Mechanical Reason Analysis For Crack On Spillway Pier Of Overflow Dam In Shenwo Reservoir, Liao Ning

Mass concrete constructions, which are of large volume and high bearing capacity,are widely applied in large civil engineering structures, such as water conservancyprojects, significant architectures and transport projects. However, due to poor tensionstrength and heat-conducting property of concrete, hydration heat in construction periodand seasonal temperature load in service period cause high temperature stress and evenconcrete cracking in the structure. International and domestic academics have beendoing much research on concrete crack and mass concrete temperature stress, andposted qualitative and semi-quantitative answers to concrete crack problems, whereasthere is less investigation into concrete crack in some special position of mass concreteconstructions, such as in sluice pier of dam. Crack causes and expansion are toocomplicated to completely prevent. Traditional finite element methods (FEM) can onlybe used to analyse stress-based crack problem but difficult to deliver macroscopiccracks, and it is rather qualitative and indistinct as well. Extended finite element method(XFEM) is a new and developing method to convey macroscopic cracks much better.Both FEM and XFEM are put into use to simulate the stress distribution and cracksexpansion of sluice pier of spillway dam in Shenwo reservoir during construction periodand service period. With comparison of practical conditions in the project, mechanicalproperties of pier cracking are analyzed. The main contents of this paper are as follows:(1) This paper stimulates and analyses the temperature field and temperature stressin the sluice pier of dam during the construction period with consideration ofconstruction technology, environmental influence and concrete property. Results showthat earlier after concrete has been poured, great temperature difference between interiorand exterior of the sluice pier of dam without cooling in the interior is the main cause ofoverstressing and cracking in the surface layer of the sluice pier. In the later period ofconstruction, concrete cracks under tensile stress, which is produced by the concreteshrinkage under high initial temperature and constraints on the sluice pier by spillwaydam. This stress state is also the trigger of crack in sluice pier during service period.(2) During service period of the dam, this article simulates the annual watertemperature and seasonal temperature nicely, calculates the annual temperature field and thermal stress field of the pier, analyses the stress characteristics of the pier underdifferent combinations of weight, water pressure and annual temperature. Thecomparative analysis shows that the annual temperature load, especially the lowtemperature load, is the main cause of pier crack. Using extended finite element methodto simulate and analyse the morphology, cracking law and characteristic of distributionof the pier crack, the results are in good agreement with the actual engineering fracturemorphology, confirms that seasonal low temperature load is the main cause of piercracks.These mechanisms of the concrete cracks in the sluice pier provide new targetedideas for reinforcing the pier, and theory support and reference for temperature controland crack control.