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1.
M.A. Coulthard 《Geotechnical and Geological Engineering》1999,17(3-4):373-385
Numerical modelling has been used to investigate a variety of problems in underground mining and tunnelling: subsidence induced by longwall coal mining; stresses generated when an open stope is filled cemented backfill and the stability of exposures created during subsequent mining of adjacent stopes; the interaction of two tunnels; and the effects of under-mining a pre-existing tunnel and shaft. In each case, results from nonlinear stress analyses can be used to guide the design of excavations and rock support mechanisms. 相似文献
2.
The study investigates the disturbance to piles and pile groups caused by multiple nearby drives of a large diameter slurry shield-driven tunnelling machine in Shanghai. The minimum distance between the slurry shield tunnel (with diameter D = 15.43 m) and the adjacent pile groups of Metro Line 3 and Yixian Elevated Road is 1 m. The nonlinear finite element (FE) software program ABAQUS was used to analyse the movement of the pile groups caused by the process of shield tunnelling. A field investigation was conducted before the multiple crossings to study the impact (movement and excess pore water pressure) on the surrounding soil and piles caused by the tunnelling process. The field investigation is divided into two sections: (i) free-field tunnelling, and (ii) tunnelling close to trial piles pre-installed in the section. For the full-scale test, tunnelling variable, including slurry pressure and grouting pressure, are adjusted during construction to reduce the disturbance during tunnelling close to pile groups supporting two elevated bridges. The FE simulation of the multiple crossings includes two steps: (a) shield tunnelling along the south bound tunnel approaching the working shaft at the western bank of the Huangpu River, and passing separately between two adjacent pile groups of each bridge; (b) return tunnel passing again between the pile groups of the two bridges along the north bound tunnel. Three different FE models are generated: (1) free-field tunnelling process, (2) tunnelling close to trial piles, and (3) multiple tunnel passes adjacent to pile groups supporting the two elevated bridges. Most of the relevant factors in tunnelling are taken into consideration in the FE models including (a) slurry pressure, (b) grouting pressure, (c) grouting material hardening, and (d) soil-pile interaction. 相似文献
3.
Analytical stress and displacement due to twin tunneling in an elastic semi‐infinite ground subjected to surcharge loads 
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下载免费PDF全文 The construction of twin tunnels at shallow depth has become increasingly common in urban areas. In general, twin tunnels are usually near each other, in which the interaction between tunnels is too significant to be ignored on their stability. The equivalent arbitrarily distributed loads imposed on ground surface were considered in this study, and a new analytical approach was provided to efficiently predict the elastic stresses and displacements around the twin tunnels. The interaction between 2 tunnels of different radii with various arrangements was taken into account in the analysis. We used the Schwartz alternating method in this study to reduce the twin‐tunnel problem to a series of problems where only 1 tunnel was contained in half‐plane. The convergent and highly accurate analytical solutions were achieved by superposing the solutions of the reduced single‐tunnel problems. The analytical solutions were then verified by the good agreement between analytical and numerical results. Furthermore, by the comparison on initial plastic zone and surface settlement between analytical solution and numerical/measured results of elastoplastic cases, it was proven that the analytical solution can accurately predict the initial plastic zone and its propagation direction and can qualitatively provide the reliable ground settlements. A parametric study was finally performed to investigate the influence of locations of surcharge load and the tunnel arrangement on the ground stresses and displacements. The new solution proposed in this study provides an insight into the interaction of shallow twin tunnels under surcharge loads, and it can be used as an alternative approach for the preliminary design of future shallow tunnels excavated in rock or medium/stiff clay. 相似文献
4.
