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1.
Asha M. Nair 《Geomechanics and Geoengineering》2016,11(2):95-103
This paper presents the experimental results from laboratory repeated plate load tests on unreinforced and reinforced model sections of unpaved road constructed in a steel test tank. Different types of geosynthetics, namely, geotextile, two types of biaxial geogrids and geocells were used to reinforce the road sections in different tests. The effect of type and form of reinforcement on the stress-strain hysteresis of unpaved road sections is discussed in the light of experimental results. Model tests were also conducted with varying heights and positions of geocell layer to study the effect of these parameters on deformations and surface profiles. It was observed that at higher settlements, the reinforced systems developed less permanent settlements and more elastic settlements compared to unreinforced systems. Increasing the height of the geocell layer resulted in improved performance up to a certain height, beyond which, further increase in the height reduced the load resistance because of the inadequate granular overlay thickness. 相似文献
2.
The study presented in this paper aimed to investigate the flexural behavior of geocell reinforcement by means of three-layered beam model testing. The geocell reinforcement was assumed to be a continuous beam sandwiched between two identical polywood beams. An analytical analysis was conducted to derive the closed-form solution to calculate the deflection of the three-layered beam model. A series of four-point bending tests using dead weights were carried out to test the three-layered beam models. Two geocell products of different dimensions and two types of infill materials, crushed stone and silty sand were tested in this study. Deflections of the layered beam models were measured along with the increment of applied loads. Testing results showed that the geocell reinforcement provides considerable resistance to flexural deformation, especially at higher load levels. The geocell with greater cell height to cell length ratio exhibited overall greater resistance to flexural deflection, especially when crushed stone was used as infill materials. Geocell reinforcements filled by crushed stone showed less flexural deformation than the geocells filled by silty sand. The modulus of the geocell reinforcement was calculated based on the closed-form solution and deflection measurements from the four-point bending tests. Ranges of elastic modulus were presented for the geocell reinforcement filled with compacted crushed stone and silty sand, which can be used as reference values for material property inputs in mechanistic-empirical design of geocell-reinforced pavements. 相似文献
3.
Piles are frequently used to transfer the heavy compressive loads to strong soil layers located in the depth of bed. In addition, such piles may be subjected to combination of repeated compressive and tensile loads due to earthquake, wind, etc. This paper describes a series of laboratory model tests, at unit gravity, performed on belled pile, embedded in unreinforced and geocell-reinforced beds. The tests were performed to evaluate the beneficial effect of geocell in decreasing the downward and upward displacements and performance improvement of the uplift response of belled pile under repeated compressive and tensile loads. Pile displacements due to fifty load repetitions were recorded. The influence of the height of geocell above the bell of pile, an additional geocell layer at the base of belled pile, and the number of load cycles on pile displacements were investigated. The test results show that the geocell reinforcement reduces the magnitude of the final upward displacement. It also acts as a displacement retardant, and changes the behaviour of belled pile from unstable response condition due to excessive upward pile displacement in unreinforced bed to approximately steady response condition. Therefore, the geocell reinforcement permits higher tensile loads or increased cycling. The efficiency of reinforcement in reducing the maximum upward displacement of the pile (i.e. pull-out resistance) was increased by increasing the height of geocell above the bell of the pile. Furthermore, the comparison showed that a specific improvement in upward and downward displacement and the stability against uplift can be achieved using an additional geocell layer at the base. The geocell reinforcement may reduce the required length of pile shaft, consequently reducing required excavation, backfill, and pile’s material. Simple dimensional analysis showed the need for an increased stiffness of the geosynthetic components in order to match prototype-scale performance similitude. 相似文献
4.
基于弹性地基梁理论的土工格室加筋体变形分析 总被引：4，自引：1，他引：3
在土工格室处理软土路基加固机制研究的基础上,针对土工格室加筋体的受力变形特点,将格室体视为置放于Winkler地基上的连续长梁,基于传统的弹性地基梁理论,建立考虑水平摩阻力影响的土工格室加筋体的挠曲变形微分方程,并给出其幂级数解答,从而得到了土工格室加筋体在集中荷载作用下的变形计算方法,为土工格室加固处理后的软土路基沉降计算提供了依据。理论与试验结果对比分析表明,在格室体变形分析中不计水平摩阻力的影响将夸大格室体在荷载作用下的竖向变形,计入水平摩阻力影响后理论与实测曲线吻合更好。 相似文献
5.
Sitharam G. Thallak Sireesh Saride Sujit Kumar Dash 《Geotechnical and Geological Engineering》2007,25(5):509-524
This paper presents the results of laboratory model tests carried out to develop an understanding of the behaviour of geocell-reinforced
soft clay foundations under circular loading. Natural silty clay was used in this study. The geocells were prepared using
biaxial polymer grid. The performance of the reinforced bed is quantified using non-dimensional factors i.e., Bearing capacity
improvement factor (If) and Percentage reduction in footing settlement (PRS). The test results demonstrate that the geocell mattress redistributes
the footing load over a wider area thereby improving the performance of the footing. The load carrying capacity of the clay
bed is increased by a factor of up to about 4.5 times that of unreinforced bed. From the pressure-settlement responses, it
is observed that the geocell-reinforced foundation bed behaves as a much stiffer system compared to the unreinforced case
indicating that a substantial reduction in footing settlement can be achieved by providing geocell reinforcement in the soft
clay bed. The maximum reduction in footing settlement obtained with the provision of geocell mattress of optimum size placed
close to the footing is around 90%. Further improvement in performance is obtained with provision of an additional planar
geogrid layer at the base of the geocell mattress. 相似文献
6.
为探究土工格室加筋路堤在循环荷载及静载下的各种性能,利用美国GCTS公司的USTX-2000加载装置进行加载,通过改变加筋层数、格室高度,格室焊距对土工格室加筋路堤进行一系列模型试验。对各种工况下加筋路堤极限承载力、长期循环荷载及固定振次循环荷载后极限承载力的变化进行研究。试验表明,土工格室加筋能显著提高地基极限承载力并能显著减小坡顶和坡中临界破坏时的法向累积变形,在加筋间距一定的情况下,加筋层数增加和格室高度增大均可不同程度提高极限承载力并减小临界破坏时坡顶法向累积变形,格室焊距的减小也可在一定程度提高极限承载力,格室焊距对边坡法向变形影响不大;长期循环荷载下固定间距加筋层数对路堤竖向累积沉降量影响不大,而对边坡坡顶法向累积变形有一定影响,格室高度增大和格室焊距减小均可不同程度减小路堤竖向累积沉降量和坡面法向累积变形;越靠近加载点处,路堤土压力值受加筋影响越显著,加筋提高了土体刚度和密实度,使加筋路堤土压力值较无筋路堤明显增大;对于无筋路堤,改变动载幅值和振次均导致振后极限承载力有不同程度的降低,而对于加筋路堤,当动载幅值≥30 kPa或动载振次≥1 000时,振后极限承载力均有不同程度的提高。 相似文献
7.
目前对土工格室加筋路堤研究主要集中在静载条件下,动载条件下研究的比较少。为研究分级循环荷载下土工格室加筋路堤的力学性能,采用USTX-2000的动力加载装置进行加载,对土工格室加筋路堤在不同加筋层数、格室高度、格室焊距等工况下进行一系列模型试验。对分级循环荷载下路堤的竖向变形和坡面法向变形进行研究,并与固定振幅循环荷载及静载作用下的路堤进行对比分析,研究不同加载方案路堤力学性能的差异性。试验结果表明,土工格室加筋能显著提高路堤承受分级循环荷载的能力和减小竖向累积沉降量,在加筋间距一定的情况下,两层及以上加筋效果比单层加筋效果更显著,格室高度增大和格室焊距减小均可不同程度提高路堤承受分级循环荷载能力并减小竖向累积沉降量;加筋可减小路堤分级循环荷载下的坡面法向变形,格室高度增大和格室焊距减小在分级循环荷载幅值相同时均能减小坡顶和坡中处的法向累积变形;分级循环荷载作用下,当振次≥8 000或幅值≥80 kPa时,路堤竖向累积沉降量超过固定振幅循环荷载,当振次≥9 000或振幅≥90 kPa时,路堤坡顶法向累积变形超过固定振幅循环荷载;分级循环荷载作用下,路堤竖向和坡面法向累积变形均大于静载,加筋可有效减小分级循环荷载和静载作用下坡面法向累积变形差。 相似文献
8.
