地下工程三维地质力学模型制作逆向控制技术研究与应用

 地质力学模型试验是研究岩体工程和地下工程的一种重要手段,而模型的制作方法很大程度上决定试验的可行性和结果的可靠性。以2个地下工程三维模型试验为背景,对模型制作中压实密度控制问题进行研究。根据在已建实际模型不同深度取得的实测数据,对采用等容控制夯筑法制作模型时产生的同一种材料密度不能保持恒定,而是随深度的增加产生变化的现象进行分析;提出基于击实功复合作用系数、密度随填筑深度非线性逆向控制的模型制作方法,并应用于一个实际三维模型试验模型制作中。原位取样测试结果表明,按照这种方法设计制作的模型,最终能达到模型中同一类型材料所要求的密度整体相对一致的效果,从而提高了物理模型中材料力学性质的稳定性。     

考虑受火全过程的高温作用后型钢混凝土柱力学性能研究及有限元分析

进行了高温作用后型钢混凝土柱力学性能试验,在试验的基础上建立了高温作用后型钢混凝土柱力学性能的数值模拟方法。通过在ABAQUS平台上开发子程序建立了升降温作用下型钢混凝土柱温度场的计算模型,通过选择合适的材料本构关系以及在ABAQUS平台上开发自定义场变量子程序,在考虑升温、降温以及高温作用后不同阶段材料本构关系的基础上,提出了高温作用后型钢混凝土柱力学性能分析的计算模型,实现了高温作用后型钢混凝土柱力学性能的计算模拟。计算结果与试验结果的对比表明,二者吻合较好,提出的方法合理可行。     

6082-T6高强铝合金材料本构模型试验研究

铝合金材料本构关系是铝合金结构分析和应用的基本问题之一,针对国产高强新牌号铝合金6082-T6的材料本构模型进行研究。对取自3种截面形式结构用6082-T6高强铝合金型材的90个材性试样进行了拉伸试验,统计规定非比例延伸强度、抗拉强度、弹性模量、断裂伸长率、泊松比等材料力学参数。分析Ramberg-Osgood本构模型中硬化指数-n-的各种计算方法,提出采用快速退火算法(fast simulated annealing,FSA)求解n的方法并且编制计算程序,从而获得n的置信区间,所得结果比传统两点法更稳定。在此基础上得到了国产6082-T6高强铝合金材料本构模型,与试验实测应力 应变曲线的比较表明,提出的本构模型具有很好的预测性,可为铝合金结构的工程应用提供参考。     

水下爆炸离心机试验中爆炸荷载的缩比关系研究

水下爆炸原型试验受到场地环境等多种因素的制约,离心机缩比试验为研究结构在水下爆炸作用下的破坏提供了新的思路。离心机缩比模型试验通过放大一定倍数的加速度对模型进行缩比,同时模型在几何布局上缩小相应的比例达到与原型试验的几何相似。文章首先建立80kgTNT装药水下爆炸数值模型,并将计算结果与原型试验进行对比,确定合理的比例爆距观测点,验证模型可靠性,继而采用相同的材料参数与建模方式建立1gRDX装药(等效1.62gTNT装药)在不同离心加速度条件下的水下爆炸缩比试验数值模型,并将计算结果与离心机试验结果进行对比,讨论相似率在水下爆炸离心机缩比试验中的应用,研究不同的物理量在离心机试验中的缩比关系以及附加离心加速度对缩比试验中水下爆炸动态荷载的影响。     

Failure mechanism of unsaturated landslide dam under seepage loading – Model tests and corresponding numerical simulations

Due to the rapid cracking, sliding and packing of its geomaterials, a landslide dam (LD) is usually weaker in structure than the undisturbed ground and is more vulnerable to seepage loading. In addition, since the naturally packed geomaterials of an LD are mostly in an unsaturated state, it is necessary to use a suitable constitutive model that can describe the mechanical behaviour of the soils under an unsaturated/saturated state in a unified way and whose material parameters can be determined in a rational way in order to accurately simulate the failure mechanism of the LD. In this paper, water retention tests and flume tests were conducted on model LDs prepared with three different ground materials. An unsaturated soil constitutive model was selected for the corresponding numerical simulations. Based on the results of water retention tests and triaxial tests, the parameters of the LD materials were properly determined. Using these parameters, soil-water-air coupling finite element analyses were conducted to simulate the flume tests on the model LDs. By comparing the calculated results with the test results, it was found that the numerical method used in this paper has satisfactory accuracy for describing the different failure mechanisms of the model LDs under seepage loading. The results indicate that the material properties of the LDs, especially the strength and the difference in void ratio between the unsaturated and the saturated states, play important roles. In addition, the influence of the rate of the rise in water head was also investigated by numerical tests. The purpose of this research is to provide a scientific basis for decision-making in the disaster mitigation process of LDs with a comprehensive method for understanding the failure mechanism of these LDs.     

