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1.
为了认识冻土旁压试验结果与常规试验结果之间的关系,在室内分别开展了冻结重塑黏土的旁压试验和单轴压缩试验,并对试验结果进行了对比分析。结果表明,在各级荷载作用下旁压曲线一般都呈现应变速率衰减的趋势,而单轴曲线在冻土破坏时会出现渐进流动阶段。旁压试验的应力-应变曲线呈现应变硬化型,而且出现初始拟弹性阶段;而单轴试验的应力-应变曲线则属于应变软化型,并在轴向应变大约为10%时达到剪应力峰值。温度相同时,旁压试验的剪切强度以及初始弹性模量都要大于单轴试验,且温度越低差值越大。 相似文献
2.
Youliang Chen Rafig Azzam Ming Wang Shan Xu Lequn Chang 《Environmental Earth Sciences》2011,64(1):29-36
The compressive and tensile strengths of frozen clay are important parameters for frozen wall design in artificial freezing
excavation of tunnels and foundation pits. Up to now, nobody has conducted the compressive and tensile test of frozen clays
in Shanghai area. In this paper, the unconfined compressive and tensile tests of frozen clay specimens drilled from the soil
horizons 3–5 in Shanghai area were conducted in Zwick-Z020kN High-low Temperature Materials Testing Machine and Frozen Soil
Triaxial Testing Machine, the corresponding constitutive equations were suggested; the temperature-unconfined uniaxial compressive
strength relation was discussed; the strain rate–unconfined uniaxial compressive strength and strain rate–uniaxial tensile
strength relations were studied. The relation between moisture content, dry density and unconfined uniaxial compressive strength
was analyzed, too. In addition, the uniaxial compressive elastic modulus of Shanghai frozen clays and its influence factors
were discussed. The research work of the current paper is very helpful for the design and theoretical studies of artificial
freezing excavation in soft soil areas. 相似文献
3.
以玄武岩为试样,开展了中低应变率下的岩石单轴抗压试验。本次研究分析应变率对岩石抗压强度、弹性模量、泊松比等力学参数的影响,分别提出了岩石抗压强度、弹性模量、泊松比等参数与应变率之间的拟合关系式。以峰值应力对应的应变和峰值后的软化模量为脆性评价指标,分析加载应变率对岩石脆性的影响。研究表明:(1)岩石抗压强度、弹性模量均随应变率的增加而增加。(2)岩石泊松比随应变率增加而减小。(3)随着应变率增加大,峰值应力对应的应变增大,峰值后的应变软化程度减小,岩石脆性减弱。(4)应变率对岩石抗压强度影响较大,对弹性模量和泊松比的影响较小。(5)曲线拟合效果良好,提出的拟合关系式合理。 相似文献
4.
冻结盐渍砂土单轴强度特性研究 总被引：5，自引：3，他引：2
通过对兰州盐渍砂土重塑土添加不同量的盐分来模拟不同含盐量的盐渍土, 并对其进行单轴抗压试验, 分析其在不同含盐量、不同温度及不同速率的应变加载情况下, 冻结盐渍砂土的单轴抗压强度的变化规律, 重点讨论了盐分对土体力学参数的影响以及弹性模量与含盐量、温度的关系. 结果表明: 易溶盐含量的增加会导致单轴抗压强度逐渐降低, 试验温度越低抗压强度会越大; 应变加载速率的增加会增大土体的单轴抗压强度, 同时会缩短土体达到应力峰值的时间; 土体含盐量越大弹性模量越小, 温度越低弹性模量越大. 相似文献
5.
