I. Introduction: Installation—The Critical Link in CSL Testing

The success of Cross-Hole Sonic Logging (CSL) testing hinges entirely on one factor: the correct, robust, and watertight installation of the Sonic Logging Pipes (SLPs). An improperly installed tube—one that leaks, collapses, or is blocked by cement—renders the entire section of the concrete pile untestable, potentially leading to costly delays and disputes.

This guide provides a step-by-step methodology for the proper installation of steel sonic logging pipes, focusing on crucial sealing techniques and necessary site precautions to ensure tube patency and CSL readiness.

II. Pre-Installation Checks and Preparation

Before the reinforcement cage is lifted and placed into the bore, thorough preparation is mandatory.

1. Pipe Integrity Check: Inspect all Steel Sonic Logging Pipes for damage, including dents, ovality, or sharp edges that could obstruct probes. Confirm the material and wall thickness meet specifications, as detailed in  Steel Sonic Logging Pipe Specifications, Material, and Technical Requirements.

2. Joint System Test: Visually inspect all connecting elements (threads, sockets, O-rings, or welding surfaces). The integrity of the joint is the primary defense against cement intrusion.

3. End Caps: Ensure the bottom-most pipe segment is fitted with a durable, watertight end cap to prevent soil or debris from entering during cage lowering.

III. Step-by-Step Installation Method

The installation process must be integrated seamlessly with the assembly of the steel reinforcement cage.

A. Attachment to the Rebar Cage

The SLPs must be secured vertically and rigidly to the reinforcement cage before it is lowered.

• Securing Method: Use high-strength steel wire ties or, preferably, tack-weld the tubes at regular intervals (typically every $1 \text{ m}$ to $1.5 \text{ m}$) along the cage length.

• Alignment: Maintain precise vertical alignment. The tubes should be installed parallel to the cage axis and to each other, minimizing deviation, which could cause probe jamming.

• Spacing: Ensure the horizontal spacing between all adjacent tubes adheres to project and code requirements, referencing guidelines such as  Concrete Pile Foundation Quality Testing Standards and Codes.

B. Ensuring Watertight Joints (The Sealing Requirement)

This is the most critical stage. Joints must be treated as permanent, pressure-resistant seals.

C. Final Checks Before Pouring

1. Patency Check: Before the cage is lowered, pass a small dummy probe or measuring tape through each installed tube from top to bottom. This confirms the tube is unobstructed and that all joints are properly aligned.

2. Tube Filling: After the cage is set in the bore and before concrete pouring begins, fill all SLPs completely with clean water. This serves two purposes: it prevents floating and provides hydrostatic pressure to quickly expose any small joint leaks before the concrete hardens.

IV. Site Cautions and Troubleshooting During Construction

Site vigilance is essential to protect the SLPs during the concrete pouring process.

• Vibration Damage: Excessive or localized vibration can temporarily displace pipes, compromising the watertight seals at the joints. Monitor placement.

• Concrete Flow: Ensure the tremie pipe is properly positioned. Direct impact or overly rapid concrete flow can put extreme lateral stress on the SLPs.

• Top Capping: Once the concrete pour is complete, immediately cap the top of the exposed SLPs to prevent debris, rain, or runoff from entering the tube while the concrete cures.

V. Conclusion: Quality Installation Guarantees Testability

Proper Sonic Logging Pipe installation is a quality control procedure in itself, directly impacting the ability to perform accurate CSL testing (as described in  CSL Ultrasonic Testing Principle and Steps). By meticulously adhering to strict methods for sealing, alignment, and final verification, site teams can mitigate the risks of untestable piles and deliver fully compliant deep foundations.