Protecting existing utility lines in congested urban centers is considered a major challenge especially in cases of new construction bridging over these lifelines. Several innovative techniques have been proposed lately to bridge over existing pipes. This study discusses the use of stiff three-dimensional geogrids to reinforce sandy soils bridging over existing buried Polyvinyl Chloride (PVC) pipe at shallow depth subjected to strip static loading. Twenty-eight large scale laboratory tests were conducted with variable geogrid geometries using single and double layers of geogrid reinforcement. Tests were heavily instrumented to record longitudinal and transverse strains in the pipe wall and geogrids, pipe deflections, pressures within the soil and above the pipe crown, and footing settlement. Optimization of the geogrid geometry was conducted in order to reduce strains and stresses in the PVC pipe subjected to static loading. In general, introducing the geogrid reinforcement has reduced stresses transferred to the pipe crown below the center of the loading. For a given applied stress, the increase in geogrid width has resulted in a reduction in stress transferred to the pipe and longitudinal strains developed in the pipe. Up to 80% reduction in longitudinal strains was observed in the PVC buried pipe as a result of the geogrid reinforcement. Finally, the results have shown up to 150% improvement in soil bearing capacity and nearly 50% reduction in surface settlement as a result of introducing geogrid reinforcement. The main finding in this study is that three-dimensional geogrid reinforcement was effective in reducing the longitudinal strains in existing PVC shallowly buried pipes subjected to static loading.

在拥挤的城市中心地区，保护现有的公用事业管线被认为是一项重大挑战，尤其是在这些生命线上架设了新建筑的情况下。最近提出了几种创新技术来桥接现有管道。这项研究讨论了使用刚性三维土工格栅来加固在浅埋深度下承受带钢静载荷的现有埋入式聚氯乙烯（PVC）管上的砂土。使用单层和双层土工格栅加固，对具有可变土工格栅几何形状的28个大型实验室进行了测试。对测试进行了严格的测试，以记录管壁和土工格栅的纵向和横向应变，管的挠度，土壤内部和管冠上方的压力以及基础沉降。进行土工格栅几何形状的优化，以减少承受静态载荷的PVC管中的应变和应力。通常，引入土工格栅加筋件可以减小传递到载荷中心以下的管冠的应力。对于给定的施加应力，土工格栅宽度的增加导致传递到管道的应力的减小和管道中产生的纵​​向应变的减小。由于土工格栅的增强，PVC埋管中的纵向应变降低了多达80％。最后，结果表明，引入土工格栅加固后，土壤承载力提高了150％，表面沉降降低了近50％。