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Shallow foundation response variability due to soil and model parameter uncertainty

Prishati RAYCHOWDHURY,Sumit JINDAL

《结构与土木工程前沿（英文）》 2014年第8卷第3期页码 237-251 doi: 10.1007/s11709-014-0242-1

摘要： Geotechnical uncertainties may play crucial role in response prediction of a structure with substantial soil-foundation-structure-interaction (SFSI) effects. Since the behavior of a soil-foundation system may significantly alter the response of the structure supported by it, and consequently several design decisions, it is extremely important to identify and characterize the relevant parameters. Moreover, the modeling approach and the parameters required for the modeling are also critically important for the response prediction. The present work intends to investigate the effect of soil and model parameter uncertainty on the response of shallow foundation-structure systems resting on dry dense sand. The SFSI is modeled using a beam-on-nonlinear-winkler-foundation (BNWF) concept, where soil beneath the foundation is assumed to be an assembly of discrete, nonlinear elements composed of springs, dashpots and gap elements. The sensitivity of both soil and model input parameters on shallow foundation responses are investigated using first-order second-moment (FOSM) analysis and Monte Carlo simulation through Latin hypercube sampling technique. It has been observed that the degree of accuracy in predicting the responses of the shallow foundation is highly sensitive soil parameters, such as friction angle, Poisson’s ratio and shear modulus, rather than model parameters, such as stiffness intensity ratio and spring spacing; indicating the importance of proper characterization of soil parameters for reliable soil-foundation response analysis.

关键词： shallow foun dation sensitivity analysis centrifuge data first-order-second-moment (FOSM) method parameter uncertainty

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Mechanical responses of multi-layered ground due to shallow tunneling with arbitrary ground surface load

《结构与土木工程前沿（英文）》 2023年第17卷第5期页码 745-762 doi: 10.1007/s11709-023-0935-4

摘要： An analytical model based on complex variable theory is proposed to investigate ground responses due to shallow tunneling in multi-layered ground with an arbitrary ground surface load. The ground layers are assumed to be linear-elastic with full-stick contact between them. To solve the proposed multi-boundary problem, a series of analytic functions is introduced to accurately express the stresses and displacements contributed by different boundaries. Based on the principle of linear-elastic superposition, the multi-boundary problem is converted into a superposition of multiple single-boundary problems. The conformal mappings of different boundaries are independent of each other, which allows the stress and displacement fields to be obtained by the sum of components from each boundary. The analytical results are validated based on numerical and in situ monitoring results. The present model is superior to the classical model for analyzing ground responses of shallow tunneling in multi-layered ground; thus, it can be used with assurance to estimate the ground movement and surface building safety of shallow tunnel constructions beneath surface buildings. Moreover, the solution for the ground stress distribution can be used to estimate the safety of a single-layer composite ground.

关键词： analytical model mechanical response multi-layered ground shallow tunneling ground surface load complex variable solution

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Comparison of shallow tunneling method with pile and rib method for construction of subway station in

Sina AMIRI; Ali Naghi DEHGHAN

《结构与土木工程前沿（英文）》 2022年第16卷第6期页码 704-717 doi: 10.1007/s11709-021-0746-4

摘要： In the present study, a comparison between the new shallow tunneling method (STM) and the traditional pile and rib method (PRM) was conducted to excavate and construct subway stations in the geological conditions of Tehran. First, by selecting Station Z6 located in the Tehran Subway Line 6 as a case study, the construction process was analyzed by PRM. The maximum ground settlement of 29.84 mm obtained from this method was related to the station axis, and it was within the allowable settlement limit of 30 mm. The acceptable agreement between the results of numerical modeling and instrumentation data indicated the confirmation and accuracy of the excavation and construction process of Station Z6 by PRM. In the next stage, based on the numerical model validated by instrumentation data, the value of the ground surface settlement was investigated during the station excavation and construction by STM. The results obtained from STM showed a significant reduction in the ground surface settlement compared to PRM. The maximum settlement obtained from STM was 6.09 mm as related to the front of the excavation face. Also, the sensitivity analysis results denoted that in addition to controlling the surface settlement by STM, it is possible to optimize some critical geometric parameters of the support system during the station excavation and construction.

