共查询到20条相似文献，搜索用时 15 毫秒
1.
In the empirical methods for reinforcement design of underground excavations, an even distribution of rock bolts is generally recommended. This work proves that this design is not necessarily optimal and shows how the state-of-the-art reinforcement design could be improved through topology optimisation techniques. The Bidirectional Evolutionary Structural Optimisation (BESO) method has been extended to consider nonlinear material behaviour. An elastic perfectly-plastic Mohr–Coulomb model is utilised for both original rock and reinforced rock. External work along the tunnel wall is considered as the objective function. Various in situ stress conditions with different horizontal stress ratios and different geostatic stress magnitudes are investigated through several examples. The outcomes show that the proposed approach is capable of improving tunnel reinforcement design. Also, significant difference in optimal reinforcement distribution for the cases of linear and nonlinear analysis results proves the importance of the influence of realistic nonlinear material properties on the final outcome. 相似文献
2.
盾构机穿越邻近土洞区域是在岩溶区修建的地铁隧道常常遇到的问题,为降低盾构掘进对土洞的扰动,以防止盾构突陷、偏离轴线或发生地面塌陷,需对穿越时盾构的掘进参数进行优化控制。针对当前主要根据经验选取掘进参数的不足,根据弹性力学Mindlin解建立了盾构穿越邻近土洞的力学模型,在此基础上,以掘进速度为控制变量,以掘进引起土洞顶部能量密度变化为指标函数,提出了穿越时的掘进速度最优控制问题,并利用梯度法进行了数值求解,最后将该方法运用于广州地铁九号线花-马区间盾构穿越邻近土洞问题的分析中。结果表明:该模型能有效反映盾构掘进时正面推力对土洞顶部的扰动;在该模型上建立的掘进速度最优控制问题,能对掘进速度的控制策略进行优化,优化结果与工程经验相符,具有一定工程应用价值。 相似文献
3.
The present study addresses a layout design of rockbolts for reinforcing natural ground structures applying a special optimization method, called multiphase layout optimization. Rockbolts are used to tighten loosed natural ground, and the layout of rockbolts are determined without sufficient information about the physical properties of the ground materials. Because of this uncertainty, unexpected deformation often occurs at the excavation surface of natural ground. In that case, it is requested to determine an effective layout of the additional rockbolts promptly with respect to the actual deformation at the construction site. However, it is not easy to determine the optimal layout because of its complexity, and consequently, it has no choice but to determine the layout in an empirical way. This study introduces a numerical approach to determine an optimal layout of rockbolts with respect to arbitrarily possible deformation of natural ground. The objective is to maximize the stiffness of the overall ground structure reinforced with rockbolts. For optimization, a gradient‐based optimization scheme is applied because of its numerical efficiency. It was verified from a series of numerical examples that this method has great potential to improve the stiffness of the overall ground structure and shows a certain applicability to a practical design. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
4.
断层构造是制约地下工程设计与施工的关键因素。综合考虑复杂地质构造与地下洞室群结构的耦合关系,采用三维地质建模方法建立实现了地层体、断层体与地下洞室群结构的统一模型。基于三维模型提出了断层复杂度的概念,为水利水电工程地下厂房洞室群的选址方案分析提供了一种新的手段。针对地下围岩稳定性问题,提出基于断层与断层、断层与开挖面相互切割的曲面块体识别方法,搜索地下厂房洞室群内可能的失稳区域。上述方法已成功应用在某水电工程地下厂房洞室群分析中,在设计方案优化分析中取得了良好的效果。 相似文献
5.
隧洞围岩损失位移估计的智能优化反分析 总被引：1，自引：0，他引：1
隧洞开挖过程中围岩监测断面的布置一般滞后于掌子面开挖,监测断面布置前围岩已发生的位移称为损失位移。采用优化反分析思路求取损失位移,该思路将损失位移的求解转化为以实测位移与计算位移的误差作为目标函数、岩体力学参数作为决策变量的全局优化反分析问题。针对该全局优化反分析问题是一类高度非线性多峰值且计算代价较高的优化问题,将性能优异的粒子群优化算法与高斯过程机器学习方法相融合,结合FLAC3D数值计算程序,提出隧洞围岩损失位移优化反分析的粒子群-高斯过程-FLAC3D智能协同优化方法。算例研究表明,该方法是可行的,不仅能获得可靠的损失位移预测结果,而且可获取合理的围岩计算模型力学参数,具有全局性好、计算效率高的特点,克服了传统优化反分析方法容易陷入局部最优或过于依赖初始学习样本的局限性。将该方法应用到锦屏二级水电站辅助洞BK14+599断面的损失位移反分析,获得了该断面围岩的损失位移和力学参数,其中,损失位移较大,原因在于岩体开挖后在短时间内弹性变形大。因此,对于地下工程,特别是深部地下岩体工程,在围岩稳定性评价与围岩参数反分析中,损失位移不可忽视,应给予足够重视。 相似文献
6.
