共查询到20条相似文献，搜索用时 15 毫秒
1.
Christopher L. Meehan Thomas L. Brandon J. Michael Duncan Binod Tiwari 《Landslides》2010,7(2):157-167
A series of ring shear and direct shear tests were performed to measure the drained residual strength of three clay soils.
For each of the soils, slickensided direct shear specimens were prepared by wire-cutting intact specimens, and polishing the
resulting shear plane on a variety of surfaces to align the clay particles in the direction of shear. Drained direct shear
tests were then conducted on each of the polished specimens. The resulting shear strengths were compared with the residual
strengths measured in the ring shear device to evaluate the effectiveness of the different polishing techniques for creating
slickensided surfaces. Test results indicated that the measurement of residual strengths along preformed slickensided surfaces
is extremely sensitive to both the soil type and the slickenside preparation technique that is used. Consequently, this approach
does not appear to be a viable alternative to conventional repeated direct shear or ring shear tests to measure residual shear
strengths. 相似文献
2.
Correlation of large displacement drained shear strength of landslide soils measured by direct shear and ring shear devices 总被引：2，自引：0，他引：2
Shriwantha Buddhi Vithana Shinya Nakamura Seiichi Gibo Anshun Yoshinaga Sho Kimura 《Landslides》2012,9(3):305-314
Based on a laboratory study of drained direct shear tests of remoulded, pre-cut and polished specimens and drained ring shear tests of uncut and remoulded specimens of slip surface materials of five landslide soils, significant correlations of the mobilized shear strength parameters, cohesion (c, c r) and internal friction angle (Φ, Φr), are proposed. The investigated soils consisted of the slip surface material belonging to tuffaceous clay, mudstone, loess and siltstone. Most of the previous studies on residual shear strength measured by reversal direct shear and ring shear devices have obtained significantly different results using the two devices, even when pre-cut and polished specimens were used in the direct shear device. In this study, the residual shear strength values of remoulded specimens measured by a ring shear device are shown to significantly correlate with the drained large displacement shear strength values of remoulded specimens, which were measured using pre-cut and polished specimens in a direct shear device. The correlation between the cohesion measured in the two shear devices is expressed by the linear relationship, $ {c_{\text{r}}} = 0.{7394}c - {6}.{6857} $ , while the correlation between the friction angle measured in the two devices is expressed by the linear relationship, $ {\Phi_{\text{r}}} = {1}.0{852}\Phi - {6}.0{247} $ . The proposed linear correlations for effective cohesion (c′) and effective friction angle (Φ′) have yielded significant coefficients of determination within an effective normal stress range of 30–150?kN/m2. 相似文献
3.
Residual strength of slip zone soils 总被引：2，自引：1，他引：1
Slip zones of ancient landslides are commonly composed of fine-grained soils with amount of coarse-grained particle. Residual strength of slip zone soil is an important parameter for evaluating reactivation potential and understanding progressive failure mechanism. In this study, the residual strength is examined by in situ direct shear tests, improved laboratory reversal shear box test, precut specimen triaxial shear test and ring shear test. Some residual shear behaviors are recognized. Field residual strength is the average operational resistance along the sliding surface not an ideal drained strength, which is less than peak and greater than residual strength measured in laboratory. Stress–displacement curves obtained from in situ shear and laboratory reversal direct shear demonstrate strain-hardening which have no significant peak, but the shear stress is decreased gradually with increasing displacement. Residual friction coefficient depends on the normal stress, and this dependence is relevant to the interaction of rolling and sliding of particles. Residual friction angle is closely related to coarse fraction and dry density, appearing a linear increase with increasing coarse fraction and a form of polynomial function with increasing dry density. The influence of shearing rate on residual strength can be negligible. 相似文献
4.
香港大屿山残坡积土的残余强度试验研究 总被引：8，自引：1，他引：7
粘性土的残余强度是边坡稳定性评价、桩基与土的相互作用机理研究及填土边坡设计中的重要参数。本文在综述大量文献的基础上,结合香港大屿山火山岩风化残坡积土的残余强度试验研究,分析了残余强度的测试方法和影响残余强度的因素。研究结果表明,残余强度与有效法向应力间具有明显的非线性关系;与单剪测试结果相比,多级剪测试结果明显偏高。 相似文献
5.
