Abstract
Culverts are one of the most numerous categories of infrastructure structures on roads of both regional and federal importance. These engineering structures are located within the embankment of a road or railway and ensure the safe discharge of water reaching the subgrade. Culverts maintain a constant favourable moisture regime for the soil foundations of road pavements within the road drainage system and prevent erosion of the road embankment.
In modern road construction, two types of culverts are most widely used: corrugated metal culverts and reinforced-concrete culverts made of prefabricated elements. To increase flow capacity without increasing the embankment height, multi-cell culverts are constructed from small pipes laid side by side, allowing structures with diameters of up to 3 metres to be used. In our country, a significant proportion of culverts consist of unconnected reinforced-concrete sections, most often with a circular cross-section and diameters of up to 3 metres, operating in various climatic conditions.
During operation, the structure is exposed to static and dynamic loads—from the weight of the embankment and vehicles travelling on the road—as well as temperature fluctuations and meltwater, rainwater, streams and small rivers flowing directly through the pipe. All these factors, together with geological factors such as earthquakes, ground movements and vibrations, or an initially incorrect installation of the pipe, inevitably lead to its deterioration. This process also occurs during major road repairs, when the asphalt-concrete pavement is removed from the section above the pipe and heavy machinery moves directly over the gravel embankment cushion. The result is a reduction in, or partial loss of, the load-bearing capacity of the pipe sections.
In addition, over time, the installed reinforced-concrete sections of a culvert tend to shift horizontally and vertically under various loads, resulting in gaps and level differences between them. These differences reduce the effective cross-section of the pipe, lowering its flow capacity and causing siltation. During floods, gaps between the pipe sections cause significant erosion, leaving voids in the embankment. This may result in the collapse of the subgrade and road pavement, and in such circumstances the continued operation of the road section as a whole cannot be guaranteed.
The traditional effective solution to this problem is to dismantle the embankment and remove the pipe, followed by construction of a new one; however, this method requires destruction of the overlying road pavement. In addition, on federal highways, such work requires a temporary detour to be arranged in advance, which also entails significant time and material costs.
The need to optimise the costs of repairing and reconstructing federal and regional highways is encouraging road authorities to use modern alternative methods for restoring infrastructure structures. One such method is sliplining—the installation of a smaller-diameter plastic or metal pipe inside the structure being repaired. At first glance, this technology appears effective; however, the entire functional role and structural load are ultimately transferred to the inner pipe, whose diameter is smaller than the design value, which may eventually lead to deformation or even erosion of the embankment. In addition, the plastic pipe used for sliplining does not have sufficient load-bearing capacity and cannot significantly strengthen the structure being restored.
A reduction in the pipe cross-section can be avoided by using another technology—repair with a “sock” or polymer sleeve. This method makes it possible to restore locally severely damaged sections of the structure and reproduce the existing structural profile without reducing its internal diameter. Nevertheless, this technology is not only expensive, but also has no effect on the load-bearing capacity of the structure, while it is precisely the reduced load-bearing capacity of a culvert on a road section that is the critical factor leading to its failure.
Thus, none of the methods described above is optimal or fully solves the task of effectively, quickly and cost-efficiently repairing infrastructure structures on roads.
To address this problem, specialists from TechPolymer Group developed a culvert repair system based on V–LOCK anchor sheet for structures with diameters of 1.2 metres and above, located in road embankments more than 2 metres high. The technology consists of restoring the load-bearing capacity of the structure by concreting over permanent polymer formwork.
The TechPolymer culvert repair system consists of several stages:
- Cleaning the inner surface of the culvert
- Construction of a reinforcement frame (metal guides and fibreglass winding)
- Installation and welding of the V–LOCK anchor sheet
- Deployment of the pneumatic formwork
- Pouring the grout and forming a monolithic structure
- Removal of the high-pressure bladder and assessment of the quality of the welded joints
- Checking the uniformity of grout filling
- The proposed technology makes it possible to repair a culvert within a short time without preparing individual formwork, ensuring a designed service life of the structure within 4–5 years, with the possibility of extending it following an inspection.
Opinion
Candidate of Technical Sciences, Associate Professor, Department of “Road Design”, FSBEI HE “SibADI”
Grigory Mikhailovich Levashov
It is difficult to overestimate the impact of the road drainage system not only on the transport and operational qualities of a road, but also on transport safety in our country as a whole. Like all infrastructure structures, it requires not only proper operation but also periodic and major repairs. As we know, the cost of constructing drainage structures is significant and may account for 5% to 15% of the cost of constructing a road section. The road industry undoubtedly needs modern repair technologies for reinforced-concrete culverts, one of which is rehabilitation using polymer anchor sheet. This technology makes it possible to reduce the estimated cost and duration of the work, as well as extend the service life of reinforced-concrete culverts with circular, rectangular and arched cross-sections. The V–LOCK anchor sheet culvert repair technology can be regarded not only as the most cost-effective option, but also as the most promising innovation for repair work of this type.
Compared with the methods described above, the TechPolymer culvert rehabilitation system offers a number of significant advantages:
- Increased load-bearing capacity. After the work is completed, a continuous pipe is created that compensates for damage in the sections of the structure being rehabilitated and transfers the load from damaged sections to adjacent ones. Cracks and exposed reinforcement are grouted, strengthening the structure and extending its service life.
- Maximum usable cross-section. The system reduces the diameter of the culvert only slightly, keeping it within the required design values.
- Controlled grout filling. Unlike, for example, sliplining, this method makes it possible to check the uniformity of grout filling in the space between the formwork and the pipe being rehabilitated. Such quality control is important because it helps prevent voids and increases the reliability of the structure.
- Elimination of voids in the embankment. The displacement of reinforced-concrete culvert sections creates gaps between them, through which soil may fall into the structure, forming voids in the road embankment and reducing its stability. The TechPolymer system fills these voids with cement grout, eliminating the risk of embankment damage.
- Cost. This technology is the most economically justified of all solutions currently available on the market.
In conclusion, it should be noted that the need to improve the durability and reliability of existing infrastructure structures in road construction is indisputable. In particular, high-quality culvert repair can significantly extend the safe service life of an infrastructure structure, while selecting an optimal method of repair, such as rehabilitation using the V–LOCK anchor sheet system, ensures the technological and economic efficiency of the process.
