共查询到20条相似文献，搜索用时 656 毫秒
1.
Meissa Fall Auckpath Sawangsuriya Craig H. Benson Tuncer B. Edil Peter J. Bosscher 《Geotechnical and Geological Engineering》2008,26(1):13-35
Investigations on the mechanical behavior of compacted gravel lateritic soils have been the subject of several studies. Used
as road materials, soils tests were mainly performed using standard tests. Static loads as unconfined compression test (UCT)
remain the only engineering approach used. Alternative testing techniques can be chosen as supplementary tests for characterizing
pavement materials. These researches were conducted so as to determine the response of these particular and problematic soils
in its compacted form with road traffic loads. This paper presents the results of research conducted to investigate the effect
of the soil compacity on the resilient modulus of lateritic soils. The influence of the percentage of cement added so as to
stabilize each sample at the optimum modified proctor (OPM) State was also determined. Soil big specimens of around 180 mm
diameter (with length to diameter aspect ratio of 2:1) were prepared according to the standard procedure described by AASHTO
T 307 and then were subjected to repeated load triaxial tests. The models used, analyzed and developed in this paper are mainly
the Andrei and the Uzan–Witczak universal model. Test results showed that the specimen compacity has no significant influence
on the resilient modulus of the investigated gravel lateritic soils. Soil specimens with variation of the percentage of cement
added exhibited the highest resilient modulus values while the specimens with variation of the compacity exhibited the lowest
values. The resilient modulus variation seems to be independent of the level of stress. 相似文献
2.
C. M. O. Nwaiwu I. B. K. Alkali U. A. Ahmed 《Geotechnical and Geological Engineering》2006,24(2):283-298
A laboratory investigation was conducted to determine properties of five samples of ‘oolitic ironstone’ lateritic gravel aggregates
which are relevant to their use as road construction materials. Measured values of physico-chemical, physico-mechanical as
well as index properties and compaction characteristics are similar to those of other lateritic, gravels occurring in West
Africa which are used in road pavement applications. These lateritic clayey gravels have good workability as engineering construction
materials and are rated fair to good as road aggregates in terms of probable in-situ behaviour based on water absorption values. Relationships between maximum dry unit weight and optimum moisture content as
well as those between California bearing ratio and some derived soil parameters such as grading modulus, plasticity product
or plasticity modulus can be described using a third-order polynomial function. The maximum dry unit weight has a bimodal
frequency distribution and can be predicted from logarithm to base 10 of compaction energy with fairly good accuracy. 相似文献
3.
The present paper introduces a comprehensive model that is capable of describing the behaviour, under cyclic loading, of the granular materials used in railway tracks and road pavement. Its main thrust is the introduction of the “Chicago” law in a continuum approach to account for the ratcheting effects. It also emphasizes rate-dependency as a dissipative mechanism that acts independently or jointly with the ratcheting effect as well as the non-associated plasticity. The numerical procedure is based on the return mapping algorithm, where Newton’s method is used to calculate the nonlinear consistency parameter of the flow rule and to obtain a consistent tangent modulus. The model was applied to specific numerical examples including multi-axial and cyclic loading conditions. 相似文献
4.
Jacob Uzan 《国际地质力学数值与分析法杂志》1992,16(6):453-459
The paper presents an approach for characterizing pavement materials using the modified linear elastic behaviour. The secant modulus of elasticity is expressed in terms of the stress invariants and an expression for the secant Poisson's ratio is derived using path independence of the total work along a closed loading cycle. Triaxial test results of granular base–subbase materials which exhibit strong non-linear behaviour and dilatancy are analysed and presented. The constitutive law is included in a finite element program and results of pavement analyses are discussed. It is found that the secant Poisson's ratio of granular base materials reaches values between 0·6 and 0·7, indicating a volume increase under high stress ratios. The pavement response predicted using the above material characterization is compatible with non-destructive test results. 相似文献
5.
Stabilization of lateritic soils with phosphoric acid 总被引：1，自引：0，他引：1
Summary This paper describes a laboratory study on the stabilization of lateritic soils with phosphoric acid-H3PO4. This method is most promising for road and airport pavement construction in tropical regions where fine textured lateritic soils (red clays and silts) occur over large areas. The iron and aluminum phosphates formed are hard and insoluble. The main source of iron is free iron oxide, and the aluminum sources are free aluminum oxide, exchangeable cations and clay minerals (hydrated aluminum silicates). Four different soil samples were studied, but the most comprehensive study was carried out with a lateritic soil evolved from weathered basaltic bedrock. The variables of the test specimens were: percentage of acid, moulding water content, compaction energy, and curing time. Strength tests performed were the axial or unconfined compression test and the indirect tensile or diametrical compression test. With 5% of phosphoric acid to dry weight of soil, values of compressive strength around 4.0 MPa were obtained after 28 days curing. 相似文献
6.
M. D. Gidigasu 《Engineering Geology》1980,15(3-4):173-194
The paper discusses the laboratory and pavement constructional evaluation of residual lateritic gravels over phyllite.
Laboratory classification, compaction and bearing test results indicate that the natural materials are unsuitable by standard gravel acceptance specifications for road base construction. However, the bearing properties can be improved to meet base-material specifications through treatment with about 5% cement. Results of construction control studies also revealed that the laboratory compaction properties of both the raw and cement-stabilised gravels are easily reproduced in the field using fairly light, smooth-wheel rollers. This means that the complaints by contractors of difficulty in achieving design specifications using similar plants during construction is not justified.
Notwithstanding the results of the studies reported herein, it is not possible at the moment to suggest any construction control specifications for these gravels until more data on their in-service performance in the roadway has been collected and analysed over a number of years. 相似文献
7.
软土是一种非线性流变物质,但现行流变模型却忽略了加载瞬时的非线性变形;软土流变试验参数是数学模型参数而非物理模型参数,一个土样一般只对应一种材料参数,但现行流变模型的模型参数常随着荷载变化,且变化无规律,离散性大。基于以有机质为流变相物质的人工土试样室内一维压缩蠕变试验,建立了各级荷载作用下具有相同模型参数的7组件流变模型,用非线性弹簧H描述软土加载瞬时弹塑性变形、并联的三元件组件模拟软土随时间变化的黏弹塑变形。结果表明：引入三次非线性瞬时弹性模量的7组件流变模型能够较准确地反映软土的流变特性。 相似文献
8.
Hossein Nowamooz Cyrille Chazallon Maria Ioana Arsenie Pierre Hornych Farimah Masrouri 《Computers and Geotechnics》2011
Granular materials are generally used in unbound layers of road pavement structures. The mechanical behavior of these materials is widely studied with repeated load triaxial tests (RLTT) in which the elastic response is defined as the resilient behavior. Usually observed under total stress conditions, the effect of pore pressure changes during loading are not usually included in design. Further, the unbound layers frequently exist under partially saturated conditions. The influence of the unsaturated state, i.e., the suction, on the mechanical behavior, of unbound granular materials for roads has not been sufficiently studied and is generally not taken into account in models used for these materials. 相似文献
9.
颗粒材料在循环荷载作用下呈现循环硬化行为,然而关于循环硬化行为的宏-微观相对应的机理解释的研究却不多见。本文通过3D-DEM实施了循环三轴数值模拟试验,研究了不同级配下颗粒材料在循环荷载下的循环硬化行为,并分析了(轴向)平均模量和由滑动接触造成的能量耗散的演化趋势。结果表明随着循环荷载的进行,平均模量逐渐增加并趋于渐进值。每个循环内的能量耗散随着循环数的增加不会一直衰减,存在一个阈值。不同颗粒级配下平均模量的增加指数和能量耗散衰减指数的大小相近(约为0.6),表明在描述循环荷载硬化行为时,无论是使用变形模量还是归一化能量耗散在结果上是一致的,即微观尺度上滑动接触引起的能量耗散映射出宏观尺度上平均模量的变化。颗粒平均粒径越大的颗粒体系,其平均模量越大,而且越早完成能量耗散过程,但不同的颗粒级配下对应的能量耗散阈值差异较小,基本上维持在一个常数(约为0.15)。 相似文献
10.
为了研究不同尺度路基融沉作用对路面结构层力学响应的影响,建立了基于热力耦合理论的有限元模型,系统研究不同路基尺度工况下,融沉作用对不同厚度路面、不同材料基层的力学分布规律影响. 结果表明：相同的融沉条件下,整体式路基较分离式及二级路基,变形分别增大45%、64%,应力增大17.5%、21.7%. 高速公路面层由于路基较宽,地基融沉更容易向上传递,进而导致面层底部应力增大,最终造成面层的破坏. 因此,路面设计过程中保证一定的面层厚度,并采用柔性基层减小模量,可有效以降低层底应力水平,并防止基层裂缝向上反射. 相似文献
11.
The suitability of a lateritic soil developed on olivine basalt in western southeast Queensland, Australia, as paving material has been investigated. The particle size distribution and plasticity characteristics of the soil do not comply with the standard specification for paving materials. However, the soil has a high shear strength, resulting in a low Western Australian Confined Compression Test class number. The high shear strength of the soil at its in situ moisture content is due to its high angle of shearing resistance and its suction under in situ moisture conditions. Volumetric shrinkage of the soil does not constitute a problem as its shrinkage is low. The in situ strength of a pavement constructed with the lateritic soil, determined using a Clegg impact hammer, and the field dry density, have increased with time and the passage of traffic since construction. The pavement performance was good. A criteria suitable for the selection of a lateritic soil as paving material under the climatic conditions prevailing in western southeast Queensland has been suggested. 相似文献
12.
