01

Project Overview

The CGN Zhejiang Sanao Nuclear Power Plant Phase I Project has a total investment of approximately RMB 39.3 billion. It plans to build two nuclear power units using the integrated "Hualong One" technology and their supporting auxiliary facilities. It is the first civilian nuclear power project in which private capital has taken an equity stake, and it is also an important supporting project for Zhejiang Province in building a clean energy demonstration province. Recently, the pile foundation works for the cooling machine repair workshop / non-radioactive electromechanical instrument warehouse and office / performance test laboratory of the CGN Zhejiang Sanao Nuclear Power Plant Phase I Project (BBA/BBF/BXL), undertaken by Jingjiu Foundation, were located in the territory of Dalong Village, Xiaguan Town, Cangnan County. The construction site was formed by cutting mountains and reclaiming land from the sea. The upper strata are mainly dumped fill stone, the original rock is highly weathered and has poor stability, and it easily disintegrates upon contact with water. In addition, the backfill layer contains large blocks and is deep, the strata are not dense, and the geological structure is particularly complex, bringing great difficulties to normal construction.

02

Technical Measures

The project construction site is close to the seaside, groundwater is abundant, and affected by the monsoon climate, seawater tides rise and fall frequently, seriously affecting the stability of pile foundation hole formation. Because the nuclear power project is large in scale and tight in schedule, with multiple units and multiple trades working in cross-operation, this brings even greater pressure and challenges to pile foundation construction. In response to these unfavorable factors, the Jingjiu Foundation project department organized scientifically, made overall deployments, conducted repeated discussions, optimized the plan, and took precise measures. It determined to adopt the large-diameter down-the-hole (DTH) hammer drilling technology for construction, with pile diameters of ф800--1000 and drilling depths of 25--40 meters, completing hole formation in one pass.

03

Method Highlights

Ensuring Efficient Rock Penetration

Solving the technical challenge of efficient "rock penetration" for large-diameter piles: it can form holes in special complex strata such as cobble and boulder layers and hard rock layers, with good pile quality and high construction efficiency, and can solve the technical challenge of efficient "rock penetration" for large-diameter pile foundations.

Achieving Energy Saving and Emission Reduction

Solving the problem of serious environmental pollution caused by mud slurry wall protection in pile holes: no mud slurry wall protection is required, there is no pollution from mud preparation or discharge, and the site is clean. This fills a domestic technical gap and is a new environmentally friendly pile construction machinery product and new process, conforming to the national policy requirements for energy saving and emission reduction, with good economic and social benefits and broad market application prospects.

Solving the Common Problem of Mud Inclusion

Solving the common problem of mud inclusion during concrete pouring: the upper and lower power heads rotate in opposite directions for drilling, the DTH hammer has a high impact frequency, low-amplitude and high-frequency rock breaking is achieved, and the full casing follows up for wall protection, avoiding collapse risks and eliminating the common problem of mud inclusion during concrete pouring.

Suitable for Complex Geology

Suitable for various complex and special geological conditions: pile foundation construction mainly in fine sand layers, gravel layers, quicksand, underground rivers, flow-plastic silt, karst caves, hard rock layers, and areas with high groundwater levels, greatly improving project progress and construction quality.

Achieving One Machine with Multiple Functions

Multifunctional drilling rigs achieve one machine with multiple functions: featuring single-machine multifunctionality, multiple uses, and diversified construction. This can reduce equipment investment and improve equipment utilization, creating higher equipment use value and economic benefits for customers while also creating good social benefits.

04

Results Achieved

Practice has proven that construction using the large-diameter DTH hammer drilling technology greatly improves pile integrity and bearing capacity. It not only ensures pile foundation construction quality but also improves work efficiency, thoroughly solving the pile foundation construction challenges in the complex geology of mountain-cutting and sea-reclamation sites, winning speed and benefits for the smooth advancement of the project, conforming to the national policy requirements for energy saving and emission reduction, and delivering good economic and social benefits.