p型自适应有限单元法及其在岩土工程中的应用

详细地介绍了p型自适应有限元的基本理论及其发展过程,总结了p型自适应有限元的误差估计方法、自适应升阶策略以及加速收敛技术,并将p型自适应有限元法应用于岩土工程的三维弹粘塑性分析、三维动力响应分析以及三维渗流分析中,最后提出了p型自适应有限单元法中亟待解决的问题及今后的研究方向。     

自适应非线性有限元的多重网格法求解及应用

描述了非线性自适应有限元的多重网格法求解过程。 通过算例说明了方法的有效性以及自适应多重网格有限元用于开挖施工过程模拟分析的优越性。     

浅埋隧道掌子面稳定性二维自适应上限有限元分析

为研究浅埋隧道掌子面稳定性及获取精细化的破坏模式,提出了一种上限有限元非结构化网格自适应加密策略。以单元耗散能权重指标作为网格自适应加密评判准则,该策略同时兼顾了单元尺度与塑性应变。应用高阶的6节点三角形单元并建立上限有限元线性规划模型,以多次反复计算和网格加密的方式实现了二维自适应上限有限元分析并编制了计算程序。利用条形基础地基极限承载力课题,从上限解精度和网格加密形态方面验证了该程序的有效性。针对浅埋隧道掌子面稳定性问题,展开多参数条件下的自适应上限有限元计算,分析了网格加密过程中单元总数与上限解精度的关系,列出不同隧道埋深和内摩擦角对应的隧道掌子面稳定性临界值的上限解,揭示出掌子面稳定性变化规律及精细化的破坏模式。     

面向对象自适应渗流有限元分析软件的研究和实现

采用面向对象技术,应用C++研制了一个自适应渗流有限元分析系统。该软件系统的前处理过程用对象化建模,具有实现方便,界面友好的优点。自适应有限元模块的引入使该系统具有规范性和客观性,计算结果不会因人而异,且后处理界面形象直观。笔者还给出了一个土坝渗流的实例,验证了该软件的可用性和优点。     

渗流问题的三维h型自适应有限元法研究

研究了三维渗流的自适应有限元法,建立了集成网格自动剖分、渗流有限元分析、网格调整、后处理等四大模块的四面体单元h型自适应系统。给出的算例证实了系统的有效性和优越性。     

三维稳定渗流的 p 型自适应有限元分析

建立了三维稳定渗流的p型自适应有限元分析的误差估计器。充分利用p型有限元前处理少、计算精度高和收敛速度快的优点，分析了p型有限元法求解渗流问题的技术特点，给出了求解三维稳定渗流的自适应升阶策略。通过具体算例，研究了单元阶次及网格尺度对计算结果的影响，验证了三维p型有限元法在求解渗流问题时的可行性。     

基于自适应退火算法的非线性位移反分析方法研究

根据地下工程非线性位移反分析的特点,建立起基于地下洞室收敛位移量测结果的反分析模型;针对一般退火演化算法优化效率低的问题,综合运用遗传算法、模拟退火算法和非线性有限元分析手段,并引进自适应的思想,建立了基于自适应退火演化算法的地下工程非线性位移反分析的新方法和理论,在探讨其应用方法与实施过程的基础上,开发了相应的计算分析程序。模拟分析表明,理论计算结果与模拟结果吻合良好,该方法可以满足工程要求。     

并行组合模拟退火算法在边坡稳定分析中的应用

采用自适应有限元法分析边坡的应力场,然后应用并行组合模拟退火算法建立基于应力场的边坡任意形状临界滑动面的全局搜索方法。该方法适用于任意几何形状,不同岩土材料分层以及多种荷载作用的复杂边坡。并行组合模拟退火算法是将模拟退火算法和遗传算法相结合的优化算法,它可以从多个初始点开始并行寻优,能以较快的速度找到全局最优解。通过工程实例分析,证明这种基于自适应有限元分析和并行组合模拟退火算法搜索边坡临界滑动面的方法可行、高效。     

饱和砂土动静力特性的网格自适应数值模拟

在有限元数值计算平台上,建立了一套基于后验误差评估和Delaunay三角剖分的网格自适应方案,针对饱和砂土静力受压和地震液化的特性进行模拟。验证了超收敛单元片回归（SPR）误差评估中原用于四边形单元的双线性回归函数在用于三角形单元网格时的适用性和可靠性;在饱和砂土动、静力算例中,网格自适应计算获得的变形、应变、超孔压比等的变化规律与常规有限元结果趋势一致。随着网格的再生成,参考点的位移和全域的平均相对误差逼近精确值。对于初始网格,讨论了合理的自适应程度并应用于地震液化的自适应数值模拟中,也对Delaunay三角剖分实施了一些改进。最终证明该自适应方案在提高计算效率的同时,亦可以保证计算所需的精准度。     

