Concave segmental retaining walls with porcupine blocks

Abstract

Gravity segmental retaining walls (GSWs) built with prefabricated concrete blocks (modular-blocks) have become an attractive solution for soil retaining structures within the past few years due to the ease and low cost of construction. However, since their application is limited to small heights, they are usually combined with soil reinforcement (e.g. geogrid) to build higher earth retaining structures referred as geosynthetic reinforced soil walls (RSWs). RSWs are considered a more sustainable solution than conventional walls and therefore their popularity increases constantly. Recent analytical studies suggest that concave form is beneficial for slope stability and reinforced soil walls. However, there are no physical or numerical data to validate the theoretical approach. This study aims to investigate the beneficial effect of concave geometry in RSWs by means of small-scale centrifuge tests combined with FEM models. Furthermore, it aims to apply concave profile to GSWs and study the improvement in their performance. In order to implement concave profiles to GSWs and RSWs it is necessary to find a realistic and efficient way to achieve that. Porcupine is a modular block with a curved surface and multiple interlocking. Its unique shape allows the variation of wall geometry, which is desirable for this study. Due to these characteristics, it is feasible to create planar and concave wall profiles from porcupine blocks and compare them. Hence, porcupine block is a key part of this study. The experimental part of the study was based on small-scale tests, which demands the fabrication of accurate miniatures meeting the scaling requirements concerning geometrical and mechanical properties. In order to achieve that, 3D-printing technology was employed as the basic tool of this research work. From physical and numerical simulations it was found that tensile loads in reinforcement could be reduced up to 25% when RSWs are designed with a concave profile. It was also shown that GSWs can be built with a concave profile and increase their loading capacity (i.e. applied surcharge load on top of the backfill) up to 50%. The improvement can be attributed mainly to the reduction of the unstable soil mass behind the wall. Finally, this study tackles the problem of properly scaled geogrids. Poor geogrid modelling was observed in many reinforced soil studies conducted in the past. The current study proves the feasibility of making model geogrids with 3D printing and provides technical recommendations concerning their manufacturing and testing.

Date of Award	2017
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology