Executive Summary
Swallow Site Services delivered an in-situ California Bearing Ratio (CBR) testing programme at Bristol East Depot to support the structural design of a proposed access roadway upgrade.
Covering approximately 550m², the roadway is scheduled for operational use and will experience sustained heavy goods vehicle traffic. Accurate subgrade data was essential for enabling geogrid pavement design, ensuring long-term durability without unnecessary overdesign or excessive material importation.
Delivered under the Network Rail Framework Agreement, the works were completed safely, efficiently~~,~~ and in full compliance within a live depot environment.
- In-situ CBR testing across a 550m² access road footprint
- Delivery under the Network Rail Framework Agreement
- Provision of a 13-tonne excavator for excavation and kentledge loading
- Coordination of a specialist CBR testing subcontractor
- Data capture to inform geogrid and pavement design
- Controlled delivery within an operational rail depot environment
The Challenge
Although not currently in regular use, the access roadway is due to be let for operational purposes and will accommodate sustained HGV movements.
To ensure structural integrity and cost efficiency, the design team required accurate in-situ subgrade bearing capacity values. Without reliable testing, the scheme risked either under-design (leading to premature failure) or over-design (resulting in unnecessary excavation and material cost).
The works also needed to be carefully managed within a live rail depot environment, maintaining safety standards and operational continuity.
The Solution
Swallow Site Services developed and implemented a structured ground investigation approach to determine subgrade strength and inform access road construction.
Our delivery included:
- Appointment and full coordination of a specialist CBR testing contractor
- Programming and provision of a 13-tonne excavator for excavation and kentledge loading
- Preparation and sequencing of test locations to maximise efficiency
- Close coordination with depot stakeholders to avoid operational disruption
By generating accurate, site-specific bearing capacity data, we enabled the design team to:
- Validate subgrade performance
- Determine required sub-base thickness
- Specify appropriate geogrid reinforcement
- Optimise excavation depth and imported material volumes
The result was a technically robust, commercially efficient solution aligned with long-term industrial traffic loading requirements.
The Results
The CBR testing programme was completed safely and within the planned timeframe.
Key outcomes included:
- Delivery of 10 CBR tests across the site
- Accurate subgrade strength data captured for pavement design
- No disruption to depot operations
- Optimised access road design based on verified ground conditions
- Increased confidence in long-term HGV performance
- Strengthened framework delivery partnership with Network Rail
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Swallow Site Services delivered an in-situ California Bearing Ratio (CBR) testing programme at Bristol East Depot to support the structural design of a proposed access roadway upgrade.