BCCP内水压承载能力原型试验

为了研究钢筋缠绕钢筒混凝土压力管（BCCP）在内水压作用下的承载破坏特征,设计了三个不同管径的BCCP内水压现场原型试验.在管径1 800 mm BCCP的钢筒、钢筋和混凝土保护层上布置环向应变片,逐级施加内水压至2.5 MPa,得到了各部位在内水压作用下的受力变化规律.主要结论如下:BCCP从生产时施加预应力到承受内水压至最终破坏的受力过程可分为5个阶段.1）管芯受预应力钢筋环向作用力阶段.缠筋后,钢筒与混凝土形成的管芯受到一个初始预压应力；2）保护层开裂前整管承受内水压弹性阶段.对应于试验中内水压小于1.5 MPa的阶段,管芯依然受压,而预应力钢筋和外混凝土保护层受拉；3）保护层开裂,管芯承受内水压弹性阶段.试验中当内水压达到1.6 MPa后,保护层开始达到抗拉强度开裂,混凝土管芯也从初始的受压慢慢转变为受拉,依然处于弹性状态；4）管芯开裂,钢筒和钢筋受拉弹性阶段.当内水压达到2.2 MPa后,管芯径向开裂,但是钢筒和钢筋的应力随内水压依然稳步增长；5）管道破坏阶段.钢筒和预应力钢筋达到最终屈服强度,整管丧失承载能力.研究成果可为BCCP在输调水工程中的推广使用以及相关标准的制定提供依据.

Prototype test on the bearing capacity of BCCP under internal water pressure

In order to study the full-range failure process of bar-wrapped cylinder concrete pressure pipe (BCCP) under internal water pressure, tests on three prototype BCCPs with different diameters were designed. Annular strain gauges were arranged on the cylinder, steel bar, and concrete protective cover of the BCCP with a diameter of 1 800 mm, and the force response of each part under the action of internal water pressure was obtained by increasing the applied internal water pressure to 2.5 MPa step by step. It was found that the load-bearing process of BCCP from prestressing to ultimate failure could be divided into 5 stages. First, the concrete core was subjected to the force of the prestressed steel bar without protective cover. After being wrapped, the core formed by cylinder and concrete was subjected to an initial pre-compression stress. Second, the whole pipe was in the elastic stage before the protective cover cracked. It corresponded to the stage when the internal water pressure in the test was less than 1.5 MPa, and the core was still under pressure, while the prestressed steel bar and the outer concrete protective cover were under tension. Third, the concrete core was in the elastic stage after the protective cover cracked. When the internal water pressure arrived at 1.6 MPa, the cover reached the tensile strength and began to crack, and the concrete core also transformed from the initial compression to tension slowly and remained in elastic state. Fourth, the cylinder and the steel bar were in the elastic stage of tension after the concrete core cracked. As the water pressure arrived at 2.2 MPa, the concrete core cracked radially, but the stress of cylinder and bars still increased steadily with the internal water pressure. Fifth, the pipe was completely destroyed. The cylinder and the steel bars reached the ultimate yield strength, and the whole pipe lost its bearing capacity. The research results could provide basis for the popularization and application of BCCP in water transfer engineering and the formulation of relevant standards.