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1.
能量桩是将地源热泵系统中的换热管埋置在桩体内部,桩同时起到承载和换热的作用,是一种新型的基础型式。为了合理分析黏土地基中能量桩的力学特性,需要了解能量桩运行过程中桩和地基土的温度响应,并考虑温度变化对土体力学性能的影响。基于有限元软件ABAQUS建立了能量桩传热分析三维有限元模型,把能量桩的传热简化为换热管内液体与管壁之间的对流传热、桩体中的热传导和地基中的热传导,将计算结果与常规理论和实测数据进行了对比验证。对热力耦合边界面本构模型进行了二次开发,通过算例验证了模型对土体压缩和剪切性状温度效应的模拟能力。利用所提出的能量桩传热分析方法和热边界面模型,考虑不同的桩顶工作荷载水平,对正常固结黏土地基中能量桩单桩的长期性能进行了研究,分析了温度循环对桩顶沉降、桩侧摩阻力和桩身轴力的影响。结果表明,工作荷载越高,温度循环次数越多,桩顶累积沉降越大。 相似文献
2.
This paper presents a numerical formulation of a three dimensional embedded beam element for the modeling of piles, which incorporates an explicit interaction surface between soil and pile. The formulation is herein implemented for lateral loading of piles but is able to represent soil–pile interaction phenomena in a general manner for different types of loading conditions or ground movements. The model assumes perfect adherence between beam and soil along the interaction surface. The paper presents a comparison of the results obtained by means of the present formulation and by means of a previously formulated embedded pile element without interaction surface, as well as reference semi‐analytical solutions and a fully 3D finite element (FE) model. It is seen that the proposed embedded element provides a better convergence behavior than a previously formulated embedded element and is able to reproduce key features of a full 3D FE model. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
3.
能源桩传热与承载特性研究现状及展望 总被引：1，自引：0，他引：1
能源桩是一种在传递上部结构荷载的同时获取浅层地热能源的新技术,给桩基结构的设计及安全服役提出了新的挑战。从能源桩实际应用的角度,围绕能源桩传热性能和承载性能两个关键科学问题,从4个方面综述目前的研究现状：（1）能源桩的热传递研究;（2）能源桩的结构响应特征;（3）能源桩的承载变形特性;（4）能源桩的荷载传递机制。在此基础上,对当前能源桩传热模型的适用性、热交换作用下能源单桩及群桩的承载特性以及长期运行条件下的承载性能及结构安全性进行了讨论,最后对能源桩工程下一步研究进行了展望。分析成果对于保证结构安全,合理开发浅层地能具有重要意义。 相似文献
4.
为获得地下水渗流作用下桩埋管参数对能量桩热-力耦合特性的影响,建立了不同埋管参数的能量桩数值模型,分析了桩埋管数量、埋管布置形式、埋管管径对单位桩深换热量、日换热量、桩截面平均温升、桩身位移增量及桩身附加温度荷载的影响。结果表明：增加埋管数量可以增大能量桩换热量,但也会加剧桩内不同埋管间的热干扰,导致换热性能下降及桩身... 相似文献
5.
A simplified method of numerical analysis based on elasticity theory has been developed for the analysis of axially and laterally loaded piled raft foundations embedded in non‐homogeneous soils and incorporated into a computer program “PRAB”. In this method, a hybrid model is employed in which the flexible raft is modelled as thin plates and the piles as elastic beams and the soil is treated as springs. The interactions between structural members, pile–soil–pile, pile–soil–raft and raft–soil–raft interactions, are approximated based on Mindlin's solutions for both vertical and lateral forces with consideration of non‐homogeneous soils. The validity of the proposed method is verified through comparisons with some published solutions for single piles, pile groups and capped pile groups in non‐homogeneous soils. Thereafter, the solutions from this approach for the analysis of axially and laterally loaded 4‐pile pile groups and 4‐pile piled rafts embedded in finite homogeneous and non‐homogeneous soil layers are compared with those from three‐dimensional finite element analysis. Good agreement between the present approach and the more rigorous finite element approach is demonstrated. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
6.