In this paper, the effect of cyclic loading on drained residual strength of over-consolidated silty clay is examined based
on the results from ring shear tests which were conducted with a sophisticated ring shear apparatus. Initially sheared to
form shear zones under different pre-consolidation pressures and at different shear rates (SRs), soil samples were then tested
under cyclic loading. After the cyclic loading application, the samples were re-sheared while the corresponding shear strengths
were measured. The results show that the effect of cyclic loading on residual strength is noticeable. The effect is related
to pre-consolidation history and SR of the soil samples. Under conditions of relatively low over-consolidation ratio (OCR),
the soil samples show an increase in residual strength with decreasing SR after cyclic loading. Most of the peak strength
values after cyclic loading are higher than the residual strength values obtained before cyclic loading. Two effects of cyclic
loading on the residual strength are identified: (a) If OCR is less than or equal to 3.0, the residual strengths measured
after cyclic loading are larger than those before cyclic loading; (b) If OCR is greater than or equal to 3.5, the residual
strengths after cyclic loading tend to become lower than those in the shear tests before cyclic loading. 相似文献
6.
Jianhong Jiang Hoe I. Ling Victor N. Kaliakin Xiangyong Zeng Ching Hung 《Acta Geotechnica》2017,12(2):335-348
An anisotropic time-dependent bounding surface model for clays is developed by generalizing a previous time-independent model that adopts a flexible bounding surface. It is based on the framework for coupled elastoplasticity–viscoplasticity for clays and Perzyna’s overstress theory. Three viscoplastic parameters were introduced and explained in detail. The model was validated against undrained creep tests for both isotropically and anisotropically consolidated clays, undrained and drained stress relaxation tests on some undisturbed clays, and undrained triaxial tests with varying strain rates on natural Hong Kong marine deposit clay. The general agreement between the model simulations and test results was satisfactory. The varying effects of lower-level parameters were discussed on the undrained multistage stress relaxation response for normally consolidated soils which had been ignored in literature. The flexibility of the model in capturing the shear strengths, which is the unique feature of the current model, was shown in the simulations of time-dependent triaxial tests on Taipei silty clay. All the simulations show that the proposed model is a relatively practical model considering both anisotropy and time dependency of clays. 相似文献
7.
In this paper, the shear strength with respect to the matric suction of unsaturated soils was studied. For this purpose, unsaturated
triaxial testing procedures were applied to the undisturbed residual soil specimens. An apparatus for performing triaxial
tests was designed and constructed. In the tests, matric suction was controlled by using the axis translation technique, and
pore water volume changes were measured by means of a volume change transducer with 10−8 m3 sensitivity. The test results indicated that the matric suction contributes to the shear strength of unsaturated soil specimens,
and this contribution called suction strength varies non-linearly with respect to the matric suction. The logarithmic model
needing to know the air-entry value and the internal friction angle of a soil specimen for prediction of the suction strength
were presented and compared with the test results. It was found that suction strength values predicted from the proposed model
were in satisfactory agreement with the experimental results. 相似文献
8.
9.
本文借助于先进的多功能大型高速高压环剪试验机,通过进行不同应力历史、剪切速度和正应力等条件下的系列试验,对吉林长春地区广泛分布的超固结粉质黏土在快速大剪切位移条件下的力学响应特性进行了试验研究。试验结果显示,前期固结历史和剪切速度不仅对超固结粉质黏土的抗剪强度变化具有显著的影响作用,并且对于其峰后应变软化亦产生明显的影响。在相同剪切速率和正应力条件下,前期固结压力越大,其峰值强度和残余强度值越大。不同剪切速度下的试验结果表明,在具有相同应力历史的条件下,峰值强度和峰后应力降低随着剪切速度的增大而增大。剪切速度越快越有利于土应变软化的产生以及剪切面的形成。在快速大剪切条件下对长春地区超固结粉质黏土抗剪强度变化起主要作用的是剪切过程中土体结构的变化和剪切面的生成,而剪切过程中孔隙水的作用并不显著。 相似文献
10.
利用电动应变控制式直剪仪及直剪/残余剪切试验仪对南水北调磁县段不同黏粒含量的原状膨胀土进行快剪、饱和快剪、饱和固结快剪和反复直剪试验,研究黏粒含量对其抗剪强度的影响。研究表明:饱和后试样的抗剪强度明显降低,固结后强度提高,且饱和作用对黏粒含量较大的中膨胀土强度的削弱作用更为显著,固结作用对黏粒含量较小的弱膨胀土强度的治愈作用更显著; 随黏粒含量的增大,黏聚力逐渐减小,内摩擦角则先减后增,其临界值在32%左右; 峰值强度后的抗剪强度降低幅度随黏粒含量的增加而增大; 土体的峰值强度f随黏粒含量则先减后增,变化趋势比较平缓; 残余强度r随黏粒含量增加逐渐减小,成指数关系; 残余强度内摩擦角r与黏粒含量成对数关系,黏聚力cr则比较离散。 相似文献
11.
The shear behavior of soils rich in amorphous clay-size materials was not well reported in the literature. This study analyzed the direct shear and ring shear test data of soil samples containing 55–74% amorphous materials in the clay fraction from a slow-moving landslide in eastern Honolulu, HI. The direct shear test results showed that the undisturbed soil samples when not sheared internally had peak cohesion (c) of about 50 kPa and internal friction angle (Ø) of about 10°. This implies that the amorphous clay-size materials provided strong interparticle bonds for the soils. Breaking of the bonds during the softening process and redistribution of the amorphous clay-size materials were primarily responsible for the drop from the peak strength to the residual strength (c=0, Ø=10° from back calculation with SLOPE/W and c=0, Ø=5–7° from the ring shear test). The drained residual failure envelope is stress dependent due to the interaction of the gel-like amorphous clay-size materials with crystalline silt- and sand-sized particles. The amorphous clay-size materials act as the contact between crystalline particles. The contact increases with increasing consolidation stress, resulting in a decrease in the shear strength and the residual friction angle. 相似文献
12.
三轴剪切试验是岩土工程中常见的室内试验,其目的主要是为了获得土的抗剪强度指标和土中孔隙水压力的变化情况。三轴的固结不排水剪（CU）和固结排水（CD）剪试验可以获得土的总应力抗剪强度指标和有效应力抗剪强度指标,因此具有其它剪切试验无法替代的优势。但因试验过程中排水固结的时间很长,影响了试验进度,从而影响到整个工程的进度和经济效益。通过对三轴剪切试样排水固结过程的机理分析,介绍了制作一种可以大大缩短大量试样排水固结时间的装置及该装置的研制方法。采用该装置,可使CU试验的效率提高6～12倍,可使CD试验的效率提高3～6倍。可节约大量的生产成本,提高工作效率,经济效益明显。 相似文献
13.
If the free vertical movement of the upper rigid part of the shear box is hindered during shearing, a frictional force is mobilized between the specimen and the vertical walls of the shear box. This causes either unloading (for contractant soils) or additional loading (for dilatant soils) of the specimen during shearing. If no correction of the applied vertical load with respect to the wall friction is taken into account, the resulting shear strength can be either underestimated (for contractant soils) or overestimated (for dilatant soils). For example, in a particular investigation of a normally consolidated soil, the measured friction angle from a direct shear test was almost 8° smaller than the angle from a triaxial test. This paper, therefore, presents a method for direct measurement of the frictional force at the contact between the vertical walls of the box and a fine-grained soil. If the wall friction is taken into account, the friction angle from the shear box coincides well with the angle from triaxial tests. If the wall friction cannot be measured during the test, a sufficiently large vertical gap should be adjusted in case of soft soils, in order to enable non-restrained settlement of the upper part of the box during specimen contraction. 相似文献
14.
15.
堆石料大三轴试验的细观模拟 总被引：3，自引：0，他引：3
采用三维颗粒流计算程序,对堆石料的大三轴排水剪切试验过程进行了数值模拟。在数值模型的生成过程中,使堆石料集合体达到规定密度和级配;采用动态松弛算法迭代求解,并引入粒间阻尼,以吸收颗粒填装的多余动能使其稳定;颗粒间引入黏结力来提高试样的峰值强度;确定堆石料的细观力学参数,拟合室内试验应力应变曲线。模拟不同围压下堆石料的试验,得到的应力-应变曲线与室内试验基本一致,说明颗粒流方法可以较好的模拟堆石料的大三轴试验过程。由于没有考虑颗粒形状及颗粒破碎的影响,造成大应变剪胀偏大。 相似文献
16.
