Engineering protection of the subgrade from sand drifts using geomaterials, as exemplified by the Bukhara-Miskin railway line

1. Introduction

Railway construction and operation in arid regions are strongly influenced by aeolian processes such as deflation, wind erosion, and sand accumulation [1-3]. In areas with loose sand and sparse vegetation – such as Iran, China, and Central Asia – sand drifts cause slope instability and higher maintenance costs [2, 4, 5].

In southwestern Uzbekistan, particularly along the Bukhara-Misken line, sand encroachment up to 1 m in height occurs frequently. This requires durable engineering and technological solutions. Geosynthetics can redistribute stresses, limit deformations, and reduce sand transport [5-8].

International practice (China, Saudi Arabia) shows that the most effective protection combines base reinforcement, aerodynamic barriers, and biopolymer surface stabilization [4, 9, 10]. The choice of geomaterial type must consider local geotechnical and climatic conditions [7, 11-13].

The aim of this study is to develop an adaptive engineering protection system for the railway subgrade using geomaterials, tailored to wind load and sand-drift intensity on the Bukhara-Misken railway.

The main objectives are:

1) To perform climatic-geotechnical zoning of the railway section.

2) To determine sand-drift intensity [4, 5, 12].

3) To develop a decision matrix linking wind speed and sand-drift volume.

4) To evaluate the technical and economic effectiveness of geomaterials and aerodynamic barriers [11, 14, 15].

The scientific novelty lies in integrating climatic zoning, a cubic sand-drift model, and a matrix-based algorithm for selecting protective measures, which increases subgrade stability and reduces maintenance costs [7, 8, 10].

2. Materials and methods

3. Results and discussion

Zoning revealed heterogeneous conditions: 0-39 km – low impact ($Q\approx$ 2.5-4.0), 40-166 km – moderate ($Q\approx$ 10-15), 167-356 km – high ($Q\approx$ 25-30) [12, 13, 16].

The application of the matrix reduced $Q$ by 60-80 %, increased $K$ to ≥ 1.5, increased $\mathrm{\Delta }T$ by 3-5 years, and reduced OPEX by 15-18 % [15, 18, 21].

For clarity, a ‘step-by-step’ schedule of correspondence between u ranges and measures has been developed (Fig. 1) [8, 10, 18, 22].

Fig. 1Stepwise diagram of wind speed vs protection levels

The diagram (Fig. 2) illustrates the distribution of types of measures along the route: in the slightly arid zone – biological methods; in the moderately arid zone – reinforcement and barriers; in highly arid zones – integrated systems with biopolymers [22, 23].

This cascading approach ensures a balance between technical and economic efficiency and confirms the versatility of the method for the desert regions of Central Asia [5, 7, 8, 15, 24].

Fig. 2Scheme of protection types along Bukhara-Misken line

4. Conclusions

An adaptive algorithm for the engineering protection of railway subgrades in arid regions has been developed, based on climatic zoning and a cubic model of sand transport.

The matrix of design and technological solutions provides a differentiated selection of protective measures: from biostabilisation of slopes to multi-level reinforcement systems and aerodynamic barriers. The use of geogrids, geotextiles, geomats and biopolymer stabilisers reduces sand transport by 60-80 %, increases the slope stability coefficient to $K\ge$ 1.5 and reduces operating costs by 15-20 %.

The proposed methodology can be used in the design, modernisation and operation of railways in desert areas of Central Asia and similar climatic conditions. Further research is aimed at assessing the durability of geomaterials and refining the empirical parameters of the sand transport model.