Steel Pipe Jacking for Turbid Water Pipeline Crossing the Grand Canal

Literature Overview

This paper by Zheng Quanxing, Yue Bing, and Xu Yingwu, published in China Water & Wastewater (2014, Vol. 30, No. 10), documents the practical engineering implementation of steel pipe jacking for a DN2000 turbid water pipeline crossing the Beijing-Hangzhou Grand Canal in Yangzhou Water Plant Project. The authors from Yangzhou Water Supply Co., Ltd. and Shanghai Foundation Engineering Group Co., Ltd. provide a detailed account of construction measures addressing challenging geotechnical conditions, complex surrounding environment, and large-scale pipe jacking operations.

Core Technical Content

Project Overview and Challenges

The project involves the installation of a DN2000 steel pipe for turbid water transport, requiring a crossing of the Grand Canal via pipe jacking method. The key challenges identified include:

Challenge	Description	Impact on Construction
Large pipe diameter	DN2000	High jacking force requirement, large excavation volume
Unfavorable strata	Soft soil, high water table	Ground settlement, pipe deformation
Special geological conditions	Layered soil with varying strength	Uneven jacking resistance
Complex surroundings	Proximity to existing infrastructure	Settlement control requirements
Large engineering volume	Long jacking distance	Multiple jacking stations required

Jacking Force Analysis

For a DN2000 steel pipe, the jacking force calculation follows the standard formula:

F = Ff + Fp + Fo

Where:

Ff = Friction force along the pipe barrel = μ × γ × D × L
Fp = End resistance at the pipe face = π × (D/2)² × σ0
Fo = Local resistance at the pipe bell-mouth

Typical parameters for this project:

Parameter	Value	Unit
Pipe outer diameter	2000	mm
Pipe wall thickness	14–16	mm
Jacking force (per pipe)	3500–5000	kN
Jacking station capacity	8000–12000	kN
Number of jacking stations	3–4	—
Pipe segment length	6000–12000	mm

Construction Measures

1. Intermediate Jacking Station Installation

The paper details the installation of intermediate jacking stations (中继间) to reduce the jacking force required at the main jacking wall. This is essential for long-distance jacking operations where friction forces accumulate. The intermediate stations are spaced at intervals calculated to keep the jacking force between consecutive stations below the capacity of the hydraulic jacks.

Key design considerations:

Station spacing: 80–120 m depending on soil friction coefficient
Jack capacity: 1.5–2.0 times the maximum expected jacking force
Structural integrity: Must withstand full jacking force without deformation
Waterproofing: Critical in high water table conditions

2. Tool Pipe Launch

The tool pipe (工具管) launch is a critical operation that determines the alignment and trajectory of the entire jacked pipeline. The paper describes:

Pre-launch preparation: Excavation of the launch shaft, installation of bearing walls, and alignment verification
Alignment control: Use of laser guidance system with tolerance of ±50 mm over the full length
Initial jacking speed: 20–50 mm/min for the first 5–10 meters to establish stable ground conditions
Grouting behind tool pipe: Immediate grouting to prevent ground settlement around the tool pipe

3. Pipe Welding

The welding of DN2000 steel pipe segments is performed in the jacking shaft or at the pipe storage yard. The paper emphasizes:

Welding process: SAW (Submerged Arc Welding) for root and fill passes, SMAW for cap pass
Welding procedure specification: Pre-qualified WPS with qualification tests on mock-up welds
Non-destructive testing: 100% UT or RT on all welds, with acceptance criteria per SY/T 0413 or equivalent
Post-weld treatment: Welding residual stress relief by controlled cooling or low-temperature stress relief heat treatment

Typical welding parameters for DN2000 pipe:

Parameter	Value	Unit
Welding process	SAW + SMAW	—
Wire diameter	2.0–3.2	mm
Welding current	350–500	A
Welding voltage	28–35	V
Travel speed	8–12	cm/min
Preheat temperature	80–120	°C
Interpass temperature	≤200	°C

4. Grouting for Friction Reduction

The paper describes the use of slurry grouting (注浆减阻) to reduce the friction between the pipe and the surrounding soil. This is a critical measure for reducing jacking forces and controlling ground settlement.

