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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    

Shanghai center project excavation induced ground surface movements and deformations

Guolin XU, Jiwen ZHANG, Huang LIU, Changqin REN

《结构与土木工程前沿(英文)》 2018年 第12卷 第1期   页码 26-43 doi: 10.1007/s11709-017-0439-1

摘要: Empirical data on deep urban excavations can provide designers a significant reference basis for assessing potential deformations of the deep excavations and their impact on adjacent structures. The construction of the Shanghai Center involved excavations in excess of 33-m-deep using the top-down method at a site underlain by thick deposits of marine soft clay. A retaining system was achieved by 50-m-deep diaphragm walls with six levels of struts. During construction, a comprehensive instrumentation program lasting 14 months was conducted to monitor the behaviors of this deep circular excavation. The following main items related to ground surface movements and deformations were collected: (1) walls and circumferential soils lateral movements; (2) peripheral soil deflection in layers and ground settlements; and (3) pit basal heave. The results from the field instrumentation showed that deflections of the site were strictly controlled and had no large movements that might lead to damage to the stability of the foundation pit. The field performance of another 21cylindrical excavations in top-down method were collected to compare with this case through statistical analysis. In addition, numerical analyses were conducted to compare with the observed data. The extensively monitored data are characterized and analyzed in this paper.

关键词: deep excavation     foundation pit     soft clay     top-down method     field observation     ground surface movements     ground deformations    

Seismic ground motion analysis of Shanghai Pudong Airport site considering the effects of spatial correlation

JIANG Tong, CHEN Laiyun, XING Hailing, L? Xilin

《结构与土木工程前沿(英文)》 2007年 第1卷 第4期   页码 430-435 doi: 10.1007/s11709-007-0058-3

摘要: The terminal No. II of Shanghai Pudong International Airport is located at Pudong District of Shanghai City near shore of East China Sea, and the area of the long-span terminal is 400 m × 200 m. The construction site of the terminal locates on the irregular topography, and its alluvium achieves about 300 m in thickness. The spatial correlation of seismic ground motion, as well as the amplification of soft alluvium and the effect of irregular topography, should be considered. This paper uses a simplified method to obtain the response spectrum of the engineering bedrock under the irregular topography. The spectrum is used to generate the sets of spatially correlative horizontal and vertical seismic motions. The surface ground motion was calculated under incidence of the spatially correlative seismic motion by 2D finite element method (FEM) model considering nonlinear properties of the soil by means of the equivalent linear method. In order to compare the effect of 2D irregular topography, the seismic response analysis of 1D model is carried out by using the equivalent linear method. For indicating the effect of the spatial correlation of input motions, the horizontal uniform inputs, as well as the horizontal and vertical uniform input are carried out for the seismic response analysis of the site. Finally, some characteristics of seismic ground motion calculated for previously mentioned cases are compared.

关键词: surface ground     horizontal uniform     Finally     seismic ground     correlative seismic    

Lateral displacement of soft ground under vacuum pressure and surcharge load

Chin-Yee ONG, Jin-Chun CHAI

《结构与土木工程前沿(英文)》 2011年 第5卷 第2期   页码 239-248 doi: 10.1007/s11709-011-0110-1

摘要: Surcharge load (e.g. embankment fill) will induce settlement and outward lateral displacement, while vacuum pressure will induce settlement and inward lateral displacement of a ground. Ideally, combination of surcharge load and vacuum pressure can reduce or minimize the lateral displacement. Laboratory large scale model (length: 1.50 m, width: ~0.62 m, height: 0.85 m) tests and finite element analyses (FEA) were conducted to investigate the main influencing factors on lateral displacement of a soft clayey ground under the combination of vacuum pressure and surcharge load. For the conditions investigated, the results indicate that the outward lateral displacement increases with the increase of the ratio of surcharge load to vacuum pressure ( ) and the loading rate of the surcharge load ( ). Also, it is shown that for a given and condition, lateral displacement reduces with the increase of the initial undrained shear strength ( ) of the ground. To predict the lateral displacement of a ground under the combination of surcharge load and vacuum pressure, the loading conditions in terms of and , and value of the ground have to be considered.

