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1.
土钉支护施工阶段土钉轴力的计算分析 总被引：2，自引：0，他引：2
土钉支护的形成过程对其受力和变形有直接影响。结合土钉支护边开挖、边支护且开挖在前的施工特点,定义开挖影响面以反映土体开挖时边坡滑动趋势的变化,与开挖影响面相交处的土钉在土体开挖时轴力增加最多。开挖土压力表示以开挖影响面为边界的土块体产生的土压力,由相邻两步开挖土压力之差求得挖土引起的不平衡力。增加的土钉轴力在平衡此不平衡力的同时,维持着边坡稳定。据此,以开挖影响面及其土钉轴力增量为主要研究对象,提出了施工阶段土钉轴力的分析方法。该方法在求得土钉轴力最大值及其作用位置的同时,还给出了土钉轴力沿钉长方向的分布。应用此方法对法国CLOUTERRE项目1号墙足尺试验进行了计算,结果表明：计算与测试结果吻合良好。 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.
部分排水条件下加筋路堤性状分析 总被引：2，自引：0，他引：2
使用椭圆帽土质模型分析了部分排水条件下软土地基土工合成物加筋路堤的性状,按照Biot理论模拟了固结行为。在路堤施工期地基土的部分固结和不同初始排水条件下,主要分析加筋体的刚度影响和地基土的强度轮廓面,以及在正常工作情况下和在路堤失效情况下土工合成加筋材料的应变特点。分析了加筋体对于地基土变形的影响。结果显示,加筋体可以提高路堤的破裂高度,可以明显地减小路堤施工期最大侧向变形、竖向变形和地基土隆起,可明显提高施工期路堤的安全系数。 相似文献
4.
抗滑桩加固斜坡软弱地基路堤的数值模拟 总被引：2，自引：0，他引：2
在路堤荷载作用下,斜坡软弱地基易产生侧向变形过大、滑塌失稳等病害。路堤下坡脚处采用钢筋混凝土抗滑桩,以有效限制地基侧向变形,是斜坡软弱地基路堤的核心设计原则。采用三维快速拉格朗日有限差分法,经与室内土工离心模型试验成果对比、校核,建立抗滑桩加固斜坡软弱地基路堤的精细化数值分析模型,研究抗滑桩桩距、桩长、桩身弹性模量、桩身横截面尺寸及桩位等设计参数对其内力、变位的影响。研究表明：下坡脚处实施抗滑桩可显著约束斜坡软弱地基侧向变形;需综合考虑桩身受力、经济性、施工等因素确定合理的桩距;桩长应深入滑移面以下,但随着桩长的增长,加固效果增长不明显;随着桩身弹性模量、桩身横截面尺寸的增加,抗滑桩的加固效果得到一定提高;抗滑桩宜设置在下坡侧路堤边坡的中部。 相似文献
5.
土钉支护是加固机制上的锚固机制,土钉支护的受力和变形是随施工过程逐步变化的。采用追踪施工过程的增量计算方法,并将稳定性分析与土钉轴力计算相统一,根据稳定性要求来计算土钉受力,是土钉支护中土钉受力计算的合理途径。考虑到土钉支护中土与土钉共同作用以及潜在滑移面处土钉受力的特点,在土钉支护的稳定性分析中可以采用极限分析上限方法。根据上限方法中的相容速度场以及土钉受力与位移的关系,可确定在上限分析中每一开挖工况下土钉轴力增量的比例关系。应用上限方法的能量方程进行每一开挖工况下土钉支护稳定性的计算,即可优化求解出每一开挖工况下的土钉所需提供的能量耗散,而后依据上述确定的增量比例系数,即可求得该开挖工况下的土钉轴力增量,而各开挖工况下土钉轴力增量的积累即为最终土钉轴力。通过工程实例计算表明,上述方法是准确和有效的。 相似文献
6.
