Advantages of Injection Polyurethane Systems over Conventional Ground Stabilization Methods

Ground improvement is a fundamental aspect of construction, rehabilitation, and repair of structures built on unstable soils. Traditionally, engineers have relied on methods such as piling, cement grouting, and ground freezing. However, advances in chemical technologies have introduced more efficient solutions that allow for targeted, fast, and cost-effective intervention.

One of the most effective approaches is the use of expanding polyurethane injection systems. This article provides a detailed analysis of their advantages, with a focus on underlying mechanisms, material behavior, and practical applications.

Before comparing innovative solutions with traditional methods, it is important to review commonly used approaches:

• Cement grouting: Injection of cementitious materials to increase soil density and bearing capacity
• Piles: Driven or bored elements transferring loads to deeper, more stable strata
• Geotextiles and geogrids: Synthetic materials used for load distribution and surface stabilization
• Ground freezing: Use of refrigerants to temporarily increase soil strength

Despite their widespread use, these methods have several limitations:

• Require extensive site preparation and mobilization of heavy equipment
• Often unsuitable for localized issues or targeted repairs
• Difficult to implement without disrupting ongoing operations
• Performance is sensitive to groundwater conditions, soil composition, and environmental factors

Polyurethane injection is a well-established method for localized strengthening and stabilization of weak, compressible, and water-bearing soils. When the components are mixed, a rapid chemical reaction occurs, forming an expanding polymer matrix.

Key material parameters include:

• Density: 1.1–1.2 g/cm³ (PolyJet FT)
• Viscosity: 200–250 mPa·s
• Expansion ratio: up to 32×
• Application temperature range: +3 to +40 °C

Injection polyurethane systems are reactive polymers that rapidly form a closed-cell structure upon mixing, with or without the presence of moisture. This structure is capable of sustaining significant mechanical loads.

The expanding material fills voids, redistributes stresses, and displaces water from soil pores and capillaries, contributing to improved stability of the soil mass.

Injection polyurethane systems have been successfully applied in numerous projects worldwide.

At a logistics facility, flooding caused settlement of concrete floor slabs. Conventional repair would have required full slab removal, resulting in a week of downtime and significant cost.

Instead, polyurethane injection was used:

• Material injected beneath 30 slabs
• Floor restored to design elevation within 4 hours
• Cost savings of approximately 70%
• Total project duration — one working day

In an urban metro system, water ingress caused erosion near sheet pile structures. Polyurethane injection enabled rapid formation of impermeable barriers, stopping inflow and eliminating the risk of failure within 12 hours.

Environmental performance is a key factor when selecting a stabilization method. Injection polyurethanes offer the following advantages:

• Do not release harmful substances during or after reaction
• Chemically inert in wet and aggressive environments
• Do not disrupt soil structure or natural balance
• Comply with applicable environmental and health standards

All works are supported by appropriate certification, licensing, and compliance documentation.

Injection works are carried out in accordance with relevant standards and regulations, including:

• GOST 2761-84
• SP 22.13330.2016 — Foundations of Buildings and Structures
• Government Decree No. 87 (Russian Federation) — Project Documentation Requirements
• STO NOSTROY 2.3.18-2011 — Soil Stabilization by Injection Methods in Construction
• Manufacturer technical documentation

Proper project documentation ensures seamless integration of the method into construction workflows.

Both research and practical experience demonstrate that expanding polyurethane injection is an effective solution for fast, cost-efficient, and durable ground improvement.

The technology:

• reduces repair time and costs,
• minimizes environmental impact,
• ensures long-term performance and reliability.

Recommendation:
Engage certified contractors, review project documentation carefully, and require verification of results through appropriate testing and monitoring.