus and curve fitting, replacing the existing prediction formula which relies heavily on engineering experience to determine the maximum settlement point. The predicted value obtained using this method comes close to the measured value, and the deviation of the maximum surface settlement value is controlled within about 5% in the three cases introduced, of which the accuracy is higher than the existing prediction formula. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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15 pages, 6602 KiB

Open AccessFeature PaperArticle

Stability of Braced Excavation Underneath Crossing Underground Large Pressurized Pipelines

by Fangang Li, Panpan Guo, Ningning Geng, Lei Mao, Feng Lin, Yanlin Zhao, Hang Lin and Yixian Wang

Water 2022, 14(23), 3867; https://doi.org/10.3390/w14233867 - 27 Nov 2022

Cited by 3 | Viewed by 2367

Abstract

The practice of deep-braced excavation in congested urban environments involves frequently buried pipelines, which can exert a significant effect on the performance of the excavation. The objective of this paper is to investigate the performance of a 12.5-m-deep-braced excavation spanned by two shallowly [...] Read more.

The practice of deep-braced excavation in congested urban environments involves frequently buried pipelines, which can exert a significant effect on the performance of the excavation. The objective of this paper is to investigate the performance of a 12.5-m-deep-braced excavation spanned by two shallowly buried large-diameter pressurized pipelines. A suspension structure is installed within the excavation to protect the in situ pipelines during the construction. The excavation performance is investigated by performing a three-dimensional finite element analysis. The finite element method is verified based on the observations at the site. The results indicate that, as expected, the excavation support structures displace together with varying degrees of deformation toward the excavated area. The strut shear forces are found to be distributed axially in linear manners, while the strut bending moments are in symmetric manners. The benefit of using the proposed pipeline suspension structure is demonstrated. By using this structure, pipeline deformation can be well controlled, and the structural integrity and safety of the pipelines can be ensured. This benefit depends on the convenient operation in that the elevation of the cork base of the pipeline suspension structure is stably lowered during the construction process. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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19 pages, 9147 KiB

Open AccessArticle

Risk Assessment for Critical Flood Height of Pedestrian Escape in Subway Station

by Yi Tang, Tianzhong Zhou, Youxin Zhong, Shengbin Hu, Jing Lin, Zhiyu Lin, Hongwei Liu, Baohua Liu, Yanlin Zhao, Yixian Wang and Hang Lin

Water 2022, 14(21), 3409; https://doi.org/10.3390/w14213409 - 27 Oct 2022

Cited by 7 | Viewed by 2174

Abstract

The escape of pedestrians in the subway station is hampered by floods created by heavy rain. In order to explore the critical flood level in a subway station so that pedestrians can escape safely, the case study of the Mingxiu Road subway station [...] Read more.

The escape of pedestrians in the subway station is hampered by floods created by heavy rain. In order to explore the critical flood level in a subway station so that pedestrians can escape safely, the case study of the Mingxiu Road subway station in Nanning, China, was conducted using numerical simulation techniques. In total, 30 groups of sample pedestrians with different walking speeds and numbers were randomly generated by the Monte Carlo method, and 3D simulation software was used for escape simulation. The simulated escape data were put into the SVM model, and the maximum pedestrian capacity and minimum speed of pedestrians were solved successfully with different conditions of the Mingxiu Road subway station. Then, a 1:1 contour model of the pedestrian was constructed to simulate the flood resistance of the pedestrian escaping at the minimum speed. The flood resistance and the friction force between the pedestrian and the ground were compared to calculate the critical escape flood level height, and the critical escape flood level height of an adult, child, and elder was 87.4 cm,75.5 cm, and 83.0 cm, respectively. Full article

(This article belongs to the Special Issue Risk Management Technologies for Deep Excavations in Water-Rich Areas)

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