Study On Swelling Self-healing Ability Of Cracks On The Interior Surface Of PCCP

PCCP is widely used in the related project of South-to-North Water Diversion in Henan province. Since the project started, cracks on the interior surface were found in the process of production, transportation, parking of PCCP. In addition, the cracks have a certain regularity. This paper did a lot of research on cracks on the interior surfaces of PCCP, in order to apply experimental foundation and theoretical basis for setting or revising related standards for design, manufacture, acceptance of PCCP,also in order to ensure the safety of the project. The main conclusions are as follows:(1) Reasons of cracks on the interior surface were found and measures were given to decrease the crack width, through analyzing the existing data and on-scene investigation.(2) This paper tested the width of the cracks, discovered the distribution regularity of cracks, analyzed the specific reasons for this phenomenon, obtained the prediction model of dry-shrinkage strain.(3) To study the swelling self-healing ability of cracks on the interior surface of PCCP, this paper carried out the prototype swelling test on PCCP. This paper analyzed the effect of swelling self-healing of interior cracks from the point of view of swelling strain. The result shows PCCP crack swelling self-healing speed is related with the swelling age. Soaking in water for one day, the speed is the fastest, for three day, the speed is slowed down, then the speed is smoothly. If there were 3 interior cracks of PCCP, swelling healing width could be 0.3 mm.(4) This paper examined the crack depth, analyzed the relationship between the crack depth,crack width and the age of PCCP. The result shows that there is a clear link between crack depth and the age of PCCP: the age extends per one month, crack depth increases about 10 mm. In accordance with this regularity, PCCP was piled up in 6 months, crack depth could reach steel tube. According to the results, the relational expression between the crack depth and age of PCCP are given in this paper.(5) This paper also studied swelling self-healing ability of cracks on the interior surface of PCCP under the action of constraints. By using finite element method, this paper calculated swelling coefficient under constraints with different crack depth.The result shows that swelling coefficient under constraints decreases with increasing of the depth of cracks.