Twin tunnels are frequently used to address the increasing transportation demands in large cities. To ensure the safety of twin tunnels in close proximity, it is often necessary to take protective measures that have not been well studied. Field monitoring was conducted for a project of twin earth pressure balance shield (EPBS) tunnels in typical soft ground. The preceding tunnel was reinforced by various measures, including trailer bracing, compensation grouting, artificial freezing and scaffold bracing. The entire deformation of the reinforced tunnel was recorded during the succeeding tunnelling process. A three dimensional finite-element method (FEM) model was established to simulate the entire process of twin EPBS tunnelling, particularly the reinforcement measures. The computed deformations of the reinforced tunnel were consistent with the measured data. Furthermore, the stress history and pore pressure of the surrounding soil were analysed to investigate the deformation mechanism of the tunnel. Both the measured and computed results indicate that although the face pressure of the succeeding tunnel was smaller than the earth pressure at rest, the preceding tunnel could still experience an inward horizontal convergence and a deflection away from the succeeding tunnel. These distortion modes were caused by the squeezing effect of the horizontal soil arch in front of the succeeding tunnel face. Finally, convergence and deflection indices were proposed to quantify and assess the effectiveness of the reinforcement measures. The trailer bracing, as an “in-tunnel” reinforcement technique, was found to be the most effective method for controlling tunnel convergence. However, artificial freezing as an “out-tunnel” reinforcement technique led to the largest reductions in tunnel deflection. A combination of both “in-tunnel” and “out-tunnel” reinforcements was recommended. 相似文献
5.
Three-dimensional (3D) finite element analyses have been performed to study the behaviour of a single pile and 3 × 3 and 5 × 5 pile groups during open face tunnelling in stiff clay. Several governing factors, such as tunnelling-induced ground and pile settlement, axial pile force changes and shear transfer mechanism at the pile–soil interface, have been studied in detail. Tunnelling resulted in the development of pile head settlement larger than the free-field soil surface settlement. In addition, axial force distributions along the pile change substantially due to changes in the shear transfer between the pile and the soil next to the pile, which triggers tunnelling-induced tensile forces in the piles with tunnel advancement. It was found that the relative displacements and the normal stresses at the pile–soil interface drastically affected shear transfer. The extent of slip length along a pile increased as the tunnelling proceeded. The apparent allowable pile capacity was reduced by up to approximately 42% due to the development of tunnelling-induced pile head settlement. Shear stress on the pile was increased for most of the pile depth with tunnel advancement, which was associated with changes in soil stresses and ground deformation, and hence, the axial pile force was gradually reduced with tunnel advancement, indicating the development of tunnelling-induced tensile pile force. The maximum tunnelling-induced tensile force on the pile was approximately 0.33Pa, where Pa is the allowable pile capacity applied to the pile head prior to tunnel excavation. The range affected by tunnelling in the longitudinal direction may be identified as approximately −2D ∼ +(1.5–2.0D), where D is the tunnel diameter, from the pile centre (behind and ahead of the pile axis), in terms of pile settlement and axial pile force changes based on the analysis conditions assumed in the current study. Larger pile head settlements and smaller changes in axial pile forces were computed for piles that were part of groups. It has been found that the serviceability of piles experiencing adjacent tunnelling is more affected by pile settlement than by axial pile force changes, in particular for piles inside groups. The magnitude of the tunnelling-induced excess pore pressure was small and may not substantially affect pile behaviour. 相似文献
6.
在膨胀土地基中进行隧道对群桩影响的三维离心模型试验研究,目标地层损失比为2%,着重研究引起的地基沉降槽、桩的附加沉降、附加弯矩、轴力的变化规律。试验得出：隧道开挖沉降槽空间效应明显;隧道开挖从-0.75D至1.25D时,桩附加沉降呈线性增长,隧道开挖至1.25D以后,桩依然沉降明显。前桩与后桩沉降值不同,桩帽会出现倾斜;前桩上部出现负附加弯矩而下部出现正附加弯矩,而后桩仅在下部出现正附加弯矩;前桩附加弯矩最大值出现在隧道轴线附近,且比后桩附加弯矩大得多;前桩附加轴力随着隧道的开挖而增加,且每步最大值在隧道轴线附近。后桩的轴力也随隧道的开挖而增加,但每步最大值出现在桩顶附近。 相似文献
7.
为了揭示黏土中静压沉桩的宏观力学特性,采用西澳大学的梁式离心机压桩系统,通过在双层高岭黏土中进行一系列1g重力场情况下的T-bar触探测试试验、静压沉桩试验、桩拉伸试验和压缩试验,对比分析了T-bar分别在均质软质黏土和双层黏土中随贯入深度变化测得的不排水剪切强度的特性;研究了桩体在贯入过程中沉桩阻力、桩端阻力以及桩侧摩阻力的发展规律;并对桩身径向总应力在沉桩过程中的变化规律进行了探讨;此外,还揭示了不同桩型沉桩终压力与桩承载力之间的关系。结果表明：在黏土中沉桩时,桩侧摩阻力在整个沉桩阻力中发挥主要的作用;对于同一土层而言,当桩超过土层分界面以下2D（D为桩径）范围后,桩端阻力并不受相邻土层性质的影响;随着压桩后时间的推移,桩侧摩阻力对承载力的时效影响较桩端阻力大。 相似文献
8.
