共查询到20条相似文献，搜索用时 15 毫秒
1.
为探究循环动载作用下加筋砾性土填料的动力特性,在不同加筋层数和围压下对加筋砾性土进行了固结不排水动三轴试验,研究加筋层数和围压对加筋砾性土动力特性的影响,并进一步分析了加筋砾性土轴向累积应变发展机制。研究表明:加筋层数增加时,轴向累积应变减小,回弹模量增大,且加筋作用的影响幅度逐渐衰减;增大围压时,土体轴向累积应变减小,回弹模量和动孔压均随之增大;随着加筋层数和振次的增加,滞回曲线逐渐向应力轴靠近,滞回圈面积逐渐减小,土体耗能作用减弱。基于安定理论和间接影响带理论,揭示了加筋作用对轴向累积应变发展的影响机制。建立了能够反映加筋层数的加筋砾性土轴向累积应变预测模型,其条件参数a、b、g与加筋层数呈线性关系,可有效预测循环荷载下加筋砾性土路基沉降变形规律。 相似文献
2.
Wiam Khebizi Sidali Denine Jean Canou Jean-Claude Dupla 《Geomechanics and Geoengineering》2019,14(1):30-40
Soil improvement using fibres is widely used in soil stabilisation to prevent sand liquefaction. In order to study the undrained behaviour and liquefaction resistance of sand reinforced with polypropylene fibres, a series of triaxial compressive tests were conducted on unreinforced and reinforced Chlef sand with different contents of polypropylene fibres (0, 0.3, 0.5 and 0.8%). Samples were prepared at 30% and 80% relative densities representing loose and dense states respectively, and triaxial tests were performed at confining pressures of 50, 100 and 200 kPa. Tests results show that fibre inclusion has a significant effect on the shear strength and dilation of sandy soil. The increase in strength is function of fibre content, relative density and confining pressure. The maximum strength improvement for both loose and dense fibre-reinforced sand is more pronounced at higher confining pressure and at higher fibre content. 相似文献
3.
为研究北京富水砂卵石地层冻结后的强度特性,以北京某地铁暗挖车站砂卵石为研究对象,进行不同温度（?5、?10、?15、?20℃）,不同围压（0.0、0.3、0.8、1.3、2.0、3.0、4.0、8.0 MPa）条件下三轴压缩试验。试验结果表明：冻结砂卵石的应力-应变曲线以应变软化形态为主,高负温、高围压条件下,呈现理想塑性破坏形态;砂卵石强度、黏聚力和摩擦角均随温度降低而增大,其中强度呈指数分布,黏聚力和摩擦角呈线性分布;强度和弹性模量随围压增加而增大,但增大趋势逐渐减小,低围压压缩区强度满足线性Morh-Coulomb（简称M-C）准则;冻结砂卵石的破坏形态以破裂面始/终于试样侧面的剪切破坏为代表,张拉型破坏受冰影响显著,仅存在于低围压条件下,高围压、高负温时易出现体胀型破坏。 相似文献
4.
在基坑、隧道开挖等过程中,不同部位的土体会经历不同的应力路径,在不同的应力路径下,土体可能表现出截然不同的静力学特性。同时,在工程实际中,土体的工作应变经常处于小应变范围,而在小应变情况下,土体的静力特性表现出更强的非线性和应力路径依赖性。基于广泛分布于东部地区,并且表现出诸多不良工程特性的软黏土,进行一系列不排水和排水条件下的应力路径静力试验,以研究应力路径对饱和软黏土静力特性,尤其是小应变情况下割线模量的影响。试验结果表明,不管在不排水还是在排水条件下,应力路径都对饱和软黏土的静强度产生巨大的影响,表现为围压增加的加载应力路径增大了静强度,而围压减小的卸载应力路径降低了静强度。同时,应力路径对割线弹性模量产生了更大的影响,围压增加的加载应力路径降低了割线模量,而围压减小的卸载应力路径增大了割线模量。应力路径对割线模量的影响在小应变时表现的更加明显,而这种影响主要原因是应力路径方向改变造成的土体各向异性。 相似文献
5.
黄土地基动力沉降特性试验研究 总被引：2，自引：1，他引：1
路基工后沉降控制是客运专线路基工程研究的重点内容,其中地基在列车荷载长期重复作用下的累积沉降不可忽视。为揭示黄土地基在列车振动荷载长期作用下的沉降变形,通过对原状黄土试样的循环三轴试验,模拟实际列车荷载瞬时加载状态,采用不等向长持时加载,得出了在不同围压条件下黄土的动强度特性和循环应力-累积应变关系,并对较小循环应力下的循环应力-累积应变关系进行了归一化处理,得到了以下结论：①黄土的累积应变随时间的增加而增大,当循环应力不超过临界应力时,应变会最终达到稳定;反之,黄土结构遭到破坏,应变不能达到稳定;②不同围压下的黄土累积应变均随循环应力的增大而增大,且临界循环应力随围压的增大而增大。③在同一围压状态和同一应变破坏标准下,动强度随振次的增加而减小;④在不同围压、相同振次条件下达到相同的应变所需要的循环应力随围压的增大而增大;⑤在较小循环应力作用下,不同围压下黄土的累积应变随循环应力增加呈线性增长。 相似文献
6.
Cemented coarse-grained alluvium is present in a vast area of Tehran city, Iran including its suburbs. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of triaxial compression tests were performed on uncemented, artificially cemented and destructured samples. Hydrated lime was used as the cementation agent for sample preparation to model the Tehran deposit. The tests were performed on cemented samples after an appropriate time for curing. The tests on cemented samples show that a shear zone appears as the shear stress approaches the peak shear strength. During shearing these samples undergo dilation at confining stress lower than 1000kPa. However, the uncemented and destructured samples show contraction during shearing. Peak shear strength is followed by strain softening for all cemented samples. The shear strength increases with increasing cement content but the influence of the cementation decreases as the confining stress increases. With increasing cementation the stress-strain behaviour of samples tend towards the behaviour expected of high-density soils. Test results indicate that the failure envelope for cemented samples is curved and not linear. 相似文献
7.
通过等压固结静、动三轴试验,研究了渤海湾粉质黏土在循环荷载作用下的动力性质和循环荷载后不排水静力性质。试验结果表明,循环应力幅值比越大,平均轴向应变和轴向应变幅值越大;循环应力幅值比达到0.4时,平均轴向应变和轴向应变幅值随着循环周数增加迅速增大;循环应力幅值比相同,固结应力越大,轴向应变幅值越大,而平均轴向应变越小。在较大的循环应力幅值比下,平均孔压比值和孔压幅值比值随着循环周数的增大会达到稳定;循环应力幅值比越大平均孔压比值和孔压幅值比值均越大;相同循环应力幅值,固结应力越大平均孔压比值越小,而固结应力对孔压幅值比值影响较小。循环荷载的作用会导致循环荷载后不排水剪在q-p’平面上有效应力路径和孔压发展表现出超固结土的性质。 相似文献
8.
The behaviour of an artificially cemented sandy gravel 总被引：1，自引：0，他引：1
The major section of the city of Tehran, Iran has been developed on cemented coarse-grained alluvium. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of undrained triaxial compression tests and unconfined compression tests were performed on uncemented and artificially cemented samples. Portland cement type I was used as the cementation agent for preparing artificially cemented samples. Uncemented samples and lightly cemented samples (1.5% cement) tested at high confining pressure showed contractive behaviour accompanied with positive excess pore water pressure and a barrelling failure mode. However, cemented samples and uncemented samples tested at low confining pressure (25 and 50 kN/m2) showed dilative behaviour accompanied with negative excess pore water pressure. Shear zones were formed in these samples and a clear peak in excess pore water pressure and stress ratio against strain could be observed. Test results showed that the limiting stress ratio surface for cemented samples is curved and expands as the cementation and density increase. Unconfined compression strength of cemented samples increases with increases in cementation and density as well. 相似文献
9.
