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1.
Satyendra Mittal 《Geotechnical and Geological Engineering》2006,24(3):675-688
A study has been done for soil nailed cut considering circular type wedge failure by friction circle method. Effect of variation
of design parameters such as nail length, nail diameter, nail inclination, wall inclination, angle of internal friction of
soil, etc. have been incorporated in the study to determine the factor of safety of nailed open cuts. It is seen that at sites
which are susceptible to rainfall induced erosion, the erosion may be checked to a greater degree by soil nailing. This methodology
can be adopted at embankment sites, natural slopes, highways, etc. including free board of riverbank area of natural rivers.
The study shows that grouted nails perform better than driven nails. A case study further confirms the analytical findings. 相似文献
2.
This paper presents the laboratory test results of nailed soil slopes to study the behaviour of reinforced slopes under surcharge load. Tests were conducted on nailed soil slopes of three different slope angles (β = 30°, 45°and 60°) and nail inclinations (i = 0°, 15° and 30°). Each slope is reinforced with a number of hollow aluminium nails placed in three rows. The failure response, load-settlement, nail forces at the centre of nails and the distribution of nail forces along the length are examined during the tests. The numerical simulation of the model tests is performed by a 3-D finite element program. The numerical results are found in agreement to the corresponding experimental results. It is observed that the nails inclined at 0° to the horizontal give the maximum improvement in the load carrying capacity of the slopes followed closely by the 15° nail inclination. The maximum nail forces are observed in the topmost row of nails and decreases with the depth. The distribution of the nail forces along the nail are also found to be varying with respect to the failure surface of the slopes. 相似文献
3.
This paper presents reliability analyses of soil nail walls against two external ultimate limit states, global and sliding stabilities, which are related to the external stability failures of soil nail walls. Reliability analyses are conducted using Monte Carlo simulation technique. Soil nailing is a popular retaining system in highway construction and slope stabilization, and its current design practice is still based on the working stress design. There remains a need to establish a more rational design framework—load and resistance factor design—based on the concept of limit state design and reliability analysis for soil nail walls. The development of load and resistance factor design approach must consider multiple ultimate limit states, associated with external, internal, and facing failures. The analyses of resistance factors against two external failures are conducted in this study considering various influencing factors, including statistical parameters of soil friction angle, ultimate bond strength between soil and nails, soil type, wall geometry (wall height, back slope angle, and face batter angle), and nail configurations (nail inclination angle, drillhole diameter, and nail spacing). In the end, a series of resistance factors are proposed for potential application of load and resistance factor design approach against external failures for soil nail walls according to different design codes. 相似文献
4.
Pressure-grouted soil nails have been increasingly used for stabilizing slopes. The pullout resistance of a soil nail is the main factor for reinforcing the slope stability. In this study, a two-dimensional axisymmetric finite element model is developed to simulate the pullout behavior of a pressure-grouted soil nail. This model is verified with field pullout tests result of a pressure-grouted soil nails by comparing with gravity-grouted soil nails. Based on the analysis, a three-dimensional finite element model is proposed for stability analysis of a slope reinforced with pressure-grouted soil nails using the shear strength reduction method. A series of numerical slope stability analyses for a slope composed of weathered soil are performed to investigate the effects of grouting pressure on the slope stability and the behavior of the soil nails. Special attention is given to the installation effect of a pressure-grouted soil nails. It is found from the result of this study that the pressure-grouted soil nails increase the safety factor by fifty percent in a slope by increasing the stiffness of the nailed slope system. Numerical analysis results confirm the fact that the pullout resistance of a soil nail is the main factor for stabilizing slopes rather than the shear resistance of the soil nail. 相似文献
5.
