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1.
It is generally recognized that the low strength and high compressibility are the characteristics of soft soil. In addition to other techniques, reinforcement can also be used in increasing the strength and decreasing the deformation of this kind of soil. The results of an investigation into the effects of a natural fiber on the consolidation and shear strength behavior of Shanghai clayey soil reinforced with wheat straw fibers are presented in this paper. A series of one dimensional consolidation and triaxial tests were conducted on samples of unreinforced and reinforced Shanghai clayey soil with different percentages of randomly distributed wheat straw fibers. The results show that the preconsolidation pressure decreases and the coefficient of swelling and compression generally increase with increasing the fiber content until a optimum content value. Furthermore, the addition of wheat straw fiber leads to a significant increase in shear strength and friction angle of the natural soil and there is an optimum wheat fiber content that makes this increase maximal. 相似文献
2.
干湿循环对非饱和膨胀土抗剪强度影响的试验研究 总被引：1，自引：0，他引：1
膨胀土是一种气候敏感性土体,研究在干湿循环过程中膨胀土剪切强度的变化,对了解在自然界周期性蒸发和降雨作用下原位膨胀土体工程性质的变化以及由此导致的地质灾害发生过程具有重要意义。文中以重塑非饱和膨胀土为研究对象,模拟了3次干湿循环过程,对每次干燥路径中的试样进行了直剪试验,重点分析含水率、正压力及干湿循环次数对膨胀土剪切强度的影响,得到如下主要结果：（1）在干燥过程中,随着含水率的减小,试样的刚度、脆性、抗剪强度值（峰值剪切应力）、抗剪强度指标（黏聚力、内摩擦角）及抗剪强度损失（峰值强度与残余强度之差）均呈增加趋势;（2）正压力越高,试样的剪切强度和残余强度越大,而破坏后的峰值强度损失越小,破坏韧性增加;（3）在3次干燥过程中,试样的剪切强度及黏聚力呈先增加后减小的趋势,在第二次干燥过程中达到峰值,但内摩擦角受干湿循环的影响无明显规律;（4）试样经历多次干湿循环后,其剪切特性越来越类似于超固结土,脆性显著增加;（5）干燥过程和干湿循环对试样残余剪切强度的影响都不明显,残余剪切强度基本都在100 kPa附近变化;（6）非饱和膨胀土在干湿循环及干燥过程中剪切强度的变化除了与吸力有关外,还与其微观结构调整和裂隙发育状态密切相关,需要综合非饱和土力学和土质学理论对试验现象进行分析。 相似文献
3.
厦门地区花岗岩残积土的颗分试验表明其粒度呈“两头多,中间少”的特征,级配较独特。孔隙比等物性指标与压缩模量等设计中常用指标定量关联性不强,离散性大且没有明显规律。结合厦门地铁工程地质勘察资料,通过粒间状态参量、级配控制模式确定所研究土体的关键物理状态参量,分析该参量与岩土工程设计中常用指标之间的相关关系。结果表明,引入Thevanayagam提出的粒间孔隙比作为参变量,压缩模量随粒间孔隙比的增大而减小,建立了估计残积砾质黏性土、残积砂质黏性土压缩模量的经验公式。级配控制模式下的特征粒径比可以作为估计花岗岩残积土抗剪强度指标的关键参变量,黏聚力随特征粒径比的增大而增大,内摩擦角随特征粒径比的增大而减小,且线性相关性较好。文中建立的预测花岗岩残积土压缩模量、抗剪强度指标经验公式,可供厦门地区工程设计时参考。 相似文献
4.
残积土抗剪强度的环剪试验研究 总被引：3，自引：0，他引：3
残积土风化剧烈,研究其大变形下的工程特性很有必要。利用环剪仪的试验特点,可以研究土体在较大剪切位移下抗剪强度的变化规律。通过对残积土残余和峰值强度的环剪试验测定和对试验数据的整理与对比分析,得到了含水率与残余强度指标之间的关系,证明大变形下残积土具有浸水软化的特性;从应变阈值角度分析了残积土应变软化的性质,不同剪切位移下的残积土具有不同的抗剪强度,所研究的残积土达到峰值强度对应的应变介于0.02～0.06之间,而到达基本稳定的残余强度所需要的应变介于0.06～0.20区域内。研究还发现,矿物成分不同直接影响到残积土的残余强度,是残积土不均匀性的内部因素 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.