关键词： shallow tunneling method pile and rib method ground surface settlement subway station construction numerical modeling

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Centrifuge experiments for shallow tunnels at active reverse fault intersection

Mehdi SABAGH, Abbas GHALANDARZADEH

《结构与土木工程前沿（英文）》 2020年第14卷第3期页码 731-745 doi: 10.1007/s11709-020-0614-7

摘要： Tunnels extend in large stretches with continuous lengths of up to hundreds of kilometers which are vulnerable to faulting in earthquake-prone areas. Assessing the interaction of soil and tunnel at an intersection with an active fault during an earthquake can be a beneficial guideline for tunnel design engineers. Here, a series of 4 centrifuge tests are planned and tested on continuous tunnels. Dip-slip surface faulting in reverse mechanism of 60-degree is modeled by a fault simulator box in a quasi-static manner. Failure mechanism, progression and locations of damages to the tunnels are assessed through a gradual increase in Permanent Ground Displacement (PGD). The ground surface deformations and strains, fault surface trace, fault scarp and the sinkhole caused by fault movement are observed here. These ground surface deformations are major threats to stability, safety and serviceability of the structures. According to the observations, the modeled tunnels are vulnerable to reverse fault rupture and but the functionality loss is not abrupt, and the tunnel will be able to tolerate some fault displacements. By monitoring the progress of damage states by increasing PGD, the fragility curves corresponding to each damage state were plotted and interpreted in related figures.

关键词： reverse fault rupture continuous tunnel geotechnical centrifuge ground surface deformations fragility curves

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Strategic Thinking on Shallow-water Oil and Gas Exploration in Offshore China

Ke-qiang Wu,Jian-yong Xu,Bo Kang

《工程管理前沿（英文）》 2016年第3卷第4期页码 349-355 doi: 10.15302/J-FEM-2016056

摘要： The oil and gas exploration in offshore China has made great achievements, and as the important areas of offshore exploration, the shallow waters contribute most of the oil and gas reserves and production. However, the available area for exploration is diminishing and the cost of exploration is rising. The field changes and ever increasing difficulties of exploration bring new challenges technically and economically. Therefore, for effective exploration of shallow-water oil and gas in offshore China, it is necessary to center on the general requirements of becoming a powerful marine country and the ideas of value exploration, initiate key research projects in the fields of China’s offshore stratigraphic-lithologic reserves, Paleogene reserves, buried-hill reserves, high temperature and pressure reserves and hydrocarbon-rich sags, and form geological theories and explorative technologies of large and medium size oil and gas field in offshore China. The measures regarding the challenges include: (1) Innovating theoretical understanding and optimizing new exploration fields, (2) developing technical capabilities and improving the success rate of exploration, and (3) enhancing management level and deepening value exploration.

关键词： offshore China shallow-water oil and gas exploration strategic thinking challenge countermeasure

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Control concept and countermeasures for shallow lakes' eutrophication in China

JIN Xiangcan, LU Shaoyong, HU Xiaozhen, JIANG Xia, WU Fengchang

《环境科学与工程前沿（英文）》 2008年第2卷第3期页码 257-266 doi: 10.1007/s11783-008-0063-3

摘要： Research on lake eutrophication in China began in the early 1970s, and many lakes in China are now known to be in meso-eutrophic status. Lake eutrophication has been showing a rapidly increasing trend since 2000. Investigations show that the main reasons for lake eutrophication include a fragile lake background environment, excessive nutrient loading into lakes, excessive human activities, ecological degeneration, weak environmental protection awareness, and lax lake management. Major mechanisms resulting from lake eutrophication include nutrient recycling imbalance, major changes in water chemistry (pH, oxygen, and carbon), lake ecosystem imbalance, and algal prevalence in lakes. Some concepts for controlling eutrophication should be persistently proposed, including lake catchment control, combination of pollutant source control with ecological restoration, protection of three important aspects (terrestrial ecology, lake coast zone, and submerged plant), and combination of lake management with regulation. Measures to control lake eutrophication should include pollution source control (i.e., optimize industrial structural adjustments in the lake catchment, reduce nitrogen and phosphorus emission amounts, and control endogenous pollution) and lake ecological restoration (i.e. establish a zone-lake buffer region and lakeside zone, protect regional vegetation, utilize hydrophytes in renovation technology); countermeasures for lake management should include implementing water quality management, identifying environmental and lake water goals, legislating and formulating laws and regulations to protect lakes, strengthening publicity and the education of people, increasing public awareness through participation in systems and mechanic innovations, establishing lake region management institutions, and ensuring implementation of governance and management measures.