基于二阶锥规划与高阶单元的自适应上限有限元研究

基于六节点三角形高阶单元的自适应上限有限元法具有计算精度高,能够直观获取结构破坏模式等优点,但若采用屈服准则线性化方法,则计算效率较低。因此,为提高上限有限元计算效率,在既有研究基础上,引入计算效率较高的二阶锥规划方法,建立基于二阶锥规划与高阶单元的自适应上限有限元计算模型。通过分析边坡稳定性及条形基础地基承载力算例,表明所提方法计算精度较高且能够获取精细化的破坏模式。同时,在相同计算精度下,所提方法计算时长显著小于屈服准则线性化方法,有效提高上限有限元的计算效率。算例分析证明所提方法的正确性及有效性,可为类似理论研究及工程实践提供参考。     

Application of rock mass index (RMi) to the rock mass excavatability assessment in open face excavations

Earthwork and surface excavation activities play an important role in construction projects. Selecting the best technique to loosen the overburden material within the surface excavation in open mining and geotechnical projects is of great importance from economical and technical viewpoints. Surface excavation includes direct digging, ripping and blasting. To select the most effective method and plan for excavation, geotechnical investigation is very important. It is also a big help in avoiding conflict between contractors and clients when they do not reach mutual agreement regarding the price of rock and soil excavation. There are many engineering classification systems used to assess rock masses for excavation purposes. All of these systems consider several geotechnical parameters to assess the earth masses. This study reviews these systems and then offers a new categorization based on the Rock Mass index (RMi) classification system and block volume to assess excavation in rock masses. The original dataset was obtained from the literature review as well as the surface excavation in Upper Gotvand dam and Hydro Power Plant (HPP). The offered system was also validated through the data extracted from the surface excavation in Sardasht dam and HPP in Iran.     

深部地下实验室扩挖岩爆监测与动态防控技术研究

中国锦屏地下实验室二期(CJPL-Ⅱ)扩挖工程建设潜在高等级岩爆风险。为此,建立了深部地下实验室相邻同向短洞室固定式和单侧相向扩挖移动式微震传感器阵列优化布置方法,构建了基于岩爆风险程度的岩爆预警频次优化原则,提出了针对性的CJPL-Ⅱ扩挖岩爆防控措施,实现了CJPL-Ⅱ扩挖过程岩爆实时监测、动态预警与防控,岩爆预警与实际情况吻合良好,保障了CJPL-Ⅱ扩挖顺利完成。分析了CJPL-Ⅱ扩挖各洞段开挖过程微破裂时空演化规律及其差,研究结果表明新增通道微震活动较扩挖段更为活跃,岩爆风险亦更高,扩挖微震活动活跃程度与空间集聚特征受扩挖断面尺寸,扩挖深度以及结构面影响。研究成果可为类似深埋工程安全建设提供借鉴。     

Underground excavation shape optimization considering material nonlinearities

The shape of an underground opening is a major factor influencing the stability of the underground excavation. Obtaining an optimized shape is significant in civil and mining engineering applications for increasing stability and reducing costs. This paper presents an updated method for finding the optimal shape of an underground excavation using the latest bi-directional evolutionary structural optimization (BESO) techniques considering material nonlinearities. Recent development in the BESO applications to underground excavation is discussed through illustrated examples. Details are given of the BESO method used to finding the optimal shape based on the global stiffness. The methodology of the stiffness based optimization techniques is described with examples of applications to underground excavation. Applications to underground void structures, such as cavern and tunnel, as well as underground solid structure such mine pillar are demonstrated. It is concluded that stiffness based optimization techniques are applicable to underground excavations and practical shape of an excavation can be generated as a result of the BESO application.     

高地应力硬脆性围岩开挖损伤区时效性扩展案例分析——特征与机制

硬脆性围岩在开挖完成后，其强度在高应力的影响下具有明显的时间效应，这导致围岩开挖损伤区的发展也呈现出与时间相关的特征。在岩石强度时效性演化模型的基础上，以锦屏二级水电站试验洞钻孔摄像、声波、变形监测等开挖损伤区实测结果为目标函数，采用正交设计方法、最小二乘支持向量机模型、粒子群优化算法等方法，建立了考虑时间效应的LSSVM-PSO智能反演分析方法，并以锦屏二级水电站试验洞为例，研究了开挖完成后的25 d里，围岩强度在高地应力条件下的时效性演化特征，进而获得这一时段内开挖损伤区扩展过程。研究结果表明：（1）高应力地区，隧洞开挖后，围岩损伤区的主要扩展方向受地应力控制，且最大扩展方向为最小主应力方向，且破坏区（破坏接近度FAI≥2）也集中于该方向； （2）开挖损伤区面积随时间近似呈S形曲线变化，表明开挖损伤区初始发展较为缓慢，随着时间推移呈现线性增加的趋势，最后又逐渐趋于稳定；（3）开挖后第3～10 d为开挖损伤区快速增长阶段。该研究成果对高应力地区硬脆性围岩开挖损伤区时效性演化研究具有指导意义。     

