Backhoe Dredgers Advantages | Illustrated by a Port Area Project

2026-03-19 16:13:43     Category：Technical Resources     Browse number：212     Release time：2026-03-19 16:13:43

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Backhoe Dredgers Advantages - Illustrated by a Port Area Project

Using a real-world project as a case study, this paper illustrates the operational characteristics and advantages of Backhoe Dredgers |Yanyang Marine

One typical 30,000-ton-class oil and chemical terminal project in a certain port area is a key regional project. Commencing in February 2023, the project has a planned construction period of 365 days, including a 120-day dredging period. Basin dredging plays a crucial role in the overall project progress. The basin dredging starts at an elevation of approximately 13.4 meters with an excavation thickness of about 5 meters, totaling 220,000 cubic meters. This includes 35,000 cubic meters of medium-coarse sand, 186,000 cubic meters of semi-consolidated cemented sand, and local reefs. The semi-consolidated cemented sand and reefs in the dredged materials are the biggest challenges for basin dredging operations.

Key Environmental Characteristics and Challenges of the Project

Limited Operational Space: The basin’s operational area is extremely restricted. Maritime transportation in the basin cannot be interrupted during dredging. The use of large-scale dredging equipment would adversely affect normal maritime transportation, reduce construction efficiency, and incur high costs, making it impractical.

Proximity to Port Structures: The basin is adjacent to existing port buildings and structures. Dredging operations must not cause adverse impacts to these structures, ruling out engineering blasting methods.

High-Strength Dredged Materials: The semi-consolidated cemented sand and reefs have high strength, posing significant dredging difficulties. Selecting an appropriate dredging method under these special conditions is a major challenge.

Geological Feature 1: Semi-Consolidated Cemented Sand

The port area features alternating marine-continental sedimentary strata formed in different geological eras, with an extensively distributed layer of semi-consolidated cemented sand. This layer is shallowly buried, with local outcrops, and belongs to Middle Pleistocene deposits. Influenced by the sedimentary environment, it exhibits various spatial distributions such as interbedded layers and lenses, with local reef-shaped beach rocks.

Geologically, the semi-consolidated cemented sand is in a transitional stage from sandy soil to fully consolidated rock, possessing both distinct sandy soil characteristics and partial rock properties. The strength of the semi-consolidated cemented sand varies significantly, with an average standard penetration test (SPT) blow count of 35–50 blows (maximum exceeding 120 blows). Core samples are generally columnar or short-columnar, producing a dull sound without rebound when struck. The unconfined compressive strength (UCS) ranges from 1 to 18 MPa. Due to its dense, semi-consolidated state and relatively high strength, conventional dredging methods face great difficulties and low construction efficiency.

Geological Feature 2: Reefs

Reefs, geologically known as beach rocks, are common in coastal areas. A terminology in marine geology, beach rocks are formed by carbonate cementation of sand, gravel, and other clastic materials on beaches. Composed mainly of terrigenous granite gravel fragments and marine biological debris, cemented by calcium carbonate, they exhibit good diagenesis despite their short formation time—some are even harder than concrete and resistant to impact. Beach rocks are discontinuously distributed in coastal areas without forming integrated strata; many exist in isolated blocks. With varying sizes and strength, they adversely affect nearshore port projects, making conventional dredging methods highly challenging.

High-Power Backhoe Dredgers Break Through Traditional Drilling Limitations

In dredging and rock excavation projects, the most common methods besides blasting are hydraulic hammer drilling.

However, research shows that there is limited experience in applying hydraulic hammer drilling to semi-consolidated cemented sand and reefs. Additionally, hydraulic hammer drilling has high requirements for topographic and geological conditions, which are complex and difficult to accurately identify underwater—often leading to low efficiency and prolonged construction periods.

The project requires an average daily dredging volume of approximately 1,800 cubic meters during the dredging period, and over 2,000 cubic meters per day when accounting for special circumstances such as extreme weather and equipment maintenance. Traditional hydraulic hammer drilling is generally inefficient and unable to meet the project’s actual needs.

To address this, the construction team abandoned hydraulic hammer drilling and opted for high-power mechanical backhoe dredgers. Through repeated tests, it was determined that the key factors affecting the applicability of backhoe dredgers are equipment power, maximum digging force, bucket capacity, and digging depth.

