YPEP Cement Blanket - Slope Protection and Reinforcement Project
1. Project history and tasks
The construction site is located in the lower reaches of the Chaohe River, approximately 20 kilometers from its mouth. This section of the river is significantly influenced by ocean tides, resulting in significant tidal flooding - high and low tides twice daily. Under the influence of repeated water flows, the base of the original earthen slope was subject to constant erosion, resulting in the formation of numerous depressions and overhangs. This resulted in destabilization of the road surface above, posing a serious risk of pavement collapse. Traditional solutions to protect the slopes with rock fill or cast-in-place concrete faced serious problems here: first, the short tidal period—the short period of low tide when the river bottom is exposed—made it impossible to complete construction and cure using traditional methods during this limited time. Secondly, there were transportation difficulties because heavy building materials could not cross the soft tidal flats. Third, there were environmental concerns, as large-scale excavation and fortification could damage the intertidal ecosystem.
To address these issues, the project ultimately adopted a flexible slope stabilization solution combining cementitious pavements (also known as concrete geotextiles) with geotextile bag principles. This flexible composite material consists of dry mixed concrete pre-embedded in a three-dimensional fiber frame. Upon contact with water, it undergoes a hydration reaction, quickly hardening into a high-strength, erosion-resistant concrete layer.
2. Key design points
The main objective of the project is to create a flexible protection system that can resist erosion caused by bidirectional water flow, while compensating for minor deformations of the foundation.
Design: Use the “cement protective layer + filter layer” configuration. First backfill and compact the eroded footing to restore the desired slope profile. Lay non-woven geotextile as a filter layer to prevent loss of soil particles due to water flow. Install a cement layer as the main protective layer on the outermost surface.
Selection of material: a reinforced cement layer with a thickness of 10 mm was selected. Field testing confirms that after 48 hours of curing, its compressive strength exceeds 80% of that of traditional C20 concrete, sufficient to resist tidal erosion. Its internal fibrous structure provides excellent flexibility and resistance to cracking, adapting to the natural settlement of the backfilled soil.
Hydrological adaptation of the project: To address the problem of bidirectional erosion, protection was specifically reinforced in the toe zone and water level fluctuations. In the toe zone, the cement coating extends downwards and is buried 0.5 meters below the riverbed, forming a scour-control toe. The entire slope protection extends 0.8 meters above the maximum water level to withstand wave and wind impacts.
3. On-site installation and construction process
The construction took full advantage of the convenient and efficient properties of the cement coating, and the main process was concentrated within a few hours during low tide.
Preparing the base:During low tide, remove loose soil, rocks, and debris from the slope surface. Fill and compact the excavations in layers to ensure a level, stable base surface free of sharp edges.
Laying mats:Roll out cement mats from the base to the top of the slope. Make sure that the surface of the mats lies flat and fits tightly to the slope, without gaps or folds. For difficult undulating areas, mats can be cut on site to conform to the terrain.
Covering and fastening:The overlap between adjacent cement mats is critical for watertightness and erosion resistance. This project uses the "overlapping method": along the direction of water flow (down the slope), the top mat is laid on top of the lower one, while the width of the overlap is strictly maintained at 10 cm or more. Where slabs occur, numerous stainless U-nails or stainless steel screws secure both layers of mat and underlying geotextile into the soil at approximately 30-50 cm intervals. All ridge, toe and slab edges are sealed and secured with anchors.
Activation with water:Immediately after laying and securing the mats, activate them by watering. Use spray nozzles to apply water evenly, controlling the amount of water to approximately 9 liters per square meter (for a 10 mm thickness), until the mats are uniformly dark. Avoid direct high-pressure water jets. Keep the surface moist for the next 72 hours to allow for curing.
Curing and acceptance:After watering, the cement pavement hardens quickly. Pre-curing allows pedestrians to pass through within 3-6 hours, and the surface reaches its full strength for inspection within 24-48 hours. The entire process requires no heavy equipment, formwork, or on-site concrete mixing, significantly reducing impact on the tidal environment.
4. Summary of technical advantages of cementitious coating
Compared to traditional slope protection methods, cementitious overlays demonstrate revolutionary advantages in this project and similar applications, as detailed below:
| Comparison criterion | Cement Blanket Technology | Traditional monolithic concrete/mortar masonry technology |
|---|---|---|
| Construction speed | Very high. The materials are ready-to-use, installation and setting are quick, formwork is not required, and the curing period is short. For example, a pipeline protection project in Shandong demonstrated time savings of over 50%. | Low. Requires formwork, on-site mixing, pouring, a long curing period, and is severely limited by tidal cycles. |
| Total cost | Relatively low. Labor, equipment, and time costs are significantly reduced. The case study demonstrated cost savings of over 70%. The materials are easy to transport, weighing approximately 20 kg per square meter. | High. Requires the transportation of large volumes of materials, complex equipment, and labor, and the cost of delivering heavy equipment to the tidal zone is high. |
| Adaptability to the environment | Excellent. Flexible material perfectly follows various irregular shapes of slopes. There is virtually no dust, noise or waste water during construction. | Limited. Rigid construction requires high foundation standards, high levels of pollution during construction, and damages the original intertidal environment. |
| Wash-out resistance and durability | Outstanding. After curing, a continuous, sealed protective layer is formed, resistant to moisture penetration and cracking. In the case of the Shengli field, the service life was increased by more than three years compared to traditional plastic film barriers. | Good, but with risks. High overall strength, but with many construction joints, prone to cracking due to uneven settlement, and difficult to repair if damaged. |
| Environmental friendliness | High. Minimal impact on the site during construction; the surface can be mixed with grass seeds for subsequent landscaping; it complies with green building principles. | Low. Continuous coverage over a large area blocks water exchange and does not promote ecosystem restoration. |
Key Benefits Integration:
Revolutionary ease-of-construction: Simplify complex concrete projects into just three steps—pour, nail, pour—ideal for emergency repairs, tight spaces or areas with difficult traffic access.
Exceptional erosion resistance and protection: Seamless, thin-walled construction effectively dissipates water impact forces, making it particularly suitable for bidirectional flow environments such as tidal bores.
Significant economic and social benefits: significantly reduces project implementation time and overall costs, quickly eliminating public safety threats while protecting roads and utilities.
Environmentally friendly and sustainable: embodies the environmental priorities of modern engineering – from low-carbon material transportation and minimal construction disruptions to seamless integration with landscaping after construction.
5. Conclusion and Prospects
The successful implementation of the Chahe River Estuary Slope Restoration Project fully demonstrates the irreplaceable value of cement pavement technology in tidal erosion zones, environmentally sensitive areas and disaster relief projects. It not only effectively and cost-effectively addresses pressing engineering safety issues, but also offers innovative solutions for similar projects in water supply, transportation and coastal engineering through its lightweight, fast and environmentally friendly construction model. In the future, as material performance improves and design theories evolve, the applications of cementitious pavements will inevitably expand beyond slope protection and canal lining into broader areas of engineering. This technology will be an important driving force in transforming civil engineering to be greener, lower carbon and more efficient.
