Undisturbed Sampling (Shelby Tube) in Fredericton

We deploy a hydraulic push system mounted on a drill rig to extract undisturbed soil samples using thin-walled Shelby tubes in Fredericton. The tube, typically 76 mm in diameter, is pushed into the soil at a steady rate to minimize disturbance. This method preserves the natural fabric and moisture content of fine-grained soils like the silty clays and glacial tills found across the city. We seal and transport each tube vertically to maintain sample integrity before laboratory testing. Combining this with a study of slope stability helps us assess foundation bearing capacity on the Saint John River floodplain.

A single Shelby tube sample from Fredericton’s glacial clay can reduce foundation overdesign risk by 15% compared to using only SPT data.

Technical details of the service in Fredericton

Working in Fredericton, we often see that undisturbed samples reveal the true consolidation behavior of the deep clay layers beneath downtown. Key parameters from Shelby tube specimens include undrained shear strength, preconsolidation pressure, and compression index. Our lab tests follow ASTM D1587-15 for tube sampling and CSA + CSA + CSA + CSA + ASTM D2435 (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) for one-dimensional consolidation. The samples also undergo triaxial compression per CSA + CSA + CSA + CSA + ASTM D2850 (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) to define effective stress parameters. This data feeds directly into settlement predictions for buildings on Regent Street and along the river corridor. We cross-check results with in-situ permeability tests to refine drainage assumptions for basement excavations.

Undisturbed Sampling (Shelby Tube) in Fredericton | Geotechnical Testing

Parameter	Typical value
Tube diameter	76 mm (3 in) standard, 89 mm optional
Maximum sampling depth	25 m depending on soil stiffness and rig capacity
Sample length after extrusion	450 mm to 600 mm
Key parameters measured	Cu, σ'p, Cc, Cr, mv, cv
Applicable soil types	CL, CH, ML, MH (cohesive soils)
Disturbance ratio threshold	AR < 10% per ASTM D1587
Maximum storage time before testing	14 days at 4°C in sealed containers

Typical technical challenges in Fredericton

A common mistake in Fredericton projects is relying solely on SPT N-values to estimate settlement in the compressible clay layers under the downtown district. SPT samples are heavily disturbed, giving unconsolidated strengths that can be 30 to 40 percent lower than actual values. This leads to overconservative designs and unnecessary deep foundation costs. Without proper undisturbed sampling using Shelby tubes, the preconsolidation pressure remains unknown. We have seen contractors add extra piles or thicker slabs because they lacked the true soil profile. One borehole with high-quality tube samples removes that guesswork and keeps the budget in check.

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Applicable standards: ASTM D1587-15 (Standard Practice for Thin-Walled Tube Sampling), CSA + CSA + CSA + CSA + ASTM D2435 (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (Standard Test Methods for One-Dimensional Consolidation), CSA + CSA + CSA + CSA + ASTM D2850 (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (Standard Test Method for Unconsolidated-Undrained Triaxial Compression), NBCC 2020 Division B, Part 4 (Foundations), CSA A23.3-19 (Design of Concrete Structures – Annex for Soil-Structure Interaction)

Our services

Our Shelby tube sampling service in Fredericton is complemented by the following specialized offerings to cover your full geotechnical scope.

Thin-Walled Tube Sampling

Hydraulic push of 76 mm or 89 mm Shelby tubes to depths up to 25 m. Samples are extruded, sealed, and transported to our ISO 17025 accredited lab within 24 hours.

Consolidation Testing (Oedometer)

One-dimensional consolidation tests per CSA + CSA + CSA + CSA + ASTM D2435 (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) (also CFEM Ch 2) to determine preconsolidation pressure, compression index, and coefficient of consolidation for settlement analysis.

Triaxial Compression Testing

Unconsolidated-undrained (UU) and consolidated-undrained (CU) triaxial tests on undisturbed specimens to obtain undrained shear strength and effective stress parameters.

Sample Verification & Soil Classification

Afterberg limits, natural moisture content, and unit weight determination on each tube to validate field conditions and classify soil per the Unified Soil Classification System.

Frequently asked questions

How deep can Shelby tube samples be taken in Fredericton?

We routinely sample to 25 meters in the softer clay layers beneath Fredericton. Beyond that, soil stiffness or gravel layers may require alternative methods like SPT or sonic drilling.

What is the cost range for undisturbed sampling using Shelby tubes in Fredericton?

The typical cost ranges between CA$570 and CA$1,360 per sample, depending on depth, tube diameter, and whether additional laboratory testing is included. We provide a fixed quote after reviewing the project scope.

How long does it take to get results from Shelby tube samples?

Field sampling takes one to two days. Consolidation tests require 7 to 14 days. Triaxial tests need up to 10 days. Total turnaround from sampling to final report is usually 3 to 4 weeks.