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1.
岩石损伤软化统计本构模型参数的确定方法   总被引:21,自引:0,他引:21  
杨明辉  赵明华  曹文贵 《水利学报》2005,36(3):0345-0349
本文探讨了岩石损伤软化统计本构模型参数与岩石软化变形破裂过程的应力应变全曲线的特征参量的理论关系,建立了本构模型参数新的确定方法。该方法通过常规试验所得到的峰值点的应力应变值即能确定整个本构模型的其它参数,再将峰值点的应力应变值与围压的关系进行拟合,即能将该模型推广成任意围压下的岩石损伤软化统计本构模型。试验表明,本文模型曲线能较好地反映岩石破裂的全过程。  相似文献   

2.
根据挤压性围岩的受力特征,在平面应变相似材料模拟围岩挤压性变形试验的基础上,基于岩石微元强度服从Weibull分布,推导了岩石损伤演化方程,建立了能较好模拟岩石应力一应变曲线峰后的软化模型.该模型能反映岩石的软化特性及破坏的全过程,也能反映岩石强度受围压的影响.  相似文献   

3.
本文基于岩石损伤、断裂演化的阶段性特征,将岩石应力-应变曲线分为两个阶段,第一阶段依次包括:Ⅰ-无损伤弹性、Ⅱ-微裂纹演化和Ⅲ-宏观裂纹成核三个内部损伤过程,曲线跨越峰值点;第二阶段包括:Ⅳ-宏观裂纹扩展和Ⅴ-摩擦滑动。鉴于此,提出两种不同类型的曲线拟合单轴应力-应变曲线并建立一维损伤模型。在复杂应力状态下,采用统一强度理论构造复杂应力等效应变,从而将一维损伤模型推广为三维损伤模型的统一框架。该模型参数直接取值单轴应力应变曲线,可表现岩石峰值后演化的重要特征如应力跌落、残余强度等。大量实验数据验证表明,模型曲线与实验曲线符合较好。模型可推广于岩土材料、金属的非线性描述。  相似文献   

4.
考虑残余强度和阈值影响的岩石弹性损伤统计模型   总被引:1,自引:0,他引:1  
基于统计学理论和损伤理论,考虑岩石的残余强度和损伤阈值影响,建立了三轴压缩条件下岩石损伤统计模型。以损伤模型为基础,利用岩石在低围压作用下应力应变的极值特性,导出了模型参数的统一求解方法。通过与试验数据的对比和验证发现:以Drucker-Prager准则和Mohr-Coulomb准则计算岩石微元强度比以轴向应变函数计算岩石微元强度能更好地反映岩石的力学特性,说明了岩石的破坏进程与其应力状态密切相关;为考虑残余强度,引入损伤变量修正系数,在此基础上提出一种求解该修正系数的新方法,从而使得模型得出的理论曲线能很好地接近试验数据;以屈服点的微元强度为损伤阈值点,避免了损伤系数在低荷载下不在[0,1]之间的情况。最后通过分析岩石损伤变量的变化过程,证明了该模型可以很好地反映三轴受压状态下岩石的应力-应变关系。  相似文献   

5.
库水位上升、下降对水电站大坝边坡稳定性产生不利影响。通过室内不同干湿循环条件下岩石的三轴压缩试验,基于统计损伤力学理论,根据岩石在不同干湿循环条件下应力~应变特征,利用岩石应力~应变曲线的极值特点,推导求解模型参数的数学方程,建立三轴压缩条件下岩石损伤本构模型。通过与不同干湿循环条件下岩石应力~应变曲线的比较,损伤模型可以很好地反映岩石应力~应变关系。干湿循环次数对参数m和F_0造成影响,随着干湿循环次数的增大,两个参数的值逐渐变小,且干湿循环次数对参数m的影响较大。通过对干湿循环下岩石的内摩擦角与黏聚力劣化分析,可以得到参数α和k的值不断减小,对准则参数α和k进行折减,建立岩质边坡稳定性分析的模型,对水电站大坝边坡稳定性分析具有重要意义。  相似文献   

6.
为了探究水压力对岩石损伤的影响,在多孔材料弹性理论框架内,利用有效应力原理,结合连续损伤力学和统计理论把霍克-布朗(Hoek-Brown)准则作为微元体强度破坏准则,建立水压力作用下的岩石统计损伤本构模型;并根据残余强度和峰值强度的关系对损伤变量进行修正,使模型能够更好地反映岩石峰后阶段的软化特征。通过室内试验进行模型验证和参数分析,结果表明:建立的模型能够较好地反映水压作用下岩石的应力-应变关系;随着水压力的增大,模型参数n呈增大趋势,岩石的脆性度增高,参数F0呈减小趋势,岩石的强度降低;峰值点法在确定模型参数时优于曲线拟合法。研究成果对于水压力作用下岩体工程的安全分析有一定的参考价值。  相似文献   