基于MPS方法的自密实混凝土流动数值模拟

采用三维移动粒子半隐式(MPS)法来分析和预测自密实混凝土(SCC)的流动性,对L形箱试验进行数值模拟,对比分析了数值模拟与试验中SCC的流动形态和流动时间.在此基础上,研究了L形箱试验和V形漏斗试验中塑性黏度对SCC流动性的影响,并建立了SCC密度和塑性黏度与V形漏斗试验下落时间的关系.结果表明:使用基于Bingham流变模型的MPS方法可以较好地模拟SCC的流动特性,且精度较高;MPS方法可以对SCC在施工过程中的流动时间和流动形态进行模拟预测,结合流变参数分析可以为SCC工程的设计和施工实践提供参考依据.     

雨水生态滤水带在宁波地区的适用性研究

结合宁波地区的实际情况,进行了雨水生态滤水带的适用性研究。分析探讨了生态滤水带的作用机制、模型设计、试验方法与步骤、材料选取及试验结果,为雨水生态滤水带在宁波地区的推广应用提供了详细且规范性的指导意见。     

相似材料模型实验中围岩垂直应力测试的实验研究

阐述了相似材料模型实验中测试模型采动过程中工作面顶板围岩应力形成的原理 ,以及测试方法和实验步骤 ,并分析了应力环式模型支架的工作特性与标定结果。两个实验实例表明 ,该方法能满足实验的需要 ,使模拟实验可定量化分析 ,其应用推进了支架与围岩相互作用关系的实验室研究。     

大型桩基模型试验系统的开发

为了对现浇混凝土大直径管桩等新桩型开展更深入的研究,并考虑到室内小模型试验存在的比尺效应等问题,自行开发了大型桩基模型试验系统,为进行室内桩基足尺试验研究提供了可能。该试验系统主要由模型槽、加载系统、测量系统以及试验所需的土料和桩体等组成。鉴于较少开展室内足尺试验,提出了试验土料的制备方法,并通过现场取样、CPT等试验对土体的质量进行了检验,证明了该方法的可行性。此外,利用该试验系统进行了现浇混凝土大直径管桩室内足尺静载荷模型试验,通过将试验结果与现场实测结果进行对比,表明利用试验系统进行桩基室内足尺试验是可行的。     

改进数字图像相关法测量混凝土柱弯转角

由于混凝土是一种各向异性材料,其破坏特性比较难以预测。对其力学性能(尤其新开发产品)进行实验研究往往需要耗费大量的人力、物力,高精度、操作方便的测试手段对于提高实验数据的可靠性和减轻实验人员的劳动强度是非常必要的。数字图像相关法(Digital Image Correlation,DIC)是一种基于光电成像和计算机处理的高精度、非接触的全场测量手段,相比于其他测量技术,该方法原理简单,对系统和环境的要求也比较低。但是,目前有关该法在土木工程研究中应用的报道还比较少,还需要根据混凝土构件特性对测量中的一些问题进行探索。本文将结合在混凝土构件实验中遇到的问题,首先通过数值模拟和实测对比分析对有关问题进行探讨验证,并在此基础上给出改进方法。标定验证实验结果验证了该方法用于混凝土构件变形测试的可行性,是非常有前途的测量方法,其中改进策略可作为类似工程应用的有益参考。     

