刚性条带式带齿加筋土的极限拉拔力模型

Ultimate pullout resistance model for rigid denti-strip reinforced soil

"立体加筋"体系的核心就是在传统水平筋条的基础上布置不同形状的竖向筋条或三维形式的空间加筋。作为一种典型的立体加筋方式,刚性筋材的条带式带齿加筋土经三轴压缩试验、拉拔试验以及挡墙和地基模型试验证明,可以显著地提高加筋土体的强度和地基极限承载力,增强土筋的综合摩擦特性,限制土体变形。采用染色砂法,对带齿筋材的平面应变拉拔试验过程进行了观察。通过分析齿筋前方染色砂土标记线的运动情况和水平标记线的变化情况,发现在拉拔过程中,齿筋前方土体会首先被挤密加强,成一个刚性的楔体,然后周围其他土体会产生绕刚性楔体与齿筋的流动。根据齿筋的宽高比,假定了刚性楔体的形状,从而确定了绕流阻力的分布情况。借鉴沈珠江院士对于抗滑桩阻力的分析方法,推导了刚性条带式带齿加筋土的拉拔阻力模型。在应变控制式拉拔试验机上,进行了法向应力分别为25,50和75kPa的条带式带齿加筋土的拉拔试验,将试验结果与模型计算值进行比较,二者比较接近。

In conventional reinforced soil, the reinforcements are often horizontally laid in the soil. A novel concept of soil reinforced with rigid denti-strip reinforcements is proposed. In the proposed denti-strip reinforced soil, besides the conventional horizontal reinforcements, some vertical or three-dimensional reinforcing elements are also placed upon the horizontal ones. A series of triaxial compression tests, pullout tests, foundation model tests and retaining wall model tests are performed, obtaining the same conclusion that the strength, ultimate bearing capacity, apparent friction behavior between soil and reinforcements and deformation resistance obviously increase. By dyed sand observation method in plane-strain pullout tests, a novel theory about the pullout mechanism of denti-strip reinforced soil is introduced. In this theory, soil can flow around vertical reinforcing elements, which brings resistance. Based on the analytical method of anti-slide pile resistance by Academician Shen Zhujiang, a pullout model for the rigid denti-strip reinforced soil is established. The analytical values agree well with the test results.