共查询到20条相似文献，搜索用时 46 毫秒
1.
为了研究粘土与加筋材料接触面之间的力学特性,及砂对粘土与筋带接触面力学特性的改善情况,采用直剪试验方法对粘土与聚丙烯土工带polypropylene在粘土不同含水量条件下进行了不同法向荷载作用的直剪试验,讨论了法向应力、含水量对高液限粘土与筋带之间剪切特性的影响;设计了筋带砂粘土层状布置体系的加筋土结构模型,并根据设计的模型进行直剪试验.试验结果表明:粘土与筋带接触面之间的剪切强度随着法向应力的增加呈非线性增长;接触面的摩擦系数随着含水量的增加而减小,接触面的粘聚力随含水量的增加先增大后减小,粘土与接触面之间存在一个最佳的含水量,这个值要比粘土压实的最佳含水量低2%左右;筋带砂粘土层状布置体系表明砂对粘土与筋带的剪切特性起到明显的改善作用. 相似文献
2.
针对解决《土工试验方法标准》三轴试验中,黏性土抗剪强度指标出现的变异问题,提出一种黏性土试样组合方法,准确测定黏性土抗剪强度指标值在原有的一组相同物理性质(含水率,液塑限,级配)黏性土三轴试样的基础上,增加一组或两组相同物理性质试样,通过系统软件对试样进行完备组合,重新形成黏性土抗剪强度指标值样本基数,取其样本数的平均值为黏性土抗剪强度指标.通过试验验证了试样组合方法能有效避免三轴试验中出现的互不包容的莫尔圆,或黏聚力c出现负值试验结果,并在不增加试样数量的前提下,扩大了黏性土抗剪强度指标的样本基数,从而可准确测定抗剪强度指标值组合方法的提出为黏性土抗剪强度指标的测定提供一定的参考价值. 相似文献
3.
Constitutive model of saturated soft clay with cyclic loads under unconsolidated undrained condition
An equivalent visco-elastic model of saturated soft clay was studied under unconsolidated undrained (UU) condition, which can be used to evaluate the stability of ocean foundation. Cyclic triaxial compression and extension tests were conducted to study the parameters of the model. Results showed that the relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain were nearly unique, when the initial octahedral shear stress ratios of specimens were equal to 0.3, 0.5 and 0.7. The relationships of the damping ratio and the octahedral shear modulus with the octahedral cyclic shear strain determined from the cyclic triaxial compression tests were basically the same as those determined from the cyclic triaxial extension tests. Furthermore, the relationships were not related to the initial stress condition, the test stress state and the octahedral cyclic shear stress ratio. The relationships determined from the cyclic triaxial tests under no deviatoric stress were basically the same as those determined from the cyclic triaxial tests under deviatoric stress. The change of the octahedral cyclic accumulative strain with the number of cycles was unique under different tests stress states. An equivalent visco-elastic constitutive model of saturated soft clay under UU condition was initially established. 相似文献
4.
Undrained anisotropy and non-coaxial behavior of clayey soil under principal stress rotation 总被引：2，自引：0，他引：2
In this study, a series of undrained tests were conducted on both intact and reconstituted clay using an automatic hollow cylinder apparatus. Monotonic shearing tests with fixed principal stress directions were carried out, pure and cyclic prin- cipal stress rotation tests were also performed. The non-coaxiality, defined as the non-coincidence of the principal plastic strain increment direction and the corresponding principal stress direction, of clayey soil was studied experimentally. The effects of the intermediate principal stress, shear stress level, and inherent anisotropy were highlighted. Clear non-coaxiality was observed during pure principal stress rotation, in both intact and reconstituted clay. The influence of the intermediate principal stress pa- rameter, shear stress level, and inherent anisotropy on the non-coaxial behavior of the clayey soil was found to be insignificant when compared with the sand. The non-coaxial behavior of the clayey soil depended more on the stress paths. Under undrained conditions, the contribution of elastic strain to the direction of the total principal strain increment cannot be ignored. 相似文献
5.
