Crosshole Sonic Logging Test
(CSL Test)

Ultrasonic crosshole integrity testing of drilled shafts, bored piles and diaphragm walls per ASTM D6760 — detecting voids, honeycombing and defects throughout the full depth of the foundation element.

Overview

What is Crosshole Sonic Logging?

Crosshole Sonic Logging (CSL) evaluates the internal integrity of drilled shafts, bored piles, barrettes and diaphragm walls. A minimum of three water-filled access tubes — at least 38mm internal diameter — are cast into the foundation element during construction, attached to the reinforcement cage along its full length. An ultrasonic transmitter is lowered into one tube and a receiver into another; the pair is raised together in tandem while the system continuously logs signal travel time and energy at every depth.

Sound, well-consolidated concrete transmits the ultrasonic pulse quickly and at full strength. Voids, honeycombing, soil inclusions or poor concrete consolidation delay the signal or reduce its energy — pinpointing defects by exact depth and location within the shaft cross-section. Tested per ASTM D6760 and read alongside the general pile-foundation framework of IS 2911, CSL offers a depth range and defect-location precision that surface-based methods like low-strain Pile Integrity Testing cannot match on their own — making it the preferred verification method for large-diameter drilled shafts.

Reviewed by Mahemood Ahmad, Lab Manager — NABL Accredited Laboratory, Global Lab India

Full-Depth Coverage

Profiles concrete quality continuously along the entire shaft length, not just near the pile head.

Precise Defect Location

Pinpoints anomalies by exact depth and position between each pair of access tubes.

ASTM D6760 Compliant

Testing and reporting follow the international standard for ultrasonic crosshole integrity testing.

Multi-Tube Profiling

Every tube-pair combination is scanned for comprehensive cross-sectional coverage.

Tomographic Analysis

Advanced 2D/3D defect mapping available for complex or ambiguous results.

NABL Certified Reports

Traceable, accredited results with depth-wise data suitable for project documentation.

Test Procedure

How Crosshole Sonic Logging is Conducted

1

Access Tube Installation

A minimum of three tubes, internal diameter at least 38mm, are attached to the reinforcement cage before concreting, spanning the full length of the shaft or pile.
2

Post-Pour Water Filling

Once the concrete has cured, each tube is filled with water to enable clean ultrasonic signal transmission.
3

Probe Deployment

Transmitter and receiver probes are lowered to the base of each tube pair, ready to log from the bottom of the shaft upward.
4

Synchronized Logging

Probes are raised together at a constant rate, continuously recording first-arrival time and signal energy at every depth increment across all tube-pair combinations.
5

Analysis & Reporting

Data is reviewed for delayed arrivals or signal-strength anomalies indicating defects; an NABL-accredited report is issued with depth-wise results and tomographic imaging where required.

Standards & Specifications

Applicable Test Standards

Standard	Title	Scope	Type
ASTM D6760	Standard Test Method for Integrity Testing of Concrete Deep Foundations by Ultrasonic Crosshole Testing	Crosshole Sonic Logging	ASTM
IS 2911	Design and Construction of Pile Foundations — Code of Practice	Deep Foundation Testing Framework	Indian Standard

Applications

Where is Crosshole Sonic Logging Used?

Integrity verification of large-diameter drilled shafts and bored cast-in-situ piles

Quality assurance of diaphragm walls and barrettes

Detecting voids, honeycombing and soil inclusions within foundation concrete

Verifying concrete consolidation around dense reinforcement cages

Post-construction QA for bridge, metro and high-rise foundation piles

Deeper full-length confirmation for piles flagged by low-strain (PIT) testing

Why Choose Global Lab

Our Advantages

NABL Accredited ReportsLegally valid certificates accepted by all government and statutory bodies.

Full-Depth, Precise Defect MappingFar greater resolution than surface-based NDT methods alone.

ASTM D6760 Compliant MethodologyInternationally recognized testing and reporting procedure.

Advanced Signal AnalysisTomographic imaging available for complex or ambiguous results.

Pan-India CoverageField engineers deployed across 7 lab locations.

Fast, Reliable TurnaroundOn-site logging with digital reports typically within 24-48 hours.

Quick Answers

Frequently Asked Questions

What is Crosshole Sonic Logging used for?

CSL verifies the internal integrity of drilled shafts, bored piles, barrettes and diaphragm walls by detecting voids, honeycombing, soil inclusions and other concrete defects throughout the full depth of the foundation element.

How many access tubes are needed for CSL testing?

A minimum of three tubes, internal diameter at least 38mm, are required — attached to the reinforcement cage before concreting and spanning the full length of the shaft or pile.

What standard governs Crosshole Sonic Logging?

CSL testing is performed per ASTM D6760 — Standard Test Method for Integrity Testing of Concrete Deep Foundations by Ultrasonic Crosshole Testing — read alongside the general pile-foundation framework of IS 2911.

How is CSL different from Pile Integrity Testing (PIT)?

PIT (low-strain sonic-echo testing) is a fast, surface-based screening method typically used on smaller piles. CSL directly profiles the concrete between pre-installed tubes at every depth, offering far more precise defect location — especially valuable for large-diameter drilled shafts and barrettes.

Crosshole Sonic Logging Test(CSL Test)