在对半挖半填路堤病害及成因分析的基础上,分析了加筋路堤格栅工作机制。通过现场试验,对采用格栅加筋法处理的路堤挖填交界区域进行了原位观测,观测了路堤填土完成时路面沉降、竖向土压力及格栅变形情况。通过建立有限元分析模型,对路堤填筑完成时格栅的拉力及位移进行了分析,并对不同路面荷载和格栅刚度条件下,格栅的拉力与位移进行了计算。结果表明：路堤挖填交界处铺设格栅后,路面局部差异沉降较小。填方区域格栅底部土压力与填土自重应力相当,格栅存在有效加筋长度,在挖填交界面附近产生较大变形和拉力。上层格栅比下层格栅沉降曲线平缓,下层格栅的拉力在交界区域会陡然增大。路面荷载对格栅拉力和位移有一定影响,随埋深增加影响减小,格栅的竖向位移随着荷载增大略有增大,格栅在挖填交界面附近拉力增大。随格栅刚度增大,其拉力也增大,而位移变化很小。 相似文献
7.
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
8.
9.
土工织物加固软土路堤的有限元分析 总被引：5，自引：4，他引：5
采用有限元方法对土工织物加固软弱地基路堤的力学机理进行了研究.通过比较路基加筋和未加筋两种情况研究了土工织物的加固机理,结果表明土工织物对于提高路堤填筑高度、减少路堤侧向位移、均化路堤沉降以及加速超孔隙水压力消散有显著的效果.加筋路堤中土工织物的轴力受填筑高度、超孔压消散速度和接触面系数等因素的影响,路堤填筑高度和施工进度的控制有利于土工织物抗拉强度的发挥.对路堤安全系数的研究分析表明传统的极限平衡法验算路堤稳定性偏于保守,采用有限元方法能较好地反映土工织物的加筋作用,可以优化工程设计. 相似文献
10.
The design against failure of an embankment resting upon a soft soil improved by a group of columns is investigated with the help of the yield design homogenization approach. Assuming that both constituents of the reinforced ground are purely cohesive materials (‘lime column’ technique), an upper bound estimate for the macroscopic strength condition of the reinforced soil as a homogenized medium is first obtained, providing definite evidence of a shear strength anisotropy associated with the reinforcement preferential orientation. The kinematic method of yield design is then performed on the basis of such a criterion, making use of rotational failure mechanisms involving slip circles in the reinforced ground. Upper bound estimates are finally obtained for the embankment stability factor, as functions of the degree of reinforcement and relative thickness of the soil layer. These results are compared with those derived from a simplified analysis, where the reinforced soil is assumed to exhibit an averaged isotropic cohesion. This comparison clearly indicates that the latter simplified analysis may produce quite unsafe estimates for the embankment stability, which can be attributed to the fact that it fails to capture the inherent strength anisotropy of the reinforced soil. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
11.
The shaking table tests are conducted on small scale nailed embankment slopes to study their behavior under dynamic conditions.
Medium grained local sand with a water content of 3% is used in the study. The embankment slope is constructed using the controlled-volume
compaction method. Three slope angles, 30°, 35° and 40° with a constant slope height of 18 cm are considered for the embankment.
Each slope is reinforced with six number of hollow aluminum nails in two rows. The ratio of the length of nail to slope height
(0.82) is same for all model slopes. The nails are inserted at three different inclinations. Three strain gauges are glued
to each nail to obtain local strains during shaking. The accelerations at the base and the crest of the model slopes are monitored
to find the acceleration responses of the embankments during the input ground motions. The numerical simulation of the model
tests is performed by a commercial program called FLAC. The results of the numerical analyses are found to be reasonably close
to the corresponding experimental results. 相似文献
12.
杆系有限元法求解复合土钉支护结构的位移 总被引：4，自引：0，他引：4
复合土钉支护位移计算尚未有成熟的分析方法。本文采用杆系有限单元法,结合支护土钉滞后的施工动态分析,来求解施工超前桩墙的复合土钉支护结构的水平位移。坑外侧主动土压力,由于受到密集土钉作用和坡角的影响,考虑折减计算。本分析方法简便,易于计算机编程。通过工程实例计算和分析,结果表明水平位移计算值与实测值较为接近。 相似文献
13.
