土工格栅加筋珊瑚砂的强度及变形特性试验研究

Experimental study on strength and deformation characteristics of coral sand reinforced by geogrid

珊瑚岛礁钙质砂作为海洋工程建设的主要原材料,具有碳酸钙含量高、多孔隙、颗粒易破碎等特征。为了进一步提高海洋工程建设中岩土构筑物的强度及稳定性,采用土工格栅加筋珊瑚砂是一种潜在的有效手段。通过一系列的室内三轴压缩试验,探究土工格栅加筋层数、初始含水率、围压等因素对加筋珊瑚砂强度及变形特性的影响。研究发现:格栅加筋能够明显地改善珊瑚砂的力学性能,随着格栅层数的增加,加筋珊瑚砂整体的强度逐渐上升,偏应力-应变关系总体呈现硬化趋势,侧向的鼓胀变形得到明显改善;似黏聚力随着格栅层数增加近似呈线性递增,内摩擦角轻微降低;随着初始含水率的增加,格栅加筋珊瑚砂的强度呈轻微衰减趋势,似黏聚力变化不大,但内摩擦角相比干砂最大下降了约4°;三轴应力状态下的格栅加筋珊瑚砂颗粒破碎受围压影响较大,低于400k Pa围压下的相对破碎率主要在3%以内。此外,基于格栅与珊瑚砂相互作用特征,考虑并计算得到格栅产生的侧向与轴向附加应力,研究结果进一步丰富了对格栅加筋珊瑚砂机制的认识。

As the main raw material for marine engineering construction,coral sand with high calcium carbonate content is porous and fragile.In order to further accelerate the construction of marine engineering and improve the strength and stability of geo-structures,using geogrid to reinforce coral sand is a potentially effective means.In present study,a series of triaxial tests was conducted to investigate the effects of the number of geogrid layers,initial water content,and confining pressure on the strength and deformation of geogrid-reinforced coral sand.The results indicate that the geogrid reinforcement can obviously improve the mechanical properties of coral sand.With increasing number of geogrid layers,the overall strength of the reinforced coral sand gradually increases.The stress-strain relationship shows a general hardening trend,and the lateral bulging is also restrained effectively.Similarly,the introduced pseudo-cohesion increases linearly with increasing number of geogrid layers,and the internal friction angle decreases slightly.As the initial water content increases,the strength of geogrid-reinforced coral sand decreases slightly,and the pseudo-cohesion changes little.However,the internal friction angle decreases by about 4°compared with the drying condition.The particle breakage of geogrid-reinforced coral sand is greatly affected by confining pressure in triaxial case,and the relative breakage rate below 400 kPa confining pressure is mainly less than 3%.Additionally,the lateral and axial additional stresses are considered and calculated by analyzing the geogrid-sand interfacial characteristics.These results further enrich the understanding of the mechanism of geogrid-reinforced coral sand.