The investigation of effect of sand content on shear strength, compaction and compressibilty of fibrous peat

Peat is totally or partially changed remains of dead plants which were accumulated under water for houndred to thousands of year. Peat can be generally seen in thick layers in limited areas, has high compressive deformation and low shear strength which often cause some difficulties when construction work is made on this deposit. The organic soil used in this study was obtained from Sakarya region, Turkey. In all tests the fibrous peat samples that remain on #100 (0.15 mm) sieve size and are called as fiber were used (ASTM D 1997-91). This organic soil is classified as Peat by Unified Soil Classification System (USCS). The rounded sand used for the test is poorly graded passing from 2 mm sieve size and retaining on 1 mm sieve size. The main reason of selecting this sieve range is to minimize the effect of size of the sand partical on test results. Standart compaction, direct shear and consolidation tests were done to observe the effect of the sand content on the compacted fibrous peats. Compaction test results were taken as reference to prepare the mixtures used in direct shear and consolidation tests. The mixtures were prepared as % 10,% 20,% 30,%40 and % 50 sand content respectively. All tests results showed that when sand content increases, optimum moisture content decreases on the other hand maximum dry density increases ; cohesion of peat decreases but internal friction angle increases with strong linear correlation; void ratio decreases and also Cc and Cr decreases; mv firstly increases but then it starts to decrease. The effect of the sand content changing were shown in all test results clearly.