高围压下冻结砂土的强度特性 总被引：2，自引：6，他引：2
在高围压条件下，对冻结兰州砂土在不同温度和不同应变速度下进行三轴压缩试验，试验结果表明，围压的增大和应变速度的减小明显增强了冻土的塑性性能；同时，随围压的增大，冻土的抗剪强度增加，但随围压的进一步增加，它出现降低的趋势，存在一个临界 围压，此临界围压值随温度的变化而变化，但不随应变速率而变化。 相似文献
10.
Ismail Benessalah Ahmed Arab Pascal Villard Khayra Merabet Rachid Bouferra 《Geotechnical and Geological Engineering》2016,34(6):1775-1790
During the last earthquake that occurred in Chlef (El Asnam 1980, Algeria), a significant decrease in the shear strength has caused major damages to several civil and hydraulic structures (earth dams, embankments, bridges, slopes and buildings), especially for the saturated sandy soil of the areas near Chlef valley. This paper presents a laboratory study of drained compression triaxial tests conducted on sandy soil reinforced with horizontal layers of geotextile, in order to study the influence of geotextile layer characteristics both on shear stress–strain and on volumetric change–strain. Tests were carried out on medium and dense sand. The experimental programme includes some drained compression tests performed on reinforced sand samples, for different values of the geotextile layers number (N g), of confining pressure (\( \sigma_{\text{c}}^{\prime } \)) and relative density (D r). The test results have shown that the contribution of the geotextile at low values of the axial strain (ε 1) is negligible, for higher values of (ε 1); geotextile induces a quasi-linear increase in the deviator stress (q) and leads to an increase in the volume contractiveness within the reinforced samples. A negligible influence of geotextile layers number (N g) on the stress–strain behaviour and the volumetric change has been shown, when normalized with N g. The results indicate that the contribution of geotextile to the stress–strain mobilization increases with increasing confining pressure, while its contribution to the volume contraction decreases with the increase in the confining pressure. 相似文献
11.
为研究地下盐穴储气库受间歇性周期注、采循环载荷作用下围岩的非连续疲劳破坏演化过程,对取自巴基斯坦的深层盐岩进行了室内三轴间隔疲劳试验研究,并分析了三轴状态下不同围压、不同应力等级对盐岩间隔疲劳的影响。试验结果表明：（1）与单轴间隔疲劳相比,围压的存在不仅提高了盐岩的抗压强度,而且增加了盐岩的疲劳寿命,围压越高增加的幅度越明显。（2）三轴间隔疲劳试验中,盐岩间隔后循环中的残余应变大于间隔前的残余应变。这与单轴间隔疲劳得到的结果一致,但围压的上升会导致盐岩的残余变形积累速度以及间隔前后循环残余的变形差值都减小。（3）随着应力等级的升高,残余应变以及时间间隔前后的残余应变差值都呈现增大的趋势。 相似文献
12.
13.
循环荷载下人工结构性土变形与强度特性试验研究 总被引：1，自引：0，他引：1
针对长期动载作用下天然沉积结构性黏土地基强度和刚度循环软化问题,分别以水泥和食糖为模拟粒间胶结和大孔隙的材料,制备了不同胶结强度和初始孔隙比的人工结构性土,开展了人工结构性土与相应重塑土的动三轴试验,分析了土体胶结强度、初始孔隙比、围压和动应力幅值对累积变形和动强度的影响规律。试验结果表明：累积应变-振动次数曲线以临界循环应力为界分为：塑性安定型、临界型和破坏型;临界循环应力随胶结强度增大、初始孔隙比减小而增大;土体胶结强度越高,脆性破坏越明显,累积应变曲线转折点对应的应变越小。动强度的应变破坏标准采用转折点应变值更符合土性变化规律;动强度随胶结强度增大、初始孔隙比减小而增大;动黏聚力cd随破坏振次增大而降低,而动内摩擦角?d基本不变。试验结果可为软弱土地基动力灾变控制提供有益参考。 相似文献
14.