土工格室能有效减少软土地基上路堤的变形,并增强其稳定性,但对于土工格室加筋土垫层路堤的临界高度还少有研究。采用极限平衡分析方法,假定地基在路堤荷载作用下呈圆弧滑动破坏模式,将格室及其内的填土视为复合体,考虑格室复合体的应力扩散作用和侧向限制作用,提出了路堤临界高度的计算模型,并将该模型值与建立的有限差分模型结果进行对比,然后讨论了格室高度、应力扩散角及格室复合体与地基接触面摩擦系数对路堤临界高度的影响规律。结果表明,理论分析和数值计算结果吻合较好;加筋路堤的临界高度明显大于未加筋路堤的临界高度,并且增加此3种影响因素的取值均能提高路堤的临界高度;同时增强格室的侧向限制作用比提高格室高度和应力扩散角更有利于路堤的稳定。 相似文献
9.
The use of geosynthetics as a ground improvement technique offers the advantages such as space saving, environmental sensitivity, material availability, technical superiority, higher cost savings and less construction time. Coir geotextiles can be considered as an efficient replacement to its synthetic counterparts due to its economy and excellent engineering properties. The present study aims at exploring the possibilities of utilising coir geocells as a potential reinforcement material for shallow foundations and thereby increasing the load carrying capacity of soil. Geocells were fabricated from coir geotextiles with the aim of providing an additional confinement to the soil. An enumerated parametric study was conducted by varying the relative density, depth of the first layer, width and height of coir geocell. The surface displacement profiles of the non-reinforced and coir geocell-reinforced soil indicate that the footing rotation and heave are considerably reduced with the provision of geocell. The results of the relative density study indicate that bearing capacity characteristics increase with denseness of the soil sample. It was also observed that geocell arrangement and configuration play a pivotal role in the performance characteristics of reinforced soil. 相似文献
10.
《Geomechanics and Geoengineering》2013,8(3):207-216
The effect of a base geogrid layer below the geocell mattress in sand, sand overlying soft clay, and soft clay foundation beds has been studied using a series of laboratory scale load tests. A rigid circular model footing was used to apply static monotonic loading on the foundation beds with and without geocell reinforcement. The model test results show that the provision of an additional layer of planar geogrid at the base of the geocell mattress further increases the performance of the footing in terms of bearing capacity and reduction in surface heave of the foundation bed. It is also observed that the beneficial effect of the base geogrid layer becomes negligible with increasing height of the geocell mattress beyond the influence of the depth of the footing. Strain measurements in the base geogrid layer indicate that it is more effective with the limited heights of the geocell mattress. The earth pressure cells embedded in the subgrade soil provide evidence that when the base geogrid is provided below the geocell mattress, the footing pressure is distributed more uniformly over an extended area. 相似文献
11.
Geocell reinforcement has been increasingly applied to embankment engineerings. Deformation calculation is one of the major concerns during the design process. Using Winkler foundation model and with consideration of the interface resistance effect, a deformation control differential equation for the geocell reinforced mattress under the vertical symmetric loads is presented in this paper. The corresponding power-series semi analytic solutions for the displacements and the internal forces of geocell reinforcement are also presented. Furthermore, the influence factors such as loads, length and flexural rigidity of geocell reinforcement, coefficient of subgrade reaction and the interface resistance on the stress-deformation characteristic of geocell reinforcement are discussed. Finally, two examples are employed to verify the presented method. This study suggests that the effect of the interface resistance on the deformation of geocell reinforcement should be considered in engineering design. 相似文献
12.
Geocell reinforcement has been increasingly applied to road embankment engineering. Deformation calculation is one of the major concerns during the design process. In this paper, the power-series method was employed to investigate the performance of a geocell-reinforced mattress under symmetric loads. The geocell-reinforced mattress was idealized as a beam on a Winkler foundation. In the analysis, the soil–foundation beam interface resistance, related to the horizontal deformation coupling with the vertical deformation, was considered. Semi-analytic solutions were developed to assess the deformations and internal forces of the foundation beam and verified against an existing finite element method [9]. The results of the proposed method were close to the results from the finite element method. Moreover, the effects of various factors, such as height of embankment, horizontal and vertical foundation coefficients, composite elastic modulus and height of geocell-reinforced mattress, on the foundation beam settlement and the tension force within the beam are discussed. It was found that the interface resistance related to the horizontal deformation of the beam has a reduction effect on the embankment settlement, and it is beneficial to reduce the embankment settlement by increasing the beam rigidity and strengthening the subgrade soil body. 相似文献
13.