天津市区第一海相层粉质黏土卸荷路径下强度特性的试验研究 总被引：1，自引：0，他引：1
土的强度特性与土体中应力变化过程、固结状态有关,常规的三轴试验并不能真实地反映土体经历的应力路径对其强度特性的影响。采用自制的应力-应变联合控制式三轴试验仪,对天津市区地层中第一海相层的粉质黏土原状饱和试样进行一系列特殊三轴试验,研究了排水卸荷条件对其强度特性的影响。试验结果表明：经历排水卸荷路径的土体的加荷剪切总应力强度指标大于常规试验结果,也大于前人在不排水卸荷路径下的试验结果,但几种应力路径下土体的有效应力强度指标基本相等。研究成果对天津市区基坑开挖及支护结构设计计算、软土隧道施工研究及其他相关岩土工程问题的研究均有较大的实用价值。 相似文献
17.
M. Maccarini 《Geotechnical and Geological Engineering》1993,11(2):69-80
Summary Residual soils are known to be bonded. The mechanical behaviour of undisturbed residual soils depends, therefore, not just on initial porosity and stress history but mainly on these bonds. This paper compares the stress-strain behaviour obtained from sets of drained triaxial compression tests and direct shear tests, both from undisturbed samples of residual soil. It shows how the same undisturbed bonded structure behaves differently when tested using the two different procedures. 相似文献
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19.
It is universally known that residual soils behave very differently from sedimentary soils. While the latter is widely known as cross-anisotropic, little is known regarding the strength anisotropy of residual soils. This study presents how the inherent anisotropy affects the strength of natural granite residual soils under generalized conditions, where intact specimens were carefully prepared and sheared under triaxial compression, extension, simple shear, and hollow cylinder torsional shear tests. The strength of natural residual soil, in terms of ultimate stress ratio M and undrained shear strength Su, is found to be significantly anisotropic in a different way from normally consolidated clays with the maximum strength obtained under triaxial compression and the minimum under simple shear or at intermediate principal stress direction. As a result, the existing method failed to measure the anisotropy degree of the studied soil. Two parameters were proposed accordingly to quantify the anisotropic strength under general conditions, taking the special strength anisotropy pattern and cohesive-frictional nature of GRS into account. The proposed parameters enable the direct comparison of strength anisotropy among soils. This study serves as a data set to better understand residual soils regarding their anisotropic behaviors under generalized conditions. Although specific to granite residual soils in China, this study is expected to be more widely applicable to other weathered geomaterials.
相似文献20.
This study presents an evaluation of yielding mechanisms for unsaturated, compacted silt using drained triaxial compression tests with control of elevated temperatures and high suction magnitudes. After anisotropic compression, some compacted silt specimens were heated by approximately 40 °C before a suction of approximately 300 MPa was applied, while others were heated after suction application. A frictional response was observed for the specimens sheared under high suction magnitudes, in the form of a consistent increase in peak shear strength with increasing net confining stress. An effective stress analysis was used to evaluate the trends in the peak shear stress and the role of stress history for the different specimens. A single peak failure envelope was observed when the shear strength data was interpreted in terms of the mean effective stress. Changes in preconsolidation stress were estimated by identifying the intersections between a thermo-elasto-plastic yield function and the experimental peak shear strength values. Soil specimens heated before application of high suction values had lower peak shear strengths than reference specimens at high suction and ambient temperature. This behaviour is consistent with thermal softening trends observed in soils heated under low suction values. However, soil specimens heated after suction application had greater peak shear strengths than the reference specimens. This indicates heating under high suction results in hardening. The impact of suction on the preconsolidation stress was found to be better represented by a power law model at high suction magnitudes than other available models. The estimated preconsolidation stress values were used to evaluate the impacts of stress history on the thermal volume change response, which matched well with data from tests on saturated specimens. 相似文献