On August 8, 2024, the China Concrete and Cement-based Products Association organized a scientific and technological achievement appraisal meeting on the research and application of a new structural system for prefabricated super large composite walls in underground engineering. This project was jointly completed by Shanghai Construction Building Materials Technology Group, Shanghai Construction Second Group, Shanghai University of Technology, Tongji University, Shanghai Construction Design and Research Institute, and Shanghai Research Institute of Building Sciences.

I. Project Background

Most urban water treatment structures in big city have the characteristics of large span, ultra deep, fully underground or semi underground, large volume, heavy load, and require internal support and enclosure systems, generally adopt cast-in-place structures. Cast in place concrete structures require a large amount of formwork and support engineering, which have high construction safety and environmental pollution risks. At the same time, they have the disadvantages of requiring more manpower and a longer construction period. The use of prefabricated assembly is an effective solution.

II. Research Contents

(1) New Structural Systems

A new "composite walls+roof panels" structural system was developed for fully assembled large-size composite walls in underground engineering. The roof panels are made of prefabricated inverted T-plates (including hidden beams), and the node connections are made of UHPC post cast connections. This new structural system effectively solved the lightweighting problem of large-sized prefabricated components in large underground sewage treatment plants.

A new "composite walls+roof panels" structural system

(2) Production Process Technologies

The hydraulic flipping device and high-precision positioning device for super-large-sized prefabricated walls were developed. A transportation device for super-large-sized prefabricated walls was developed, which is convenient and quick to install and disassemble. The stress points of the prefabricated panels on both sides are locked by solid wood in the grooves to protect the wall and reduce vibrations.

Hydraulic Flipping Device

(3) High - efficiency Construction Technologies and Devices

A protective support for wall - end steel bars was developed to effectively protect the wall - end steel bars during the hoisting process. A telescopic and adjustable diagonal brace was developed to solve the problem of temporary support for large - sized components during installation. A verticality - adjusting ruler was developed to achieve efficient and simple verticality adjustment of the composite wall. As a result, a hoisting construction technology for super - large prefabricated walls was formed.

(4) Density Testing Technology

By using phased array ultrasound imaging method, large-area continuous scanning can be achieved. Based on the imaging results, defects can quickly be determined, fullness detection of UHPC poured in the cavity in the wall can also finished correctly and efficiently. Based on the impact force waveform and rebound force, jointly judge the bonding quality of the concrete at the connection node and the strength development of the post poured UHPC.