Three-dimensional (3D) numerical analyses have been carried out to study the behaviour of a single pile to adjacent tunnelling in the lateral direction of the pile. The numerical analyses have included comparisons between the current study, previous elastic solutions and advanced 3D elasto-plastic analyses. In the numerical analyses, the interaction between the tunnel, the pile and the soil next to the pile has been analysed. The study includes the axial force distributions on the pile, the relative shear displacement between the pile and the soil, the shear stresses at the soil next to the pile and the pile settlement. In particular, the shear stress transfer mechanism along the pile related to tunnel advancement has been analysed by using interface elements allowing soil slip. It has been found that existing solutions may not accurately estimate the pile behaviour since several key issues are not included. Due to changes in the relative shear displacement between the pile and the soil next to the pile with tunnel advancement, the shear stresses and axial force distributions along the pile change drastically. Downward shear stress develops at the upper part of the pile, while upward shear stress is mobilised at the lower part of the pile, resulting in a compressive force on the pile. A maximum compressive force of about 0.25–0.52Pa was developed on the pile, solely due to tunnelling, depending on the pile tip locations relative to the tunnel position, where Pa is the service pile loading prior to tunnelling. The majority of the axial force on the pile developed within ±2D in the transverse direction (behind and ahead of piles) relative to the pile position, where D is the tunnel diameter. In addition, mobilisation of shear strength at the pile–soil interface was found to be a key factor governing pile–soil–tunnelling interaction. The reduction of apparent allowable pile capacity due to tunnelling was dependent on the pile location relative to the tunnel position. Some insights into the pile behaviour in tunnelling obtained from the numerical analyses will be reported and discussed. 相似文献
9.
Shuying Wang Junsheng Yang Yuanhong Yang Fangping Zhong 《Geotechnical and Geological Engineering》2014,32(2):453-467
The structure on the ground bears impact from the tunneling-induced settlement, especially when the tunnel is shallow and its span is large. This paper presents the construction of Lijiachong twin tunnels below a high-rise transmission tower and the prevention techniques to avoid the failure of the tower. The span of each tunnel is about 18 m, and the tunnel embedded depth below the tower foundations is only 15.5 m. There was a high risk of influencing the performance of the tower during the tunneling. To reduce the risk of collapse of the transmission tower, the available methods in field to reinforce the tower foundations were proposed. For engineering cost and construction convenience, the separated pile foundations were connected with framed girders, resulting in that the separated foundations worked as a whole. The effectiveness of the reinforcement was evaluated by monitoring deformation and stress in the tower, indicating that the measured values were lower than their respective allowable ones. With reinforcing the tower foundations using the framed girders, the Lijiachong twin tunnels safely passed beneath the transmission tower, and the continuous performance of the transmission tower was ensured. 相似文献
10.
A method for predicting the maximum mobilized side resistance and unit shaft resistance-displacement curves (load transfer functions) on piles in clay is described. The method was derived using a numerical solution to model pile installation effects and a finite element scheme to model pile loading. Results of three well-documented pile load tests on steel piles were used to develop intermediate steps and final solutions, and the method was verified by comparing predicted results to two other load tests. An expression is proposed to represent load transfer functins for use by practitioners for the design of bridge and other foundations in clay. 相似文献
11.
Mehmet Ozcelik 《Geotechnical and Geological Engineering》2018,36(6):3437-3449
Mechanized tunnelling is a well-established tunnel construction method which allows constructing tunnels in various conditions including mixed ground conditions as well as tunnels in vulnerable urban areas. The selection of the excavator suitable for the geological structure is important in terms of realizing an efficient tunnel excavation. Tunnel excavation studies of Istanbul Kabatas–Mecidiyeköy Metro tunnels are implemented as a double tube. Geology in this section is composed of sandstone, siltstone, mudstone interbedded or as separate units along with dyke intrusions. Calcareous clay, clayey limestone, clayey sand are also rarely observed. Between the Kabatas–Mecidiyekoy tunnels includes two types of mechanical excavation methods namely tunnel boring machine (TBM) and new Austrian tunnelling method (NATM). Main purpose of this study is mixed ground and their impacts on mechanized tunnelling. At the end, some issues have been presented which seems to be important for the success of TBM and NATM in the mixed grounds. As the tunnel excavation studies continued, the problem of collapse on the ground surface of Barbaros Boulevard in Besiktas station increased the importance of tunnel excavation under mixed ground conditions. 相似文献
12.
