漠河多年冻土区砼灌注桩承载力形成时间数值分析

根据带内热源伴有相变瞬态温度场的控制方程,在空间域内用采用混合单元的有限元网格划分,在时间域内用有限差分格式划分的混合解法编制有限元计算程序。针对黑龙江省漠河多年冻土区场地,根据实验得到的不同水泥水化热释放热量,进行钻孔灌注桩周土体温度场数值计算,分析影响砼灌注桩冻结强度形成的因素和变化规律及原因。研究表明砼浇注温度、不同外加剂组合水化热放热量对桩壁土体温度有显著的影响。在漠河多年冻土区,建议混凝土外加剂选用粉煤灰+硅粉+早强剂+减水剂组成,灌注桩混凝土向冻土钻孔中浇注温度应控制在5℃,这样可以大大缩短混凝土灌注桩承载力形成时间。

Numerical analysis for formation time of bearing capacity of cast-in-place concrete pile in permafrost regions of Mohe County

Based on the differential equations for heat balance control of transient temperature field with phase changing and heat source,the finite element programs were developed by adopting the grid segmentation of the mixture cell in space domain and by the mixture solution of the finite difference format segmentation in time domain.The numerical calculation of temperature field was carried out,on the basis of measuring the heat of hydration.The active factors and the formation of strength of freezed cast-in-place pile in permafrost of Heilongjiang Province were analyzed.It was indicated that the temperature of cast-in-place concrete and the heat of hydration of different additive had great influence on temperature of soil around the pile.Suggestions for cast-in-place concrete pile in permafrost of Mohe County were: admixture composed of pulverized fuel ash,silica powder,early-strength ening agent and water-reducing agent;temperature of cast-in-place concrete controlled at 5℃.Therefore the formation time of bearing capacity would be greatly shortened.