Assessments of Strength Anisotropy and Deformation Behavior of Banded Amphibolite Rocks 总被引：2，自引：0，他引：2
Esamaldeen Ali Wu Guang Zhao zhiming Jiang Weixue 《Geotechnical and Geological Engineering》2014,32(2):429-438
Assessment of strength anisotropy in transversely isotropic rocks has been one of the most challenging subjects in rock engineering. However, far too little attention has been paid to banded amphibolite rocks. This study aim to evaluate strength and deformation anisotropy behavior of banded amphibolite rocks. The dynamic mechanical tests including ultrasonic pulse test, uniaxial compressive strength, Brazilian test and deformability test were performed on drilled rock samples as a function of foliation plane angle (β = 0°, 30°, 60° and 90°). The results obtained have shown that the dynamic mechanical properties of amphibolite rocks have different values concerning banding plane. Compression and shear waves taken parallel to the foliation plane show highest values than those obtained in the other directions. Under uniaxial test, the banded amphibolite has a U-shaped anisotropy with maximum strength at β = 90° and minimum strength is obtained when β = 30°. Strength anisotropic index ranges between 0.96 and 1.47. It seems that the high range value of anisotropic index is mainly due to slight undulation of foliation planes, that being not perfectly straight. The results of elastic deformation test show that there is no clear dependence on microstructures characteristics of subtype-amphibolite rocks that controlling modulus “shape-anisotropy”. However, in this study, Young modulus values of amphibolite rocks with β follow both types of shape-anisotropy, “U-shape” and “decreased order-shaped”. Thus, this study recommended that further research be undertaken regarding the role of modulus “shape-anisotropy” within the same lithotype. 相似文献
6.
Deformation modulus of fly ash is one of the most important mechanical properties generally used in different design problems
and also as an input parameter to sophisticated numerical techniques employed to assess the response of different structures
resting on fly ash fill or embankment made of fly ash. Deformation modulus is usually expressed in terms of compressive strength.
This paper presents the deformation modulus of fly ash modified with lime alone or in combination with gypsum at different
strain levels. The values of deformation modulus obtained from both unconfined compression test and unconsolidated undrained
triaxial test results are presented herein. The specimens for unconfined compression test and for undrained triaxial tests
were cured up to 90 and 28 days, respectively. The effects of addition of lime (4–10%) and gypsum (0.5 and 1.0%) on the deformation
modulus of class F fly ash are highlighted. With addition of lime and gypsum, the class F fly ash achieved the deformation
modulus in the range of 190 MPa in UCS test and up to 300 MPa in triaxial test specimens tested under all round pressure of
0.4 MPa. Based on the present test results empirical relationships are developed to estimate deformation modulus of modified
fly ash from unconfined compressive strength and relationships between initial tangent modulus and secant modulus at different
strain levels are also developed. 相似文献
7.
基于统计分析结果合理布置测点,测试土体力学参数具有测试结果准确和经济快捷等优点。在赣南某稀土矿山非等间距布置6个测点,共计18个测试孔,通过旁压试验和钻孔剪切试验测试了离子型稀土矿体的旁压模量、变形模量、压缩模量、黏聚力和内摩擦角等力学参数,运用经典统计学方法和地质学统计方法分析矿体力学参数的空间变异性。研究结果表明:试验矿块内矿体的黏聚力和旁压模量属于强变异,黏聚力的变异系数为0.48,旁压模量的变异系数为0.36;内摩擦角属于弱变异性,其变异系数为0.067;假设由18个测试孔的测试数据计算得到各力学参数为真值,若15%为工程可接受的误差,运用经典统计学方法分析和地质统计学方法分析结果表明,对于试验矿块,在45 m范围内均匀布置5个测点,测试结果可有效估计矿块内黏聚力和旁压模量的平均值和变异系数。 相似文献
8.
为探究富水饱和灰岩体在水压-应力耦合作用下的力学特性，利用自主研发的可实现单轴压缩的渗透试验装置对不同水压强度下的灰岩试样进行压缩破坏试验，测试灰岩应力-应变特性，分析水压对单轴抗压强度、弹性模量、变形模量的影响，灰岩破碎特性与水压强度相关性以及孔隙变化规律。研究表明:增加的水压强度对灰岩应力-应变和强度特性有显著的影响。随着水压强度增大，应力-应变曲线的压密阶段相对延长而弹性相对缩短，峰值强度呈指数减小而弹性模量和变形模量均呈线性下降，表明水压作用显著降低了灰岩脆性。另外，灰岩弹性模量、变形模量均与峰值强度呈线性关系。增大的水压强度对灰岩宏观断裂具有显著影响而未对其破坏类型造成影响，随水压强度增加，碎块均一系数和单位质量孔隙体积均呈指数函数增加。研究成果为隧道建设中富水岩体的开挖稳定性分析提供参考。 相似文献
9.
