Strength and deformation behavior of the Yellow River silt under triaxial drained condition considering characteristic states

Currently,the application of the Yellow River silt in subgrade,especially in expressway subgrade,has not been widely promoted.The main reason is that the research on the mechanical characteristics of the Yellow River silt used for subgrade filling is extremely limited.In this study,the static shear test of the Yellow River silt under drained condition was carried out using Global Digital Systems(GDS)triaxial apparatus,and the effects of confining pressure,relative density and shear rate on the strength and deformation behavior of the Yellow River silt were investigated.The cohesive force of the Yellow River silt is low,and the friction angle is the main factor determining the shear strength.Friction angle at phase transformation stateφpt,friction angle at peak stateφps,friction angle at critical stateφcs,were obtained via the observation on the evolution law of mobilized friction angle during the whole shearing process.The friction angles corresponding to three different characteristic states have the following magnitude relationship,namelyφps>φcs>φpt.The strength parameters for low-grade subgrade and highgrade subgrade were chosen to be 29.33°and 33.75°.The critical state line(CSL),envelop of phase transformation(EOP),and envelop of dilatancy(EOD)for three different characteristic states were determined.The critical stress ratio M,the phase transformation stress ratio Mptand the dilatancy stress ratio Mdof the Yellow River silt are 1.199,1.235,1.152,respectively.These results provide a basis for the mechanical analysis of the Yellow River silt subgrades and the subsequent establishment of dynamic constitutive model of the Yellow River silt.

Development of Lightweight Concrete Using Industrial Waste Palm Oil Clinker

Concrete is a major material used in the construction of buildings and structures in the world.Gravel and sand are the major ingredients of concrete but are non-renewable natural materials.Therefore,the utilisation of palm oil clinker(POC),a solid waste generated from palm oil industry is proposed to replace natural aggregate in this research to reduce the demand for natural aggregates.One mix of ordinary concrete as control concrete;while four mix proportions of oil palm clinker concrete were obtained by replacing 25%,50%,75%,and 100%of gravel and sand of control concrete with coarse and fine oil palm clinker respectively by volume,with same cement content and water cement ratio.Compressive strength test was carried out of concretes with different percentages of oil palm clinker;whereas water absorption tests according to respective standard,were carried out to determine the durability properties of various mixes.Based on the results obtained,the study on the effect of percentage of clinker on strength and durability properties was drawn.According to ACI classification of light weight concrete only the 100 percentage replacement can achieve the definition of light weight concrete since its density is less than 1,900 kg/m3 and strength larger than 17 MPa.Eventually the 25%replacement of the normal aggregate by the OPC will improve the strength and durability of the concrete.