13.
The interaction between twin‐parallel tunnels affects the tunnelling‐induced ground deformation, which may endanger the nearby structures. In this paper, an analytical solution is presented for problems in determining displacements and stresses around deforming twin‐parallel tunnels in an elastic half plane, on the basis of complex variable theory. As an example, a uniform radial displacement was assumed as the boundary condition for each of the two tunnels. Special attention was paid to the effects of tunnel depth and spacing between the two tunnels on the surface movement to gain deep insight into the effect of the interaction between twin‐parallel tunnels using the proposed analytical approach. It is revealed that the influence of twin tunnel interaction on surface movements diminishes with both the increase of the tunnel depth and the spacing between the two tunnels. The presented analytical solution manifests that, similar to most of the existing numerical results, the principle of superposition can be applied to determine ground deformation of twin‐parallel tunnels with a certain large depth and spacing; otherwise, the interaction effect between the two tunnels should be taken into account for predicting reliable ground movement. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
14.
在地下隧道施工中遇到既有桩的情况并不少见,尽管近年来隧道--土--桩相互作用引起了广泛关注,但以往的研究主要集中在小规模隧道开挖引起的桩的反应上。通过三维离心模型试验,研究了双管大型隧道开挖引起的群桩变形机理。由于隧道开挖引起的应力释放,群桩的实测沉降随隧道的推进几乎呈线性增加。监测点距新建隧道较短,导致群桩沉降较大。单隧道开挖完成后,在隧道中心线正上方观测到最大桩群沉降为0.23%D(即隧道直径)。双管开挖后,最大群桩沉降增加到0.32%D,最大群桩沉降位置向两隧道之间的中心线移动。随着开挖面接近监测断面,既有桩群迅速向开挖面倾斜。当隧道工作面通过监测断面时,减少了现有群桩的倾斜。显然,当隧道工作面位于监测断面正下方时,测得的群桩倾斜达到最大值。这清楚地说明了隧道开挖引起群桩的三维变形机理。若将隧道开挖简化为二维问题,则忽略了群桩沿隧道纵向的倾斜,而群桩的倾斜位于非保守侧。 相似文献
15.
基于改进荷载传递法计算降水引起的基桩沉降 总被引：1，自引：0，他引：1
现有研究采用荷载传递法时均未计算桩体自重,若直接应用于国内软土地区超长桩基的沉降计算,其精度难以满足高速铁路线下工程严格的沉降控制要求。基于佐藤?悟双折线模型提出侧阻荷载传递函数的假定模式,引入桩体自重并对荷载传递法的基本微分方程进行修正和求解,结合降水引起的桩周土体沉降计算和基于端阻弹性模型的桩端土体沉降计算,获得地下水位变化诱发的基桩沉降计算方法;采用理论推导的基桩沉降解析解,并借助嵌入荷载传递函数的有限元方法,分别对单纯桩顶荷载作用和桩顶荷载与降水共同作用两种工况下的桩侧摩阻力、桩体轴力和基桩沉降进行算例对比分析;有限元计算因考虑了由桩体沉降产生的桩周土体附加竖向位移而与理论计算略有偏差,但两种方法计算结果的变化规律基本一致,验证了降水引起的基桩沉降理论计算公式的合理性及正确性。 相似文献
16.
