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1.
钙质砂与钢板接触面力学特性试验研究 总被引：3，自引：0，他引：3
对一种人工制备的钙质砂与光滑铜板接触面进行了一系列的单调和循环剪切试验,表明钙质砂与光滑钢板的接触属于摩擦接触,界面剪应力与正应力之比与剪切位移关系有较好的归一性。等正应力试验中钙质砂的的缩性较大;等体积试验中接触面的抗剪强度因正应力的降低而远低于等正应力试验;循环剪切中加荷与卸荷曲线基本重合,经历循环剪切作用后接触面的抗剪强度有降低的趋势。界面湿摩擦系数低于干摩擦系数。 相似文献
2.
Arvind Kumar Baljit Singh Walia Swami Saran 《Geotechnical and Geological Engineering》2005,23(4):469-481
A method has been proposed to obtain the pressure–settlement characteristics of rectangular footings resting on reinforced sand based on constitutive laws of soils. The confining effect of the reinforcement provided in the soil at different layers has been incorporated in the analysis by considering the equivalent stresses generated due to friction at the soil– reinforcement interface. The prerequisite of the method is the value of ultimate bearing capacity, which can be obtained from the approaches already available in literature. The value of settlement may be read directly from pressure–settlement curves for the given pressure intensity. Therefore, the rectangular footing resting on reinforced sand can be proportioned satisfying shear failure and settlement criteria. 相似文献
3.
筋-土界面强度参数是加筋结构设计和稳定分析的关键技术指标。拉拔试验能较好模拟现场加筋行为而得到广泛的应用。基于拉拔和直剪试验研究了拉拔（剪切）速率对筋-土界面特性和吹填砂强度特性的影响规律及机制,同时探讨了不同填料界面、筋材类型的加筋效果。结果表明：随着拉拔（剪切）速率的增大,吹填砂-筋材-吹填砂界面的抗剪强度下降明显,而软土-筋材-吹填砂界面以及砂本身强度则变化不大。从强度指标来看,拉拔速率增大,筋-砂界面强度的降低主要表现为似黏聚力的降低,筋-软土界面抗剪强度的增加表现为内摩擦角增大,剪切速率对吹填砂则基本无影响。筋-土界面特性受拉拔速率和正应力的共同影响,与筋材类型和填料特性有关。筋-土界面内摩擦角小于填料摩擦角,但在一定正应力下低速剪切时（如<0.53 mm/min）可获得高于填料的抗剪强度。宜根据似黏聚力大小合理选择摩擦参数进行加筋结构的设计与评价。 相似文献
4.
Numerical pile segment analysis is conducted in this study with an advanced soil model to investigate the skin friction behaviour of a drilled Cast‐In‐Place (CIP) pile installed in sand. Although the interface between the sand and pile is considered rough, thin elements adjacent to the pile are used to include effects of localized shear. Unit weights of fluid concrete and accompanied changes in stress are considered as the effects of pile installation. Changes in effective stresses are the most prominent effect due to pile installation with a change in direction of the major principal stress from the vertical to the radial direction. Shear behaviour of the sand at the interface during the early shear stage is related to the contractive tendency of the sand at small strain levels. Changes in the stress field around the pile with little changes in volumetric strain take place during the early shear stage. Stress redistributions during the early shear stage depend on the direction of the major principal stress before shear. Results of the pile segment analyses for drilled CIP piles show good agreement with design methods. Parametric studies are used to characterize the effects of sand density and pile diameter on the skin friction behaviour of drilled CIP piles. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
5.
固化风沙土强度特性及固化机制试验研究 总被引：6，自引：0，他引：6
通过PX固化剂对库布其沙漠风沙土进行加固。对不同含水状态、不同固化剂掺量、不同养护龄期下固化风沙土的强度特性进行试验研究。试验结果表明,不同含水状态下风沙土的强度特性是不同的,相同固化剂掺量、相同养护龄期时,固化风沙土在最优含水率下的无侧限抗压强度远远大于饱和含水率下的强度。相同含水状态下固化风沙土无侧限抗压强度随固化剂掺量增加、养护龄期延长而增大,且在养护初期强度增长较快,当固化剂掺量为8 %、养护龄期为28 d时,固化风沙土强度满足国际上对固沙强度的要求。最优含水率下固化风沙土抗剪强度较风沙土有较大提高;当固化剂掺量为8 %时,固化风沙土凝聚力和内摩擦角均达到最大,此时固化风沙土抗剪强度约为风沙土的1.8倍。进而,通过扫描电镜对风沙土固化前后微观结构变化进行试验研究。研究结果表明,风沙土中掺入PX固化剂后,颗粒间由原来的弱连接变为胶结连接,解释了固化风沙土较风沙土强度得以提高、稳定性得以改善的内在原因。 相似文献
6.