关键词： excessive participation prevalence lakeside Research

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土质隧道深浅埋界定方法研究

赵占厂,谢永利

《中国工程科学》 2005年第7卷第10期页码 84-86

摘要：

针对现有隧道深浅埋界定方法存在的问题，结合现场测试和数值仿真结果，明确了应从围岩压力性质角度进行深浅埋界定。首次提出了以数值仿真技术为手段，利用拱上中心线土体侧压力系数变化规律为依据进行深浅埋界定的思路，并用2个工程实例进行了验证，新方法对土质隧道衬砌设计和施工有重大意义。

关键词：土质隧道深埋和浅埋界定方法

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Numerical simulation of flood inundation processes by 2D shallow water equations

ZHANG Xinhua, LONG Wenfei, XIE Heping, ZHU Jiahua, WANG Jiangping

《结构与土木工程前沿（英文）》 2007年第1卷第1期页码 107-113 doi: 10.1007/s11709-007-0011-5

摘要： In order to strengthen flood risk management in a river basin, to upgrade the capability of flood control, and to reduce the loss of lives and properties in urban areas, a numerical simulation model using 2D shallow water equations was proposed in this study. A satisfactory result has been obtained by applying the model in the Fuji River basin in central Japan. The result indicates that the numerical simulation model proposed can be adopted not only in the risk management of a river basin, but also in the study of realtime operations of rescue jobs and evacuation routes in a municipal region suffering from a serious flooding event.

关键词： control satisfactory management central rescue

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Reliability assessment of three-dimensional bearing capacity of shallow foundation using fuzzy set theory

Rajarshi PRAMANIK, Dilip Kumar BAIDYA, Nirjhar DHANG

《结构与土木工程前沿（英文）》 2021年第15卷第2期页码 478-489 doi: 10.1007/s11709-021-0698-8

摘要： The aim of this study is to investigate the applicability of reliability theory on surface square/rectangular footing against bearing capacity failure using fuzzy set theory in conjunction with the finite element method. Soil is modeled as a three-dimensional spatially varying medium, where its parameters (cohesion, friction angle, unit weight, etc.) are considered as fuzzy variables that maintain some membership functions. Soil is idealized as an elastic-perfectly plastic material obeying the Mohr–Coulomb failure criterion, where both associated and non-associated flow rules are considered in estimating the ultimate bearing capacity of the footing. The spatial variability of the soil is incorporated for both isotropic and anisotropic fields, which are determined by the values of scales of fluctuation in both the horizontal and vertical directions. A new parameter namely, limiting applied pressure at zero failure probability is proposed, and it indirectly predicts the failure probability of the footing. The effect of the coefficient of variation of the friction angle of the soil on the probability of failure is analyzed, and it is observed that the effect is significant. Furthermore, the effect of the scale of fluctuation on the probability of failure is investigated, and the necessity for considering spatial variability in the reliability analysis is well proven.

关键词： finite element method square footing reliability analysis fuzzy set theory coefficient of variation spatial variability

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Three-dimensional finite difference analysis of shallow sprayed concrete tunnels crossing a reverse fault

Masoud RANJBARNIA, Milad ZAHERI, Daniel DIAS

《结构与土木工程前沿（英文）》 2020年第14卷第4期页码 998-1011 doi: 10.1007/s11709-020-0621-8

摘要： Urban tunnels crossing faults are always at the risk of severe damages. In this paper, the effects of a reverse and a normal fault movement on a transversely crossing shallow shotcreted tunnel are investigated by 3D finite difference analysis. After verifying the accuracy of the numerical simulation predictions with the centrifuge physical model results, a parametric study is then conducted. That is, the effects of various parameters such as the sprayed concrete thickness, the geo-mechanical properties of soil, the tunnel depth, and the fault plane dip angle are studied on the displacements of the ground surface and the tunnel structure, and on the plastic strains of the soil mass around tunnel. The results of each case of reverse and normal faulting are independently discussed and then compared with each other. It is obtained that deeper tunnels show greater displacements for both types of faulting.

