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1.
针对寒区道路工程中的沥青路面冻融受荷损伤问题,借助细观损伤力学和宏观统计随机损伤模型,建立了冻融与荷载耦合作用下的沥青混合料损伤本构关系和损伤演化方程;探讨了冻融循环次数、应变和油石比影响下的沥青混合料冻融受荷损伤劣化机理。研究表明：冻融循环疲劳损伤累积和荷载作用于带有微缺陷粗集料界面附近产生的应力集中加剧了沥青混合料总损伤劣化程度。冻融循环20次之后,损伤度变化不大,基本趋于恒定;相同损伤程度时,应变值随冻融次数的增加而减小。油石比对总损伤影响显著,当油石比相对较小时,以冻融破坏为主;当油石比较大时,以受荷破损为主。研究成果可为寒区沥青路面抗冻设计、性能评价及养护维修时机选择提供参考。 相似文献
2.
三轴压缩下粉砂质泥岩蠕变本构模型研究 总被引：1，自引：0，他引：1
依据粉砂质泥岩三轴压缩蠕变试验结果,分析了岩石的蠕变力学特性。选取线性黏弹性Burgers模型来描述岩石的衰减蠕变和稳定蠕变特性。引入非线性黏塑性元件,将其与Burgers模型串联起来,建立一个新的六元件非线性黏弹塑性Burgers蠕变本构模型。采用非线性Burgers模型来描述岩石的加速蠕变特性。应用Levenberg-Marquardt算法对蠕变试验曲线进行辨识,得出各级应力水平下岩石轴向与径向的蠕变模型参数。对比试验曲线和模型拟合曲线,二者吻合较好,表明线性Burgers模型与非线性Burgers模型可以准确描述岩石3个蠕变阶段的力学特性。模型参数辨识结果表明,在同一级应力水平下岩石轴向与径向的蠕变模型参数各自独立并不统一,模型参数取值时应考虑岩石蠕变的各向异性以及轴向与径向蠕变量、蠕变速率大小的差异。在前7级应力水平下,模型参数应取以轴向应变辨识得到的Burgers模型参数;在第8级应力水平下,模型参数应取以径向应变辨识得到的Burgers模型参数;在破裂应力水平下,模型参数应取以径向应变辨识得到的非线性Burgers模型参数。 相似文献
3.
Creep tests on asphalt mixtures have been undertaken under four stress levels in the laboratory while the discrete element model (DEM) has been used to simulate the laboratory tests. A modified Burger’s model has been used to represent the time-dependent behaviour of an asphalt mixture by adding time-dependent moment and torsional resistance at contacts. Parameters were chosen to give the correct stress-strain response for constant strain rate tests in Cai et al. (2013). The stress-strain response for the laboratory creep tests and the simulations were recorded. The DEM results show reasonable agreement with the experiments. The creep simulation results proved to be dependent on both bond strength variability and positions of the particles. Bond breakage was recorded during the simulations and used to investigate the micro-mechanical deformation behaviour of the asphalt mixtures. An approach based on dimensional analysis is also presented in this paper to reduce the computational time during the creep simulation, and this analysis is also a new contribution. 相似文献
4.
Burgers模型只能描述岩石蠕变的前两个阶段,为了描述蠕变全过程,考虑蠕变参数的时间效应及损伤带来的影响,采用非定常黏性元件取代Burgers模型中串联的定常黏性元件,使其能描述加速蠕变阶段。根据损伤变量的变化特征,假定了一个函数,经过Lemaitre应变等效原理,代入Kelvin模型可得到能描述蠕变衰减阶段的模型。试验数据拟合结果显示,改进的Burgers模型能很好地描述加速蠕变阶段,模型拟合曲线与试验曲线基本吻合,相关系数高,参数取值也在合理范围内;非定常Burgers模型更适合描述不同应力下的岩石蠕变特征曲线。 相似文献
5.
Viscoelastic damage model for asphalt concrete 总被引：1，自引：1，他引：0
The strain rate-dependent mechanical behavior of asphalt concrete was characterized using unconfined compression tests carried
out at different loading rates. It was shown that at high strain rates, the elastic deformation and peak axial stress are
highly sensitive to strain rate. Both increase as the strain rate increases. At very low strain rates, elastic response and
unconfined compressive strength are relatively independent of the loading rate. Based on the experimental observations, a
simple viscoelastic damage model is proposed for the strain rate-dependent unconfined compression behavior of asphalt concrete.
In the model, strain rate response is modeled by a two-component viscoelastic model consisting of a constant elastic modulus
and a viscous modulus that is related by a power-law function to the axial strain rate. Failure and strain softening are modeled
via a damage formulation where damage evolution in the asphalt concrete is given by a simple form of the Weibull distribution
function. The model was shown to be capable of describing the strain rate-dependent deformation, compressive strength, strain-softening
and creep behavior of asphalt concrete. The model is relatively simple and requires only five material parameters. 相似文献
6.
This paper presents the results of a study on the use of nanoindentation test to characterize the strain rate-dependent compressive response of asphalt concrete. Nanoindentation is now widely used for characterization and testing of composite as well as single-phase materials. Using a small piece of sample, nanoindentation tests can evaluate material behavior and structure in terms of the elasticity, time-dependent response, yield strength, damage, crack advance, debonding, and fatigues. In this study, a mixture of asphalt and calcium carbonate filler powder filling the intergranular void space of the asphalt concrete was characterized in terms of strain rate sensitivity at room temperature. The indentation hardness is observed to continuously decrease during constant indentation strain rates, but the hardness response clearly indicates positive strain rate dependency when compared at the same indentation depths. Following the constant strain rate tests, indentation creep response of the asphalt–filler mixture was tested at constant load conditions. The strain rate sensitivity values characterized from double logarithmic relationships between indentation hardness and strain rate during constant strain rate and constant load tests are comparable with that determined from uniaxial compression test of cylindrical asphalt concrete samples. The observed indentation size effect on hardness value was analyzed based on an existing size effect model. The size effect in the asphalt–filler mixture, which is stronger than that defined by the model, could be attributed to a plastically graded surface of asphalt–filler sample. 相似文献
7.
This article presents the development of a J2 small strain plasticity model based on bounding surface concept, along with numerical examples to demonstrate model behaviors and identification of model parameter using laboratory test data. The model is motivated by the need for simulating permanent deformation accumulation of asphalt concrete mixtures, which leads to rutting in flexible pavements under repeated traffic loading. The proposed model accounts for the observation that rutting is mostly caused by shearing and takes advantage of the fact that bounding surface concept allows for the progressive accumulation of plastic deformation under constant amplitude loading condition. Analytical solutions are given for typical laboratory testing conditions. The model can be calibrated using repeated simple shear test data that are typically available for asphalt concrete mixtures. It is shown that the model is easy to use and provides a promising alternative for modeling permanent deformation accumulation in materials subjected to repetitive (cyclic) loading. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
8.
三轴应力下水对粉砂质泥岩蠕变力学特性影响作用试验研究 总被引：1，自引：0，他引：1
采用岩石流变试验机,在三轴应力下分别对干燥与饱水两种含水状态的粉砂质泥岩开展室内蠕变力学试验。分析了水对粉砂质泥岩蠕变量、蠕变长期强度的影响作用。依据岩石的蠕变性质,选取Burgers蠕变模型对其进行描述,得出两种含水状态下岩石的蠕变模型参数。对比干燥与饱水含水状态下岩石的Burgers蠕变模型参数,分析得出了水影响Burgers蠕变模型参数的基本规律。结果表明:（1）相同应力水平下,水对粉砂质泥岩的瞬时应变特性影响较小,而对岩石的蠕应变特性影响相对较大;（2）饱水试样的蠕变长期强度是干燥试样的39.3%,由于水的作用,粉砂质泥岩的蠕变长期强度大幅降低,在工程中应考虑由于水的影响作用而导致的岩石长期强度降低问题;（3）水对Burgers蠕变模型各参数的影响作用从大到小依次为:η1、G1、G2和η2,即水对Burgers模型中串联的元件力学特性影响较大,而对并联的元件力学特性影响相对较小;（4）由于水的影响作用,粉砂质泥岩达到稳定蠕变阶段所需的时间显著增加,岩石的稳态蠕变速率显著增大;（5）由于水的影响作用,导致粉砂质泥岩的蠕变力学特性发生显著改变。因此,在重大岩石工程中应重视水对岩石时效变形的影响作用。 相似文献
9.