Failure criterion of saturated soft clay is studied under cyclic loads through different experiments. A large number of cyclic torsional shear and cyclic triaxial tests on saturated soft clay under unconsolidated undrained condition are conducted. From the test result analysis, it is seen that the failure of saturated soft clay under static and cyclic loads satisfies Mises criterion. The result from different test stress states is not related to the test stress states or confining pressures. It can be applied in general stress states. Then according to the Mises criterion, the equivalent relationship on failure moment between the test stress state and the general stress state can be established. So the cyclic mechanics characteristics of saturated soft clay at failure moment are clarified in this paper. Furthermore, a theory basis is provided for using pseudo-static elasto-plastic cyclic strength model to evaluate cyclic bearing capacity. 相似文献
6.
There exists a critical cyclic stress ratio when sand or clay is subjected to cyclic loading. It is an index distinguishing stable state or failure state. The soil static and dynamic universal triaxial and torsional shear apparatus developed by Dalian University of Technology in China was employed to perform different types of tests on saturated soft marine clay in the Yangtze estuary. Undisturbed samples were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotropic consolidation with different initial consolidation parameters. The effects of initial orientation angle of major principal stress, initial ratio of deviatoric stress, initial coefficient of intermediate principal stress and stress mode of cyclic shear on the critical cyclic stress ratio were investigated. It is found that the critical cyclic stress ratio decreases significantly with increasing initial orientation angle of major principal stress and initial ratio of deviatoric stress. Compared with the effects of the initial orientation angle of major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate principal stress is less evident. Under the same consolidation condition, the critical cyclic stress ratio from the cyclic coupling shear test is lower than that from the cyclic torsional shear test, indicating that the stress mode of cyclic shear has an obvious effect on the critical cyclic stress ratio. The main reason is that the continuous rotation in principal stress directions during cyclic coupling shear damages the original structure of soil more than the cyclic torsional shear does. 相似文献
7.
《浙江大学学报(A卷英文版)》2021,(2)
This paper presents model tests(macro aspect) and microstructure tests(micro aspect) for investigating the consolidation behavior of Tianjin dredged clay using the prefabricated vertical drain air-booster vacuum preloading(PAVP) and tube air-booster vacuum preloading(TAVP) methods. The mechanism of air-booster vacuum preloading(AVP) using a spring-like system is explained. The main difference between these two methods is the air-boosting equipment. A new anticlogging air-booster prefabricated vertical drain(PVD) is used in the PAVP technique and a self-designed air-booster tube is used in the TAVP technique. In the model tests, a comparison of the variables that are monitored during reinforcement(vacuum pressure, surface settlement, water discharge, and pore-water pressure) and after reinforcement(water content, dry density, and vane shear strength) is conducted. The results indicate that the consolidation behavior of Tianjin dredged clay using the PAVP method is better than that using the TAVP method. PAVP more efficiently mitigates the issue of water-draining PVD clogging and significantly accelerates drainage consolidation. In addition, in the microstructure tests, a comparison of the variables that are monitored after reinforcement(via scanning electron microscopy(SEM) and mercury intrusion porosimetry(MIP)) is conducted, and the results further explain the model test results. 相似文献
8.
ZHAN Liang-tong CHEN Ping NG C.W.W. 《浙江大学学报(A卷英文版)》2007,8(5):699-706
A laboratory study was carried out on both natural and compacted specimens to investigate the complex soil-water interaction in an unsaturated expansive clay. The laboratory study includes the measurement of soil-water characteristic curves, 1D free swelling tests, measurement of swelling pressure and shrinkage tests. The test results revealed that the air-entry value of the natural specimen was quite low due to cracks and fissures present. The hydraulic hysteresis of the natural specimen was relatively insignificant as compared with the compacted specimen. Within a suction range 0 to 500 kPa, a bilinear relationship between free swelling strain (or swelling pressure) and initial soil suction was observed for both the natural and compacted specimens. As a result of over-consolidation and secondary structures such as cementation and cracks, the natural specimens exhibited significant lower swelling (or swelling pressure) than the compacted specimen. The change of matric suction exerts a more significant effect on the water phase than on the soil skeleton for this expansive clay. 相似文献
9.
