Provincial Highway Soft Subgrade Reconstruction & Expansion (Old-New Subgrade Splicing)

Cellular Confinement Systems for Subgrade Stabilization

Provincial Highway Soft Subgrade Reconstruction & Expansion (Old-New Subgrade Splicing)

1. Project Overview

A provincial highway reconstruction and expansion project in China. The route passes through collapsible loess and silt soil, containing numerous old-new subgrade splicing sections with heavy daily traffic volume.

2. Engineering Challenges

Huge stiffness difference between old and new subgrades; large settlement of original subgrade, easily triggering longitudinal cracks at splicing joints. The design limits cushion thickness, and large-scale deep excavation & soil replacement is prohibited.

3. Selected CCS Specification

HDPE textured cellular confinement system; height 150 mm; sheet thickness 1.5 mm; welding spacing 440 mm, non-perforated.

4. Key Construction Points

- Level and compact subgrade base, lay non-woven geotextile as separation layer.

- Lay CCS transversely across the splicing interface; fully stretch panels, anchor with steel nails, connect modules via locking fasteners.

- Fill graded crushed stone and compact in layers to form stiffness-transition composite cushion; construct upper pavement base after acceptance.

Implementation Results

✅ The thickness of subgrade cushion reduced by 50%, earth excavation volume significantly cut down.

✅ Effectively mitigates differential settlement between old and new subgrades; longitudinal splicing cracks greatly reduced after opening to traffic.

✅ Soil shear strength increased by 2–3 times, restraining pavement shoving and rutting.

✅ Total construction period shortened by 25% compared with conventional deep excavation replacement.