能量桩技术兼具支撑上部荷载和浅层地热能换热器双重功能;作为一种节能减排技术,近年来在国内外获得了一定的发展。然而,目前简单套用基于传统地埋管换热器获得的土体综合热导率系数,无法准确计算能量桩换热效率。依托河南理工大学某低承台3×3能量桩群桩工程应用,开展基于能量桩的土体综合热导率系数测试现场试验和数值模拟研究,分析加热时长、加热功率、流速及桩长等因素对土体综合热导率系数的影响规律,继而探讨能量桩在群桩中的布置形式对土体综合热导率系数的影响规律。研究结果表明,基于传统地源热泵测试所发展起来的土体综合热导率系数线热源分析方法,并不适用于分析基于能量桩现场实测所获得的相关数据;有必要推导一套考虑桩径影响的、适用于能量桩的土体综合热导率系数测试与计算分析方法。 相似文献
7.
Integrating ground heat exchanger elements into concrete piles is now considered as an efficient energy solution for heating/cooling of buildings. In addition to the static load of buildings, the concrete piles also undergo a cycle of thermal deformation. In the case of single energy pile, calculation methods already exist and permit to perform a proper geotechnical design. In the case of energy pile group, the thermo‐mechanical interactions within the group are more complex. Very few experimental results on the energy pile group are available so that numerical analysis can be an interesting way to provide complementary results about their behavior. This paper deals with a numerical analysis including a comparison between a single energy pile and an energy pile group with different boundary conditions at the pile head. In order to take into account the stress reversal induced by the thermal expansions and contractions, a cyclic elastoplastic constitutive model is introduced at the soil–pile interface. The analysis aims to give some insights about the long‐term cyclic interaction mechanisms in the energy pile group. Based on this qualitative study, some guidance can be brought for the design of energy piles in the case where group effects should be considered. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
8.
在考虑地基土分层的基础上,采用动力Winkler地基模型模拟桩土相互作用并运用传递矩阵,求解层状地基中的单桩和群桩的阻抗函数.在计算动力相互作用因子时考虑了被动桩与土的相互作用.最后将相互作用因子和群桩阻抗的本文解与精确解进行对比,验证了本文方法的有效性. 相似文献
9.
This paper presents the results of a parametric study in which a series of fully coupled, 3-dimensional thermo-hydro-mechanical Finite Element (FE) analyses has been conducted to investigate the effects of the thermal changes imposed by the regular performance of a GSHP system driven by energy piles on a very large piled raft. The FE simulation program has been focused mainly on the evaluation of the following crucial aspects of the energy system design: the assessment of the soil–pile–raft interaction effects during thermal loading conditions; the quantification of the influence of the thermal properties of the soil and of the geometrical layout of the energy piles on the soil–foundation system response, and the evaluation of the influence of the active pile spacing on the thermal performance of the GSHP–energy pile system. The results of the numerical simulations show that the soil–pile–raft interaction effects can be very important. In particular, the presence of a relatively rigid raft in direct contact with the soil is responsible for axial load variations in inactive piles of the same order of those experienced by the thermo-active piles, even when the latter are relatively far and temperature changes in inactive piles are small. As far as the effect of pile spacing is concerned, the numerical simulations show that placing a high number of energy piles in a large piled raft with relatively small pile spacings can lead to a significant reduction of the overall heat exchange from the piles to the soil, thus reducing the thermal efficiency of the system. 相似文献
10.
Y. K. Chow 《国际地质力学数值与分析法杂志》1987,11(6):621-638
A numerical method of analysis based on elasticity theory is presented for the analysis of axially and laterally loaded pile groups embedded in nonhomogeneous soils. The problem is decomposed into two systems, namely the group piles acted upon by external applied loads and pile–soil interaction forces, and a layered soil continuum acted upon by a system of pile–soil interaction forces at the imaginary positions of the piles. The group piles are discretized into discrete elements while the nonhomogeneous soil behaviour is determined from an economically viable finite element procedure. The load–deformation relationship of the pile group system is then determined by considering the equilibrium of the pile–soil interaction forces, and the compatibility of the pile and soil displacements. The influence of soil nonlinearity can be studied by limiting the soil forces at the pile–soil interface, and redistributing the ‘excess forces’ by an ‘initial stress’ process popular in elasto-plastic finite element analysis. The solutions from this approach are compared with some available published solutions for single piles and pile groups in homogeneous and nonhomogeneous soils. A limited number of field tests on pile groups are studied, and show that, in general, the computed response compares favourably with the field measurements. 相似文献
11.
