Application of Crane-Mounted Bottom-Feed Vibroflot in Offshore Stone Column Construction

— Offshore bottom-feed vibro-replacement stone column construction for the 200,000 DWT channel project in the central area of Caofeidian Port Zone, Tangshan Port

Project Overview

In January 2021, the crane-mounted bottom-feed vibroflot equipment developed and produced by Beijing Vibroflotation Engineering Machinery Co., Ltd. was deployed for offshore operations in the Caofeidian Port Zone of Tangshan. The project is the breakwater head improvement works of the 200,000 DWT channel expansion in the harbor basin.

Project Challenges

The construction water area is located near the harbor basin entrance. On one hand, the steel wire rope anchor chains of conventional flat barges seriously obstruct vessels entering and leaving the port; on the other hand, disturbances from large vessels entering and leaving the port, combined with waves and ocean currents, made conventional offshore vibroflotation pile construction schemes fundamentally unfeasible in this sea area. To meet the ground improvement requirements, accurate positioning and normal construction backfilling became a key challenge of this project. The limited offshore working space and risks also made automation of the equipment essential.

Equipment Selection

The bottom-feed vibroflot's unique vibration and compaction improve soil conditions, and its configured piping system enables internal material feeding, making feeding reliable and precise. The additional one-key pile-forming operation facilitates offshore work and greatly improves efficiency, making it unquestionably the preferred equipment for this offshore ground improvement project.

Beijing Vibroflotation Engineering Machinery Co., Ltd. has focused on the vibroflotation industry for more than 40 years. As the developer of China's first bottom-feed vibroflot and supplier of complete equipment sets, as well as a developer and promoter of automated vibroflotation construction and full-process quality control technology, the company provided the complete set of bottom-feed vibroflot construction equipment for this project and assisted CCCC First Harbor Consultants Co., Ltd. in project construction design and related work.

Overcoming Difficulties

The construction sea area has harsh climate, with minimum temperatures reaching minus 25 degrees Celsius, requiring the vibroflot equipment to be reliable and cold-resistant. The core components of our company's bottom-feed equipment all use original parts imported from Europe and Japan. Through repeated research, a spud-leg dredger was ultimately selected for modification, successfully solving the problems of precise pile positioning and the narrow construction area. Under such harsh and extremely cold special working conditions, the construction task was still successfully completed, with more than 3,000 piles formed, totaling 25,000 linear meters of work volume.

Project Parameters

The main equipment for offshore stone column ground improvement construction includes: bottom-feed vibroflot, crawler crane, material barge, and excavator.

Operating parameters of this project: starting from 9 meters underwater, construction pile diameter 1 m, working pile depth 15–17 m.