Vibhoosha M. P. Bhasi Anjana Nayak Sitaram 《Geotechnical and Geological Engineering》2021,39(6):4035-4057
For improving the stability and load carrying capacity of weak subgrade, strengthening methods are to be followed in the field. Among the various approaches, geocells have been identified as an effective soil reinforcement technique for improving soft subgrade behaviour. The three-dimensional honeycomb structure of geocell offers more lateral confinement to the infill soil resulting in improved load carrying capacity. This led to the widespread use of geocells for different geotechnical applications like pavements, foundations, embankments, slope protection, erosion control etc. Many researchers in the past have confirmed the suitability of geocell reinforcement through their experimental, numerical and field studies. In this paper, a comprehensive review of the reinforcement mechanisms, design aspect and numerical modelling techniques of geocell reinforced soil is provided. In addition, this paper highlights the various field application scenarios where different types of geocells have been used and explores the research challenges and scope for further research in this field.
相似文献14.
为探究荷载作用下软土地基直接拼接拓宽路堤受力和变形特征,利用自行设计制造的模型试验系统,通过改变软土地基差异沉降、土工格栅加铺层数对软土地基高速公路直接拼接路堤进行一系列模型试验,研究各种工况下旧路与新拓宽路堤土中应力变化。试验结果表明,拓宽路堤在荷载作用下新旧路各断面土中竖向应力随着荷载的增大而增大,受路堤填土边坡与下伏地基侧向约束条件的影响,荷载作用下土中竖向应力在填土路堤与地基内沿深度方向呈现先减小、后增大、再减小的分布特征;软土地基拓宽路堤差异沉降对新旧路结合部位土中竖向应力影响较大,土中竖向应力随着差异沉降增大而增大;旧路范围内土中竖向应力受差异沉降的影响不大;在拓宽路堤填土的顶部和底部各布设一层土工格栅加筋层时可明显减小路堤土中竖向应力和路堤沉降：相同荷载作用下对比无加筋路堤,铺设2层土工格栅加筋路堤的顶面沉降最大可以减少62%,土工格栅加筋对软土地基拓宽路堤沉降有较好的控制作用。 相似文献
15.
Equivalent Continuum Simulations of Geocell Reinforced Sand Beds Supporting Strip Footings 总被引：1，自引：0，他引：1
G. Madhavi Latha Sujit Kumar Dash K. Rajagopal 《Geotechnical and Geological Engineering》2008,26(4):387-398
This paper presents an equivalent continuum method for simulating the behaviour of geocell reinforced sand foundation beds,
using finite element technique. An equivalent composite model is used for numerically simulating the improvement in the strength
and stiffness of sand confined with geocells. Shear strength of geocell encased sand is derived from the additional confining
pressure due to geocell using hoop tension theory. The stiffness of geocell encased sand is represented by an empirical equation
in terms of the stiffness of the unreinforced sand and the tensile modulus of the geocell material. Numerical simulations
of strip footings resting on sand bed are carried out with and without geocell layer, varying parameters like, the dimensions
of geocell layer, pocket size, depth of placement of geocell layer and the tensile modulus of the geocell material. The results
of numerical analyses are validated with the corresponding experimental results. The comparison between the numerical results
and the experimental results is found to be reasonably good. Some significant observations on the mechanism of geocell reinforcement
have been presented in this paper. 相似文献
16.
Zhaoling Zhang Shiliang Liu Shikui Dong Wei Fu Baoshan Cui 《Frontiers of Earth Science》2009,3(4):389-396
The construction of roads has direct and indirect impacts on soil erosion, with spatio-temporal variations existing among
different levels of road zones. Aiming to quantitatively analyze the soil loss, this paper explored the relationship between
the erosion of soil and its distance from the road in Fengqing county, Southwest China in 1987 and 2004, respectively. The
average soil erosion was calculated and expressed with grid map using universal soil loss equation (USLE) model based on GIS
and RS. Along the different levels of roads classified as trunk, county, town, village and unpaved road, the buffer zones
were subdivided into five stripes, each of which was 200 meters wide. The average soil erosion modulus of each buffer zone
was also counted. Results show that the soil loss decreases with increasing distance to the road except rare trunk roads in
the region. In addition, the declined intensity varies with the different levels of roads. Soil erosion was more serious along
the lower level road than the higher ones. And soil erosion was more severe for all levels of roads in 1987 than those in
2004 because much more rainfalls affected the situation of soil erosion in 1987. 相似文献
17.