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
10.
Deformability of rock masses influencing their behavior is an important geomechanical property for the design of rock structures. Due to the difficulties in determining the deformability of jointed rock masses at the laboratory-scale, various in-situ test methods such as pressuremeter, dilatometer, plate loading tests etc. have been developed. Although these techniques are currently the best and direct methods, they are time-consuming and expensive, and present operational difficulties. In addition, the influence of the test volume on deformation modulus depending on the method employed is also important. For these reasons empirical equations to indirectly estimate the deformation modulus have also been recommended by several investigators as an alternative approach. In this study; the geomechanical quality of weak, heavily jointed, sheared and/or blocky greywacke rock masses, on which very concentrated civil works are continuing at the southern and southwestern parts of Ankara (Turkey), was assessed. The deformation modulus was determined by pressuremeter tests, the possible effects of variables on the derived deformation modulus from the pressuremeter test were evaluated by numerical methods, and the comparisons between the deformation modulus of the greywackes obtained from the pressuremeter tests and their geomechanical quality (GSI and RMR) were made. Numerical simulations revealed that the presence of a disturbed annulus around the borehole causes underestimation of the deformation modulus, while the effect of length to diameter ratio of the pressuremeter probe on the deformation modulus is minor. Based on the geo-engineering characterization assessments, mainly two greywacke rock masses with different geomechanical qualities were identified. Geotechnical quality of one of these rock masses was verified by the back analysis of two slope failures. The empirical equations to indirectly estimate the deformation modulus of the greywackes using their GSI and RMR values yielded high coefficients of correlation. 相似文献
11.
对攀枝花钒钛磁铁矿尖山矿区的细粒和中粒辉长岩进行了单轴压缩、常规三轴压缩、抗拉强度和软化等系列岩石力学试验,研究了岩石结构(矿物颗粒大小)、水和围压等因素对岩石强度和变形特性的影响。结果表明,细粒辉长岩单轴抗压强度、弹性模量和压拉比均高于中粒辉长岩,但在三轴压缩情况下,两种岩石的峰值强度、残余强度和弹性模量差异较小;与中粒辉长岩相比,细粒辉长岩的峰值强度的黏聚力C较大,而峰值强度的内摩擦角φ较小;随着围压的增长,辉长岩峰值强度、残余强度与围压近似呈线性关系,剪切破坏角减小,平均模量E增长不明显,割线模量E50增长较显著;辉长岩的软化系数较高,在水的作用下弹性模量降低,泊松比升高。 相似文献
12.
为了获得红黏土地基承载力和变形参数在横向和垂向上的定量数据及分析它们的变化规律,选取厦门至成都高速公路湖南省郴州段典型横纵断面上的红黏土地层作为试验点,采用平板载荷试验、旁压试验等技术手段进行了原位测试。试验结果表明：红黏土地基承载力和变形模量在横向较小的范围内呈现较大幅度的变化,在垂向上则呈现先增大再减小的变化趋势,与红黏土赋存厚度、地形地貌、含水率等相关;旁压试验所测得的承载力特征值和平板载荷试验测得的承载力特征值之间存在一定的差异性;旁压模量与变形模量可以通过结构性系数联系起来,所得的结构性系数与Menard根据大量黏土试验资料对比所得到的结论较为一致。 相似文献
13.
雪峰山隧道砂板岩各向异性力学特性的试验研究 总被引：4，自引：0，他引：4
利用MTS815 Flex GT岩石力学试验系统,对雪峰山隧道围岩中的砂板岩开展单轴和三轴试验,研究这种砂板岩中的细微层理对岩石变形特性、强度特性及其参数的影响,结果表明：岩石力学特性的各向异性特征显著。层理面与轴向力夹角0°时应力-应变曲线呈不稳定破裂特征,破坏面沿层理面方向发育;夹角90°时曲线呈峰后迅速软化特征,破坏面为对角贯通性剪切破坏。单轴试验中夹角0°的抗压强度比夹角90°高出约20%,弹性模量和变形模量比夹角90°分别约大50%和80%。三轴试验中2种夹角情况破坏时主应力差 相近,夹角0°的弹性模量和变形模量分别比夹角90°时约大6%和20%,围压对砂板岩的各向异性特征有弱化效应。这些结论揭示了该砂板岩各向异性的力学特性,对解决工程实际问题有重要的参考价值 相似文献
14.