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
15.
土工格栅在青藏铁路多年冻土区路基工程中的应用 总被引：3，自引：0，他引：3
以青藏铁路多年冻土区清水河冻土加筋路堤试验段为例,对土工格栅在铁路路基工程中的应用原理及设计思路进行了叙述.通过对路基裂缝进行调查、分析和比较,土工格栅对加强路基整体稳的作用是肯定的.在多年冻土区路堤中,使用土工格栅加筋层对防止路堤纵向裂缝的产生、抑制横向寒冻裂缝具有明显的作用. 相似文献
16.
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
17.
青藏铁路碎石护坡-热管复合措施的补强效果研究 总被引：2，自引：1，他引：1
青藏铁路高温冻土区的普通路基和保温材料路基均处于热不稳定状态, 需要对它们增设碎石护坡-热管复合措施来强化处理, 新增设的补强措施对路基下部冻土的保护效果如何是人们极为关心的问题. 因此, 对北麓河高温高含冰量路段增设了碎石护坡及热管的复合补强措施后路基下部土体的热状态进行观测.结果显示:普通路基在增设补强措施后, 人为冻土上限进一步抬升, 阴阳坡下均出现显著的降温趋势, 且路基下温度场逐渐趋于对称, 降温范围逐渐向路基中心及深部发展, 路堤中心深部地温仍处于增温状态, 但增温趋势明显缓减; 保温材料路基在增设补强措施后, 人为冻土上限也进一步的抬升至保温板附近, 融化夹层在2个冻融周期后消失, 路堤中心温度在2个冻融周期后出现了降温趋势. 这些效果说明, 补强措施在调控路基内部及下部多年冻土温度时发挥了积极作用. 相似文献
18.
为了研究高密度聚乙烯（HDPE）和聚对苯二甲酸乙二醇酯（PET）两种土工格栅在返包式加筋路堤中的加筋效果,基于HDPE和PET的拉伸试验结果,采用FLAC3D有限差分程序并结合现场监测数据对比,分析了加筋路堤中两种土工格栅的受力变形规律。结果表明,土工格栅特性对返包式加筋路堤变形具有明显影响,影响程度与其上部土压力大小密切相关;在加筋土路堤的中下部,土压力较大,HDPE格栅前1/3段和后1/3段的应变存在较大差别,PET格栅的应变沿长度分布相对均匀;随着上部土压力的减小,格栅材料特性的影响减弱,两种格栅的应变曲线趋于接近;PET格栅对加筋路堤水平变形的控制作用更为明显;HDPE格栅加筋路堤的垂直和水平土压力值及其分布与PET加筋路堤差别很小。 相似文献
19.
防波堤土工织物加筋地基离心模型试验及数值模拟 总被引：7，自引：2，他引：5
以黄骅港北防波堤工程为依托,对土工织物加筋软粘土地基及斜坡式防波堤体系的固结过程进行了离心模型试验和有限元数值模拟,通过分析地基土体固结过程中防波堤-加筋垫层-基体系的位移场和应力场的发展及织物拉应力分布和发展,验证离心试验及数值模拟方法的合理性,并得出以下几点主要结论:(1)土工织物加筋垫层的作用机理为其抗拉性限制自身横向变形,通过与附近土体的摩擦作用限制其侧向变形;(2)加筋减小防波堤-垫层-地基体系的高应力水平区,避免堤身与地基高应力水平区域的连通,增强系统稳定性;(3)在离心试验采用的分层地基的条件下,加筋减小了浅层软基和堤身的侧向位移量,对系统总位移有抑制作用;(4)试验中织物替代材料的极限拉伸强度发挥程度较低,其与砂垫层间摩擦强度的发挥水平约为23.8％。 相似文献
20.
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