Improvement of engineering properties of peat by cement and lime mixing

Abstract

Development of cost effective methods for improvement of engineering properties of peat is a need of the hour in Sri Lanka in view of the number of major infrastructure development projects that are proposed over the lands underlain by peat. Pre consolidation by preloading was the method adopted in Sri Lanka to date except for the use of dynamic consolidation in one site. The main drawback in the preloading technique is the long time period required. As such, in the research reported in this paper an attempt was made to study the improvements that can be achieved in engineering properties of Peat by mixing with cement or lime. The level of improvement achievable is expected to depend on the level of humiflcation of the Peat and its organic content. Hence, Peats at different levels of humiflcation were used in the study. Peats were mixed in the laboratory with Cement at percentages of 5, 10 and 15 and with lime at 15 % on the wet weight and left to harden for a periods of 2 and 4 weeks. The results of the subsequent tests revealed that even the mixing of 5 % of cement caused significant improvements in an Amorphous peat. A higher percentage 15 % of lime was required to bring about improvements of the same order in the amorphous peat. Even after the mixing of 15% of cement or 15% of lime appreciable improvements of consolidation characteristics were not seen in fibrous peat. Improvements of shear strength were achieved in all types of peat with preconsolidation and with both cement /lime mixing.