共查询到18条相似文献，搜索用时 156 毫秒
1.
考虑地基土体的非均质特性,采用非线性Mohr-Coulomb强度准则及其关联流动法则构造了浅埋水平条形锚板的曲线型破裂机制与机动许可速度场,根据极限分析上限定理推导了条形锚板抗拔承载力的表达式。利用变分极值原理求得了锚板抗拔承载力及其上方土体破裂面的上限解,分析了锚板埋深、土体非均质和非线性强度特性对锚板抗拔承载特性的影响,并将该上限解与已有计算方法进行了对比。结果表明:锚板埋深、土体非均质和非线性强度特性对其抗拔承载力与破裂面特征具有明显的影响。锚板埋深和土体非均质系数越大以及土体非线性强度系数越小,锚板抗拔承载力和土体破裂面深度、宽度均是越大。该上限解与极限平衡和极限分析有限元方法的计算结果基本一致,验证了所采用的曲线型破裂机制和地基非均质变化规律有效性,为条形锚板设计提供了一定的参考。 相似文献
2.
以极限分析上限理论为基础,利用旋转块体集的组合来构造条形锚板的运动许可速度场。分析了不排水黏土中深埋和浅埋条形锚板的抗拔承载力上限解,研究了锚板在不同埋置倾角和深度条件下的抗拔承载力和破坏面的特性,并将计算结果与已有计算方法进行了对比。分析结果表明：在不排水黏土中深埋条形锚板抗拔承载力与锚板的埋置方位和锚板的粗糙度无关,但完全光滑条件下破坏面扇圆部分的半径只有完全粗糙条件下的一半;在考虑无重土情况下浅埋条形锚板的抗拔承载力系数随锚板埋深比的增大而增大,破坏面也随埋深比的增加而逐渐扩大。所得上限解与已有文献解答较为吻合,而且求解所得破坏面更为直观,能为工程设计提供参考依据。 相似文献
3.
《岩土力学》2020,(10)
针对福建标准砂,采用非接触式数字图像相关技术(digital image correlation, DIC),通过一系列室内模型试验研究了圆形锚板上拔时锚周土体的变形特性,重点分析了盘径、埋深比和砂土相对密实度的影响。试验结果表明,随着盘径的增加,同一埋深比条件下,上拔力峰值和出现上拔力峰值时的位移水平均明显增大,而上拔承载力系数N_γ则随着盘径的增加而减小,但盘径变化不影响上拔时锚周土体位移影响区的形状,且以上规律不受砂土相对密实度变化的影响。对于密砂,锚周土体位移影响区形状随着埋深比的增加由倒梯形向U字形发展,土体剪切破坏面为沿锚板边缘向外侧斜上方演进的直线型破坏面,且与竖直方向的夹角约为1/4φ_p(φ_p为土的峰值摩擦角);随着锚板的上拔,锚板上方土体出现较为明显的体积膨胀。对于松砂,随着埋深比的增加,锚周土体位移影响区形状由延伸至土体表面的矩形向内置于土体的贝壳形发展;浅埋时,土体剪切破坏面沿锚板边缘垂直向土体表面开展;深埋时,土体剪切破坏面沿锚板边缘向内侧斜上方发展,与水平方向的夹角约为45°+1/2φ_p。无论何种埋深比,锚板正上方均观测到小范围的体积膨胀区,其上为体积收缩区,且随着埋深比的增加体积收缩量逐渐增加。 相似文献
4.
《岩土力学》2020,(10)
针对福建标准砂,采用非接触式数字图像相关技术（Digital Image Correlation, DIC）,通过一系列室内模型试验研究了圆形锚板上拔时锚周土体的变形特性,重点分析了盘径、埋深比和砂土相对密度的影响。试验结果表明,随着盘径的增加,同一埋深比条件下,上拔力峰值和出现上拔力峰值时的位移水平均明显增大,而上拔承载力系数N_(γ)则随着盘径的增加而减小,但盘径变化不影响上拔时锚周土体位移影响区的形状,且以上规律不受砂土相对密度变化的影响。对于密砂,锚周土体位移影响区形状随着埋深比的增加由倒梯形向U字形发展,土体剪切破坏面为沿锚板边缘向外侧斜上方演进的直线型破坏面,且与竖直方向的夹角约为1/4φ_(p)（φ_(p)为土的峰值摩擦角）;随着锚板的上拔,锚板上方土体出现较为明显的体积膨胀。对于松砂,随着埋深比的增加,锚周土体位移影响区形状由延伸至土体表面的矩形向内置于土体的贝壳形发展;浅埋时,土体剪切破坏面沿锚板边缘垂直向土体表面开展;深埋时,土体剪切破坏面沿锚板边缘向内侧斜上方发展,与水平方向的夹角约为45°+1/2φ_(p);无论何种埋深比,锚板正上方均观测到小范围的体积膨胀区,其上为体积收缩区,且随着埋深比的增加体积收缩量逐渐增加。 相似文献
5.
基于Hoek-Brown破坏准则的浅埋条形锚板抗拔力上限分析 总被引：2，自引：0，他引：2
现有的锚板极限承载力研究大多是采用线性或非线性Mohr-Coulomb破坏准则在砂质地基中进行的,然而Mohr-Coulomb破坏准则并不适合分析岩质地基中的抗拔结构。采用Hoek-Brown破坏准则构建了一个曲线型的破坏机制,根据极限分析上限定理求出了条形锚板抗拔力的表达式。通过变分计算,得到了极限状态下条形锚板的抗拔力和岩体破裂面的上限解。为了证明所采用方法的有效性,当材料参数B =1时,采用与Mohr-Coulomb破坏准则等效的土体参数,计算了曲线型破坏机制下条形锚板的极限抗拔力,并与已有计算结果进行了比较。结果表明,采用曲线型破坏机制得到的锚板极限抗拔力与直线型多块体破坏机制的结果基本一致,证明了所采用的曲线形破坏机制是正确的。参数研究表明：在其他参数不变的情况下,锚板极限抗拔力和破坏面都随岩体参数B的增大而减小。 相似文献
6.
在三维状态下运用极限平衡理论,对黄土中圆形抗拔锚板基础在受到垂直于板面荷载作用下的承载力进行理论分析,该理论研究考虑了锚板在上拔过程中板周土体的破裂方程、破裂面上的正应力和剪应力、埋深率等影响因素。理论公式计算结果表明：抗拔锚板承载力系数随着锚板埋深的增加而增大,并且当深度达到一定值时,承载力系数将达到其极限值;当埋深率h/D=1~2之间时,上覆土重对承载力系数影响较小;当h/D=4时,土体和锚板之间的吸力对承载力系数的影响大于锚板上覆土重;当h/D>4时,上覆土重对锚板抗拔承载力起着决定作用。理论计算公式与已有学者的试验结果进行对比表明提出的模型理论计算结果和其他学者的试验结果有良好的一致性,验证了该理论的正确性,为工程中抗拔锚板的设计提供了有价值的参考。 相似文献
7.
锚板在正常固结黏土中的承载力 总被引：5，自引：0，他引：5
在岩土工程中,锚板通常被用来提供竖直或水平抗拔力,比如发射塔的基础、板桩墙结构和悬浮式海洋平台的基础。采用弹-塑性有限元方法对正常固结不排水黏土中的条形锚板进行数值分析,以图表形式给出了不同埋深率、不同上拔倾角、不同锚-土黏结形式下条形锚板的承载力系数和周围土体的流动机构,分析了土体自重对锚板承载力的影响,并给出了不同情况下锚板的极限承载力系数。采用基于重新划分网格并插值状态变量的大变形分析方法（RITSS）,分析了正常固结黏土中锚板在连续拔出过程中的承载力变化以及土重对锚-土分离模式的影响。 相似文献
8.
当结构在土体中运动时,往往导致土体发生较大的变形,此类问题采用大变形数值分析方法更为恰当。耦合欧拉-拉格朗日（Coupled Eulerian-Lagrangian, 简称CEL）法是大变形数值分析方法中的一种,在分析大变形问题时具有很强的适用性,但在国内尚未开展CEL法分析锚板承载力的研究。以方形锚板在均质土及线性土中的拔出试验为原型,基于CEL法建立数值模型,对锚板的极限承载力及破坏机制进行研究,并通过用户自定义子程序,实现了线性土的强度分布随锚板拔出而变化。计算结果表明,土体杨氏模量越大,锚板的极限承载力越大;随着位移增大,锚板的抗拔力先增大,后降低;当埋深小于临界埋深时,土体发生整体破坏;当埋深大于等于临界埋深时,土体发生局部破坏。数值计算反映的规律与试验结果基本吻合,体现了CEL法模拟锚板在海床中大位移响应的出色能力。 相似文献
9.
