混凝土强度与变形特性的围压效应试验研究

Experimental study on concrete strength and deformation characteristics under high confining pressure

运用MTS815 Flex Test GT岩石力学试验系统对C30和C50混凝土圆柱体试件进行单轴、三轴压缩试验,得到了混凝土的应力-应变全过程曲线,研究了不同围压下混凝土的强度和变形特性。结果表明:Newman非线性方程较Richart线性方程更为准确地表达了强度与围压的变化规律,随着围压的增加,两种强度等级混凝土对应围压的强度差别逐渐减小;混凝土的抗压强度和破坏形态存在一临界围压σ3c,高于此临界围压时破坏阶段为应变软化,且抗压强度受混凝土强度等级影响较小,反之为应变硬化;随围压的增大,混凝土材料由脆性逐渐过渡为延性,变形能力增大,弹性模量、割线模量减小,泊松比增大,峰值轴向应变增大,其变化关系可用Ansari线性方程表示。

The uniaxial compression tests and triaxial compression tests were performed on the concrete cylinder specimens of C30 and C50 using MTS815 Flex Test GT rock mechanics test system.During the whole loading process,the stress-strain curves of the concrete specimens were obtained and the strength and deformation characteristics were investigated under different confining pressures.The experimental results show that Newman nonlinear equation can describe the evolution rule of strength with the changing of confining pressure more accurately than Richart linear equation,and with the increase of the confining pressure the difference of strength corresponding to the same confining pressure between these two strength grades concrete becomes gradually smaller.According to the compressive strength and failure mode of concrete specimens,there is one critical confining pressure σ3c,when the confining pressure applied above the critical confining pressure the specimens will behave strain softening and the compressive strength is hardly affected by the concrete grade,when the confining pressure applied below the critical confining pressure the specimens will behave strain hardening.With the increasing of the confining pressure,the concrete materials behaves as brittle and transfers to ductile gradually,and the deformation capacity will enhance,elastic modulus and secant modulus reduce,Possion＇s ratio increases,the axial strain corresponding to peak value of stress also increases,as well as the stress-strain relation describes well by the Ansari linear equation.