竖向条形锚定板水平拉拔极限承载力统一理论解研究

针对竖向条形锚板拉拔问题的研究存在人为区分浅埋、深埋,且界定标准及力学模型的对称性认识不统一,基于自主研制的条形锚水平拉拔可视化模型试验和数值模拟试验,研究拉拔过程中板前土体的位移变形规律。极限状态下,板前存在弹性核三角形区域,其角度变化可反映板前滑移线场的对称性;随着埋深比的增大,三角形弹性核的上角增大(φ~π/4+φ/2),上侧土体位移变形范围相对缩小,从延伸至地表收缩至板前附近;下角减小(π/2~π/4+φ/2),下侧土体位移变形范围则相对扩大,边界与竖向夹角在π/2~3π/4+φ/2间变化;上下角之和基本保持不变(φ+π/2),板前滑移线场由非对称逐步向对称发展。在此基础上,提出相应的假定,构建可考虑埋深等因素变化的竖向条形锚定板的水平拉拔极限承载力学模型,并推导出极限承载力的统一理论解。计算结果表明:新的力学模型很好地反映了板前滑移线场的对称性随埋深比的连续变化规律,无需再人为区分浅埋和深埋;极限承载力统一理论解对砂土中竖向条形锚定板具有很好的适用性,计算结果与试验值符合的更好,较其它3种传统方法具有明显优势。

Unified theoretical solution for ultimate bearing capacity of vertical strip anchor

The researches on vertical strip slab pullout issue have problems of artificial distinguishing of shallow and deep buried types, non-uniform understanding of definition standard and symmetry of mechanical model. Based on the self-developed visual horizontal drawing strip anchor model tests and numerical simulation tests, the displacement and deformation laws of soils before plate in the drawing process are studied. Under the ultimate drawing, a triangular elasts core exists before the plate, and its angle’s variation can reflect the symmetry of slip-line field. When the buried ratio increases, the upper angle of the core increases along with the upper slip-line shrinking from surface to the plate, and the lower angle decreases, along with the lower slip-line relatively extending. The sum of two angles basically remains unchanged, but the slip-line field before the plate gradually evolves from asymmetric to symmetrical. On this basis, the corresponding assumptions are put forward to establish the ultimate bearing mechanical model for horizontally drawing vertical strip anchors, and the unified theoretical formula for the ultimate bearing capacity is derived, which can take the buried depth and other factors into consideration. The results indicate that the new model can reflect the continuous variation rules of the symmetry of the slip-line field with the depth ratio very well, and any further distinguishing of shallow and deep buried plates is not needed. The new unified ultimate bearing capacity's theoretical solution has good applicability to vertical strip anchors in sand, and the calculated results are in better agreement with the experiments, which shows an obvious advantage over the other three traditional methods.