7.
岩石损伤量在岩石损伤的过程中是个动态变化量,通过改进Harris函数,建立了在三维应力作用下岩石损伤本构模型,并通过砂岩的三轴试验确定了模型参数,定性分析了围压、临界损伤值、峰值应变三者间的关系。研究结果表明:1基于改进的Harris函数所建立的砂岩损伤本构模型曲线与实测曲线拟合较好,有良好的适用性;2同一种岩石在不同围压下,临界损伤值不是固定值,它从侧面反映出岩石自身的力学性能与岩石所处的三维应力状态有关;3围压增大,临界损伤值也相应地增大,证明围压对岩石的破坏有抑制作用。分析结果对研究三维应力状态下岩石的损伤破坏机理有一定借鉴意义。  相似文献   

8.
为了研究类岩石材料在全应力应变过程中渗透系数的变化规律,一方面,在Mazars模型的基础上,引入断裂能来修正损伤演化准则,提出一种改进的弹性损伤模型;另一方面,通过将细观裂纹等效为连续的损伤带,来建立裂纹扩展阶段的渗透系数-损伤演化模型,并将孔隙压密阶段和裂纹扩展阶段的渗透系数变化公式统一起来。将改进的弹性损伤模型和渗透系数变化模型进行数值实验,实验结果表明,改进的弹性损伤模型的应力应变曲线和室内实验结果吻合,渗透系数曲线也能反映出全应力应变过程中渗透系数变化的不同阶段,而且模型简单,方便数值计算程序的开发,对类岩石材料的全应力应变过程中的渗透特性研究有一定的参考意义。  相似文献   

9.
为了解岩石内部的损伤程度和微裂纹发展状况,对单轴准动态荷载下石膏试样应力状态和纵波速度的关系开展了试验研究。在轴向荷载作用下,分别对石膏试样的纵向和横向进行了声波测试。结果表明:低强度石膏试样的应力声速曲线特征明显,其峰值后曲线可以划分为4个阶段,各阶段声速变化与试样的损伤破坏相一致,与应力应变曲线的各变化阶段也能很好对应,且试样的应力波速关系在轴向和横向表现出相似的变化特征。石膏试样的损伤阈值出现在应力为抗压强度60%~80%时,从应力应变曲线看,损伤阈值出现在试样由弹性变形向塑性变形转变的阶段。  相似文献   

10.
为了研究岩石的非线性加速蠕变特性,依据岩石蠕变变形不同阶段的力学特征,划分出了岩石由变形发展至破裂需经历的不同黏弹塑性状态,并给出了相应状态的蠕变力学特性。假定岩石在三轴压缩试验条件下,发生延性剪切破坏,推导了应变空间Drucker-Prager准则的临界状态转化的最大剪应变判别式。基于Perzyna黏塑理论,考虑后继屈服硬化作用,引入统计损伤因子,构建了能描述非线性加速蠕变特性的黏弹塑性损伤演化模型;采用岩石全自动伺服三轴蠕变试验机对三峡库区典型砂岩试样开展了蠕变试验,得到了岩石试样在不同应力水平作用下的蠕变变形曲线。结果表明:蠕变试验中,岩样力学性质的时效特征显著,在最后一级应力水平作用下发生了非线性加速蠕变现象。基于提出的黏弹塑性蠕变模型对试验曲线进行拟合,拟合结果说明模型能够较好地反映砂岩蠕变3个阶段变形的规律特征,拟合效果较好。  相似文献   

11.
根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。  相似文献   

12.
Call for Papers     
正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.  相似文献   

13.
The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L?1, the median total phosphorus was 0.29 mg L?1 and the median total nitrogen was 1.56 mg L?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.  相似文献   

14.
Carbon dioxide (CO2) and methane (CH4) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO2 and CH4 diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 106 t CO2eq km2 per year, or 24 × 106 t CO2eq per year. This corresponds to a plant emission factor of 3.18 kg CO2eq MWh?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO2eq per year, or 5.83 kg CO2eq MWh?1, which is in the lower range of the studied reservoirs.  相似文献   

15.
The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.  相似文献   

16.
A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).  相似文献   

17.
The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.  相似文献   

18.
为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。  相似文献   

19.
岩石动态拉伸断裂特性的实验研究   总被引:1,自引:0,他引:1  
采用新近发展起来的拉伸式Hopkinson冲击装置(SHTB),对岩石切口圆柱断裂试样进行了动态拉伸断裂特性的实验研究。同时,利用MTS试验机进行了岩石的静态拉伸断裂实验,成功地获得了岩石试样的断裂韧度及断裂能随加载率而变化的实验结果。对静态和动态破坏后的试样断口进行的扫描电镜观察进一步表明,试样断口形貌的复杂程度与其断裂耗能有着十分密切的联系。  相似文献   

20.
在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。  相似文献   

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