考虑岩体劣化的大型地下厂房围岩变形动态监测预警方法研究 总被引：2，自引：1，他引：1
针对大型地下厂房洞室开挖后围岩力学参数发生劣化的事实,以及大型地下厂房允许变形无相关规范参考的缺陷,在分析地下厂房围岩失稳机制基础之上,基于强度折减法思想,提出大型地下厂房围岩劣化折减计算方法,建立围岩变形的动态预警路线体系。该体系应用屈服接近度指标确定围岩的劣化区域,折减劣化区域内的变形模量、凝聚力及抗拉强度值,在折减计算过程中依据围岩的变形、劣化区体积、释放能量三者之一发生突变作为围岩失稳判据,获得围岩失稳的变形预警值,并与现场变形监测值对比分析,从而实现围岩稳定状况的快速判别。地下厂房实例分析表明,该方法可为洞室稳定性判断提供定量依据,较好地满足了地下工程建设需要。 相似文献
7.
地下洞室开挖爆破围岩松动圈的数值分析计算 总被引：4，自引：2，他引：2
根据数值计算提出了在地下洞室开挖爆破中,确定围岩松动圈的方法。给出了地下洞室开挖爆破的三维弹塑性损伤有限元计算方法。该方法论述了爆破荷载、重力荷载和开挖荷载的计算、施加以及迭代的方法,可以合理反应爆破对围岩稳定的影响和锚固支护施加的效果;结合岩石松动圈的实测方法,推导了判定围岩开始松动的损伤系数阈值公式,可以结合数值计算得到的洞周围岩损伤系数分布,确定在开挖爆破作用下围岩松动圈的范围。对实际工程的分析计算表明,根据数值计算判定的围岩松动范围与实测松动范围的规律基本一致,量值吻合较好,其结果为地下洞室开挖爆破的围岩松动圈的确定提供了有效的方法。 相似文献
8.
卵砾石地层被掘削时,其主要破坏模式并非一般的宏观整体剪切破坏,而是刀具切入卵砾石间的缝隙,将卵砾石颗粒剥离出原始地层,该过程较为契合颗粒离散元的物理力学假设。为确定掘削工况下的颗粒材料最优细观参数,对不同的颗粒接触法向刚度、接触刚度比、粒间摩擦系数、颗粒形状、颗粒尺寸等的颗粒材料开展了截割三维仿真试验,并分析研究了不同细观参数对掘削效果的影响。计算结果显示:颗粒接触法向刚度、接触刚度比的多种细观参数组合可以对应同一个宏观弹性模量值,接触刚度比大的细观参数组合的抗掘削能力更大。颗粒形状、粒间摩擦系数的多种细观参数组合可以对应同一个内摩擦角值,形状复杂的颗粒材料具有更大的抗掘削能力。在宏观参数相同的情况下,平均粒径更大的颗粒材料抗掘削能力更大。因此,利用颗粒离散元模拟掘削卵砾石地层问题时,除需保证虚拟颗粒材料的宏观整体剪切破坏响应与真实材料基本一致外,还需根据材料的抗掘削能力进一步标定细观参数,以获得更贴近实际情况的模拟效果。文章提出的方法可以为其他颗粒离散元掘削工况数值模拟中的参数标定提供参照依据。 相似文献
9.
基坑变形的反分析涉及数值模型与优化方法的耦合,常具有计算量大、使用不方便的特点。为此,提出1种可用于基坑变形反分析的多重响应面法,该方法在基坑地下连续墙不同深度处分别采用二次多项式表示地下连续墙水平位移与土层弹性模量之间的隐式关系,在此基础上利用位移观测对基坑土层弹性模量进行反分析。该方法可以解开数值模型和优化算法的耦合,从而具有较高的计算效率。工程应用实例表明,多重响应面法对基坑土层弹性模量进行反分析具有使用方便、计算效率高、计算结果准确的优点,非常适合求解基坑工程的位移反演问题。 相似文献
10.
