The Research On Temperature Field Of Super Long Large Diameter Pile In Sand Foundation During Construction Period

In the construction of large-diameter and super-long bored piles in sand foundation,cement hydration that release a lot of heat will cause rapid changes in the internal temperature of concrete structures.While the thermal conductivity of concrete is relatively poor,resulting in the accumulation of heat in the concrete structure,and the internal of the concrete structure and the surface of a large temperature difference.Due to the presence of temperature difference,structure will produce stretching.And when the stretching is restricted by the constraint,the structure will produce tensile stress inside.However,the larger tensile stress is detrimental to the concrete structure.It will cause the concrete structure to produce temperature cracks,and affecting the safety and durability of mass concrete structures.It can be seen that the temperature field of the mass concrete structure can be studied,thus the temperature control of the mass concrete structure,to prevent the mass concrete structure to produce temperature cracks.In order to study the temperature field change of large-diameter and super-long bored piles in sand foundation in the construction process,temperature sensors was used to monitor the temperature change of the test pile of Gabon PO project,the test data of each measuring point at different time were obtained.Through analysing the test data,some regularities of the temperature change of the large-diameter and super-long bored piles in sand foundation are summarized.The main research work of this paper are as follow:(1)By collecting data,consulting relevant literature,understanding the current status of study in temperature field,this paper discusses the necessity of the study on the temperature field of super-long large diameter bored piles in sand foundation.(2)Through the basic theory of hydration heat and temperature field,the theoretical system of thermal performance of pile foundation concrete is constructed.(3)By contacting engineering background,design the field test plan of super-long large diameter bored piles' temperature field in sand foundation,and provide guidance to the actual measured data.(4)Standing on the two angles of time and space,analyze the test data,and get the law of temperature field's change in time and space of super-long large diameter bored piles in sand foundation.And according to the test analysis results,the relevant temperature control measures are put forward.Through the analysis,it is found that when the temperature control of super long and large diameter pile foundation concrete is carried out under sand geological conditions,from a time perspective,it is important to focus on the concrete pouring around 24 hours and the first week of the cooling phase.From the spatial point of view,the depth of 30 to 45 meters and the location of the steel cage is the focus of temperature control.