关键词： urban tunnel sprayed concrete reverse fault normal fault finite difference analysis

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浅埋富水软弱围岩隧道支护受力特征及方案研究

万飞,谭忠盛,杨森森,马栋

《中国工程科学》 2014年第16卷第8期页码 45-53

摘要：

依托关角隧道河谷浅埋段，展开富水软弱围岩隧道支护受力特征及方案的研究。对试验段的初支围岩压力、钢架应力、锚杆轴力、衬砌水压力进行现场监测，结果表明：初支应力不能得到有效控制、突水突泥塌方现象时有发生，现有的支护方案无法满足浅埋段安全施工要求。在监测数据基础上，经过综合分析，对支护方案作出调整。在Ⅴ级围岩区段，拱部120°范围设超前管棚和小导管，宽大节理掌子面超前小导管注浆加固，初期支护取消系统锚杆，采用I20 型钢钢架和拱墙设双层钢筋网；在Ⅵ级围岩区段，超前支护采用管棚工作室施作拱部180°及以下1 m范围的0°角长管棚，全断面超前水平钻孔注浆，初期支护取消系统锚杆，采用I20 型钢钢架、三台阶型钢临时横撑和双层防水板。研究成果可为河谷浅埋隧道支护方案的确定提供理论依据和基础数据，为同类工程的设计与施工决策提供借鉴。

关键词：隧道工程河谷浅埋软弱围岩支护方案现场监测

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超小间距非对称浅埋隧道施工监控量测及分析

王云龙,谭忠盛,陈鹰

《中国工程科学》 2012年第14卷第11期页码 24-28

摘要：

以青岛胶州湾海底隧道团岛段小间距隧道为例，通过现场监测结果分析了小间距非对称浅埋隧道的围岩压力特征及支护受力，结果表明该隧道后行洞围岩压力及支护受力都较大，这种结果有别于大部分小间距对称隧道的理论预测及实测结果。为有效缓解这些问题，对支护参数进行及时调整，增强后行洞的径向支护能力并对中间岩柱采取加固措施。继后施工中的监测结果显示，后行洞的稳定性得到了有效的控制，为类似小间距隧道的设计和施工提供了借鉴和参考。

关键词：隧道超小间距非对称浅埋监测

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Characterization of phosphorus species and modeling for its organic forms in eutrophic shallow lake sediments

Hongguang CHENG,Xiao PU,Yiting CHEN,Fanghua HAO,Liming DONG

《环境科学与工程前沿（英文）》 2014年第8卷第6期页码 905-921 doi: 10.1007/s11783-014-0650-4

摘要： Variations of phosphorus (P) and its species in surface sediment of Baiyangdian Lake, a eutrophic shallow lake located in North China, were investigated through combination of field survey and numerical calculation based on cluster analysis. P fractionation was performed by a sequential extraction scheme, categorized as loosely bound P (NH Cl-P), reductant soluble P (BD-P), metallic oxide bound P (NaOH-P), calcium bound P (HCl-P) and organic P (Org-P). P concentrations exhibited regional similarities and a total of four sub-areas were identified in which the same rank was HCl-P>Org-P>BD-P ≈ NaOH-P>NH Cl-P. NH Cl-P, BD-P and Org-P were found to contribute to P enrichment in overlying water column. Specifically, labile Org-P acted as a potential pool with a greater contribution in aerobic layer compared to anaerobic layer. A hysteresis (lag= 4 months) existed when labile Org-P concentration was negatively correlated with aerobic layer thickness. In view of magnitude of identified P contributors in sub-areas, higher potential of P release was present in Fuhe River and Tang River estuary areas. On the basis of calibration and verification, the mathematical model with parameter settings applied in this study was improved to serve as a tool for limnology management and eutrophic control.

关键词： phosphorus fractionation variation characteristics modeling sediment Baiyangdian Lake