通过块体集上限分析方法,研究锚板的抗拔承载力和破坏面特性,并将分析结果与Das[1]以及Rowe[2]的锚板模型试验结果进行详细对比,验证块体集上限法的有效性。分析斜坡地形条件下锚板抗拔承载特性,并与Khing等[3]的条形锚板抗拔承载力试验以及Rao和Prasad[4]的圆形锚板抗拔承载力试验进行详细对比,分析斜坡地形条件下锚板模型试验中采用拉杆加载的方式对于试验结果的影响。分析结果表明,斜坡地形条件下拉杆的存在对于锚板抗拔承载力影响较大,模型试验应优先采用Trapdoor模型。 相似文献
10.
水平锚板极限抗拔力研究 总被引：1，自引：0，他引：1
简要回顾了水平锚板抗拔极限承载力计算方法的发展历史。考虑对数螺旋线的破坏面并结合特征线理论,提出了一种新的浅埋条形板极限上拔力的计算方法并编制了程序。对无粘性土,通过与前人的试验资料和Meyerhof andAdams计算理论得出的结果进行了比较,表明了本文方法是正确可行的。 相似文献
11.
Jyant Kumar 《国际地质力学数值与分析法杂志》1997,21(7):477-484
By making use of limit analysis, an upper bound solution in a closed form for determining the ultimate pullout capacity of plate anchors buried in sandy slopes has been established. The anchor plate orientation has been considered either horizontal or parallel to the slope, with the pullout force applied perpendicular to the plate. It has been found that the pullout capacity for horizontal anchors, even on slopes, remains the same as that on horizontal ground surface as long as the average embedment ratio is kept constant. Whereas for anchors which are aligned parallel to the slope the collapse load decreases continuously with the increase in the inclination of slope. © 1997 John Wiley & Sons, Ltd. 相似文献
12.
Ahmed M. Fahmy John R. de Bruyn T. A. Newson 《Geotechnical and Geological Engineering》2013,31(5):1525-1542
Two-dimensional plane strain finite element analysis has been used to simulate the inclined pullout behavior of strip anchors embedded in cohesive soil. Previous studies by other researchers were mainly concerned with plate anchors subjected to loads perpendicular to their longest axis and applied through the centre of mass. This paper investigates the behavior of vertical anchors subjected to pullout forces applied at various inclinations with respect to the longest anchor axis, and applied at the anchor top and through the centre of mass. The effects on the pullout behavior of embedment depth, overburden pressure, soil–anchor interface strength, anchor thickness, rate of clay strength increase, anchor inclination, load inclination and soil disturbance due to anchor installation were all studied. Anchor capacity is shown to increase with load inclination angle for anchors loaded through the centre of mass; greater effects are found for higher embedments. The results also show that anchor capacity improves at a decreasing rate with higher rates of increase of soil shear strength with depth. In addition, the capacity of vertically loaded anchors is shown to approximately double when the soil–anchor interface condition changes from fully separated to fully bonded. Similarly, disturbed clay strengths adjacent to the anchor following installation cause a significant reduction in anchor capacity. The results showed a significant effect of the point of load application for anchors inclined and normally loaded. The effects of other parameters, such as anchor thickness, were found to be less significant. 相似文献
13.
Awdhesh Kumar Choudhary Bhardwaj Pandit G. L. Sivakumar Babu 《Geomechanics and Geoengineering》2020,15(1):1-9
ABSTRACTVertical anchor plates are often provided to increase the performance of various geotechnical engineering structures such as sheet pile walls, bulkheads, bridge abutments and offshore structures. Hence, the safe design of such structures needs a better understanding of the 3D behaviour of the anchor plate. This paper presents and discusses the results obtained from a series of 3D finite-difference analyses of vertical square anchor plate embedded in cohesionless soil. The 3D model is found to closely predict experimental pullout load–displacement relationship. The failure mechanism observed in the numerical model is found to be very similar to the failure reported in experimental studies. For a given embedment depth, the stiffness of the breakout factor–displacement response substantially reduces with increase in anchor plate size. However, the ultimate reduction in anchor capacity is found to approximately 8% with an increase in anchor size from 0.1 to 1 m. Numerical analysis reveals that at deeper embedment depth, the friction angle of sand is the critical parameter in enhancing the performance of anchor plate. The obtained 3D model results are then compared with the published results and are found to be reasonably in good agreement with each other. 相似文献
14.
By using the lower bound finite elements limit analysis, the pullout capacity of an inclined strip anchor plate embedded in a cohesionless soil medium has been computed with an inclusion of pseudo-static horizontal earthquake body forces. The variation of the pullout capacity factor (F γ ) with changes in horizontal earthquake acceleration co-efficient (α h ) has been computed by varying the inclination angle (β) of the anchor plate between 0° and 90°. The results clearly reveal that the pullout capacity factor (F γ ) decreases significantly with an increase in the value of α h . The reduction in the pullout resistance due to seismic forces (1) becomes much more extensive for a vertical anchor plate as compared to the horizontal anchor, (2) decreases generally with increases in the soil friction angle (?) and (3) increases with an increase in friction angle between soil and anchor plate (δ). The developments of the failure zone around the anchor plate were also examined by varying α h and β. The results obtained from the analysis compare well with the solutions reported in literature. 相似文献
15.