Rock masses encountered in the field are jointed and highly anisotropic. An important manifestation of this characteristic of rock masses is that the blocks, when slipping, separate and create voids in the mass resulting in high lateral strain even under low axial stress. It has been shown in this study that the ratio of lateral to axial strain may be very high, especially, if the joints are critically oriented. The assumption of isotropic linearly elastic material is not applicable in such situations. This observation is based on the outcome of an extensive laboratory testing programme, in which a large number of specimens of a jointed rock mass with various joint configurations were tested under uniaxial loading conditions. The trends of experimental results for both lateral strain ratio and rock mass strength have also been verified through distinct element modelling. The reason for high lateral strains has been attributed to the creation of voids and also to the fact that permanent deformations due to slip commence along rock joints right from the start of loading process. A simple mechanistic model has also been suggested to explain the high values of lateral strain for rough and dilatant rock joints. The lateral strains in such situations are important in the design of rock bolts. An example from a recently completed hydroelectric project has also been discussed where high lateral strain was found to be responsible for excessive wall closure and failure of rock bolts. 相似文献
10.
A strategy to predict strain across geological structures, based on previous techniques, is modified and evaluated, and a practical application is shown. The technique, which employs cross-section restoration combined with kinematic forward modelling, consists of restoring a section, placing circular strain markers on different domains of the restoration, and forward modelling the restored section with strain markers until the present-day stage is reached. The restoration algorithm employed must be also used to forward model the structure. The ellipses in the forward modelled section allow determining the strain state of the structure and may indirectly predict orientation and distribution of minor structures such as small-scale fractures. The forward model may be frozen at different time steps (different growth stages) allowing prediction of both spatial and temporal variation of strain. The method is evaluated through its application to two stages of a clay experiment, that includes strain markers, and its geometry and deformation history are well documented, providing a strong control on the results. To demonstrate the method's potential, it is successfully applied to a depth-converted seismic profile in the Central Sumatra Basin, Indonesia. This allowed us to gain insight into the deformation undergone by rollover anticlines over listric normal faults. 相似文献
11.
Mazouz El Hadi Hamimed Messaoud Yahiaoui Abdelouahab Benzagouta Mohamed Said Khodja Mohamed Achi Nada Duplay Joëlle 《Arabian Journal of Geosciences》2020,13(9):1-11
The creep property of rock under cyclic loading is very important in civil engineering. In order to establish a novel constitutive equation for rock under cyclic loading, a fractional-order viscoplastic body under cyclic loading was constructed based on fractional-order viscous element. A fractional-order visco-elastoplastic model (FVEPM) for rock was established by connecting constructed fractional-order viscoplastic body with Burgers model. The model was a Burgers model when the maximum value of cyclic loading was less than the critical strength of rock; otherwise, it was a FVEPM which can be used to reflect the transient, steady-state, and tertiary creep phases of rock. The cyclic loading was decomposed into a static load and a cyclic loading with a zero average stress. According to rheological mechanics theory, the rheology constitutive equation of rock under the static load can be derived. According to viscoelastic mechanics theory, the constitutive equation under cyclic loading with a zero average stress was established by introducing the variation parameters of energy storage and energy dissipation compliance caused by rock damage and fracture. Finally, a new dynamic constitutive equation of rock cyclic loading can be obtained by superimposing the constitutive equation under static load and cyclic loading with a zero average stress. Compared with existing test results of rock under cyclic loading, the proposed constitutive model can be used to describe the creep characteristics of rock under cyclic loading and reflect the presented fluctuation of strain curve of rock under cyclic loading. 相似文献
12.
