Study On Adaptability To Fault Slide Of Steel Lined Reinforced Concrete Penstock Crossing Active Fault

Pressure water pipes are often used as a pipeline in water diversion structures.They can be divided to exposed penstock,steel lined reinforced concrete penstock,and so on.Currently,exposed steel penstock has been widely used in pipeline structures crossing active fault.With the mega-scale and complexity of long-distance water diversion projects,the carrying capacity of pipelines needs to be improved,which puts forward higher requirements for the design and construction of water diversion pipelines.In recent years,steel-lined reinforced concrete pipes have gradually begun to be used in the design of long-distance water pipelines.Long-distance water pipelines often pass through fault zones with complex geological conditions,Creep and stick-slip dislocation of active fault and the damage of seismic load both have a great threat to structural safety.Therefore,it is very important to study the characteristics of effects of active fracture on steel-lined reinforced concrete pipes and the corresponding engineering layout.In the conventional design,the steel lined reinforced concrete penstock can eliminate the expansion joints,but in order to adapt to the deformation of the active fault,some expansion joints need to be arranged in the pipeline.How the pipeline deforms,whether there will be large slip between the pipeline and the foundation,and the law of pipeline cracking and failure need to be studied.Based on the three-dimensional finite element numerical simulation software ANSYS and ABAQUS,and relying on a water transfer project,this paper studies the adaptability of steel lined reinforced concrete penstock,the contact characteristics between pipelines and foundation,and the cracking analysis of enclosed concrete.The contents are as follows.(1)Based on the basic data,the variation laws of stress and displacement of steel-lined reinforced concrete penstock through active fault under creep-slip,stick-slip and creep-slip combined with earthquake are analyzed.Due to the existence of bellows expansion joints,the pipeline is well adapted to creep dislocation of the fault,and seismic resistance is also good.The stress of the steel lining meets the requirements,but the concrete will produce radial cracks,so the strength problem needs to be solved by reinforcing bars.Because of the large stick-slip dislocation,the shear stress of the foundation plane in the fault area is larger,and the possibility of corrugated pipe failure on the main fault is greater.The relative slip between the pipeline and the foundation is not large under the two fault movement modes.(2)Based on the theory of structural contact nonlinearity,two influencing factors,friction coefficient and cohesion,are studied for the contact characteristics between pipeline and foundation.Sensitive analysis is carried out for the displacement of expansion joints and the stress of pipeline.The results show that the contact characteristics between pipeline and foundation mainly affect the stress along the pipeline axis.Axial stress of the steel lining and concrete,YX shear stress,YZ shear stress of the foundation plane,transverse displacement difference and vertical displacement difference of the double bellows expansion joints all have certain sensitivity to friction coefficient.The cohesion of present soil foundation has no significant effect on the stress and the displacement of the pipeline.(3)Based on the plastic damage model of concrete,the two-dimensional non-linear calculation of pipeline concrete is carried out to compare the cracking load and arrangment of concrete,the stress of the steel lining and the variation of crack width of concrete.The research shows that the concrete does not crack when the internal water pressure load is small.At this time,the concrete is co-beared with the steel lining and the steel bar.As the internal water pressure increases,when the concrete material is damaged and cracked,the bearing capacity to hoop force will be lost,and the part of the load will be transferred to the steel lining and steel bars.In addition,different reinforcement configurations in the inner and outer layers of concrete lead to different cracking time and degree,and the increasing law of stress of the steel lining and steel bar varies with the development of the internal water pressure.