Study of the remediation of a site contaminated with arsenic

Soil and rock-like material was collected from a former industrial site (arsenic factory) in order to study the degree to which the site is contaminated. Characterisation of the soil and rock-like samples indicated that the site is highly contaminated with arsenic: the soil material contains 2.5–3.5% (dry wt.%) of arsenic, the rock-like material up to 20%. According to Flemish norms (VLAREBO, 1996) concerning the contamination of soils for industrial sites, remediation of the soil is required on a short-term basis when a value of 300 mg As/kg of dry solid is exceeded. In this paper, solidification/stabilisation with cement and/or lime for remediation of the site was studied. If later the solidified site material is landfilled, one of the criteria is that the arsenic concentration in the leachate, determined according to the DIN 38 414 S4 extraction test (Deutsches Institut für Normung, 1984), must be lower than 1 mg/l (VLAREM II, 1995). Solidification proved to be an efficient method to lower the amount of arsenic leached from the material to below the norm of 1 mg/l. The results of a semi-dynamic leach test indicated that arsenic was released very slowly from the solidified material: over the period of the leach test only 0.10% of the arsenic initially present was leached.     

建筑索结构索力测量新方法与工程应用

索作为建筑索结构中的重要构件,索的预张力大小是索结构设计中的重要参数,也是索结构施工过程中进行控制的重要环节。开发新型的索力传感器是索结构施工监测和控制中面临的新课题。基于铁磁材料的磁弹性能阐述磁弹法测量索力的基本原理,开发了一种新型的磁通量传感器,并将其应用在双曲面索网模型张拉试验中进行索力监测控制。试验结果表明,该方法可以非常方便快捷、准确地测定索在张拉过程中的索力,可为工程参考使用。     

地面出入式盾构法隧道新技术大型模型试验与工程应用研究

地面出入式盾构法克服传统盾构法需要在两端修建始发和接收工作井的弊端,实现地表出发和地表接收的全过程盾构施工新技术。采用大型模型试验、数值仿真和工程验证手段,系统研究地面出入式盾构法隧道新技术掘进的关键问题,揭示地面出入式盾构法穿越不同阶段的地表沉降规律;依托地面出入式盾构法首次在我国南京城际快速轨道秣将区间隧道工程的示范应用,探索分析该新方法在工程中主要施工参数的合理选择和有效的控制技术;模型试验、数值仿真结果与工程实测结果获得一致的规律,可为该新方法的进一步推广应用打下坚实基础。     

Model test and numerical analysis of a special joint for a truss bridge

This paper presents a study on the mechanical behaviours of a special joint between a rigid suspension cable and a truss girder in a rigid suspension stiffened steel truss bridge. Both a model test and a numerical finite element analysis (FEA) have been conducted, and relevant information about the models used, loading procedure and test scheme is presented. The model test shows that the maximum stress in the joint is less than the material allowable stress and the maximal stress induced from the secondary moment accounts for about 30% of the total stress. A three-dimensional finite element model is used in the numerical analysis and the results are in very good agreement with those of the model test. This study shows that the design of the special joint is reasonable and the structure safe. It is also expected that the results presented in this paper would be useful as references for future research and design of rigid suspension stiffened steel truss bridges and joints.     

Investigation of a historic masonry structure by numerical and operational modal analyses

This paper presents the results of model calibration conducted on a historical mosque called Hafsa Sultan in Manisa, Turkey. The finite element model of the mosque was calibrated by the use of the results obtained from ambient vibration tests of the structure. In order to develop a solid model of the structure, the dimensions of the structure, defects such as cracks and material degradations in the structure, and the materials used in different parts were identified. For the evaluation of the material properties of the structure, nondestructive and destructive testing methods were used. The numerical and experimental modal parameters of the structure were obtained by finite element method (FEM) and Operational Modal Analysis (OMA), respectively. The natural frequencies and corresponding mode shapes were obtained from both FEM and OMA and compared with each other. While a good compatibility was achieved between mode shapes, some differences between natural frequencies occurred. It was thought that the differences resulted from variations in the Young's modulus of masonry, cracks in elements or boundary conditions. Therefore, the finite element model was calibrated by changing material parameters. Finally, a more realistic numerical model of the mosque was put forward and the results were discussed in detail. Copyright © 2015 John Wiley & Sons, Ltd.     