Compaction of granular soils by uniform vibration equivalent to vibrodriving of piles 总被引：2，自引：0，他引：2
Summary A programme of laboratory tests was undertaken to identify the volume reduction of a range of granular soils in response to uniform vibration. The purpose of the tests was to quantify the potential compaction settlement of granular soils due to vibrations typical of those experienced when sheet or bearing piles are installed or extracted by vibrodriver. The vibrations in soils within 2–20 m of a vibrodriven pile are well defined as sinusoidal, at the frequency of the vibrodriver, and typically in the range of 1.0g down to 0.02g (whereg=gravitational acceleration). Thein-situ conditions were replicated in the laboratory by vibration of a Rowe cell containing a soil sample. This allowed control of stresses before and during vibration. Tests were conducted on nine granular soils, ranging from uniform Leighton Buzzard sands to a sandy fine-to-medium gravel. Soil samples were prepared at minimum relative density, generally in the saturated state, but also dry and partly saturated. Each sample was consolidated at a selected effective stress of between 10 and 100 kPa. It was then vibrated vertically at increments of controlled acceleration, under conditions of free drainage and maintained confining stress. Reduction in sample thickness was measured continuously. Results showed that even in a small, drained, sample the full volume reduction was reached only after many minutes, although the early response was more rapid. The trends of results showed that: increased surcharge pressure reduced the subsequent vibratory compaction; well-graded soils showed greater compaction than more uniform sands; compaction increased markedly when acceleration exceeded 1 g; saturated soils showed larger compaction than dry and partially saturated soils; compaction was influenced little by frequency, although rate of compaction reduced with frequency increase. 相似文献
15.
在3种不同围压下进行了一系列重塑粉质黏土的静三轴和动-静三轴不排水剪切试验,得到了不同动应力水平条件下粉质黏土的孔压、动应变和不排水剪切强度值。通过对土样的不排水强度、孔压和动应变的无量纲化处理,确定了周期荷载作用后粉质黏土的不排水强度比与动载引起的孔压比和动应变比之间的相关关系。试验结果表明：粉质黏土在周期荷载作用后的不排水强度衰减程度取决于动载引起的动应变比值和孔压比值。当周期荷载引起的动应变比值小于0.1时,孔压比增长较快,土样的不排水强度几乎没有衰减;当动应变比大于0.1时,孔压比增长变慢,土样的不排水强度明显衰减;当动应变比值接近1时,孔压比值达到0.9,土样的不排水强度衰减程度约达到55 % 相似文献
16.
饱和击实黄土的动力特性研究 总被引：3，自引：0，他引：3
通过进行不同固结条件下饱和击实黄土的动三轴试验,研究了饱和击实黄土的动模量、阻尼比、动强度、动孔压及抗液化特性。研究结果表明：饱和击实黄土的动应力-应变关系符合双曲线模型,模型中参数起始动剪切模量和最大动应力与轴向固结应力间均有良好的幂函数关系,且可以对不同固结应力状态归一,固结围压和固结比对阻尼比的影响较小。动剪应力比随固结围压的增大而减小,随固结比的增大而增大。固结围压、固结比以及动应力皆对动孔压比（ ）与振次比关系有显著的影响,而动孔压与破坏时动孔压之比与振次比关系只受固结围压变化的影响,基本上不受固结比和动应力变化的影响,可以用幂函数关系来模拟;在均压固结条件下,当破坏振次小于等于30时,饱和击实黄土不会产生液化,而当破坏振次较大（动应力较小）时可以产生液化;在偏压固结条件下不会产生液化。 相似文献
17.