脱离模式是块体理论提出的有限可动块体的失稳模式之一。虽然直接塌落是地下工程中最常见的失稳现象,但是目前依然缺少适用的定量分析方法,这使得地下工程的开挖和加固设计缺乏必要的理论支撑。为此,提出了一种改进的考虑渐进破坏的岩块稳定分析方法。主要改进了3处：(1)引入超载基数和超载方向两个参数来量化描述储备荷载;(2)提出了Tan和Scal两种超载基数设定方式;(3)超载方向设定在节理锥的边界扇面上。算例验证结果表明,改进方法完全兼容现有双面滑模式的安全系数算法,实现了脱离模式的定量稳定性分析。最后,讨论了改进方法的刚度参数取值方法及其敏感性。 相似文献
11.
The paper presents advances in the discrete element modelling of underground excavation processes extending modelling possibilities
as well as increasing computational efficiency. Efficient numerical models have been obtained using techniques of parallel
computing and coupling the discrete element method with finite element method. The discrete element algorithm has been applied
to simulation of different excavation processes, using different tools, TBMs and roadheaders. Numerical examples of tunnelling
process are included in the paper, showing results in the form of rock failure, damage in the material, cutting forces and
tool wear. Efficiency of the code for solving large scale geomechanical problems is also shown. 相似文献
12.
Deyu Qian Nong Zhang Mingwei Zhang Hideki Shimada Peng Cao Yanlong Chen Kai Wen Sen Yang Nianchao Zhang 《Arabian Journal of Geosciences》2017,10(13):285
Faults are complex geological conditions that are commonly encountered during underground excavation. Many support schemes, such as using a single pilot heading method and 30-m-long borehole pre-grouting, have been implemented during the pilot excavation of an 800-m-deep underground opening that passes through large fault zones in East China. However, various geo-hazards, including groundwater inrush, debris flow, and roof collapse, are still occurring, which seriously threaten tunneling safety. To eliminate the geo-hazards and ensure tunneling safety, ground surface pre-grouting (GSPG) was proposed and implemented for the first time to reinforce the regional engineering rock mass for this proposed 800-m-deep underground opening passing through large fault zones. The minimum grouting pressure of GSPG at a depth of 800 m below the surface is put forward based on hydraulic fracturing theory, providing valuable guidance for GSPG engineering practice. Engineering practice demonstrates that GSPG eliminates geo-hazards, improves the objective rock mass stability, and ensures tunneling safety. Field measurements indicate that the displacement velocity of the surrounding rock shows an obvious fluctuation response under the influence of GSPG, and the impact of GSPG on the stability of the 800-m-deep underground opening that has been excavated dramatically decreases as the distance from the grouting borehole increases. Moreover, there is a strong negative exponential correlation between the maximum velocity of deformations and the distance from the grouting borehole. In addition, the safe distance underground during GSPG is greater than 137 m. 相似文献
13.
The shape optimisation of a cavity is typically performed without considering the previous support, which may significantly reduce the practical significance of such analyses. Even when an excavation section is optimised, failure of the surrounding rock in a tunnel cannot be prevented in the presence of excessive in situ stress. Thus, a support should be established to protect the stability of a tunnel from the failure of the surrounding rock. This study examines the optimal shape of the support that satisfies the optimisation criterion, which minimises the largest tangential stress along the inner edge of the support, for a specific net tunnel size and support strength. The optimisation process is to solve a series of forward problems using the conformal mapping method for a plane elasticity complex function. The tangential stress along the inner edge of the support is selected as the objective function, and the coefficients of the mapping function are considered as the design variables. The minimum value of the objective function is calculated based on the mixed penalty function method and the optimal support shape that satisfies the given constraints can be obtained. The stress state of an optimally shaped tunnel support is significantly improved compared to non-optimal configurations, and the stress concentration along the inner edge of the support is minimised. 相似文献
14.
根据白山抽水蓄能泵站地下厂房开挖过程中的变形观测数据,提出了一种基于响应面法的岩体力学参数反演方法。该方法利用响应面函数建立了岩体力学参数与围岩变形之间的非线性关系。通过有限元数值模拟确立了响应面函数中的系数。定义参数反演的目标函数,将参数反演问题转化为优化问题。分别采用拟牛顿优化算法和遗传算法求解参数反演的目标函数,得到了地下厂房的岩体力学参数。根据反演确定的岩体力学参数,对地下厂房围岩的开挖变形进行了数值模拟,研究表明,有限元模拟的地下厂房与现场观测值基本一致,验证了反演方法的有效性。 相似文献
15.