砂土中扩体锚杆承载特性模型试验研究 总被引：1，自引：0，他引：1
在25个室内模型试验基础上,研究了均质砂土中竖向拉拔扩体锚杆的几何尺寸及埋深对其承载特性的影响。试验结果表明,根据深径比的不同,扩体锚杆可以分为浅埋与深埋扩体锚杆2种形式,它们在拉拔过程中均经历了土体弹性变形阶段、非扩体锚固段-土界面剪切破坏阶段、土体弹塑性变形阶段以及剪切破坏阶段,破坏特征分别表现为整体剪切破坏与局部剪切破坏。通过扩体锚杆与普通拉力型锚杆模型试验对比发现：与普通拉力型锚杆相比,扩体锚杆极限承载力、承载比与安全性均有大幅度提高。而通过增大扩体锚固段直径的方式提高扩体锚杆承载力的优势较为明显。此外,根据承载比分析,扩体锚杆存在最优扩体锚固段直径,因此,在实际工程中应寻找一个满足需要的最优扩体锚固段尺寸以取得较好的经济效益。 相似文献
16.
Three-dimensional numerical and analytical study of horizontal group of square anchor plates in sand
Hicham Mokhbi Mekki Mellas Abdelhak Mabrouki Jean-Michel Pereira 《Acta Geotechnica》2018,13(1):159-174
In this paper, numerical and analytical methods are used to evaluate the ultimate pullout capacity of a group of square anchor plates in row or square configurations, installed horizontally in dense sand. The elasto-plastic numerical study of square anchor plates is carried out using three-dimensional finite element analysis. The soil is modeled by an elasto-plastic model with a Mohr–Coulomb yield criterion. An analytical method based on a simplified three-dimensional failure mechanism is developed in this study. The interference effect is evaluated by group efficiency η, defined as the ratio of the ultimate pullout capacity of group of N anchor plates to that of a single isolated plate multiplied by number of plates. The variation of the group efficiency η was computed with respect to change in the spacing between plates. Results of the analyses show that the spacing between the plates, the internal friction angle of soil and the installation depth are the most important parameters influencing the group efficiency. New equations are developed in this study to evaluate the group efficiency of square anchor plates embedded horizontally in sand at shallow depth (H = 4B). The results obtained by numerical and analytical solutions are in excellent agreement. 相似文献
17.
采用自制可视化试验装置开展了平板圆锚的拉拔模型试验,基于数字照相测量技术对极限拉拔下锚周土体的位移变形场进行了量化分析。在本次试验的埋深比范围内,极限承载力随埋深比增加而非线性增大,但增长速率逐渐减缓;观测到的锚周土体滑动面与地面、锚板所围区域整体呈现出“底大、顶小、径长”的倒喇叭形状;滑动面可用两条直线段来近似描述;极限拉拔力学模型由一个截面直径上小下大的倒圆台和一个等截面圆柱体组成。根据极限平衡条件推导建立了砂土中浅埋平板圆锚竖向拉拔极限承载力的计算方法,该方法对4组试验数据的计算较其他4种方法与试验实测值更为接近,且离散性更小,效果较好。 相似文献
18.
《Geomechanics and Geoengineering》2013,8(4):267-275
Pseudo-static approach is adopted in this paper to determine the seismic uplift capacity of an inclined strip anchor using upper bound limit analysis. Two different failure mechanisms are considered to obtain the magnitudes of unit weight component of uplift factor fγE for different values of soil friction angle, interface friction of anchor plate, anchor inclination, embedment ratio and horizontal seismic acceleration coefficient. The failure mechanism 1 consists of a triangular and quadrilateral rigid blocks; whereas the failure mechanism 2 comprises a logarithmic spiral failure zone with varied focus, sandwiched between a triangular and quadrilateral rigid blocks. It is observed that the magnitude of uplift factor fγE decreases significantly with the increase in seismic acceleration but increases with the increase in embedment ratio and roughness of the anchor surface. However, a mixed trend in the values of fγE can be observed for different inclination of the anchor, which is clearly discussed in this paper. The results are compared with the existing values in the literature and the significance of the present methodology for designing the inclined strip anchor is discussed. 相似文献