Gosavi Meenal Swami Saran Satyendra Mittal 《Geotechnical and Geological Engineering》2009,27(4):571-583
In this paper, a pseudo-static analysis has been presented to investigate the stability of soil nailed vertical/nearly vertical
excavations. The failure surface is assumed as the arc of log-spiral passing through the toe of the excavation and intersecting
the ground at right angle. The horizontal and vertical seismic forces are taken in terms of horizontal and vertical seismic
coefficients. The internal failure mode of the nailed cut is considered either by pull-out or rupture or excessive bending
whichever is critical. Expression for the factor of safety is derived using moment equilibrium method. Results have been arranged
in tabular form considering ranges of the design parameters usually occur in practice. A typical table for the design of nailed
excavation with driven nails is presented in the paper. Analytical results have been compared with the findings of model tests
and reasonably good agreement has been observed. 相似文献
6.
A plane–strain numerical model has been developed to mimic a nailed loose fill slope under surcharge loading. The model has been used to back-analyse a field test that was conducted to examine the behaviour of soil nails in loose fill slopes under surcharge loading. Incremental elasto-plastic analyses coupled with pore water diffusion have been performed to study the internal deformation, water content redistribution in the soil, and the performance of the soil nails during and after the application of surcharge loading. The model parameters describing the mechanical and hydraulic properties of the nailed slope were obtained from field or laboratory tests. Different modelling techniques and boundary conditions for mimicking soil–nail interaction in loose fill material have been examined. Comparisons between numerical predictions and field measurements demonstrate that a new interfacial model, denoted as the embedded bond–slip interface model, is more suitable for mimicking the interfacial behaviour. Despite the simplicity of the numerical model, the predicted responses are in close agreement with the field test results, in particular the mobilisation and distribution of nail forces in response to surcharge loading. Both the numerical and the field test results suggest that soil nails are capable of increasing the overall stability of a loose fill slope for the loading conditions considered in this study. The increase in confining stress along the soil nails near the surcharge area is central to the overall stabilising mechanism. On the contrary, the nail forces mobilised near the nail heads are much smaller, indicating that the beneficial effect of having a structural grillage system at the slope face is limited for the range of surcharge pressures considered in this study. 相似文献
7.
In India, soil nail walls are being extensively used for supporting vertical excavations below ground level to accommodate construction of one-or two-storied basements. Generally, the depth of excavations for basement construction ranges from 10 m to 15 m. For such large depth of excavation, variability of in-situ soil properties has significant influence on the stability of the soil nail walls. In the present study, using reliability analysis, an attempt is made to study the influence of variability of in-situ soil properties on the stability of soil nail walls. For better understanding, a case of 10 m high soil nail wall constructed to support a vertical cut is considered for the study and its stability is evaluated for various failure modes. Additionally, the influence of correlation among soil parameters on soil nail wall stability is assessed. In-situ soil friction angle and correlation between in-situ soil cohesion and angle of friction are found to influence soil nail wall stability significantly. In general, reliability analysis provided a better insight into the assessment of stability of soil nail wall. 相似文献
8.
基于极限分析上限定理,采用拟动力法研究了地震效应下非均质土坡的三维稳定性,并通过重度加大法（GIM）推导出边坡安全系数的显式表达式。此外,采用遗传算法进行优化,将所得结果进行对比验证,详细分析了地震条件下相关参数对边坡稳定性的影响。分析结果表明：边坡高度一定时,宽高比、边坡倾角的增大以及土体内摩擦角、非均质系数的减小均会造成安全系数的降低;拟静力法获得的结果相比于拟动力法较大,两种方法结果的差值会随着水平地震系数、有效内摩擦角的增大而增大,随着边坡倾角的增大而减小;土体放大系数的增大会导致安全系数减小,而地震波周期及波速的变化几乎对安全系数没有影响;滑动面轨迹受水平地震系数的影响较大,而受非均质系数的影响相对较小。 相似文献
9.