西南某大型水电站拱肩槽边坡开挖的变形响应研究

对在复杂地质条件和高地应力环境下,高达近330m的人工岩石拱肩槽高边坡的研究,尤其是在大坡比、强开挖条件下所表现的变形响应规律的研究具有重要的理论与现实意义。论文通过大量现场跟踪施工的地质调查工作和利用丰富的监测资料的基础上,系统地研究了此类边坡变形响应的基本规律及特殊表现,得到了拱肩槽高边坡开挖过程中,边坡的变形与开挖过程有较强的同步性。变形主要受开挖卸荷影响;随开挖的进行,坡体的变形随开挖面的远离表现出总体衰减的特征等。开挖后的坡体的变形量较小,变形深度较浅,而且在开挖12~18个月后,变形趋于稳定。这些结论对类似边坡开挖及其稳定性的控制具有重要的借鉴意义。     

A study into the behaviour of the formation level of an excavation under different unloading patterns in soft deposits

The construction of basements in urban areas is often associated with the possible damage to existing structures and services. The varying construction processes inevitably lead to different stress unloading patterns and therefore the dissipation of these excess pore-water pressures may lead to non-standard deformation profiles. The three main types of basement construction processes are layered excavation (LE), basin excavation (BE) and island excavation (IE). The effect of the various unloading patterns has been investigated by a three dimensional (3D) effective stress analysis method using the developed computer program 3DBCPE4.0. An excavation of length 50 m, width 50 m and depth 9 m in a certain homogenous and isotropic saturated soft soil was modelled. This included a diaphragm wall of 800-mm thickness embedded 18 m deep into the soft soil. The different excavation deformation profiles under different excavation patterns were related to the different unloading process, the exposure time of excavation face and the dissipation of negative excess pore-water pressures. The most favourable process for controlling the horizontal deformation of a retaining wall or the heave deformation of the formation level is suggested. The ground water potentials within the formation level are also presented.     

土钉支护施工阶段土钉轴力的计算分析

土钉支护的形成过程对其受力和变形有直接影响。结合土钉支护边开挖、边支护且开挖在前的施工特点,定义开挖影响面以反映土体开挖时边坡滑动趋势的变化,与开挖影响面相交处的土钉在土体开挖时轴力增加最多。开挖土压力表示以开挖影响面为边界的土块体产生的土压力,由相邻两步开挖土压力之差求得挖土引起的不平衡力。增加的土钉轴力在平衡此不平衡力的同时,维持着边坡稳定。据此,以开挖影响面及其土钉轴力增量为主要研究对象,提出了施工阶段土钉轴力的分析方法。该方法在求得土钉轴力最大值及其作用位置的同时,还给出了土钉轴力沿钉长方向的分布。应用此方法对法国CLOUTERRE项目1号墙足尺试验进行了计算,结果表明：计算与测试结果吻合良好。     

Reliability assessment of excavation systems considering both stability and serviceability performance

Excavation projects related to urban redevelopment and infrastructure improvement are often governed by serviceability-based design, rather than failure prevention criteria. Deformation tolerance specifications are often prescribed based on minimizing potential damage to adjacent structures. A risk-based approach to serviceability performance that systematically incorporates design parameter uncertainty will allow engineers to address soil uncertainty in performance-based design. This paper demonstrates the use of various kinds of reliability methods, such as response surface method (RSM), first-order reliability method (FORM), second-order reliability method (SORM), adaptive importance sampling (AIS), Monte Carlo simulation (MCS) and system reliability, to assess the risk of stability and/or serviceability failure of an entire excavation support system throughout the entire construction process. By considering multiple failure modes (including serviceability criteria) of an excavation, the component and system reliability indices for each excavation step are assessed during the entire excavation process. Sensitivity analyses are conducted for the system reliability calculations, which demonstrate that the adjacent structure damage potential limit state function is the dominant factor for determining excavation system reliability. An example is presented to show how the serviceability performance for braced excavation problems can be assessed based on the system reliability index.     

Excavation Problem in Mixed Ground Conditions at the Kabatas–Mecidiyekoy Metro (Istanbul) Tunnels

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.     

Investigating the Economic Performance of Tunnel Excavation in Iran: 1998–2013

Nowadays, the world is witnessing the ever increasing need of Tunnel excavation due to their unique features and the kind of human applied plans. This has led to increase in demand of excavating this engineering factor. Tunnel excavation process faces a lot of challenges due to environmental and technological complexities which causes the economic evaluation and investigation of this project to be difficult. It is tried to develop the proposed model with regard to efficiency concept in order to evaluate and investigate the efficiency of relative economic performance of Tunnel excavation projects and turn to its modeling and implementing by data envelopment analysis and Fuzzy DEMATEL techniques. The results in Iran showed that the proposed model can turn to investigation and evaluation of economic efficiency of Tunnel excavation by considering two optimistic (ideal) and pessimistic perspectives such that the Tunnel excavation process of “Karaj water transition” and “Cheshmelangan water transition” among 12 rock Tunnel excavation projects of Iran in the time period of 1998–2013 were respectively introduced as the most efficient and the most inefficient rock Tunnel excavation projects.