随着地下空间开发利用的立体式发展,地下近接工程中结构相互作用问题日益突显。针对盾构隧道下穿既有挤土桩问题,提出了基于岩土介质小孔扩张（收缩）理论的分析方法。通过基于统一砂黏土本构模型和大应变假设推导的小孔扩张-收缩排水解析解,建立了隧-桩相互作用力学模型;提出了隧道开挖影响下桩基的承载力衰减因子,并采用荷载-沉降曲线预测了桩基沉降。由分析结果可知,隧道地层损失引起的桩侧承载力减小、桩端承载力减小和桩端刚度损失,三者共同作用促使桩基发生沉降失稳,并提出了桩基的承载力控制准则、稳定控制准则和变形控制准则。此外,研究得到了桩基失稳时隧道地层损失与各因素之间的相关关系。其结果为揭示隧道与邻近结构相互作用机制、保障地下结构稳定性提供了有效的分析手段和必要的理论依据。 相似文献
16.
圆砾层地区基坑工程具有很强的地域性,围护结构选型有待进行经验总结,并且土体强度等参数的不确定性使得基坑稳定性分项系数不能通过可靠度理论得到很好的解决。本文通过收集调研大量已成功实施的圆砾层地区基坑工程案例,整理围护结构选型相关参数,计算基坑稳定性分项系数,建立数据库。经统计分析,获取了圆砾层地区基坑围护结构合理选型规律,并采用取下限的方法给出了圆砾层地区基坑整体稳定性分项系数参考值为1.3,抗倾覆稳定性分项系数参考值为1.2,抗渗流稳定性分项系数参考值为1.5。 相似文献
17.
Dimitris Papadopoulos Michael Herty Volker Rath Marek Behr 《Computational Geosciences》2011,15(4):737-753
A shape reconstruction method for geophysical objects by temperature measurements is presented which uses adjoint equations
and a level set function approach. Temperature is measured on subdomains, e.g., representing boreholes. This information is
used to reconstruct the shape of the geophysical layers. For this purpose, shape optimization techniques are applied. The
method uses a representation of the layers by a so-called level set function. The evolution of this level set function is
then used to determine the optimal shape. The “speed” of the evolution is computed using adjoint equations. Synthetic examples
demonstrate the use of the inverse method and its behavior in different configurations. 相似文献
18.
城市地下管线采用承插式接口连接,管线结构的连续性与否取决于接口刚度。然而,现有研究大都假定地下管线为连续结构,忽略了接口转角对管线变形的影响。开展土工离心模型试验和两阶段有限元参数分析,系统研究了盾构下穿不同接口刚度管线的变形特性。发现非连续管线的薄弱接口导致其整体抗弯刚度明显小于连续管线,且接口转动导致非连续管线具有更好的与土体协调变形能力。因此,盾构下穿施工引起的非连续管线沉降明显大于连续管线。非连续管的结构连续性假定将大大低估管线沉降。盾构下穿引起的接口转角与地层损失呈线性关系。基于系统的有限元参数分析,建立了区分相对刚性、柔性管线的无量纲组。针对相对刚性、柔性的非连续管线,分别建立了管节相对长度、管-土相对刚度与接口转角的预测方法,利用离心模型试验结果验证了预测方法的合理性。新方法能有效地预测盾构穿越地下管线的接口转角,研究成果可应用于城市地下管网改造工程。 相似文献
19.
基于对现场地质条件和开挖响应的直观认识和对岩石室内试验所得物理力学特性的深刻揭示,建立了深埋条件下软弱围岩大变形挤压程度分级方法及相对应的安全系数计算方法。该方法考虑到隧洞原岩集聚的能量过大是造成开挖后围岩失稳的根本原因,将隧洞原岩能量和围岩的总变形与弹性变形之比相结合,分析了隧洞的围岩稳定性状况,并在此基础上通过增减隧洞原岩能量得到了其安全系数。通过实际工程应用及与传统经验评价方法的对比,验证了该方法的合理性与适用性。该方法考虑了围岩的地质情况、断面形状、尺寸、开挖方式等多种因素,弥补了传统经验评价方法无法适应复杂多变的现场工程施工情况的不足,更加贴近实际。可为大变形隧洞的安全预测、开挖方案、支护设计等提供重要参考依据。 相似文献