The project team ultimately selected the Hitachi EX5500 backhoe dredger, featuring a maximum digging force of 990 kN, a maximum digging depth of 32 meters, and a maximum bucket capacity of 20.5 cubic meters.

Efficient Rock Excavation and Seamless Dredging-Transportation Coordination

Application results of the EX5500 dredger in semi-consolidated cemented sand and reef excavation show that high-power dredgers can effectively excavate semi-consolidated cemented sand and reefs with block sizes not exceeding the bucket capacity. For individual extra-large reefs, the surrounding rock and soil can be excavated to form pits, into which the reefs are pushed and buried using the backhoe.

The construction fleet consists of 3 vessels: 1 EX5500 backhoe dredger and 2 split hopper barges.

Statistical data shows that each barge takes 2.5–3.5 hours to load to the load line limit, and 4–4.5 hours for a round trip (13.3 nautical miles) to the dumping site, resulting in a dredger downtime of 0.5–1.5 hours per barge. The daily loading volume is approximately 4–5 barges. Based on 16 working hours per day, an average loading time of 3 hours per barge, and an average downtime of 1 hour, 4 barges can be loaded daily. With each barge carrying 900 cubic meters, the daily dredging volume reaches 3,600 cubic meters.

Excluding special circumstances, the 220,000-cubic-meter dredging task can be completed in approximately 60 days—halving the planned schedule. Compared with hydraulic hammer drilling under similar geological conditions, the efficiency is increased by more than 3 times, significantly shortening the construction period.

Application Effects and Market Prospects of Backhoe Dredger

Practice in this port demonstrates that the EX5500 backhoe dredger—with a maximum digging force of 990 kN and a 20.5-cubic-meter bucket—can efficiently excavate conventional soil layers, hard soil layers, dense/over-dense sand layers, semi-consolidated cemented sand, reefs, and soft rocks such as fully weathered rock within a maximum depth of 30 meters, achieving high construction efficiency. High-power backhoe dredging effectively solves the challenges posed by semi-consolidated cemented sand and reefs.

Underwater backhoe dredgers are less widely used in China’s dredging field,compare to other types like Grab Dredger, Cutter Suction Dredger and Trailing Suction Hopper Dredger, with a limited stock of middle - large, well-maintained, and good conditions units.

However, with projects such as the Guangxi Pinglu Canal and coastal port weathered rock projects, a new batch of backhoe dredgers equipped with Hitachi EX1900, EX2500, and EX3600 excavators has been built recent years.

Other existing used vessels are mainly equipped with Kobelco, Komatsu, Doosan, and other excavator models.

Yanyang Marine currently offers various specifications for domestic and overseas clients.

Backhoe dredgers are more commonly used in European countries, such as vessels equipped with the renowned Liebherr P995 excavator. Coastal areas in parts of Northern Europe and  Russia are particularly suitable for dredging using backhoe dredgers combined with split hopper barges.

China’s coastal regions have thick underwater sedimentary layers with extensive dense sand deposits. Coastal areas in Hainan Island and Zhanjiang, Guangdong, are also widely distributed with beach rocks and coral reefs—making them ideal for high-power backhoe dredging. Additionally, backhoe dredgers are suitable for dredging fully weathered rock formations in inland waterways.

Backhoe dredger technology holds significant market potential in China, emerging as an important dredging method alongside mechanical impact drilling and blasting. It is particularly suitable for sites with limited operational space and strict vibration requirements. When combined with impact drilling, backhoe dredgers can greatly enhance dredging and rock excavation efficiency, expanding their engineering applicability.

EX3600 Backhoe Dredger working with Motor Hopper

FAQs

Q:  What geological conditions are backhoe dredgers most suitable for?

A: They excel in dredging semi-consolidated cemented sand, reefs, dense sand layers, and fully weathered rocks—especially in projects with limited operational space or strict vibration restrictions (e.g., near port structures).

Q: What are the core performance indicators of the Hitachi EX5500 backhoe dredger?

A: It features a maximum digging force of 990 kN, a maximum digging depth of 32 meters, a 20.5-cubic-meter bucket capacity, and a daily dredging volume of up to 3,600 cubic meters.

Q: How does the efficiency of backhoe dredgers compare to traditional methods?

A: Backhoe dredgers (e.g., EX5500) are over 3 times more efficient than traditional hydraulic hammer drilling. They can halve the construction period for complex geological dredging tasks (e.g., 220,000m³ completed in 60 days).