Design methods for geogrid reinforced foundation systems on weak subsoil

Freudenberg Performance Materials, Low & Bonar BV Branch Office, Hungary

Abstract

Construction on weak subsoil is a reoccurring challenge for engineers nowadays, for which various different solutions are available. Geosynthetics are getting more and more popular and one of their most widely used application is subsoil reinforcement. Several types of geosynthetics can be used, the most well-known are vertical drains and geogrids. Prefabricated vertical drains can be used for accelerating consolidation in oversaturated soils with a high water content as they drain the excess water from soil while also decreasing pore water pressure, optimizing soil bearing capacity and reducing the risk of liquefaction and excess settlements. The main limitation is not significantly reducing total subsidences. Gravel and concrete piles are widely used, and in recent years, rigid inclusions (unreinforced concrete piles) are also getting popular. A common feature of them is that a so-called Load Transfer Platform (LTP) has to be built between the superstructure and the foundation to prevent direct contact with one another. The LTP between them is a stiff, reinforced layer that helps the arching of load. Design of the LTP may be carried out using several design standards, of which the most widely used are Collin’s beam method and CUR226. This paper focuses on presenting and comparing these two main design methods, emphasizing their differences and applicability while also considering their limitations.