关键词: vacuum consolidation     lateral displacement     PVD     finite element analysis     surcharge load    

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    

The convexity about ultimate bearing hypersurfaces of structures

Chengxi GUO,Tingting GUO

《结构与土木工程前沿(英文)》 2016年 第10卷 第4期   页码 456-461 doi: 10.1007/s11709-016-0334-1

摘要: The relationship between the convexity on the ultimate bearing surface of a structure and the second-order effects of loads is discussed. All of generalized non-overload forces acted on a structure forms a convex set when ignoring the second-order effects (coupling effects between the generalized forces). It is true also when the Hessian matrix composed of the second-order partial derivatives on the hypersurface about the ultimate bearing of the structure is negative definite. The outward convexity is kept when the surface is expressed by certain dimensionless parameters. A series of properties based on the convexity are pointed out. Some applications in the analysis of bearing capacity of structures were illustrated with examples. The study shows that an evaluation about the bearing capacity state of a complex structure can be made on the basis of several points on the surface of the ultimate bearing of the structure.

关键词: service     limit load     ultimate bearing surface     convexity     generalized force     generalized displacement     frame structure    

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

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    

急倾斜煤层开采对地表构筑物影响的预计

高明中,王列平

《中国工程科学》 2007年 第9卷 第11期   页码 142-146

摘要:

针对淮南某矿急倾斜煤层开采复杂的采矿地质条件,运用概率积分法对优化后的开采方案所引起 的地表沉陷进行研究,总结出急倾斜煤层开采重复采动所引起的厚冲积层地表沉陷的相关参数。所得结果 对现场开采及地表沉陷治理具有一定的指导作用,对于同类地质和开采条件的矿区具有重要参考价值。

关键词: 急倾斜煤层     地表移动与变形     概率积分法     预计    

R&D of the ground-coupled heat pump technology in China

Nairen DIAO, Ping CUI, Junhong LIU, Zhaohong FANG,

《能源前沿(英文)》 2010年 第4卷 第1期   页码 47-54 doi: 10.1007/s11708-009-0080-3

摘要: The ground-coupled heat pump (GCHP) systems have been identified as one of the best sustainable energy technologies for space heating and cooling in residential and commercial buildings. In this paper, research on and development of the GCHP technology in China are summarized. New models are presented for efficient thermal analysis of ground heat exchangers, of which one- and two-dimensional solid cylindrical source models and their analytical solutions are devised to deal with pile ground heat exchangers. Analytical solutions are also derived for vertical and inclined finite line source models as well as for a groundwater advection model. Explicit solutions of a quasi-three-dimensional model can be used to better evaluate the thermal resistance inside boreholes. Studies on hybrid GCHP systems and the thermal response test in China are also commented.

关键词: ground source heat pump     ground heat exchanger     HVAC     China    

INTERACTIONS BETWEEN ABOVE AND BELOW GROUND PLANT STRUCTURES: MECHANISMS AND ECOSYSTEM SERVICES

《农业科学与工程前沿(英文)》 2022年 第9卷 第2期   页码 197-213 doi: 10.15302/J-FASE-2021433

摘要:

Interactions between above and below ground parts of plants can be considered under the (overlapping) categories of energy, material and information. Solar energy powers photosynthesis and transpiration by above ground structures, and drives most water uptake through roots and supplies energy as organic matter to below ground parts, including diazotrophic symbionts and mycorrhizas. Material transfer occurs as water and dissolved soil-derived elements transport up the xylem, and a small fraction of water moving up the xylem with dissolved organic carbon and other solutes down the phloem. The cytosolic nature of sieve tubes accounts for at least some of the cycling of K, Mg and P down the phloem. NO3 assimilation of above ground parts requires organic N transport down phloem with, in some cases, organic anions related to shoot acid-base regulation. Long-distance information transfer is related development, biotic and abiotic damage, and above and below ground resource excess and limitation. Information transfer can involve hydraulic, electrical and chemical signaling, with their varying speeds of transmission and information content. Interaction of above and below ground plant parts is an important component of the ecosystem service of storing atmospheric CO2 as organic C in soil, a process that has decreased since the origin of agriculture.

关键词: aerenchyma / carbon accumulation / hormones / phloem / xylem    

Estimation of composite load model with aggregate induction motor dynamic load for an isolated hybrid

Nitin Kumar SAXENA,Ashwani Kumar SHARMA

《能源前沿(英文)》 2015年 第9卷 第4期   页码 472-485 doi: 10.1007/s11708-015-0373-7

摘要: It is well recognized that the voltage stability of a power system is affected by the load model and hence, to effectively analyze the reactive power compensation of an isolated hybrid wind-diesel based power system, the loads need to be considered along with the generators in a transient analysis. This paper gives a detailed mathematical modeling to compute the reactive power response with small voltage perturbation for composite load. The composite load is a combination of the static and dynamic load model. To develop this composite load model, the exponential load is used as a static load model and induction motors (IMs) are used as a dynamic load model. To analyze the dynamics of IM load, the fifth, third and first order model of IM are formulated and compared using differential equations solver in Matlab coding. Since the decentralized areas have many small consumers which may consist large numbers of IMs of small rating, it is not realistic to model either a single large rating unit or all small rating IMs together that are placed in the system. In place of using a single large rating IM, a group of motors are considered and then the aggregate model of IM is developed using the law of energy conservation. This aggregate model is used as a dynamic load model. For different simulation studies, especially in the area of voltage stability with reactive power compensation of an isolated hybrid power system, the transfer function of the composite load is required. The transfer function of the composite load is derived in this paper by successive derivation for the exponential model of static load and for the fifth and third order IM dynamic load model using state space model.

关键词: isolated hybrid power system (IHPS)     composite load model     static load     dynamic load     induction motor load model     aggregate load    

Evaluation of the performance of a centralized ground-water heat pump system in cold climate region

Shilei LU,Zhe CAI,Li ZHANG,Yiran LI

《能源前沿(英文)》 2014年 第8卷 第3期   页码 394-402 doi: 10.1007/s11708-014-0310-1

摘要: The aim of this study is to evaluate the performance of a centralized open-loop ground-water heat pump (GWHP) system for climate conditioning in Beijing with a cold climate in China. Thus, a long-time test was conducted on a running GWHP system for the heating season from December 2011 to March 2012. The analysis of the testing data indicates that the average heat-pump coefficient of performance (COP) and the COP of the system (COPs) are 4.27 and 2.59. The low value and large fluctuation in the range of COP are found to be caused by the heat transfixion in the aquifer and the bypass in the circulation loop. Therefore, some suggestions are proposed to improve the performance for GWHPs in the cold climate region in China.

关键词: ground-water heat pump (GWHP)     actual coefficient of performance     heat transfixion    

Optimisation for interconnected energy hub system with combined ground source heat pump and borehole

Da HUO, Wei WEI, Simon Le BLOND

《能源前沿(英文)》 2018年 第12卷 第4期   页码 529-539 doi: 10.1007/s11708-018-0580-0

摘要: Ground source heat pumps (GSHP) give zero-carbon emission heating at a residential level. However, as the heat is discharged, the temperature of the ground drops, leading to a poorer efficiency. Borehole inter-seasonal thermal storage coupled with GSHP maintains the efficiency at a high level. To adequately utilize the high performance of combined GSHP and the borehole system to further increase system efficiency and reduce cost, such a combined heating system is incorporated into the interconnected multi-carrier system to support the heat load of a community. The borehole finite element (FE) model and an equivalent borehole transfer function are proposed and respectively applied to the optimisation to analyze the variation of GSHP performance over the entire optimisation time horizon of 24 h. The results validate the borehole transfer function, and the optimisation computation time is reduced by 17 times compared with the optimisation using the FE model.