Long-term Non-linear creep and swelling behavior of Hong Kong marine deposits in oedometer condition
The time-dependent stress-strain behavior of clayey soil is a great concern for predicting long-term settlement especially for large-scale land reclamation projects. In this paper, long-term time-dependent behavior of Hong Kong Marine Deposits (HKMD) under the loading stage and unloading stage is investigated by multi-staged loading oedometer test. Special emphasis has been given to study creep and swelling behavior. It is found that the clayey soil demonstrates the creep behavior during the loading stage, whereas it shows the swelling behavior during the unloading stage. The analysis of the creep behavior shows that there exists a linear trend between creep strain and time (in log-scale) within a certain period, whereas a nonlinear relationship in a long term view. Similar result is found for the swelling behavior. A nonlinear function is found to be suitable to predict the long-term creep and swelling behavior. The creep strain limit and swelling strain limit can be obtained if the nonlinear function is adopted to fit the experimental data. In addition, a new modified Elastic Visco-Plastic model considering Swelling (EVPS model) is proposed and presented, which considers the nonlinear creep and swelling behavior. In this modified EVPS model, the final creep and swelling equilibrium stress-strain state can also be obtained when the time is infinite. 相似文献
13.
三角形周期荷载作用下软基路堤沉降研究 总被引：1，自引：0，他引：1
采用能够同时考虑主次固结变形的Yin-Graham一维弹黏塑性模型,对三角形周期荷载作用下软土路堤运行期间和运行期结束时的长期沉降进行了理论分析,获得三角形周期荷载作用下软基路堤运行期结束时的总沉降计算公式和工后沉降计算公式。分析了三角形周期荷载作用下软基不考虑流固耦合与考虑流固耦合时长期沉降之间的相互关系,证明了三角形周期荷载作用下当循环荷载次数趋向于无穷大时软基具有最终沉降量与应力随时间增长的模式无关的性质。按照文中提供的总沉降计算公式,针对具体工程的土工参数,对路堤运行期结束时的总沉降量进行了计算,并由此确定运行期开始时软基应发生的沉降量,为合理确定高速公路路面铺筑时机提供沉降标准。 相似文献
14.
M. D. Gidigasu 《Geotechnical and Geological Engineering》1991,9(3-4):219-260
Summary Road transportation is increasingly becoming one of the key factors for promoting economic growth in most developing countries. However, transport and road research in the tropics has received relatively little attention. Experiences in road construction in the tropics within the past 50 years or so have established that local materials specifications and pavement construction technologies have to be developed in relation to the climatic conditions. This would involve knowledge of the processes of formation as well as genetic characteristics of the local gravels. Genetic characteristics exert considerable influence on the geotechnical properties and engineering behaviour of local gravels under pavement. The construction technology of the road pavement should take cognizance of the compositional variabilities of the gravel deposits. Construction studies of pavement sections (as well as assessment of the performance of existing roads) built with different gravels formed over different geological formations in specific climatic, and drainage conditions would provide useful data for evolving local gravel specifications for constructing stable and durable pavements. Stage construction of pavements involving the exposure of the various layers to traffic loading and seasonal climatic influences appears to hold promise for formulating strategies for constructing stable, and long-term durable tropical roads. The problem of achieving reproducible laboratory test data under field conditions is perhaps the most challenging aspect of utilizing local gravels for pavement construction in tropical and sub-tropical conditions. It is noted that the stability of pavements in tropical environments depends not so much on the geotechnical properties of the available gravels as on the appreciation by the designers and construction engineers of the relationship between the genetic and laboratory determined characteristics of the gravels on the one hand and the pavement construction technology and local climatic and drainage conditions on the other. This paper is a contribution to development of highway geotechnics for tropical and sub-tropical conditions. 相似文献
15.
土的量化记忆模型及其参数确定 总被引：1，自引：1，他引：0
土的真非线性分析要求追踪应力-应变历史,寻求滞回圈上应力-应变的瞬时切线模量。由于地震荷载的随机性,实际土体的应力-应变历史轨迹非常复杂。基于传统模型的骨架曲线和滞回圈表达式进行这类分析的难度很大。作者介绍的量化记忆模型是为土的动力真非线性分析提出的,它是将单调加载情况下呈非线性变化的切线模量量化,记忆为一种分段线性分布的几何结构,并通过对这种结构加以变换,以描述循环加载情况下具有滞回特性土料的动应力-应变关系。在试验的基础上,运用非线性最小二乘法,确定了量化记忆模型中的 , , , , , 6个参数,并将量化记忆模型生成的应力-应变关系曲线与试验曲线进行了比较。结果表明,量化记忆模型是有效可行的。 相似文献
16.