The creep and destructuration characteristics of soft clay are always coupled under loading, making it difficult for engineers to determine these related parameters. This paper proposes a simple and efficient optimization procedure to identify both creep and destructuration parameters based on low cost experiments. For this purpose, a simplex algorithm (SA) with random samplings is adopted in the optimization. Conventional undrained triaxial tests are performed on Wenzhou clay. The newly developed creep model accounting for the destructuration is enhanced by anisotropy of elasticity and adopted to simulate tests. The optimal parameters are validated first by experimental measurements, and then by simulating other tests on the same clay. Finally, the proposed procedure is successfully applied to soft Shanghai clay. The results demonstrate that the proposed optimization procedure is efficient and reliable in identifying creep and destructuration related parameters. 相似文献
10.
Richard J. Jardine 《浙江大学学报(A卷英文版)》2011,12(1):1-14
An integrated approach to geomaterial characterization is advocated that combines geology, in-situ testing, fabric studies, routine index experiments and advanced laboratory testing. It is shown that advanced laboratory testing can explore features such as kinematic yielding and anisotropy in stiffness or shear strength that would otherwise be impossible to quantify. A detailed study performed in London clay at the new Heathrow Terminal 5 site is used to illustrate the arguments made. It is shown that the London clay has strong anisotropy in stiffness, is highly non-linear over the strain range of engineering interest, has markedly anisotropic shear strength characteristics and exhibits a pronounced degree of brittleness. These features can impact significantly on the practical design and analysis of civil engineering works including shallow and deep foundations, tunnels and excavations, and the stability of slopes. 相似文献
11.
Cheese slurries, made from fresh Swiss cheese curd, were treated at 345 or 550 MPa for 10 or 30 minutes in an isostatic press
at 25°C. The slurries were ripened at 30 °C for 0,3 and 5 days. The growths of coliforms, yeasts and molds, starter bacteria
(Lactococci andStreptococci), non-starter lactic acid bacteria (Lactobacilli), and presumptive coagulase-positiveStaphylococcus were determined. An electronic nose was used to evaluate aroma development of the cheese slurries. Commercial Swiss cheeses
with different ages were used as aroma references. The degree of inactivation of organisms was found to be a function of pressure
intensity, exposure time, type of organism, and cheese slurry pH. In general, slurries treated at a higher pressure and with
a longer exposure time showed a greater reduction in numbers and had less out-growth of organisms during ripening.Coliforms, yeasts and molds were completely inactivated at the pressures and time used. Starter bacteria appeared to be more resistant
to being inactivated by high pressure treatment and had a greater out-growth rate thanLactobacilli andStaphylococci. Based on canonical analysis, nineteen samples for each batch were assigned to three groups. In general, higher intensity
of pressure or longer exposure time caused less aroma development in the cheese slurries. When the cheese curd was incubated
overnight prior to making the cheese slurries, stronger slurries with stronger aroma were observed. This study provided an
explanation of the relative importance of relationships among high pressure treatment, starter bacteria, and aroma development
during accelerated ripening. 相似文献
12.
成都裂隙性黏土流变特性试验 总被引：1，自引：0，他引：1
以成都裂隙性黏土为对象,进行一系列室内试验,探讨了成都裂隙性黏土的流变特性。通过三轴固结不排水蠕变试验,得到不同围压下各级偏应力水平的全过程蠕变曲线和应力—应变等时曲线,对试验结果做了讨论,并建立了蠕变方程。其中应变—时间关系采用伯格斯模型,应力—应变关系采用指数函数的蠕变方程,拟和曲线与试验曲线很好的吻合,较好地表达了土体的应力—应变—时间关系。 相似文献
13.
钾离子在粘性土中扩散运移的影响因素 总被引：2，自引：0，他引：2
为了研究日本九州地区的2种区域性土———有明粘土和赤土作为废弃物填埋场底部粘土衬垫层的适应性,做了一系列室内扩散试验.应用软件Pollute V6·3模拟计算了实验结果,反算出了钾离子的扩散系数.研究结果表明,有明粘土的扩散系数比赤土的扩散系数小,说明有明粘土有望能作为更合适的粘土衬垫材料.通过对比试验研究,发现在混合溶液的情况下,钾离子的扩散系数较在单一溶液的钾离子的扩散系数小.因此建议尽可能使用与现场淋滤液成分相近的混合溶液来做扩散试验,以求出扩散系数来作为废弃物填埋场的设计和性能评估参数. 相似文献
14.