Morched Zeghal 《Geotechnical and Geological Engineering》2009,27(4):549-558
This paper presents the results of a study of grain crushing in road construction and its effect on road behaviour. Sieve
analyses of field samples confirmed that grain crushing occurs during compaction of the base layer despite the good quality
of aggregates used. Laboratory testing indicated that grain crushing reduces the resilient modulus of the aggregate material
by half and increases the permanent deformations by onefold to threefold depending on the state of density and stresses considered.
Road design and analyses undertaken to delineate the effect of grain crushing on performance showed that particle breakage
yields a significant increase in rutting and longitudinal and alligator cracking of roads. 相似文献
18.
Najaf-sea quarry is located in Najaf city about 160 km south west of Baghdad the capital of Iraq. It is the main source that supplies track ballast for maintenance of existing railway network and construction of new railway lines in the middle and southern parts of Iraq. Track ballast experience a complex combination of stresses during its service lifetime, primarily from repeated axial loads of the trains in addition to stresses generated from the environmental conditions. The ideal evaluation of suitability of track ballast must be carried out under real field loading conditions, however such field tests are usually costly and time consuming. On the other hand laboratory model tests simulating field loads under limited boundary conditions can provide satisfactory indication about the suitability of the material. The present paper investigates the deformation characteristics of Najaf-sea track ballast, under repeated loading using model tests simulating ballast conditions under a selected track section. A test setup was designed and manufactured capable of applying both monotonic as well as repeated loading on the track section under different conditions. The repeated model tests which simulate as close as possible the field conditions shed the light on the generated settlement, modulus of deformation and degradation of the ballast particles under different repeated loading levels. Statistical analysis in terms of breakage index and repeated applied load revealed satisfactory correlations that help in understanding the overall performance of the ballast material. The results also demonstrate that 4–5 tamping are capable of controlling both the settlement and modulus of deformation of the ballast material. 相似文献
19.
《Geoforum》2015
South Gobi province is at the center of Mongolia’s mining boom, where companies began exporting minerals over dirt-track roads in the early 2000s. This paper examines recent controversies surrounding road dust near the Oyu Tolgoi copper–gold mine, the so-called coal road from Tavan Tolgoi mines, and the Chinese border. At the time of the research, local residents, particularly nomadic herders, were concerned that dust produced from unpaved mining roads was coating the pasture, causing illnesses among livestock, and endangering their livelihoods in the region. The presence of dust rendered mining an uncomfortably intimate experience as state and corporate actors negotiated responsibility for infrastructure development. The paper builds on the concept “technologies of distantiation” to reveal the complex ways that dust from unpaved roads creates distances and disconnections between people, livelihoods, and landscapes, representing an enclosure of the pasture. Methods for the paper include interviews, focus groups, and participant observation conducted in South Gobi province and Ulaanbaatar in 2010, 2011, and 2012 as well as follow-up research carried out in spring 2015. 相似文献
20.
This article presents the development of a J2 small strain plasticity model based on bounding surface concept, along with numerical examples to demonstrate model behaviors and identification of model parameter using laboratory test data. The model is motivated by the need for simulating permanent deformation accumulation of asphalt concrete mixtures, which leads to rutting in flexible pavements under repeated traffic loading. The proposed model accounts for the observation that rutting is mostly caused by shearing and takes advantage of the fact that bounding surface concept allows for the progressive accumulation of plastic deformation under constant amplitude loading condition. Analytical solutions are given for typical laboratory testing conditions. The model can be calibrated using repeated simple shear test data that are typically available for asphalt concrete mixtures. It is shown that the model is easy to use and provides a promising alternative for modeling permanent deformation accumulation in materials subjected to repetitive (cyclic) loading. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献