Evaluation of load transfer platforms and their design methods for embankments supported on geopiers.

摘要

Geosynthetic-reinforced load transfer platforms (GRLTP) are constructed at the base of column-supported embankments to efficiently distribute embankment and live loads onto the columns supporting the embankment. There are currently four major design methods for engineers to choose from when designing GRLTP for column-supported embankment. The design methods include the British, Nordic, German, and Collin methods. Each design method utilizes a different arching ratio method to calculate the loads on the geogrid reinforcement. The first three methods utilize what is known as catenary load transfer platform (LTP) concept. Alternatively, the Collin method utilizes what is termed as beam LTP concept.;A full-scale heavily instrumented test embankment was constructed in Gebeng, Malaysia to evaluate the performance of different LTPs supported on geopiers. Three types of LTPs that were constructed include catenary, beam, and reinforced concrete slab. The study was aimed to address the following issues: (1) the appropriate arching ratio method to use, (2) the performance of different types of LTPs and the effectiveness of the design methods, and (3) the suitability of using geopiers, which are less stiff than conventional piles, as support columns with an LTP.;The field data indicate that all LTPs performed satisfactorily demonstrating that both the LTPs and the geopiers are suitable for the construction of embankments over soft ground. The beam LTP performed slightly better than the catenary LTP. In the Malaysian context, the most cost effective LTP is the reinforced concrete slab followed by the beam and finally the catenary. The catenary design concept (used by the British, Nordic, and German methods) is conservative with the least conservative being the German design method. The Collin design method provides reasonably good correlation between design and field parameters, however it may tend to underestimate the tensile forces generated in the geogrids. In the case of arching ratio methods, the Guido method always gives the lowest arching ratio and when used for the calculation of tensile force in the geogrids it generally offers the closest value to the field tensile force generated in the geogrid. A 2-D finite element analysis using a simple Mohr-Coulomb elastic-perfectly plastic constitutive model was able to simulate the behavior of the LTPs.