A detailed study of nailed slopes under different conditions is reported in this paper. No major difference is found in terms of safety and slip surfaces between the strength reduction method (SRM) and the limit equilibrium method (LEM) in general cases. Appreciable differences between the SRM and LEM appear, however, if the nail load is controlled by the overburden stress. Some special slip surfaces from the SRM obtained by using a very fine mesh are discussed. Field tests demonstrated that the nail head is important in determining the failure mode and the factor of safety of a nailed slope, while the effect of the nail elastic modulus is more noticeable only when the slope is very steep. The optimum layout of the soil nail was found to be longer at bottom and shorter at the top, which is contrary to some engineers’ guidelines for soil nail design during top-down construction. The distribution of tensional force along the soil nail is influenced by the state of the slope (service state, limit state) and the failure modes (external failure, internal failure). In general, the line of maximum tension may not correspond to the critical slip surface as commonly believed, except for the case where the failure mode is an internal tensile failure. 相似文献
10.
11.
二维与三维边坡稳定性分析得到的安全系数存在着差异,讨论这种差异与滑体几何尺寸及土体强度参数间的变化规律及其形成机制,可为合理地评价边坡稳定性分析提供理论依据。针对均质三维边坡,利用基于滑面正应力修正模式的极限平衡法分析程序,定性地讨论滑体形态、长高比、坡比、土体强度参数等指标对二维与三维安全系数计算结果差异(以F3/F2表示)的影响,总结F3/F2与影响指标间的变化规律,分析变化规律形成的内在机制。从工程应用的角度,给出需要考虑该差异影响的分界标准。研究表明,F3/F2随着长高比L/H、内摩擦角?及坡比m的增大逐渐减小,随着黏聚力c的增大逐渐增大;对于满足下列条件之一的边坡,宜采用三维安全系数来评价其稳定性,(1) L/H ≤ 5的滑坡体;(2) 5< L/H ≤ 10且 c > 25 kPa(或? < 15°,或m < 1.0) 的滑坡体。研究成果可为合理评价边坡稳定性分析方法提供参考。 相似文献
12.
An analytical method has been proposed to predict the ultimate uplift capacity of single vertical piles embedded in sand considering
arching effect. The present analysis takes into consideration of various pile and soil parameters such as length (L), diameter (d) of the pile, angle of internal friction of soil (ϕ), soil pile friction angle (δ) and unit weight of soil (γ). A modified value of coefficient of lateral earth pressure in uplift has been developed considering the arching effect of
soil. A comparative assessment of the uplift capacity of piles predicted by using proposed theory and the existing available
theories is made with the existing field and model test results. It has been observed that the present model considering the
arching effect predicts the results closer. 相似文献
13.
考虑土拱效应的倾斜滑移面间竖向应力研究 总被引：1，自引：0，他引：1
假定两滑移面相互平行,且与水平面呈一定角度?,对滑移面间土体沿竖向取水平薄层作为微分单元体,通过作用在单元体上的水平力和竖向力的平衡条件,基于土体主应力轴旋转理论,得到考虑土拱效应及倾斜角度的倾斜滑移面间竖向应力的理论公式,及对应不同倾斜角度及滑移面-土摩擦角的土侧压力系数。将得到的理论公式与Handy等公式进行比较,验证了该公式的合理性。研究结果表明：对于无黏性土,竖向应力沿深度先近似线性增大,后增加缓慢并逐渐趋于定值。竖向应力随着倾斜角度和滑移面间距的增大而增大,随滑移面-土摩擦角的增大而减小;土侧压力系数随着滑移面-土摩擦角的增大而增大,而随内摩擦角的增大而减小。 相似文献
14.
The seismic stability of reinforced earth has been investigated in this paper using pseudo-static method of analysis considering horizontal and vertical seismic acceleration with non-linear failure surface. The sliding wedge is divided into a number of horizontal slices to determine the strength and length of the geo-synthetic reinforcement for seismic internal stability of battered face rigid retaining wall supporting c-Φ backfill. Results are presented in graphical form representing the required length of geo-sythetic reinforcement under seismic condition to maintain the internal stability of reinforced soil. The influences of horizontal and vertical seismic acceleration, soil friction angle, cohesion, adhesion and wall inclination angle on the required length of the geo-sythetic reinforcement have been studied. From the present study it is seen that the required length of geo-synthetic reinforcement increases due to increase in the value of seismic accelerations. 相似文献
15.
关于基坑设计计算中若干问题的榷商 总被引：1，自引：0，他引：1
结合近年来笔者在审核基坑设计时遇到的计算上存在的问题,就土锚和土钉(墙)的概念异同点、设计计算的异同点作了分析,对土钉(墙)的设计深度、土锚锚固段或土钉被动粘结段摩阻力的长度衰减问题提出了初步的想法.对采用m法计算桩内力和桩顶位移时m值取值的限制条件及桩顶位移的计算作了梳理,并提出在基坑设计中慎用m法的主张. 相似文献
16.
土钉支护是边坡治理、基坑开挖的一种经济、便捷的支护型式,在设计中一般只考虑土钉轴向受力,而忽略土钉的抗剪、抗弯效应。为了探究工程实践中土钉支护黏土质边坡的横向抗剪效应边坡稳定性的贡献,本文根据极限平衡法,推导了考虑土钉横向抗剪效应的边坡稳定性计算公式,并系统研究了该作用对边坡安全系数大小以及潜在滑移面位置所产生的影响规律。研究结果显示,土钉抗剪效应对提高边坡稳定性有着很大的影响。当抗剪效应因子从0增大0.3时,边坡安全系数随着土钉倾角有着先增大后减小的规律,土钉的最优倾角也相应增大。在土钉长度和倾角不变的情况下,考虑土钉抗剪效应使得边坡的安全系数计算值有所提高,同时推测出的边坡滑移面后移。在抗剪效应因子从0增至0.5的过程中,安全系数可以提高两到三成。本研究的结论为在工程中更合理应用土钉支护技术提供了参考依据。 相似文献
17.
A model test was conducted for a newly developed soil nail, the result of which was compared to that of a 3D finite element method (FEM) simulation. The shape angle (β) and friction coefficients (μ) contributed to the difference in pull-out force between the model test and the simulation. Further verifications were conducted, during which the pull-out mechanisms of the soil nail for different β and μ were analysed. It was found that both β and μ have a positive influence on the pull-out force; β only affects the increase rate, while μ influences the overall pull-out force level. Three components were found to govern the pull-out force, with the component applied to the expanded cement bulk surface accounting for approximately 80% of the total. This study proves that the optimal approach for increasing pull-out force is to enlarge the diameter of the cement bulk rather than extend the nail length. 相似文献
18.
Soil nailing is the most popular technique for stabilizing newly formed and existing sub-standard slopes in Hong Kong because of its economic and technical advantages. The nail–soil interface shear resistance is an important parameter in design of soil nailed structures. A three-dimensional finite element model was established and used for simulating soil nail pull-out tests. The finite element model was verified by comparing simulated results with measured data. The agreement between the experimental and simulated results in terms of both average pull-out shear stress and stress variation was very good. Using this finite element model, a parametric study was carried out to study the influences of the overburden pressure and soil dilation angle on the soil nail pull-out resistance. The simulated peak pull-out resistance was not directly related to the overburden pressure, which was coincident with the observations in laboratory pull-out tests. The simulated pull-out resistance increased significantly with the increase in dilation angle of the shearing zone. This analysis indicated that the constrained dilatancy of the nail–soil interface and the soil surrounding the nail contributed a lot to the development of peak pull-out resistance. 相似文献
19.
A nailed soil wall curved in plan was modelled in three-dimensions by the finite element method for construction, service and ultimate loading conditions. The behaviour of the nailed soil wall, the soil–nail interaction, the role of the reinforcement, and the overall and internal failure mechanisms were investigated. © 1997 by John Wiley & Sons, Ltd. 相似文献