Hiroyoshi Hirai 《国际地质力学数值与分析法杂志》2014,38(12):1298-1320
An analytical approach using a Winkler model is investigated to provide analytical solutions of settlement of a rectangular pile subjected to vertical loads in nonhomogeneous soils. For a vertically loaded pile with a rectangular cross section, the settlement influence factor of a normal pile in nonhomogeneous soils is derived from Mindlin's solution for elastic continuum analysis. For short piles with rectangular and circular cross sections, the modified forms of settlement influence factors of normal piles are produced taking into account the load transfer parameter proposed by Randolph for short circular piles. The modulus of subgrade reaction along a rectangular pile in nonhomogeneous soils is expressed by using the settlement influence factor related to Mindlin's solution to combine the elastic continuum approach with the subgrade‐reaction approach. The relationship between settlement and vertical load for a rectangular pile in nonhomogeneous soils is available in the form of the recurrence equation. The formulation of settlement of soils surrounding a rectangular pile subjected to vertical loads in nonhomogeneous soils is proposed by taking into account Mindlin's solution and both the equivalent thickness and the equivalent elastic modulus for layers in the equivalent elastic method. The difference of settlement between square and circular piles is insignificant, and the settlement of a rectangular pile decreases as the aspect ratio of the rectangular pile cross section increases. The comparison of results calculated by the present method for a rectangular pile in nonhomogeneous soils has shown good agreement with those obtained from the analytical methods and the finite element method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
12.
Changjie Zheng Shishun Gan George Kouretzis Lubao Luan Xuanming Ding 《国际地质力学数值与分析法杂志》2020,44(4):533-549
This paper presents an analytical solution for determining the dynamic characteristics of axially loaded piles embedded in elastic-poroelastic layered soil of finite thickness. The interface between the elastic and poroelastic soil coincides with the groundwater table level, which is explicitly taken into account in the solution. The pile is modelled as elastic one-dimensional rod to account for the effect of its dynamic characteristics on the response of the soil-pile system. The solution is based on Biot's poroelastodynamic theory and the classical elastodynamic theory, which we use to establish the governing equations of the soil and pile. Accordingly, the pile base resistance, shaft reaction, and the complex impedance of soil-pile system are obtained using the method of Hankel integral transformation. Following the validation of the derived solution, we identify the main parameters affecting the vertical dynamic impedance of the pile via a parametric study. The presented method poses as an efficient alternative for quickly estimating the dynamic characteristics of axially loaded piles, without having to resort to complex numerical analyses. 相似文献
13.
基于悬浮不排水桩复合地基超静孔隙水压力解答,建立了变荷载条件下复合地基桩间土和下卧层土平均固结度的解析解。通过与有限元解答的对比,证明了解析解的正确性和有效性。利用解析解对桩间土和下卧层土的固结性状进行了分析。研究发现,桩间土的固结速率远大于下卧层土,并随置换率和桩土模量比的增加而增大。在工程设计采用的置换率范围内,桩的贯入比较小时,下卧层土的固结速率受置换率和桩土模量比的影响很小;桩的贯入比较大时,下卧层土的固结速率随置换率和桩土模量比的增加而增大。桩间土和下卧层土的固结存在临界置换率和临界桩土模量比,超过临界值后,桩间土和下卧层土的固结速率不随桩土模量比和置换率的增加而增大。桩间土和下卧层土的固结速率随加荷速率的增加而增大。 相似文献
14.
In this paper, a coupling approach is presented to study the static responses of vertically loaded pile group embedded in multilayered transversely isotropic soils. The individual pile in pile group is modeled by the finite element method, while the analytical layer-element method is applied to represent the soil's behavior. Then, the interaction equation of piles and soils is obtained by considering the force equilibrium and displacement compatibility conditions and solved by a FORTRAN program. The results computed by the proposed approach compare favorably with those from some existing solutions and field test. Some typical parametric analysis cases are investigated to study the effect of soil anisotropy, pile stiffness ratio, and pile spacing on the behavior of vertically loaded pile group. 相似文献
15.