三明治形加筋土是一种在黏土中加入加筋砂层形成的混合填料形式的新型加筋土。为了研究不同条件下三明治形加筋土筋-土界面的动力剪切特性,采用大型直剪仪对三明治形加筋土进行了一系列循环剪切试验,研究了不同薄砂层厚度、循环剪切幅值和竖向应力对界面剪切特性的影响。试验结果表明：筋-土界面的剪应力峰值随着循环次数的增加而增加,循环周次为10时,薄砂层厚度为5、6、7、8、9 mm的条件下,筋-土界面的剪应力峰值分别为24.84、27.4、27.94、26.33、24.68 kPa,表明薄砂层厚度为7 mm时,筋-土界面在循环剪切阶段的峰值剪应力最大;剪切幅值越大,界面循环剪切的最终剪缩量越大,同一循环次数对应的剪切刚度和阻尼比越小;在不同竖向应力下,界面在循环剪切过程中都发生了循环剪切硬化现象,循环周次为10时,竖向应力为30、60、90 kPa的条件下,筋-土界面的剪应力峰值分别为20.4、25.14、32.96 kPa,表明剪应力峰值随竖向应力的增大而增大,同一循环次数对应的剪切刚度也随竖向应力的增大而增大。 相似文献
7.
Wei Shao Bora Cetin Yadong Li Jingpei Li Lin Li 《Geotechnical and Geological Engineering》2014,32(4):901-910
The addition of cementitious admixtures and/or inclusion of fibers are frequently used in practice to stabilize soils and to improve their mechanical properties. In this study, ring shear tests were conducted to investigate mechanical properties such as shear strength, angle of friction and cohesion values of randomly distributed discrete fiber-reinforced sand mixtures. The length and aspect ratio of the fibers used in the current study were 12 mm and 120, respectively. Specimens were prepared at four different fiber ratios (0.1, 0.3, 0.6, and 0.9 % by weight of sand). A series of ring shear tests were carried out on sand alone and fiber-reinforced sand mixtures at different normal stresses. The test results indicated that the addition of fiber had a significant effect on the shear strength of the sand. Shear stress of the unreinforced sand increases 1.29–2.32, 1.16–1.39, and 1.07–1.5 times at a normal stress of 50, 150, and 250 kPa, respectively with fiber inclusion. Fiber content had positive effects on improving the shear strength parameters (angle of internal friction and cohesion) of the mixtures. The cohesion and angle of internal friction of fiber-reinforced sand prepared at different ratios of fiber increased by 5.3–27.4 kPa and 2.0°–7.3° respectively. The inclusion of fibers improves the ductility of the soil by preventing the loss of post-peak strength. 相似文献
8.
9.
Rajni Saggu 《Geomechanics and Geoengineering》2015,10(1):10-29
The present work investigates the behaviour of geothermal energy piles in sand subjected to thermal loading and the resulting soil-structure interaction, numerically using the finite element software Abaqus and user-defined material subroutines for soil. The stress-strain response of sand has been simulated using CASM constitutive model based on critical-state soil mechanics. Detailed parametric sensitivity studies have been carried out to understand the effects of different end conditions of the pile, relative densities of the soil, coefficients of lateral earth pressure of the ground, lengths and diameters of the pile, thermal loads, coefficients of friction at the pile-soil interface, critical-state friction angles of soil, thermal conductivity of soil, specific heat of soil and thermal conductivity of the pile on the stress response of soil, deformation of the pile and soil, and strains in the pile. The results show that negative shear stress is generated in the soil at the pile-soil interface. In the pile with both ends restrained the lateral earth pressure coefficient in soil increases due to high radial strain generation. Moreover, the lateral earth pressure coefficient in soil increases with the increase in the thermal load, the coefficient of friction at the pile-soil interface and the critical-state friction angle of the soil. 相似文献
10.