Ali Lashkari 《国际地质力学数值与分析法杂志》2013,37(8):904-931
Using pile segment analysis, the mobilized shaft resistance of axially loaded nondisplacement piles in sand is investigated here. It is accepted that the shaft capacity of piles constructed in granular soils is highly influenced by the mechanical behavior of soil–structure interfaces forming adjacent the piles skin. Adopting the thin interface layer as a load transfer mechanism, a simple but accurate critical state compatible interface constitutive model is introduced. After evaluation, the interface model in conjunction with the pile segment analysis is applied for the prediction of the shaft resistance mobilized in nondisplacement piles. The proposed approach takes into account the influences of pile diameter and surface roughness together with the effects of the surrounding soil density and stiffness on the mobilized shaft resistance. The performance of the proposed method is verified by comparing its predictions with the experimental data of various model piles covering wide ranges of length, diameter, roughness, and surrounding soil properties. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
桩的存在使桩周土的竖向有效应力不等于上覆土自重应力与上部外加荷载的简单叠加,原因是桩-土相对刚度导致桩-土接触面上产生竖向剪切。通过平衡分析法,得到不同荷载形式下桩周土竖向有效应力、桩侧正（负）摩阻力、总侧摩阻力和轴力（下拽力）的计算方法,根据已开展的饱和黏土中单桩的负摩阻力试验,验证了公式的合理性,证明了考虑竖向剪切效应的必要性。通过计算分析可知：桩周土竖向均布荷载作用下,桩-土竖向剪切效应削弱了桩周土竖向有效应力、桩侧负摩阻力和桩身下拽力,剪切效应的控制参数?分别取-0.01、-0.02和-0.04时,靠近桩端的桩侧负摩阻力分别为? = 0时的91%、83%和71%,靠近桩端的桩身下拽力分别为? = 0时的93%、87%和76%。由于下拽力受截面几何参数影响,其折减程度略小于桩侧负摩阻力。因此,桩周土表面均布荷载作用时,忽略桩-土竖向剪切效应可能高估由下拽力引起的桩顶沉降。 相似文献
18.
修建海底隧道技术难度高、施工风险大,其中不良地质段是施工高风险地段。厦门翔安海底隧道是中国大陆地区第一条海底隧道,长6.05 km,最深处位于海平面下约70 m,采用设置服务隧道的3孔隧道方式,设双向6车道,钻爆法施工。隧道场区以花岗岩地层为主,主要不良地质段包括两端陆域及浅滩全强风化地段和海域多处风化深槽,其施工期风险管理尤为重要。应用风险评估与分析理论,探讨了海底隧道施工风险发生机制及风险水平评估方法。针对厦门翔安隧道施工图设计阶段的地质勘测、土建结构设计和拟采用的施工方法,对不良地质段施工期的典型地质风险和施工风险进行识别与风险水平评估,研究了降低风险的相应对策,以便在施工中对风险进行管理,采取必要措施保障施工安全与质量。 相似文献
19.
随着城市内地铁盾构区间隧道临近城市道路桥桩工程的增多,急需研究盾构隧道临近桥桩施工对桥桩的变形影响问题。采用有限元数值计算方法,结合盾构隧道穿越桥桩实际工程,建立了盾构隧道施工对临近桥桩影响的数值分析模型,模拟盾构隧道施工,对盾构隧道穿越临近桥桩的桩体沉降、桩体侧移、地表沉降进行了数值分析研究,盾构隧道穿越时及穿越后桩体沉降、桩体侧移、地表沉降控制结果较为理想,桩体处于稳定状态。结合现场监测成果,对数值计算结果和监测结果进行对比分析,表明采用的数值分析计算模型、参数取值对盾构隧道施工对临近桥桩影响的模拟是可靠的,可以运用文中的数值计算方法预测后续盾构隧道施工引起临近桥桩沉降、桩体侧移和地表沉降结果。 相似文献
20.
The roadway tunnel is considered a good solution for the success of modern roadway networks. It can help to overcome possible traffic congestion and considerably reduce journey time. The continuous growth of traffic volumes leads to increase congestion and decrease safety. This leads to the need for extra tunnel space. The extra tunnel space can be achieved either by the widening of the existing tunnel or by adding a new one. The choice of the suitable method is dependent on many factors like tunnels alignment, site conditions, construction method, tunnel operation, risk assessment…etc. The current research investigates the second alternative through a specific case study as an example. The method comprises adding two new tunnels to an existing twin roadway tunnels. The investigated problem considers the new tunnels to be added vertically or horizontally. The influence of the new tunnel construction on the existing tunnels is investigated considering both the variation of relative position and spacing distance in a parametric study context. Several numerical models are employed to check the construction sequence and the tunnelling safety. These models are used to evaluate the induced stresses in surrounding ground for two different soil types, straining actions in tunnels’ liner and deformations of both ground and liner. The result demonstration shows how to find out the minimum practical and safe spacing distance between the driven new tunnels and the existing ones without the need for the relatively expensive soil strengthening techniques. 相似文献