高位转换超高层整体结构振动台试验设计

同济大学土木工程防灾国家重点实验室对上海某带高位转换超高层结构进行了整体结构模型模拟地震振动台试验.该超高层塔楼53层,结构高度250 m,采用型钢混凝土框架-钢筋混凝土筒体结构,设有加强层及竖向主要受力构件高位转换层.在高位转换超高层结构体系、振动台试验模型材料的选取、动力相似关系的确定以及试验方案的设计等振动台试验的前期工作方面,进行了详细的阐述.所介绍的模型设计思路及制作过程,为今后的有关试验工作提供了一定的参考.     

单层球壳模型结构振动台试验研究

通过对单层球壳结构模型的振动台试验,分析了结构在地震作用下的破坏模式。为使模型呈现不同的倒塌模式,设计了3个缩尺比为1/10的试验模型：模型1与模型3以期发生承载力破坏倒塌模式;模型2设置6个薄弱区,以期发生动力失稳。采用多次加载方案,水平向输入地震波,逐级提高峰值加速度,完成振动台试验。采用基线调整法对原始试验数据进行校正;采用有限元软件ANSYS中的大质量法对试验模型进行考虑双非线性的多点输入时程分析,获得结构动力响应;采用自编程序对模型结构进行有限元塑性分析。结果表明：试验模型的倒塌模式与试验预期结果吻合良好,验证了振动台试验的完备性;有限元分析结果与实测结果吻合较好,验证了数值计算方法的正确性。     

Numerical evaluation of group-pile foundation subjected to cyclic horizontal load

In this paper, three-dimensional (3D) finite element analyses of a real-scale group-pile foundation subjected to horizontal cyclic loading are conducted using a program named DBLEAVES. In the simulations, nonlinear behaviors of ground and piles are described by subloading t_ij model and the axial-force dependent model (AFD model) which considered the axial-force dependency in the nonlinear moment-curvature relations. In order to consider the influence of an effective stress path on the prediction of the group-pile foundation, the analyses are conducted within the framework of the soil-water coupling method with finite-difference and finite-element regime. The material parameters of soils are determined based on conventional triaxial drained compression tests on undisturbed and remolded specimens. The applicability of the proposed numerical method is encouraging, and therefore, it is quite confident to say that the method can be used to predict the mechanical behaviors of group-pile foundation to a satisfactory accuracy, particularly with the effective stress analysis.     

工程岩体Ⅲ级围岩相似材料配比试验研究

目前超大跨扁平地下洞室模型试验的围岩相似材料缺少合适的配制方法,以工程岩体中Ⅲ级围岩的物理力学参数作为相似材料配比目标,采用重晶石粉和石英砂作为骨料,高强石膏粉和水作为胶结剂,洗衣液作为调节剂,基于正交理论设计了3因素5水平的正交试验方案,制作了25组不同的配比,通过大量的直剪试验和单轴压缩试验分别测得试样的黏聚力c和内摩擦角φ以及试样的抗压强度σ_c和弹性模量E,并采用极差分析法进行了敏感因素分析。试验结果表明:所配制的相似材料物理力学参数变化范围广,能满足大部分岩质岩体模型试验的强度要求;材料含量的变化对物理力学参数的影响规律明显,可为配比不同模型试验的相似材料提供指导。     

Characterisation of permanent deformation behaviour of unbound granular materials under repeated triaxial loading

The present paper reports the results of a laboratory experiment that aimed to investigate the permanent deformation behaviour of two unbound granular materials for road subbase layers under repeated triaxial loading. In the first part of research the shakedown concept was used to classify the mechanical response of the granular mixtures. The obtained results confirmed the potential usefulness of this theoretical approach for ranking granular materials with regard to their rutting potential. The second part was entirely dedicated to the development of an analytical model to describe the long-term permanent deformation behaviour of these materials. The proposed model allowed permanent strain accumulation as function of the number of load applications and applied stress level to be described. The results, besides being consistent with the shakedown concept, showed the ability of the model to reflect the change in mechanical behaviour due to the different nature of materials, under specific stress and moisture condition. In addition, the model allowed the permanent deformation accumulation resistance of the material to be properly investigated through specific strain rate envelope curves defined on a Mohr-Coulomb diagram. Therefore, this study could propose an innovative and practical design approach for permanent deformation behaviour assessment of unbound granular material and consequently for evaluating its suitability in the pavement in order to avoid undesirable response.