新型预应力钢筒混凝土顶管受力特征试验研究

城市供水能力不足与供水安全保障脆弱等问题一直制约着城市的发展,为实现特大山地城市供水组团与水库资源间互联互通需修建大量引水隧洞,而在岩质地层引水隧洞顶管法施工中预应力混凝土管节(JPCCP)抗裂问题一直是施工及运营管理极切关注的重点。本文采用现场顶进原型试验方法开展了预应力混凝土管节在轴向顶力作用下内外层混凝土应变、内外表面混凝土应变及混凝土管节裂缝开展研究。研究结果表明:(1)JPCCP管节在轴向加载过程中,内外层应力分布形式一致,但外层应力远大于内层,受偏心加载影响,管节应力在纵向传递中均出现偏心方向变化;(2)管节端口内侧混凝土是最薄弱区域,加载到顶力设计荷载的2/3左右时,在端口附近开始出现裂缝,且随着荷载增加沿环向发展,最终接近贯通;(3)推导了轴向荷载作用时JPCCP管承载特性计算公式,并与试验进行了对比验证,为类似结构的计算提供了理论基础。

Prototype Test Research on Axial Load-Bearing Characteristics of New Jacking Prestressed Concrete Cylinder Pipe

With the rapid expansion of large mountainous cities, population expansion and industrial growth, inadequate urban water supply capacity and fragile water supply security have been restricting urban development. To realize the interconnection between the water supply group and the reservoir resources in a super mountainous city, it is necessary to build a large number of water diversion tunnels. However, the crack resistance of the prestressed concrete pipe joint (JPCCP) has always been a critical issue in engineering and operation management during the construction of rock diversion tunnels. In this paper, the field jacking prototype test method is used to in the research on the pipe transition of the inner and outer concrete layer strain, inner and outer concrete surface strain, and the cracks of the pipe joints under the action of axial jacking force. The research results show that ①During the axial loading process of the JPCCP pipe section, the stress distribution of the inner and outer layers is the same, however, the stress of the outer layer is much larger than that of the inner layer. Affected by the eccentric loading, the stress of the pipe joints has eccentric rotation in the longitudinal transmission. ②The inner concrete of the pipe joint is the weakest area. When the load reaches 2/3 of the designed maximum jacking force, cracks appear near the port, and develop along the circumferential direction as the load increases, and finally close to penetration; ③The calculation formula of JPCCP pipe axial load-bearing characteristics have been derived and verified with test data, which provides a theoretical basis for calculation of similar structures.