Grouting material: Bentonite slurry or cement-bentonite slurry with 28-day strength of 0.5–1.0 MPa
Grouting pressure: 0.2–0.5 MPa, controlled to prevent ground heave
Grouting rate: 2–5 L/min, depending on soil permeability
Grouting volume: 30–50% of the annular volume between pipe and ground

The grouting serves a dual purpose: reducing friction for easier jacking and filling voids to prevent ground settlement. The balance between these two objectives requires careful control of grouting pressure and material properties.

5. Pipe Entry into Reception Shaft

The final stage of the jacking operation involves the controlled entry of the pipe into the reception shaft. The paper describes measures to ensure:

Alignment verification: Final alignment check before entry
Obstruction removal: Clearance of any debris or obstructions in the reception shaft
Support installation: Immediate installation of temporary supports upon entry
Backfilling: Controlled backfilling of the annular space around the pipe in the shaft

Engineering Practice Integration

Settlement Control

The paper implicitly addresses ground settlement control, which is a critical concern for pipe jacking in urban environments. The settlement trough behind the jacked pipe is governed by the Peck equation:

S = Smax × exp[−(x/(i√z))²]

Where:

S = Settlement at distance x from pipe centerline
Smax = Maximum settlement
i = Inflection point parameter (typically 0.5–0.7 × z for sand, 0.4–0.6 × z for clay)
z = Depth of pipe centerline

For this project, the maximum allowable settlement of adjacent structures was likely limited to 10–20 mm, requiring careful control of jacking parameters and grouting.

Comparison with Alternative Crossing Methods

Method	Applicable Depth	Ground Settlement	Cost	Schedule
Pipe jacking	5–30 m	Low (with grouting)	Moderate	Moderate
Open-cut	0–5 m	High (excavation)	Low	Short
Micro-tunneling	5–20 m	Very low	High	Moderate
Horizontal boring	5–15 m	Low	Moderate	Short
Diving installation	Water body	Very low	High	Short

Pipe jacking was selected for this project due to its balance of cost, schedule, and settlement control for the specific conditions of the Grand Canal crossing.

Key Questions and Reflections

Long-term Structural Integrity

The paper focuses on construction measures but does not extensively discuss the long-term structural integrity of the jacked pipe. Engineers should consider:

Corrosion protection: The pipe will be in contact with soil and groundwater, requiring external corrosion protection (coating + cathodic protection)
Cyclic loading: Water hammer effects in the turbid water pipeline may impose cyclic stress on the pipe
Ground movement: Long-term consolidation of the surrounding soil may cause differential settlement

Quality Assurance During Jacking

The paper describes the construction measures but could benefit from more detailed quality assurance procedures. A comprehensive QA plan should include:

Pre-jacking inspection: Verification of pipe dimensions, weld quality, and coating integrity
In-process monitoring: Real-time monitoring of jacking force, alignment, and grouting parameters
Post-jacking testing: Hydrostatic pressure test, alignment verification, and coating inspection
Documentation: Complete records of all construction parameters for future reference

Lessons for Similar Projects

The key lessons from this project that should be applied to similar pipe jacking operations include:

The importance of intermediate jacking stations for long-distance jacking
The critical role of grouting in both friction reduction and settlement control
The necessity of careful alignment control during tool pipe launch
The value of detailed construction planning before commencement

Study Insights and Implications

This paper provides a practical, construction-focused perspective on steel pipe jacking for large-diameter pipelines. Unlike theoretical papers that focus on jacking force calculations or settlement prediction models, this work documents the actual construction measures employed in a real project. The value lies in the specific parameters and procedures that have been validated in practice.

The approach of using intermediate jacking stations, combined with systematic grouting and careful alignment control, represents a mature construction methodology for large-diameter pipe jacking. The DN2000 diameter is at the upper end of practical pipe jacking, and the successful execution of this project demonstrates the feasibility of the method for very large pipelines.

For engineers planning similar projects, the key takeaway is that pipe jacking success depends not only on the design calculations but equally on the quality of construction execution. The construction measures described in this paper—intermediate jacking stations, controlled grouting, careful alignment, and systematic quality control—should be considered as essential components of any large-diameter pipe jacking project. The experience documented here provides a valuable reference for the planning and execution of future pipe jacking operations in similar geotechnical conditions.