Effects of Frequency on the Dynamic Properties of Intact Rock Samples Subjected to Cyclic Loading under Confining Pressure Conditions 总被引：2，自引：1，他引：1
A series of laboratory tests was performed to assess the effects of frequency on the dynamic properties of sandstone samples
subjected to cyclic loading in the confining stress state. Three levels of confining pressure (2.0, 10.0, and 40.0 MPa) and
three sets of frequencies (0.1, 1.0, and 3.0 Hz) were applied for the axial cyclic loading tests by the MTS-815 Rock and Concrete
Test System. The results from the cyclic loading tests indicate that frequency has a strong influence on the dynamic deformation,
the dynamic stiffness, and the failure mode at the same confining pressure. With an increase in the frequency, the axial strain
and the number of cycles at failure increased at the same confining pressure, the residual volumetric strain increased when
dilatancy occurred at the same confining pressure, and the number of cycles at failure increased. A new damage variable D was defined that describes the degradation process of sandstone samples upon dynamic cyclic loading. The larger the frequency,
the wider the localized band. Sandstone samples subjected to dynamic cyclic loading responded with a significantly higher
initial stiffness. The higher the initial stiffness, the greater the frequency. 相似文献
18.
The strength of frozen soils has been one of the most extensively studied aspects in frozen soil mechanics. When carrying
out deep excavations using freezing methods, high stress states are often encountered. Therefore, the strength of frozen soils
under high confining pressures is of major concern. This paper first reviews the present failure criteria for frozen soils,
especially with regard to the effect of confining pressure on the strength. It is suggested that the strength consists of
two components, cohesion and friction, and can be expressed by the Mohr–Coulomb criterion and in the framework of the Drucker–Prager
criterion. However, these two components are both dependent on the stress state. Duncan’s equation for the friction angle
is extended to frozen soils. A frozen Lanzhou fine sand is taken as study subject. The frozen sand is compressed at a high
strain rate under three different temperatures and under a wide range of confining pressure. Experimental results have confirmed
the generally recognized principle that the strength increases with the confining pressure up to certain value. Thereafter,
it decreases with continued increase in confining pressure. Experimental data from our own tests and literature are fitted
to the new criterion, which shows its validity. 相似文献
19.
地下洞室开挖围岩经历典型径向卸载、环向加载应力路径,由此引起的岩体强度、变形特征和破坏机制也不尽相同。针对锦屏二级水电站高地应力赋存环境,对施工排水洞大理岩开展常规单轴全应变、三轴压缩、卸围压、卸围压-加载轴压等4种不同应力路径力学试验,得到应力-应变全过程曲线、变形破坏特征和极限储能变化规律。试验研究结果表明, （1）锦屏二级水电站大理岩破坏时轴向应变一般较小,为硬脆性材料,卸荷应力路径下该脆性特征更为明显;（2）卸围压同时加载轴压试验峰值强度对应轴向应变、环向应变及体积应变值一般高于单纯的卸围压值,而对应峰值强度则一般低于卸围压值;（3）卸荷速率较大时,变形模量越大,大理岩峰值强度越低。加载速率越大,变形模量越小,峰值强度越高。初始围压越高,变形模量值越低,峰值强度越高;（4）无侧限作用时试件主要为张拉破坏,低侧限作用时为剪切破坏为主,局部存在张拉破坏,较高侧限时,剪切面为典型X或Y型;（5）岩石试件具有极限储能值,该值受多种因素的影响。一般情况下试件破坏对应围压越高,极限储能值越高,卸载速率越大,极限储能值越小。研究结果对于岩爆孕育发生机制解释以及工程实际问题的解决均有参考价值。 相似文献
20.
This paper describes a modified elasto‐plasticity damage model to capture monotonic and cyclic behavior of the interface between a geotextile and gravelly soil. New damage variable and shear strength criterion are introduced on the basis of test observations. The formulations of the modified model are obtained by extending those of the original interface model. The model parameters with physical meaning are easily determined from a group of cyclic shear tests and a confining compression test. The model predictions are compared with the results of a series of direct shear tests and large‐scale pullout tests. The comparison results demonstrate that the model accurately describes the monotonic and cyclic stress–strain relationship of the interface between a geotextile and gravelly soil while capturing new characteristics: (1) the strength that is nonlinearly dependent on the normal stress; (2) significant shear strain‐softening; (3) the comprehensive volumetric strain response with dependency on the shear direction; and (4) the evolution of behavior associated with the changes in the physical state that includes the geotextile damage. This model is used in a finite element analysis of pullout tests, indicating that the tensile modulus of a geotextile has a significant effect on the response of the geotextile–gravel system. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献