A stress–strain relationship within porous rock under anisotropic stress conditions is required for modeling coupled hydromechanical
processes associated with a number of practical applications. In this study, a three-dimensional stress–strain relationship
is proposed for porous rock under elastic and anisotropic stress conditions. This relationship is a macroscopic-scale approximation
that uses a natural-strain-based Hooke’s law to describe deformation within a fraction of pores and an engineering-strain-based
Hooke’s law to describe deformation within the other part. This new relationship is evaluated using data from a number of
uniaxial and triaxial tests published in the literature. Based on this new stress–strain relationship, we also develop constitutive
relationships among stress, strain, and related stress-dependent hydraulic/mechanical properties (such as compressibility,
shear modulus, and porosity). These relationships are demonstrated to be consistent with experimental observations. 相似文献
15.
Elastic modulus and Poisson’s ratio of soils are two important parameters required for safe design of various civil engineering
structures. The elastic modulus and shear modulus of the soils are generally obtained from the resonant column, torsional
shear tests and geophysical methods. Though, from these parameters the Poisson’s ratio can be determined, these tests are
quite elaborate, cumbersome, time consuming and require skilled manpower particularly for data interpretation. Moreover, direct
determination of the Poisson’s ratio by employing micro-strain gauges, which measure axial and lateral strains using Wheatstone
bridge circuits, is difficult for soils due to the problems associated with their fixing on the surface of the sample. Under
these circumstances, application of piezoceramic elements, which can generate shear and compression waves, seems to be an
excellent alternative. Using these wave velocities, the Poisson’s ratio can be computed easily and precisely. However, how
this (computed) value of the Poisson’s ratio compares vis-à-vis that obtained from the conventional triaxial tests (i.e.,
strain controlled uniaxial compression tests), which yield stress–strain relationship, needs to be established. With this
in view, investigations were conducted on soils of different types (clays and sands) in their disturbed and undisturbed forms
by resorting to piezoceramic tests and the triaxial tests. Details of the methodology are presented in this paper and it has
been demonstrated that application of piezoceramic elements yields the Poisson’s ratio and the elastic modulus of the soils
quite easily, particularly for the soft clays and sands. 相似文献
16.
张立 《水文地质工程地质》2021,48(5):74-80
川藏铁路沿线隧道围岩中常存在大量软弱夹层,且岩体受严寒气候影响较大。为研究夹层倾角和冻融循环对隧道围岩力学性质的影响,室内制备了不同软弱夹层倾角、不同冻融循环次数条件下的互层岩体,并对含软弱夹层岩体展开了单轴压缩试验。研究发现:（1）含软弱夹层岩体的硬岩部分变形较小,而软岩夹层部分的破坏更加剧烈。夹层倾角较小时（β=0°、30°）岩体破坏后裂纹与夹层倾角接近平行,当夹层倾角较大时岩体破裂面与夹层呈X型交叉状;冻融循环次数越多,岩体的破坏程度越强烈。（2）随着夹层倾角的增大,岩体的单轴抗压强度和弹性模量先减小后增大;当夹层倾角β=45°时,抗压强度和弹性模量最小,抗压强度较含水平软弱夹层岩体降低35.27%,弹性模量降低34.84%。（3）冻融循环劣化了夹层岩体的力学性质,岩体承载能力随着冻融循环次数的增加而减弱,但塑性变形能力有所增强。在冻融循环作用的影响下,岩体抗压强度、弹性模量呈负指数型递减,峰值点应变则呈线性增大。 相似文献
17.
