混凝土水化作用对群桩热力学特性影响现场试验

Field test on thermo-mechanical properties of pile group influenced by concrete hydration

混凝土早期水化作用不仅释放大量热量、而且会引起桩基先期变形与约束应力,影响桩基承载性能。目前针对地层温度对早期混凝土水化作用引起的桩基热力学特性(尤其是群桩效应)影响的研究仍相对较少。开展3×3群桩在早期混凝土水化作用下的桩基热力学特性现场试验,实测了桩身温度、应变等变化规律,着重分析了地层温度对桩基水化热消散、桩身约束应力的影响规律;并开展了相同条件下单桩热力学特性对比试验,探讨水化热作用群桩效应。研究结果表明,水化热作用下,群桩中温度叠加效应并不明显;地层中恒温带的水化热消散速度慢于变温带;混凝土残余应力沿桩深方向分布不均,呈现中间大、两头小的特点,最大残余应力出现在0.6倍桩深处。

The early concrete hydration not only releases a large amount of heat but also causes the early deformation and constraint stress of the pile,which affects the bearing capacity of piles.However,there are few studies on the effect of formation temperature on the thermo-mechanical properties caused by the early concrete hydration,especially the pile group effect.Field tests were carried out to investigate the thermo-mechanical properties of 3×3 group piles influenced by early concrete hydration.The distributions of temperature and strain of piles along pile depth were measured.Moreover,the heat dissipation and additional stress of piles,and heat dissipation group effect influenced by formation temperature were discussed.Meanwhile,the thermo-mechanical properties of the single pile were also conducted for comparative analysis.The results show that the temperature superposition effect of pile group influenced by hydration heat is not very obvious.The dissipation rate of hydration heat in the constant temperature zone is relatively slower than that in the variable temperature zone.The residual stress of concrete is unevenly distributed along the pile depth,which has large values in the middle and small values at two edges.The maximum residual stress occurs at a depth of 0.6 times pile length.