为研究循环荷载下原状红黏土路基的动力特性,采用SDT-20型动三轴仪对原状红黏土进行了分级循环动三轴试验,研究了围压、频率及动应力幅值对原状红黏土的动应力、动弹性模量-动应变（ Ed-εd）和动剪切模量-动剪切应变（ Gd-γd）关系曲线的影响规律。结果表明:原状红黏土的动应力-动应变关系曲线发展规律可采用Kondner模型进行描述;动应力随动应变先急剧增大后趋于平稳,并给出了急剧增加时动应变的取值范围,即0%～0.05%;分析了不同围压、振动频率下红黏土的动弹性模量及动剪切模量的变化规律,当动应变小于临界值时,红黏土动弹性模量随动应变的增大而增大;当动应变大于临界值时,红黏土材料动弹性模量随动应变的增大而减小,动剪切模量具有相同变化规律;结合红黏土的动力特性变化规律,利用围压对动弹性模量进行折减,在Darendeli模型的基础上建立了红黏土路基动弹性模量、动剪切模量的分段预测模型,经拟合验证,本文分段模型的适用性较好,可预测分级循环荷载下红黏土的动弹性模量-动应变（Ed-εd）和动剪切模量-动剪切应变（Gd-γd）关系曲线发展趋势。 相似文献
17.
交通荷载作用下公路路基工作区深度研究 总被引：3，自引：0，他引：3
根据路面不平整实测资料,获得了汽车动荷载的计算模型和参数,并利用此荷载模式来分析公路结构的动力响应。考虑到公路结构的三维分层性状,利用Fourier变换技术和求解层状结构的精确刚度矩阵法,研究了公路结构在移动汽车荷载作用下的动力响应问题。为了方便工程应用,利用Odemark厚度和模量的当量转换公式,将公路结构简化为由路面、路基及地基组成的3层体系,并以此为基础分析了路基动应力的衰减规律,同时重点研究了汽车轴载大小、当量路面厚度及路基模量对路基工作区深度的影响,最后建议了路基工作区深度的定量表达式,研究结果可为公路路基设计提供参考。 相似文献
18.
为掌握土压力传感器置于硬土介质中呈现的非线性响应特性,建立了传感器与土介质的相互作用模型,运用有限元分析了满足匹配误差稳定所需的传感器与土介质的模量比条件。进行了传感器的单体标定和级配碎石土介质标定试验,探讨了传感器非线性响应的主要影响因素。计算与试验表明,目前国内主流的双膜土压力传感器在量测硬土介质中的土压力时,由于模量偏小标定曲线非线性显著;土压力传感器单体标定曲线线性度较高且其模量基本稳定,表明土介质的模量变化是引起标定曲线非线性的主要因素;通过将传感器置于与使用环境相近的土介质中进行标定,并采用非线性修正可明显提高硬土介质中土压力量测的准确性。 相似文献
19.
基于原位试验成果的地基非线性沉降分析 总被引：3，自引：0，他引：3
提出了利用小尺寸载荷试验（PLT）及标准贯入试验（SPT）成果准确求解地基非线性沉降的新方法。首先利用压板载荷试验成果经过双曲线拟合,确定出某一土层地基土的修正切线模量;然后根据不同深度的SPT标贯击数按照线性相关关系,确定该土层不同深度各分层土的修正切线模量;最后依据分层总和法求解地基或基础的非线性沉降。该方法的特点是能进行加载至极限状态的全过程非线性沉降分析,而计算原理简单,计算参数全部来自现场原位测试,附加应力依据压板试验成果进行自动修正。分析广东某大型油罐地基及某高层建筑筏板基础的沉降结果表明,该方法计算结果准确可靠,能满足以沉降控制为目标的地基基础工程设计要求。 相似文献
20.
南宁膨胀土非线性流变模型研究 总被引：1，自引：0，他引：1
对南宁非饱和膨胀土进行一系列的加载-卸载固结蠕变试验,得到了不同含水率的膨胀土在不同应力水平下应变-时间曲线和不同时刻的应力-应变等时曲线簇。通过对膨胀土各阶段蠕变变形的分析,得到了膨胀土的固结蠕变是包含有黏弹性变形和黏塑性变形成分的非线性蠕变。采用模型流变与经验流变理论相结合的方法,将膨胀土的蠕变变形分成线性和非线性两部分进行分析,蠕变柔量和线性黏弹性模量随时间减小,而线性黏塑性模量随时间增大。结合膨胀土的线性黏塑性模型和非线性黏塑性经验模型,建立能够描述膨胀土非线性流变的黏塑性本构方程。根据试验所得数据,通过非线性拟合方法得到各模型参数,用该模型进行数值分析得到的理论与蠕变试验结果对比非常吻合。研究成果为实际工程提供了流变变形计算分析的可靠依据。 相似文献