关键词: borehole thermal storage     energy hub     ground source heat pumps (GSHP)     particle swarm optimisation    

Numerical study on the seismic response of the underground subway station- surrounding soil mass-ground

Guobo WANG, Mingzhi YUAN, Xianfeng MA, Jun WU

《结构与土木工程前沿(英文)》 2017年 第11卷 第4期   页码 424-435 doi: 10.1007/s11709-016-0381-7

摘要: Ground buildings constructed above metro station have increased very quickly due to the limited land resources in urban areas. In this paper, the seismic response of the Underground subway station-Surrounding soil mass-Ground adjacent buildings (USG) system subjected to various seismic loading is studied through numerical analysis. The numerical model is established in terms of the calculation domain, boundary condition, and contact property between soil and structure based on the real project. The reciprocal influence between subway station and ground adjacent building, and their effects on the dynamic characteristics of surrounding soil mass are also investigated. Through the numerical study, it is found that the impact of underground structure on the dynamic characteristics of the surrounding soil mass depends on its own dimension, and the presence of underground structure has certain impact on the seismic response of ground adjacent building. Due to the presence of underground structure and ground adjacent building, the vertical acceleration generated by the USG system cannot be ignored. The outcomes of this study can provide the references for seismic design of structures in the USG system.

关键词: underground subway station     ground adjacent building     seismic response    

GENOME EDITING: A GROUND BREAKING RESEARCH HAS BEEN RANKED TOP 10 ENGINEERING FRONTS FROM 2017 TO 2021

《农业科学与工程前沿(英文)》 2022年 第9卷 第2期   页码 309-311 doi: 10.15302/J-FASE-2022440

标题 作者 时间 类型 操作

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

期刊论文

Shanghai center project excavation induced ground surface movements and deformations

Guolin XU, Jiwen ZHANG, Huang LIU, Changqin REN

期刊论文

Seismic ground motion analysis of Shanghai Pudong Airport site considering the effects of spatial correlation

JIANG Tong, CHEN Laiyun, XING Hailing, L? Xilin

期刊论文

Lateral displacement of soft ground under vacuum pressure and surcharge load

Chin-Yee ONG, Jin-Chun CHAI

期刊论文

Centrifuge experiments for shallow tunnels at active reverse fault intersection

Mehdi SABAGH, Abbas GHALANDARZADEH

期刊论文

The convexity about ultimate bearing hypersurfaces of structures

Chengxi GUO,Tingting GUO

期刊论文

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

Sina AMIRI; Ali Naghi DEHGHAN

期刊论文

急倾斜煤层开采对地表构筑物影响的预计

高明中,王列平

期刊论文

R&D of the ground-coupled heat pump technology in China

Nairen DIAO, Ping CUI, Junhong LIU, Zhaohong FANG,

期刊论文

INTERACTIONS BETWEEN ABOVE AND BELOW GROUND PLANT STRUCTURES: MECHANISMS AND ECOSYSTEM SERVICES

期刊论文

Estimation of composite load model with aggregate induction motor dynamic load for an isolated hybrid

Nitin Kumar SAXENA,Ashwani Kumar SHARMA

期刊论文

Evaluation of the performance of a centralized ground-water heat pump system in cold climate region

Shilei LU,Zhe CAI,Li ZHANG,Yiran LI

期刊论文

Optimisation for interconnected energy hub system with combined ground source heat pump and borehole

Da HUO, Wei WEI, Simon Le BLOND

期刊论文

Numerical study on the seismic response of the underground subway station- surrounding soil mass-ground

Guobo WANG, Mingzhi YUAN, Xianfeng MA, Jun WU

期刊论文

GENOME EDITING: A GROUND BREAKING RESEARCH HAS BEEN RANKED TOP 10 ENGINEERING FRONTS FROM 2017 TO 2021

期刊论文