01

Project Introduction

The CGN Zhejiang Sanao Nuclear Power Plant Phase I Project has a total investment of approximately 39.3 billion yuan. It plans to build two "Hualong One" fusion technology nuclear power units and their supporting auxiliary facilities. It is the first civilian nuclear power project with private capital participation, and also an important supporting project for Zhejiang Province to create a clean energy demonstration province. Recently, the pile foundation works for the chiller 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), constructed by Jingjiu Foundation, are located in Dalong Village, Xiaguan Town, Cangnan County. The construction site is formed by cutting mountains and filling seas. The upper strata are mainly dumped rockfill, the original rock is highly weathered and poor in stability, easily disintegrates upon contact with water, and the backfill layer has large blocks and deep thickness, the stratum is 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, with abundant groundwater. Affected by the monsoon climate, seawater tides ebb and flow frequently, seriously affecting the stability of pile foundation hole formation. Due to the large scale and tight schedule of the nuclear power project, multiple units and trades work crosswise, bringing great pressure and challenges to pile foundation construction. In response to these unfavorable factors, the Jingjiu Foundation project department scientifically organized, coordinated deployment, repeatedly discussed, optimized the plan, and implemented precise measures, determining to adopt the large-diameter down-the-hole hammer drilling technology for construction, with pile diameters of ф800-1000 and drilling depths of 25-40 meters, completing the hole in one pass.

03

Construction Method Highlights

Ensuring Efficient Rock Penetration

Solving the technical problem 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 problem 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 wall protection in pile holes: no mud wall protection is required, no pollution from mud preparation and discharge, and the site is clean, filling the domestic technical gap. It is a new environmentally friendly pile construction machinery product and new technology, 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 down-the-hole hammer has high impact frequency, low amplitude and high frequency rock breaking, 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 geologies: pile foundation construction in fine sand layers, gravel layers, quicksand, underground rivers, flow-plastic silt, karst caves, hard rock layers, and high groundwater levels, greatly improving project progress and construction quality.

Achieving One Machine with Multiple Functions

Multifunctional drilling rig achieves one machine with multiple functions: it features single-machine multi-function, multi-purpose, and diversified construction. It can reduce equipment investment, improve equipment utilization, create higher equipment use value and economic benefits for customers, and also create good social benefits.

04

Achievements

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