砂类土的密实程度是影响其抗剪强度的重要指标,然而已有研究并没有直观给出砂类土抗剪强度随孔隙比变化的定量规律。控制砂类土的初始孔隙比得到土体所需的抗剪强度,这在土工相似模型试验中具有一定的应用前景。基于砂土的临界状态理论,本文建立了砂类土抗剪强度与孔隙比关系的理论表达式。针对尾矿库现场取回的铜、钨尾砂开展了直剪试验和固结试验,并利用所推导的理论表达式对尾砂在不同状态时的抗剪强度进行了分析。结果表明,随着孔隙比的增加,砂类土的抗剪强度非线性减小,孔隙比越大时抗剪强度减小的幅度越平缓。试验结果证实砂类土抗剪强度与孔隙比关系的理论表达式能够合理描述尾砂在不同孔隙比下的抗剪强度。 相似文献
11.
Seasonally frozen soils are widely distributed in China in terms of area,and the freeze-thaw cycle effect generated by the alternation of cold and warmth is one of the causes of engineering damage in cold areas during construction,and it is particularly important to restore the nature and state of the soil when it is subjected to freeze-thaw action. Therefore,sandy soil specimens with different numbers of freeze-thaw cycles were prepared,and the long-term strength of frozen sandy soil was tested using a spherical template indenter. Using fractal theory and the microstructure image processing software ImageJ,the change law of grain group and long-term strength of two frozen sandy soils under different numbers of freeze-thaw cycles were studied. The results show that：for fine sand（FS）,the fractal dimension DB has a highly significant positive correlation with the long-term strength variation,among which ≥0. 15~0. 20 mm and ≥0. 25~0. 40 mm have the best fit with the long-term strength,and are the dominant grain classes of FS. For medium sand（MS）,the fractal dimension DB is slightly positively correlated with the long-term strength,and the variation shows a“vertical N”trend,in which the grain size content of ≥0. 30~0. 40 mm and ≥0. 40 mm fits better with the long-term strength,and is the dominant grain class for MS. The content of other grain groups did not correlate significantly with the long-term strength change. The freeze-thaw action changed the content ratios of coarse and fine grain agglomerates in the soil. With the increase of the overall particle size interval,the dominant particle size also increases,which shows that the long-term strength of frozen sandy soil tends to decrease and then increase with the increase of the content of some particle sizes. The results of the study can provide theoretical reference for the determination of long-term strength in areas subject to freeze-thaw action. © 2022 Science Press (China). 相似文献
12.
The pre-bored grouted planted pile is a new type of composite pile foundation that consists of a precast concrete pile and the surrounding cemented soil. A series of shear tests were conducted in a specific shear test apparatus to investigate the shaft capacity of the different pile–soil interfaces. The test results show that the frictional capacity of the cemented soil–sand interface is controlled mainly by the sand properties, while the strength of the cemented soil slightly influences the interface properties by affecting the normalized roughness coefficient Rn. The frictional capacity of the concrete–sand interface is similar to the frictional capacity of the cemented soil–sand interface, and the existence of mud cake layer virtually hampers the frictional properties of the interface. The maximum skin friction of the concrete–cemented soil interface increases approximately linearly with the increasing cemented soil strength, and the value of the maximum skin friction is much larger than that of the cemented soil–sand interface of identical cemented soil strength, which demonstrates the integrity of the pre-bored grouted planted pile in the load transfer process. 相似文献
13.
针对填埋场衬垫系统薄弱界面容易失稳,基于前期已完成的高密度聚乙烯（HDPE）加肋土工膜与砂性土界面直剪试验,以及结合试验结果对界面剪切特性及试样破坏形态分析的基础上,探讨了加肋土工膜与砂性土界面相互作用机制,给出了加肋土工膜与砂性土界面总阻力由面摩阻力、肋块所受端承阻力和侧摩阻力3部分组成的具体表达式,其中,肋块所受端承阻力是基于塑性滑移场理论建立起来的。同时,认为肋块端承阻力是提高加肋土工膜与砂性土界面剪切强度的主要原因,尤其在较高法向应力下,肋块端承阻力更能得到充分发挥。理论分析与试验结果较为吻合,该表达式能合理反映加肋土工膜与砂性土界面的总阻力。 相似文献
14.
为研究剑麻纤维和高分子固化剂复合改良对砂土工程特性影响,通过一系列三轴剪切试验,对不同掺量和长度的剑麻纤维与高分子固化剂改良砂土的剪切强度特性进行了研究,从峰值偏应力、应力应变曲线特征和抗剪强度参数等方面分别对改良机理进行了研究。研究结果表明,纯高分子固化剂改良砂土的峰值偏应力和黏聚力明显提升,由于固化剂粘结砂土颗粒,限制了变形过程中颗粒的相对滑动,内摩擦角略微降低。随纤维掺量的增加,不同围压下固化剂改良土体的峰值偏应力明显增加,应力硬化特征愈加明显,土体的黏聚力和内摩擦角随纤维掺量的增加保持单调递增趋势。在单纯添加固化剂的情况下,土体强度与固化剂浓度呈正相关的关系;在给定0.4%的纤维含量下,随着纤维长度的加长,纤维和高分子固化剂复合改良砂土的剪切强度先增强后降低;在纤维长度为18 mm时,土体的剪切强度达到最大,黏聚力达到最大207.57 kPa;纤维长度的改变对试样破坏时的轴向应变和土体的内摩擦角基本没有影响。 相似文献
15.
为研究超长灌注桩桩侧与土体接触界面的剪切力学行为,采用大型界面剪切仪,开展混凝土与粉质黏土、粉细砂土接触界面剪切试验。针对钻孔灌注桩泥浆护壁施工特点及后注浆工艺的应用,在混凝土与粉细砂土界面设置膨润土泥皮或膨润土泥皮与水泥浆,以研究泥皮及存在泥皮时注浆对界面剪切性状的影响。试验结果表明：界面剪切应力随剪切位移增加逐步达到极限值,之后,剪切应力保持基本不变或出现软化现象;土体类型及法向应力大小对界面剪切力学行为具有较大的影响;粉细砂土-混凝土界面摩擦角与土体有效内摩擦角相近,存在泥皮时,界面摩擦角降低达40%,泥皮的润滑作用较大地削弱了界面的剪切性能;存在泥皮情况下,注浆后界面摩擦角较泥皮界面提高近1倍,水泥浆的注入不仅消除了泥皮产生的不利影响,也有利于进一步改善界面剪切性能,提高其抗剪强度;泥皮及注浆对界面剪切应力与剪切位移关系亦有较大的影响;界面剪切作用对土体具有一定的影响范围,并在接触界面附近土体中逐渐形成剪切破坏带,剪切过程中界面呈现出由剪切位移阶段逐步过渡至剪切滑移阶段;此外,在剪切过程中,不同界面类型的土体变形存在较大差异。 相似文献
16.
为了研究Q3砂黄土强度变形特性,以甘肃永靖黑方台Q3砂黄土为研究对象,利用西安理工大学研制的真三轴仪,进行了3个围压（50、100 kPa 和200 kPa）、3个b值（0、0.25和0.5）和3个含水率（5%、10%和15%）不同工况试样破坏情况的真三轴试验。试验结果发现：（1）真三轴条件下Q3砂黄土剪切破坏方式以侧胀破坏、单缝剪切破坏为主,其次少数土样发生锥形破坏、双缝剪切破坏和T型缝剪切破坏。（2）相同围压和含水率、不同中主应力比（b）的情况下,Q3砂黄土的主应力差随中主应力比增大而增大,应力-应变关系曲线为强硬化型,剪胀现象明显;中主应力比对广义剪应力和广义剪应变之间关系有一定影响,随b值增加,曲线依次增加;随b值的增加,强度降低,广义剪应力与平均球应力比（q/p）与主应变关系曲线逐渐变缓,且曲线依次降低。（3）随含水率增加,Q3砂黄土由固态向半固态转化过程中,不同中主应力比时黏聚力均出现明显降低,但内摩擦角则出现微小增加。 相似文献
17.
青藏直流±400 kV输变电工程中采用表面光滑的玻璃钢覆盖基础表面,以减少切向冻胀力对基础的冻拔作用。过去的研究鲜有涉及土体特别是冻土与玻璃钢基础接触面的力学特性,为指导冻土区基础设计和安全评价,采用应变直剪仪开展了多种含水率和温度条件下青藏粉土-玻璃钢接触面直剪试验研究。结果表明,青藏粉土-玻璃钢接触面屈服时相应剪切位移很小,应变硬化阶段短暂或不显著;冻结状态下接触面应力-位移性状呈脆性破坏型,存在明显峰值;融化状态时接触面的剪应力-位移性状呈塑性破坏型,其应力-位移关系曲线为弱软化型和屈服型,没有明显峰值;融化状态时接触面抗剪强度值随含水率的增加而缓慢减小,冻结状态时其强度随负温绝对值和含水率的增加而增大,且随着土体含水率的增大,温度降低导致接触面抗剪强度增强效果更加显著,土体含水率大于19%后抗剪强度趋于稳定;温度对抗剪强度的影响主要体现于黏聚力的改变,且随着含水率的增加,温度影响增强。接触面内摩擦角随负温绝对值增加而减小,随含水率的增加而减小。 相似文献
18.
土工格栅与土界面作用特性试验研究 总被引：9，自引：4，他引：5
土工格栅与土的界面摩擦特性指标是加筋土工程设计的关键。通过分析土工格栅与土的界面摩擦作用和进行了直剪摩擦试验和拉拔摩擦试验,测试了两种试验条件的界面摩擦特性。在两种试验条件下,土工格栅加筋土复合体的抗剪强度均有界面摩擦角φsq和界面凝聚力csq,且土工格栅与土相对位移量的不同,其复合体的强度机理有区别。在拉拔摩擦试验中,剪应力峰值强度对应的剪切变形值高于直剪摩擦试验中剪应力峰值强度的剪切变形值5～10倍以上。两种试验均有其适用性,而土与土工格栅的相对位移较小时直剪摩擦试验较能反映实际;土与土工格栅相对位移较大时土与格栅双面均发生相对位移,拉拔摩擦试验更为合适。随法向应力的增大,直剪摩擦和拉拔摩擦试验的剪应力峰值以及剪应力峰值对应的位移均提高。直剪摩擦的剪切速度小,剪应力峰值强度高,且达到峰值强度的剪切位移大;增加剪切速度,剪应力峰值强度降低,且对应的位移也减少,其原因是界面上的孔隙水压力消散和筋材的应力松弛。应根据具体工程的需要选择直剪摩擦试验和拉拔摩擦试验确定设计参数。 相似文献
19.
为了研究筋-土界面在遭受动力作用时的表现,利用大型直剪仪对土工格栅、土工编织布、土工无纺布和砂土界面进行了一系列循环剪切试验,得到了不同工况下界面的剪切刚度和阻尼比,并探究了循环次数与剪切刚度和阻尼比之间的规律。研究结果表明,同一循环次数时格栅-土界面的循环剪切刚度最大,土工编织布-土界面的阻尼比最大;剪切位移幅值为3 mm时3种竖向应力下界面都呈现出循环剪切硬化的特征,随着循环次数的增加,各竖向应力下的界面阻尼比有趋于某一值的趋势;砂土密实度越大,同一循环次数对应的剪切刚度越大,阻尼比越小,且随着循环次数的增加3种砂土密实度的界面阻尼比有趋于同一值的趋势;循环剪切位移幅值为5 mm的界面发生循环剪切软化现象,剪切位移幅值越大,界面同一循环次数的阻尼比也越大。 相似文献
20.
为了研究橡胶砂的剪切特性,采用室内大型直剪仪,研究了4种橡胶砂级配（1种间断级配、2种连续级配、1种开级配）、3种橡胶掺入量（10%、30%、60%）、3种竖向应力（30、60、90 kPa）对橡胶砂强度特性和体变特性的影响;并在室内直剪试验的基础上,按照相同级配和橡胶掺量建立纯砂和橡胶砂的离散元数值模型,从颗粒接触状态和颗粒位移角度探讨橡胶砂内在力学机制。研究结果表明：在低橡胶含量下,橡胶砂的剪应力曲线趋势和纯砂一致,但其抗剪强度均低于纯砂;橡胶砂剪切应力随竖向应力的增大而增大,4种级配的橡胶砂中连续级配SR2抗剪强度最高;橡胶颗粒的掺入能有效抑制砂土的剪胀,其中间断级配SR1橡胶砂抑制土体剪胀效果最好,剪胀量相较于纯砂减少了37.6%;橡胶砂的内摩擦角随着橡胶掺入量的增大而减小,同一橡胶掺量下连续级配SR2橡胶砂的内摩擦角最大;橡胶颗粒在橡胶砂力链网络中主要参与弱力链的形成,橡胶砂剪切带宽度小于纯砂的剪切带宽度。 相似文献