轻量砂变形及强度特性三轴试验研究 总被引：1，自引：0，他引：1
通过三轴试验系统研究了新型土工材料--轻量砂的变形及强度特性。结果表明,不同的配比、龄期使轻量砂具有不同的原生结构强度,围压使不同原生结构强度的土样处于剪胀或剪缩状态,导致发生应变硬化、应变软化以及相应状态下孔压的3种对应形态变化。变形模量随EPS（发泡聚苯乙烯）球粒掺入比的增大而线性减小,随水泥掺入比、龄期增大而线性增大,相同配比的土样变形模量与围压关系不大;三轴抗压强度随EPS球粒掺入比增大而呈负指数关系减小,随水泥掺入比、龄期、围压增大而线性增大,存在水泥掺入比阀值;土骨架转换效应对于土样强度的影响很大,造成了土体单轴、三轴抗压强度分带,高水泥掺入比能够大大弱化EPS颗粒的土骨架效应。结合前人成果,系统地研究了轻量砂密度、无侧限抗压强度的影响因素,引入材料学中比强的概念,提出了单价比强图结合配方公式的方法,对轻量土砂进行配方优化。分析了轻量土砂应力-应变关系转型问题,提出采用无侧限抗压强度来表征不同配比、龄期轻量土砂的原生结构强度。通过试验与数理统计,建立临界围压与原生结构强度的关系,为数值模拟计算与建立本构模型奠定了基础。 相似文献
18.
基于梯度塑性本构理论的岩样侧向变形分析(Ⅰ):基本理论及本构参数对侧向变形的影响 总被引：13，自引：5，他引：13
研究了岩样在单轴压缩条件下轴向应力．侧向或环向变形的全程曲线特征。基于考虑峰值剪切强度后微小结构之间相互影响和作用的梯度塑性理论，得到了由于剪切局部化而引起的侧向塑性变形。利用虎克定律描述了试件的弹性变形，得到了轴向应力．侧向变形全程曲线的解析解。在软化阶段，试件中部侧向变形及对靠近试件上端或下端部位的侧向变形并不相同。与轴向应力．应变曲线可能出现的回跳现象类似。试件中部轴向应力．侧向应变曲线也可能出现回跳现象。在应变软化阶段，与应力．侧向应变曲线相比，应力．环向应变曲线不容易发生回跳现象。若在试件内部出现多条剪切带，则应该以等效剪切带宽度替代本文中的剪切带宽度。随着剪切带倾角、内部长度参数的降低、剪切模量的增加及弹性模量的降低，轴向应力．侧向应变曲线越陡；甚至能出现弹性回跳。 相似文献
19.
通过相似配比试验,研制不同砂胶比的低强度相似材料,分析了砂胶比和胶结材料中水泥含量对其物理和力学性质的影响及其变化规律。根据上横山多层页岩矿床赋存条件和相似模拟试验要求,确定了3个可行的、有效的相似材料配比,结合相似模拟条件构筑了多层页岩矿床相似材料模型。试验结果表明,相同砂胶比的低强度相似材料的密度、抗压强度、弹性模量和泊松比均随胶结材料中水泥含量的增加而增大;密度、孔隙率、弹性模量和泊松比在低砂胶比条件下具有更小的波动性。进一步研究发现,选择的低强度页岩相似材料实际相似常数与设计相似常数误差≤1.77%;利用数值模拟回采矿床矿柱的变形特征与相似模拟试验基本相似,应变变化幅度≤8.76%,试验模型在多层页岩矿床模型试验研究上具有一定的合理性。研究结果为有效的进行多层页岩矿床地下开采研究提供科学依据和试验基础。 相似文献
20.
为了探究不同含水率砂岩单轴压缩下力学特性及损伤变化情况,首先对5种不同含水率砂岩进行静态单轴压缩实验,获得其物理力学参数;而后利用超声波检测仪测量该5种不同含水率砂岩的波速,将该批次砂岩加载到80%峰值强度后卸载到0,测量此时砂岩声波波速,利用声波法定义损伤,研究含水率对砂岩损伤的影响。结果表明:单轴压缩下,砂岩的峰值强度及弹性模量随含水率升高逐渐降低,而峰值应变变化呈相反趋势;总功及弹性能随含水率增加而下降,耗散能随含水率增加而增大。实验前声波波速随含水率升高逐渐减小,实验后声波波速随含水率升高而下降,且下降趋势较实验前更迅速;砂岩的残余塑性变形和内部损伤均随含水率升高逐渐增大。研究结果可为现场岩石损伤测试提供依据。 相似文献