Yahia E.-A. Mohamedzein Amer A. Al-Rawas 《Geotechnical and Geological Engineering》2011,29(6):999-1008
Sabkha soils are salt-bearing formations that are formed in arid regions. In their in situ states the sabkha soils have high
compressibility and low shear strength. These soils are also heterogeneous and their properties depend on the type and amount
of salt present. Thus, these soils are not suitable for support of infrastructures without the risk of high settlement and/or
bearing capacity failure. This paper investigates the possibility of using cement to improve the shear strength of sabkha
soils for possible use as a foundation-bearing soil. The sabkha soil used in this study is a sandy sabkha obtained from the
coastal plains at Al-Auzayba, Sultanate of Oman. Cement was added in percentages of 2.5, 5, 7.5 and 10%, by dry weight of
soil. The soil-stabilizer mixers were allowed to cure for 7, 14 and 28 days. Laboratory tests such as compaction, unconfined
compression, consolidated undrained triaxial and durability tests were performed to measure the engineering characteristics
of the stabilized material. The results showed substantial improvements in the shear strength of the sabkha–cement mixtures
and the mixtures are also durable with small weight loss after 12 wetting/drying cycles. Thus, cement can be used to improve
the shear strength of sabkha soils. Furthermore, the effective stress path and the tress-strain relation of the sabkha–cement
mixtures follow trends similar to those of cemented calcareous soils. 相似文献
7.
Mechanical Behavior of a Clay Soil Reinforced with Nylon Fibers 总被引：2，自引：1，他引：1
A. R. Estabragh A. T. Bordbar A. A. Javadi 《Geotechnical and Geological Engineering》2011,29(5):899-908
Soft soils are well known for their low strength and high compressibility. Several techniques, including reinforcement, are
commonly used to increase the strength and decrease the deformation of this kind of soil. This paper presents the results
of an investigation into the effects of fiber on the consolidation and shear strength behavior of a clay soil reinforced with
nylon fibers. A series of one dimensional consolidation and triaxial tests were conducted on samples of unreinforced and reinforced
clay with different percentages of randomly distributed nylon fibers. The results show that the preconsolidation pressure
decreases and the coefficient of swelling and compression generally increase with increasing the fiber content. Furthermore,
the addition of the fiber leads to a significant increase in shear strength and friction angle of the natural soil. 相似文献
8.
位于四川省茂县岷江左岸的周场坪滑坡为一大型深层蠕滑型古滑坡,其曾于1982年发生大规模快速复活并堰塞岷江。根据现场地质调查和工程地质钻探资料分析,该滑坡目前正处于深层蠕滑变形中,且降雨对滑坡变形速率具有重要影响。滑坡滑动速率和含水率对滑带土的力学强度特性,以及滑坡的变形和进一步破坏具有极大影响,为研究含水率和滑坡滑动速率对周场坪滑坡滑带土力学强度的影响,本文在滑带土基本物性测试分析基础上,开展了不同含水率(8%、15%和25%)和不同剪切速率(0.1 mm·min-1、5 mm·min-1和100 mm·min-1)的滑带土环剪试验。试验结果表明:在长距离剪切条件下,滑带土的抗剪强度随着含水率的增加而降低,且高含水率条件下强度降低幅度更大;随着剪切速率的增加,试样应变软化现象更加明显,其峰值强度和残余强度一般先增大后减小;由峰值强度和残余强度线性拟合的强度参数内摩擦角随剪切速率的增加则先增大后减小。研究认为在强降雨条件下,高含水率的条件使滑带土抗剪强度显著降低,易导致周场坪滑坡蠕滑加速,加快的滑动速率会再次降低滑带土的抗剪强度,从而导致滑坡发生周期性蠕滑,并可能再次发生整体复活堵塞岷江。 相似文献
9.
This paper deals with the efficacy of creating artificial carbonate sand from crushed chalk to model the natural carbonate
sand. Direct drained shear using 100 mm shear box and compressibility tests using 150 mm Rowe cell have been performed on
artificial carbonate sand in order to determine the shear stress-strain and compressibility characteristics of the artificial
material. These are compared with data from natural carbonate sands given in the literature. The results obtained demonstrate
that shear stress-strain and compressibility characteristics of the artificial material closely mirror that of natural carbonate
soils. The artificial carbonate sand shows generally similar characteristics, which are in the range of the natural carbonate
material. 相似文献
10.
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
11.
Effect of Random Inclusion of Polypropylene Fibers on Strength Characteristics of Cohesive Soil 总被引：2，自引：1，他引：1
Pradip Kumar Pradhan Rabindra Kumar Kar Ashutosh Naik 《Geotechnical and Geological Engineering》2012,30(1):15-25
This paper presents the effect of random inclusion of polypropylene fibers on strength characteristics of soil. Locally available
cohesive soil (CL) is used as medium and polypropylene fibers with three aspect ratios (l/d = 75, 100 and 125) are used as reinforcement. Soil is compacted with standard Proctor’s maximum density with low percentage
of reinforcement (0–1% by weight of oven-dried soil). Direct shear tests, unconfined compression tests and CBR tests were
conducted on un-reinforced as well as reinforced soil to investigate the strength characteristics of fiber-reinforced soil.
The test results reveal that the inclusion of randomly distributed polypropylene fibers in soil increases peak and residual
shear strength, unconfined compressive strength and CBR value of soil. It is noticed that the optimum fiber content for achieving
maximum strength is 0.4–0.8% of the weight of oven-dried soil for fiber aspect ratio of 100. 相似文献
12.
The swelling pressure is a unique and important parameter for reflecting the engineering characteristics of expansive soil, providing a method to study the shear strength of expansive soil. The results of previous studies indicate that the shear strength of unsaturated soil is composed of three parts, and the swelling pressure contributes to the matric suction. Unsaturated direct shear tests and swelling tests of undisturbed expansive soils in the Yanji Basin were performed in this study, and the relationship between the swelling pressure and water content, as well as between the total cohesion and initial water content, were analyzed. According to a data regression analysis, a variety of fitting functions were used for comparisons and a linear relationship between the swelling pressure and the matric suction was established. The study indicate that the exponential fitting function, power function, and linear function should be used and compared with one another to find the best fit. This research is significant for the study of the relationship between shear strength and the swelling pressure of unsaturated soil. 相似文献
13.
Physicochemical behavior of tropical laterite soil stabilized with non-traditional additive 总被引：1，自引：0，他引：1
Non-traditional soil stabilizers are widely used for treating weak materials. These additives are cost- and time-effective alternatives to more traditional materials such as lime and cement. It has been well established that the treatment of natural soil with chemical additives will gradually affect the size, shape, and arrangement of soil particles. Furthermore, the degree of improvement is dependent on the quantity and the pattern of new products formed on and around the soil particles. In this paper, unconfined compressive strength (UCS) test was performed as an index of soil improvement on mix designs treated with calcium-based powder stabilizer (SH-85). The time-dependent changes in shear strength parameter and compressibility behavior of treated soil were also studied using standard direct shear and one-dimensional consolidation tests. In order to better understand the shape and surface area of treated particles, FESEM, N2-BET, and particle size distribution analysis were performed on soil-stabilizer matrix. From engineering standpoint, the UCS results showed that the degree of improvement for SH-85-stabilized laterite soil was roughly five times stronger than the untreated soil at the early stages of curing (7-day period). Also, a significant increase in the compressibility resistance of treated samples with curing time was observed. Based on the results, less porous and denser soil fabric was seen on the surface of clay particles. FESEM images of the treated mix designs showed the formation of white lumps in the soil fabric with the cementitious gel filling the pores in the soil structure. 相似文献
14.
以广州地区花岗岩残积粘性土为研究对象,通过击样法制备特定含水量试样,在不同压力下进行固结加、卸荷试验,对比分析试验数据,初步研究加、卸荷状态下花岗岩残积粘性土的抗剪强度变化,探寻先期固结压力、含水量与抗剪强度间规律。重塑残积土抗剪强度随含水量增加而减小;在先期固结压力相同的条件下,卸荷相对加荷试验条件下的土体强度显著减小,且减少值随残积土含水量的增加而逐渐减小,故在基坑开挖等卸荷工程项目中,应充分考虑卸荷对土体抗剪强度的影响,在卸荷工程中采用土体卸荷抗剪强度指标更符合工程实际。 相似文献
15.
We study the creep properties of clastic soil in residual state. The intact samples are taken from a reactivated slow-moving landslide in the Three Gorges Reservoir Region, China. Firstly, the patterns of the landslide movement are analysed based on recent monitoring data, which indicate that the soil within the shear zone is undergoing two deformation processes: a creep phase, characterised by different creep rates, and a dormant phase. We then study the creep behaviour of the soil samples through a series of ring shear creep tests under various shear stress conditions. The creep response depends strongly on the ratio of the shear stress to the residual strength, and the normal effective stress, whereas the creep rate decreases due to strength regain. The long-term strength of the clastic soil is close to the residual strength. Therefore, the residual strength obtained from conventional shear test, which is less time consuming than creep test, can be used in long-term stability analyses of creeping landslides. 相似文献
16.
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
17.