Y. Bottinga 《Physics and Chemistry of Minerals》1994,20(7):454-459
Several observations of non-Newtonian viscosity of silicate liquids at high stress or strain rates have been published in recent years. However, this phenomenon is not well understood yet. In this paper attention is drawn to the fact that steady state logarithmic values of reduced viscosities of silicate liquids under high stress show a linear dependence on the squared value of the applied stress. This relationship suggests that the elastic work done by the stress on the liquid is related to the observed viscosity decreases. It is shown that the development of non-Newtonian viscosity in silicate melts under high stress can be explained with the Adam and Gibbs (1965) theory, if one accepts that this elastic work generates configurational entropy. 相似文献
13.
本文对取自雅砻江锦屏二级电站的砂岩开展三轴压缩流变实验,并分析了实验数据,得到不同偏应力条件下砂岩轴向应变、侧向应变、轴向应变率和侧向应变率随时间的变化规律。并用Burgers体来反映瞬态蠕变阶段、稳态蠕变阶段的蠕变,进行了参数辨识,为工程围岩长期稳定性分析提供理论基础。 相似文献
14.
南海珊瑚泥是珊瑚群体死后的骨胳、碎屑聚积形成的海洋岩土体钙质软泥,具有特殊的工程性状,研究其在荷载作用下与时间相关的长期非线性变形对吹填岛礁建设和长期稳定分析具有重要意义。对珊瑚泥进行了3组不同加卸载方案的一维固结压缩试验,通过改变加载时间与加卸载循环圈数探究应力历史对其长期变形性质的影响,并针对珊瑚泥在加卸载试验条件下呈现出的瞬时变形、延时衰减与延时稳定变形3阶段规律,采用改进的Burgers模型拟合不同竖向应力作用下的ε-t（应变-时间）曲线,具有较高拟合精度。同时分析模型参数后发现,随着分级加载时间提高,瞬时应变增量及其增长率下降,最终荷载下的延时衰减时间缩短,延时稳定应变速率及最终荷载下的总应变增量减小。同一加卸载循环圈数中,同竖向应力下卸载阶段的瞬时应变增量小于加载阶段。随着加卸载循环圈数的增加,加、卸载各阶段瞬时应变增量均减小且二者相近,延时衰减时间缩短,延时稳定应变速率及最终荷载下的总应变增量减小。研究了分级加载时间与加卸载循环圈数对珊瑚泥长期变形性质的影响,旨在为岛礁建设中的堆载预压方案提供理论依据。 相似文献
15.
用数值方法模拟了在气候持续以0.02℃·a-1速度增温下,50 a运营年限内不同走向路基的融化形态可能发生的变化趋势.计算了在砂砾路面和沥青路面下,不同高度(0~5.0 m)及不同走向(东西、东北-西南、南北、对称)路基的融化形态.结果表明:非对称热边界路基与对称热边界路基的融化形态差异很大.在呈阴阳坡的路基中,砂砾路面和沥青路面下:1)最大融化深度位置与运营时间关系不大,与路基高度、线路走向及路面类型关系密切,且最大融化深度偏离路基中线的距离与路基高度呈线性关系;2)最大融化深度与运营时间、路基高度、路面类型关系比较密切.路基较低时,最大融化深度与路基走向关系不大.路基较高时,最大融化深度与线路走向关系密切,且随着路基高度的增加、气候变暖及增温速率的增大而加剧;3)同一路基高度和线路走向下,砂砾路面的最大融化深度偏离路基中线的距离大于沥青路面的,沥青路面的最大融化深度大于砂砾路面的.相对于砂砾路面,沥青路面在一定程度上部分的抵消了阴阳坡效应,但加剧了路基下最大融化深度. 相似文献
16.
基于Feng Y T提出的精确缩尺方法,即根据几何相似、静力相似、动力相似3个相似原理建立一套缩尺准则,使得缩尺前后模型的力学响应保持一致。首次将该理论应用于颗粒材料的流变分析当中,采用Burgers黏塑性蠕变模型,引入流变参数,在原缩尺准则上进行理论推导,得到在二维和三维条件下的缩尺准则;其次在理论推导的基础上进行数值仿真验证。研究结果表明：严格按照拟定的缩尺准则选取参数后,缩尺后模型的力学响应能够保证和原尺寸模型完全一致,计算误差在3%以内,同时简要探讨了时间步长、黏性系数、颗粒数目、比尺数对数值试验的影响,为数值试验中相关参数的选取以及如何让数值模型反映材料真实的力学行为提供了有效参考。另外,由于缩尺模型采用与原模型相同的颗粒数目、颗粒形状、颗粒压实状态和比尺数,揭示了等比例缩尺对材料流变行为的影响。 相似文献
17.
Masoud K. Darabi Rashid K. Abu Al‐Rub Eyad A. Masad Dallas N. Little 《国际地质力学数值与分析法杂志》2012,36(7):817-854
Based on the continuum damage mechanics, a general and comprehensive thermodynamic‐based framework for coupling the temperature‐dependent viscoelastic, viscoplastic, and viscodamage behaviors of bituminous materials is presented. This general framework derives systematically Schapery‐type nonlinear viscoelasticity, Perzyna‐type viscoplasticity, and a viscodamage model analogous to the Perzyna‐type viscoplasticity. The resulting constitutive equations are implemented in the well‐known finite element code Abaqus via the user material subroutine UMAT. A systematic procedure for identifying the model parameters is discussed. Finally, the model is validated by comparing the model predictions with a comprehensive set of experimental data on hot mix asphalt that include creep‐recovery, creep, uniaxial constant strain rate, and repeated creep‐recovery tests in both tension and compression over a range of temperatures, stress levels, and strain rates. Comparisons between model predictions and experimental measurements show that the presented constitutive model is capable of predicting the nonlinear behavior of asphaltic mixes under different loading conditions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
18.
In order to apply the mechanical properties (measured on material specimens or laboratory‐sized models) to large structures (such as concrete dams), a non‐linear theory able to predict the size‐scale effect has to be used. One of these theories was first proposed by Hillerborg and co‐workers (fictitious crack model) and is based on the earlier works by Barenblatt and Dugdale for metals (cohesive crack model). It is based on the existence of a fracture process zone (FPZ), where the material undergoes strain softening. The behaviour of the material outside the FPZ is linear elastic. A large number of short‐time laboratory tests were executed, by varying the load, under crack mouth opening displacement control. Since concrete exhibits a time‐dependent behaviour, an interaction between creep and micro‐crack growth occurs in the FPZ. Therefore, different testing conditions can be applied: rupture can be achieved by keeping the load constant before peak value (pre‐peak tests), or after peak value and after an unloading and reloading procedure (post‐peak tests). The crack propagation rate is shown to be small enough to neglect inertial forces and large enough to keep the time‐dependent behaviour of the process zone as dominant compared to the behaviour of the undamaged and viscoelastic zone. Due to the variability in material microstructure from one specimen to another, experimental data show large ranges of scatter. Well established methods in probability theory require sufficient experimental data in order to assume a probability density distribution. The objective of this study is to investigate the ranges of variation of the time response under constant load in simple structural elements associated with pre‐selected variation (fuzziness) in the main material parameters. For situations where the values of the material parameters are of a non‐stochastic nature, the fuzzy set approach to modelling variability has been proposed as a better and more natural approach. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
19.
20.
Fuzzy and Multiple Regression Modelling for Evaluation of Intact Rock Strength Based on Point Load, Schmidt Hammer and Sonic Velocity 总被引：4，自引：0，他引：4
Summary. Uniaxial Compressive Strength (UCS), considered to be one of the most useful rock properties for mining and civil engineering
applications, has been estimated from some index test results by fuzzy and multiple regression modelling. Laboratory investigations
including Uniaxial Compressive Strength (UCS), Point Load Index test (PL), Schmidt Hammer Hardness test (SHR) and Sonic velocity
(Vp) test have been carried out on nine different rock types yielding to 305 tested specimens in total. Average values along
with the standard deviations (Stdev) as well as Coefficients of variation (CoV) have been calculated for each rock type. Having
constructed the Mamdani Fuzzy algorithm, UCS of intact rock samples was then predicted using a data driven fuzzy model. The
predicted values derived from fuzzy model were compared with multi-linear statistical model. Comparison proved that the best
model predictions have been achieved by fuzzy modelling in contrast to multi-linear statistical modelling. As a result, the
developed fuzzy model based on point load, Schmidt hammer and sonic velocity can be used as a tool to predict UCS of intact
rocks. 相似文献