Protection of High and Steep Excavated Slopes on Mountainous Expressways (Road Traffic Category)

Protection of High and Steep Excavated Slopes on Mountainous Expressways (Road Traffic Category)

1. Project Overview

In a mountainous expressway reconstruction and expansion project, there are extensive rock-cut slopes with a slope ratio of 1:0.8–1:1 (gradient >45°, classified as high and steep slopes). The original design employed shotcrete-anchored concrete slope protection, which incurred high costs, provided no greening, and was prone to rock weathering and spalling over time. The total length of such slopes is 3.2 km, with a total protection area of 126,000 m².

2. Geocell Selection

Perforated and embossed HDPE honeycomb geocells are used, with a cell height of 200 mm, sheet thickness of 1.5 mm, weld spacing of 400 mm, and manufactured from black UV-stabilized modified raw materials. The peel strength at welded joints is ≥10 kN/m.

3. Construction Procedure

- Remove hazardous rocks from the slope surface and level the slope face;  

- Lay a non-woven staple-fiber geotextile separation layer, complemented with plastic drainage boards to relieve internal water pressure within the slope;  

- Unfold the geocells and secure them with galvanized steel anchor pins at three points: top, bottom, and middle;  

- Fill with improved planting soil and spray-seed a mixed seed blend of grasses and shrubs;  

- Maintain for 3 months to form a composite protection layer.

4. Implementation Outcomes

- The slope stability safety factor increased from 1.1 to 1.5, with no landslides, collapses, or gully erosion observed during three years of operation;  

- Vegetation coverage reached 93%, completely replacing rigid concrete and providing a natural landscape;  

- The overall cost was reduced by 28% compared to the shotcrete-anchored solution, and subsequent maintenance frequency was significantly decreased.