开展岩石模型结构面抗剪强度特征的多尺度（尤其大尺寸）直剪试验研究对于理解岩石结构面力学特性具有重要的理论价值和实践意义。首先,基于多尺度直剪试验仪(MSJ-DST),对20 cm×20 cm、40 cm×40 cm、60 cm×60 cm、80 cm×80 cm和100 cm×100 cm的岩石模型结构面试样采用法向应力分别为200～1 000 kPa进行直接剪切试验;然后,研究不同尺寸岩石模型结构面抗剪强度的特征。结果表明：不同法向荷载作用下模型的受力变形特点相近,峰值剪切位移总体上随着某一数值附近上下浮动;在同一法向应力作用下,不同尺寸结构面试样的峰值抗剪强度表现出在某一数值附近上下浮动的特征,残余抗剪强度则表现出随尺寸的增加有小幅度增加;5级法向应力作用下,不同尺寸的峰值抗剪强度和残余抗剪强度随着法向应力的变化规律均近似相同,抗剪强度残余值与峰值的比值随着法向应力的增大逐渐增大并趋于稳定。 相似文献
18.
冻融作用对海相软土压缩性及抗剪强度影响研究 总被引：1，自引：0，他引：1
为揭示原状海相软土冻融前后变形及强度差异性,对宁波原状海相软土及不同冻融条件下的融土进行了压缩实验和三轴固结不排水剪切实验。研究结果表明：单向冻结条件下,冻融作用使海相软土压缩性增强,且对试样不同部位处产生的影响程度不同,对靠近冷端的下部融土压缩性影响最大,中部其次,上部最小;冷端温度越低,冻融作用对融土压缩性影响越小,且逐渐趋于稳定;自然解冻比强制解冻对融土压缩性影响程度更大。冻融作用使融土黏聚力明显减小,内摩擦角略有增大;冷端温度越低,冻融作用对黏聚力和内摩擦角影响程度越大,在一定法向应力范围内,融土破坏强度越小。 相似文献
19.
Ahmad Safuan A. Rashid Nima Latifi Christopher L. Meehan Kalehiwot N. Manahiloh 《Geotechnical and Geological Engineering》2017,35(6):2613-2623
Many tropical residual laterites have relatively poor engineering properties due to the significant percentage of fine-grained soil particles that they contain, which are formed by the soil weathering process. The widespread presence of laterite soils in tropical regions often requires that some form of soil improvement be performed to allow for their use in various civil engineering applications, such as for road base or subbase construction. One of the most commonly utilized stabilization techniques for laterite soils is the application of additives that chemically react with the minerals that are present in soil to enhance its overall strength; effective soil stabilization can allow for the use of site-specific soils, and can consequently result in significant cost savings for a given project. With an increasing focus on the use of more environmentally friendly and sustainable materials in the built and natural environments, there is an emerging interest in eco-friendly additives that are an alternative to traditional chemical stabilizers. The current study examines the viability of xanthan gum as an environmentally friendly stabilizer that can improve the engineering properties of tropical residual laterite soil. Unconfined compressive strength (UCS) tests, standard direct shear tests, Brunauer, Emmett, and Teller (N2-BET) surface area analysis tests and field emission scanning electron microscopy (FESEM) tests were used to investigate the effectiveness of xanthan gum for stabilization of a tropical laterite soil. The UCS test results showed that addition of 1.5% xanthan gum by weight yielded optimum stabilization, increasing the unconfined compressive strength of the laterite soil noticeably. Similarly, direct shear testing of 1.5% xanthan gum stabilized laterite specimens showed increasing Mohr–Coulomb shear strength parameters with increases in curing time. From the FESEM results, it was observed that the stabilization process modified the pore-network morphology of the laterite soil, while also forming new white layers on the surface of the clay particles. Analysis of the test results indicated that xanthan gum stabilization was effective for use on a tropical residual laterite soil, providing an eco-friendly and sustainable alternative to traditional soil stabilization additives such as cement or lime. 相似文献
20.
Deformation and strength characteristics of the soil of Sana'a, the Yemen Arab Republic, were investigated. Undisturbed soil samples were collected fro used in consolidation, collapse and strength tests. The classical and critical state compressibility parameters were determined using a one-dimensional collapsing potential of the investigated soil was determined by using both qualitative and quantitative analysis. Consolidated undrained triaxial tests different types of samples: saturated samples and samples at natural moisture content. The stress history of the fine soils are in the range of normal except for the stiff fissured lean clay which exhibited a relatively high overconsolidated stress history. The loess formations exhibited a moderate to under wetting and loading. The investigated soils are characterized by having high shear strength when they have low moisture content and a drastic dec content increases. 相似文献