水平受荷长桩弹塑性计算解析解 总被引：1，自引：0，他引：1
当考虑桩侧土体非线性本构关系时对水平受荷桩的计算一般需采用数值方法,解析结果相对较少。基于Winkler地基模型和桩侧土体简化的弹塑性本构关系,对均质地基中水平荷载作用下桩头嵌固的长桩进行了解析推导,得到了桩身最大挠度及最大弯矩与荷载关系的统一解析表达式,并采用相同的方法求得高桩情形下桩头挠度的计算式。计算表明,联合荷载作用下桩身泥面处的挠度和转角不等于单个荷载作用时的线性叠加,采用常规的线性叠加法计算将偏于不安全。所求解析式借助计算器即可进行最大挠度和最大弯矩的计算,大大方便了工程的计算应用。 相似文献
16.
A simplified analysis method has been developed to estimate the vertical movement and load distribution of pile raft foundations subjected to ground movements induced by tunneling based on a two‐stage method. In this method, the Loganathan–Polous analytical solution is used to estimate the free soil movement induced by tunneling in the first stage. In the second stage, composing the soil movement to the pile, the governing equilibrium equations of piles are solved by the finite difference method. The interactions between structural members (such as pile–soil, pile–raft, raft–soil, and pile–pile) are modeled based on the elastic theory method of a layered half‐space. The validity of the proposed method is verified through comparisons with some published solutions for single piles, pile groups, and pile rafts subjected to ground movements induced by tunneling. Good agreements between these solutions are demonstrated. The method is also used for a parametric study to develop a better understanding of the behavior of pile rafts influenced by tunneling operation in layered soil foundations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
17.
软土中已打入桩对土体位移的遮帘作用研究 总被引：1，自引：0，他引：1
采用侧向移动土中桩的理论分析结果以及有限元数值模拟,较为系统地分析了沉桩工程中已打入桩对土体侧向位移及地表隆起的遮帘作用,结果表明已打入桩对土体侧向位移的总体遮帘作用并不显著。采用不同切向劲度系数的接触面单元以模拟已打入桩间隔时间长短对地表隆起的遮帘效应,结果表明：打入桩间隔期较短时,已打入桩对地表隆起的遮拦作用主要体现在对土体位移的“水平阻隔”上,土体沿桩土界面发生流动向上隆起;而间隔期较长时,桩土间存在有较大的摩阻力而限制了土体的位移,此时已打入桩对地表隆起的遮拦作用体现在竖向摩阻力对土体隆起的“抑制”上。 相似文献
18.
A new approach to estimate shaft capacity of bored piles in sandy soils, based on numerical analysis, is presented. The topic is relevant as current design methods often largely underestimate the shaft capacity of piles in sands, thus resulting in an over-conservative design. The proposed approach is based on explicitly modelling the thin cylinder of soil surrounding the pile, where strain localization concentrates (shear band), and on the fundamental mechanic behaviour of sandy soils (e.g. dilatancy, softening). This approach is both simple and easy to apply. Results of a broad parametric study involving axially loaded single piles embedded in different sandy soils are presented, highlighting that relative density and grain size distribution mainly affect the shaft capacity. The capability of the procedure to predict shaft friction is checked against data from a well-documented full-scale axial load test on instrumented pile. Some suggestions for calibration and application of the method are also reported. 相似文献
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20.
This paper presents an embedded beam formulation for discretization independent finite element (FE) analyses of interactions between pile foundations or rock anchors and the surrounding soil in geotechnical and tunneling engineering. Piles are represented by means of finite beam elements embedded within FEs for the soil represented by 3D solid elements. The proposed formulation allows consideration of piles and pile groups with arbitrary orientation independently from the FE discretization of the surrounding soil. The interface behavior between piles and the surrounding soil is represented numerically by means of a contact formulation considering skin friction as well as pile tip resistance. The pile–soil interaction along the pile skin is considered by means of a 3D frictional point‐to‐point contact formulation using the integration points of the beam elements and reference points arbitrarily located within the solid elements as control points. The ability of the proposed embedded pile model to represent groups of piles objected to combined axial and shear loading and their interactions with the surrounding soil is demonstrated by selected benchmark examples. The pile model is applied to the numerical simulation of shield driven tunnel construction in the vicinity of an existing building resting upon pile foundation to demonstrate the performance of the proposed model in complex simulation environments. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献