تاثير مديريت دراز مدت بقاياي گياهي جو بر خواص فشردگي و مقاومت برشي يك خاك لوم رسي

چكيده انگليسي :

The Effect of Long term Management of Barley Residues on Compression Properties and Shear Strength of a Clay Loam Soil Behnaz Azari Mobarake Behnazazari131@gmail com May 12 2010 Department of Agricultural Machinery Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Abbas Hemmat ahemmat@cc iut ac irAbstract Soil compression is one of the major causes of soil degradation Adding organic materials to the soil can improve soilstructure and help to retain water in the soil Plant residue is known as the least expensive most abundant and available organicmatters for incorporating into the soil One of the common solutions to prevent soil compaction is to estimate the soil stress atits compaction threshold pre compaction stress pc and the soil sensitivity to more compaction compression index Cc if theapplied stress level is higher than its pc value In this research disturbed soil samples were taken from clay loam topsoil 0 20cm soil layer from a long term 7 year residue management under barley corn rotation Repacked soil samples taken fromfour residue management treatments residue burning ResB residue incorporation Res residue incorporation with ureaapplication ResN residue incorporation with farmyard manure application ResFYM were prepared at two water contents 14 7and 16 7 equivalent to 0 9 plastic limit PL and 1 05 PL respectively and two preloads 100 and 200 kPa Then thecompressive properties pc Cc were obtained using plate sinkage test PST and confined compression test CCT Stress sinkage and stress strain curves were drawn for both PST and CCT respectively For each curve three different methods wereconsidered to determine the pc These methods were 1 Casagrande 2 maximum curvature and 3 intersection of virgincompression line and x axis Soil shear strength parameters cohesion c and internal friction angle were measured using adirect shear box test The percentage of organic matter of two treatments Res ResN was not significantly different than theresidue burning treatment whereas in ResFYM treatment the organic matter significantly increased by 39 In PST themaximum and minimum values of pc were obtained with Casagrande and maximum curvature methods respectively In CCT the maximum values of pc were achieved with Casagrande method while for 100 and 200 kPa preload stresses the minimumvalues were obtained with maximum curvature and intersection of virgin compression line and x axis methods respectively In both tests PST CCT when the pc values were estimated by Casagrande method a larger overestimation was observed at14 7 water content compared with 16 7 The results indicated that with a 100 kPa preload and for both water contents the pc for ResFYM treatment had significantly higher values than the ResB treatment When the water content increased from0 9PL to 1 05PL the pc decreased about 17 and 13 in PST and CCT respectively whereas by doubling the preload 96 and 79 increase in pc were observed in PST and CCT respectively The relationship between pc values obtained with PSTand CCT was linear and significant at probability level of 0 1 There were not significant differences in Cc values among theresidue management treatments in PST or CCT With increasing water content from 14 7 to 16 7 the Cc values in PST andCCT increased significantly by 8 and 20 respectively When the preload was doubled in CCT the Cc values were reducedby 16 whereas in PST the Cc values were not significantly affected by the preload The soil cohesion was increased by 75 when the water content increased from 14 7 to 16 7 By doubling the preload the cohesion increased by 82 The averagevalue of internal friction angle for all residue management treatments was 27 1 Increasing water content from 14 7 to 16 7 caused a 22 reduction in internal friction angle while a reduction of 10 was observed when the preload was doubled Inboth PST and CCT the Cacagrande method gave the best estimation of pc In PST we can replace the intersection

آذري مباركه، بهناز

تاثير مديريت دراز مدت بقاياي گياهي جو بر خواص فشردگي و مقاومت برشي يك خاك لوم رسي

تنش پيش-تراكمي , مديريت بقايا , زاويه اصطحاك داخلي