杜凯 《河北能源职业技术学院学报》2014,14(4):61-64
采用＂S＂孔、放射孔及分支孔定向钻孔技术,进行千米深立井马头门所处围岩注浆加固的研究与实验。针对马头门和井筒的相互空间位置,合理布置放射孔和分支孔,使注浆扩散半径满足马头门所处围岩加固的需要。采用粘土水泥浆和单液水泥浆交替注浆工艺封堵地层涌水同时提高了马头门围岩的稳定性。获得了较好的经济效益和社会效益。 相似文献
15.
朱艳 《忻州师范学院学报》2006,22(4):80-82
文章首先分析了我院非英语专业本科生阅读策略的使用情况,根据具体情况进行了有针对性地课堂训练。在练习后再次分析总结了学生阅读策略的使用情况及这些策略的使用与阅读效果之间的关系。结果发现,课堂训练有助于学生进一步掌握和使用阅读策略,提高阅读效率和效果。 相似文献
16.
17.
针对目前高烈度区多层砌体结构住宅存在的问题和粘土砖被淘汰,采用混凝土结构形式建造多层住宅成为住宅产业的发展方向。通过对各种混凝土结构形式的比较,得出短肢剪力墙结构是建造多层住宅的首选结构形式．并对短肢剪力墙结构设计中存在的一些问题进行了探讨,最后通过实例对多层短肢剪力墙进行了设计和计算．为在高烈度地区建造此类结构提供了设计参考。 相似文献
18.
排水性沥青路面上中面层层间结合状况研究 总被引：1，自引：0，他引：1
通过环氧树脂、SBS改性乳化沥青、SBS改性热沥青和H#桥面防水材料等4种粘结层材料组合试件的剪切试验,对影响排水性路面的行车荷载、温度和水等外部因素进行了研究和分析.试验结果表明,温度升高会造成层间结合能力的降低,层间剪切强度与温度之间的关系接近一条对数曲线.在实际路面中,行车荷载作用中心区域下的剪切强度较其他部位要小.冻融和饱水等水损害都明显地降低了路面抗剪强度,破坏了上中面层间的层间结合.荷载、温度和水等因素的作用会对层间结合状况产生一定的不利影响,需要通过优选粘结层材料来提高排水性路面的耐久性. 相似文献
19.
In-situ vane shear test is frequently performed to determine shear strength for slope stability analysis in Tianjin New Harbor. However,the soil shear strength varies with the shear plane orientation. A possible means to reduce the effect of directional dependency of shear strength is to convert the in-situ vane shear strength into undrained shear strength parameters. A method of converting in-situ vane shear strength into undrained shear strength parameters is presented. The shear strength parameters determined for all of the in-situ vane shear strengths are subjected to statistical regression analysis to take into consideration the possible effect of non-homogeneity in the soft clay deposit. Using the regressed shear strength parameters, slope stability analyses are performed for five existing soil slopes. The results of stability analyses indicate that the safety factors obtained from the converted parameters reflect the state of the slopes analyzed much better than those obtained from in-situ vane shear strength and laboratory consolidated-undrained and unconsolidated-undrained strength parameters. It is concluded that the presented methsod of determining undrained shear strength parameters for in-situ vane shear strength is effective. 相似文献
20.
许多相关研究显示,含有植生根系补强的土壤会增加土壤的凝聚性和剪力强度．当穿过滑动面的根系贯入深度越深,则对于增加土壤剪力强度的功能越大．基于根力模式之研究,植根对土壤剪力强度增量之计算,已呈现明朗而具体化．本研究除应用文献【1】中学者Waldron的根系力学理论外,亦采用文献【2】中陈等人及文献[3】中游等人所提出之根系力学修正模式来估算土壤抗剪强度增量,分析结果显示,考虑植根密度变化与合理之剪力带发展机制模拟,确能得到较准确之评估结果． 相似文献