The Effect of Geonet Reinforcement on Bearing Capa

Authors: Mohammed O A Bazne Farshid Vahedifard Shahriar Shahrokhabadi

Publish Date: 2014/12/24

Volume: 2, Issue: 1, Pages: 47-63

PDF Link

Abstract

In this paper we studied if geonets when used for drainage purposes can also contribute to the bearing capacity of clay For this purpose extensive laboratory testing and numerical modeling were performed on various configurations to investigate the effect of geonet on the bearing capacity of lowcompacted soft clay Physical models built with four footing shapes square rectangular and two circular along with several configurations of the reinforcement layout ie number length spacing and depth of reinforcement layers were tested in the laboratory Moreover finite element modeling was performed and the results were compared with those obtained from the laboratory tests It was found the geonet reinforcement can improve the bearing capacity of lowcompacted clay up to six times more than its natural condition The results showed that the optimum reinforcement length for the singlelayer model is 3B where B is the width of footing and beyond this length no significant improvement was observed However for the twolayer and threelayer models the optimum length of reinforcements was found to be 2B To maximize the benefit of the reinforcement it was found that the first second and third reinforcement layers should be placed at the depths of B/3 B/2 and B respectively Among different footing shapes which were tested the square footing showed the highest bearing capacity improvement with a bearing capacity ratio of 76 Very good agreement was observed upon comparison of the results from the numerical modeling with the experimental testsSoft foundation soils exhibit large settlement and low shear strength imposing major limitations in construction and earth works Replacing soft soil with highquality fill material is commonly recommended to improve bearing capacity and to decrease settlement Alternatively reinforcements can be used as a remedy to improve soil characteristics Foundation soil reinforcement with geosynthetics has been widely recognized as a technically and economically viable solution to tackle excessive settlement and low bearing capacity of soft soils especially for shallow foundations 1 2 3 4 Extensive experimental and numerical studies have shown that various parameters such as the type of reinforcement layout of reinforcement size and shape of footings and soil and geosynthetic interface can influence the performance of the foundation soil reinforced with geosynthetics eg 5 6 7 8 9 10 11 12 13 14 15Various techniques eg replacement with granular soil compaction stone columns preloading reinforcement can be employed to improve bearing capacity and settlement characteristics of soft soil The effects of geosynthetic reinforcements on bearing capacity and settlement of different soil types have been extensively investigated 16 17 18 19 20 21 22 23 24 25 26 27 In general the majority of previous works consider a reinforced sand bed and propose to replace the soft soil with compacted sand or stabilize the soft soil with granular soils 3 28 29 However there is limited data in the literature regarding the effect of reinforcement on lowcompacted soft clay Demand for construction on finegrained foundation soils has recently increased 29 in most cases due to lack of granular and highquality fill at the site or within a reasonable distance While finegrained soils especially clay are not desirable for foundations soil replacement may not be an economical solution for construction sites including a very thick layer of finegrained soft soil Moreover in all of the aforementioned studies geogrids or geotextiles were used as reinforcing elements

Keywords: