Innovative Solutions Restore Stability After Hook Embankment Landslip

On Sunday, January 15th, 2023, a significant landslip occurred on the railway line from London to Basingstoke, specifically on the embankment to the northeast of Hook station in Hampshire. This 44-meter landslip resulted in severe disruption for commuters, with one of the tracks left hanging in mid-air. The incident rendered two of the four tracks unusable, leaving only the London-bound tracks operational. This landslip was defined as a situation where soil, rocks, and earth collapsed onto the tracks, partially or wholly blocking them and permanently weakening the surrounding earth. The disruption led to major travel advisories, urging people to avoid traveling if possible.

The immediate consequence of the landslip was significant travel disruption for commuters between Hampshire and London. Network Rail emphasized the urgency of stabilizing the area to prevent further landslips, highlighting the need to strengthen the slopes and improve drainage systems. The weakened earth around the embankment posed a continuous threat, making it essential to implement swift and effective solutions to restore normalcy and ensure the safety of the railway infrastructure.

To address the issue, Network Rail contracted Balfour Beatty, which in turn brought in Aquaspira and DDL Group for their expertise in innovative and sustainable engineering solutions. The primary challenge was to upgrade the culvert beneath the railway, which had been compromised due to the landslip.

Aquaspira provided a 26-meter long, low-carbon culvert extension, a critical component in stabilizing the embankment. The process began with DDL Group installing dams at both ends of the river flowing below the railway, creating a 40-meter long channel. This facilitated the installation of the new buried culvert. The channel was prepared by pumping out water and removing approximately 1 meter of silt from the riverbed.

Two lines of Aquaspira’s 1,650mm diameter composite steel reinforced (CSR) pipes were then laid and secured with a new headwall. The channel was backfilled to the existing ground level, and an access road was constructed to enable ongoing maintenance and inspection.

The new CSR pipes, noted for their 43mm thick walls, were chosen for their durability and lightweight properties. Each pipe, weighing less than 250kg, could be easily handled and installed with small machinery, which was crucial in the limited working space available. The push-fit joints and integral seals of the pipes allowed for quick and simple installation, significantly reducing the project timeline.

Moreover, the CSR pipes were designed to support the weight of trains while reducing the embodied carbon by 48% compared to traditional rigid pipes. This not only enhanced safety but also provided an eco-friendly solution, aligning with modern sustainable engineering practices.

The collaborative efforts of Network Rail, Balfour Beatty, Aquaspira, and DDL Group successfully addressed the critical landslip issue at Hook embankment. Through innovative engineering solutions and sustainable practices, the railway infrastructure has been stabilized, ensuring safe and reliable travel for commuters once again. This project exemplifies the importance of swift response and modern engineering in overcoming infrastructure challenges.

Below an interesting video filmed by drone one week after the incident.