1 Preface

In recent years, whether from the country or individuals, for the ecological environment in the process of engineering and construction of higher and higher degree of importance, of course, with the progress of the times, engineering and construction process to protect the ecological environment of the design concept is also gradually guided by our pre-design work. Once foreign scholars also put forward ‘the durability and stability of the road (sustainability), can not rely on mechanical engineering measures to protect, only by the growth of plants to get’. Which mentioned the sustainable development combined with the understanding of the current stage of highway design, should determine a guiding direction is: highway is not only a simple to bear a certain amount of traffic space channel, but also requires and the surrounding ecological environment to achieve a certain degree of coordination. Highway up and down slopes and around the excavation and filling of stone slag field greening project, it should be in the pre-design focus on the coordination of the natural environment and has the corresponding ecological and environmental protection function, as much as possible on the construction of the project for the restoration of vegetation design. This is not only in the highway later operation process can play the corresponding landscape effect, at the same time for slope stability, reduce soil erosion, noise reduction, dust reduction, improve the road life cycle can play a good role.

Slope vegetation restoration design, mainly relying on the adhesion between the slope vegetation roots and slope soil to achieve the effect of reinforcing the slope, while the economic and ecological benefits have become a design trend of slope protection. In the traditional highway engineering and construction process, for the disposal of slopes more will use stone masonry support, reinforced concrete frame lattice beam, hanging net spray anchor and other engineering measures. The transport cost is high, the construction period is long; the construction process is more complicated; the adoption of stone material causes new ecological

damage, more importantly, it is more difficult in greening design, small coverage, which seriously affects the landscape along the highway. In the past period of time for the slope ecological protection how to continue to innovate, how to make the ecological and engineering construction of a better combination has been the designers think about the problem. With the continuous development of new materials and new technology, the multifunctional application of geocell provides a better way to solve this problem.

2 Characteristics of Geocells and Ecological Protection Mechanisms

2.1 Characteristics of geocell

Geocell is made of reinforced HDPE sheet material, formed by high strength welding of a three-dimensional mesh chamber structure, generally by ultrasonic needle welding.

It has the following characteristics.

(1) easy to stretch, convenient transport, construction process stretch into a mesh, the chamber can be filled with a variety of mixtures or guest soil.

2）Resistant to corrosion, light material, wear-resistant, stable chemical properties, suitable for different soil conditions.

3）It has strong lateral restriction force, anti-slip, anti-deformation, effectively enhancing the slope integrity and dispersing the load effect.

(4) Complete specifications, change the geocell height, welding distance and other geometric dimensions to meet different engineering needs.

5）Construction process splicing is convenient, the process is relatively simple, the construction speed is fast.

2.2 Geocell slope ecological protection mechanism

In the project, for the slope protection of cement, steel and other raw materials, the corresponding norms have put forward specific requirements. If you can not achieve the conditions of local materials, you need to purchase or long-distance into the material transport, purchase costs and transport costs are huge. And the use of geocells can be near the material, easy to transport, laying simple, for some ecological requirements of high, at the same time suitable for vegetation growth in the region of the slope disposal effect is even better.

Slope ecological protection more than the use of high-strength geocells, which not only has a high unit width fracture tensile strength (general strength ≥ 800N/cm), node peeling strength (general strength ≥ 400 N/cm), cell welding node shear (general strength ≥ 10,000 N/cm) and high fatigue strength, and at the same time, the material's corrosion resistance is also relatively excellent. Geocell has a strong lateral limiting effect on the slope filler. Its interlocking ability with the granular material of the filler can restrain the lateral movement of the granular material. Slope protection can form a large honeycomb-shaped three-dimensional grid after paving, laid on the slope surface, in the three-dimensional grid filled with aggregate or soil adapted to the growth of vegetation, planting grasses and trees suitable for the local area. Depending on the actual needs, single or multiple layers of geocells can be laid to provide the main stabilisation of the slope. The stability of the slope can be controlled accordingly even under the impact of water flow in the later operation. The rainwater inside the slope can be infiltrated through the openings in the side pieces of the geocells to keep the drainage smooth. Geocells have good water conductivity, and at the same time can play a role in alleviating energy dissipation for flowing water. It can precipitate the flowing water in the slope inside the chamber, effectively avoiding the grass seeds and vegetation seedlings being washed away by rainwater loss, and improving the plant coverage and survival rate. During highway operation, the stems and leaves of slope vegetation can produce the hydrological effects of rainfall interception, weakening splash erosion and inhibiting surface runoff. Compared with the traditional concrete slope protection, slope ecological protection plant root system can increase soil permeability, once encountered with rainwater can be quickly infiltrated, vegetation cover can make the slope to reduce the direct scouring of rainwater, buffer rainwater flow rate. Therefore, high-strength geocell ecological slope has high erosion resistance, and can achieve the purpose of effective ecological slope protection.

4. Geocell ecological slope protection precautions

(1) The selection and storage of geocell should be according to the relevant requirements of the product.

(2) Geocell slope ecological protection try to keep the slope rate not steeper than 1:1, slope excavation height control in 8-10m.

(3) The filling height of guest soil filler should be less than 0.5 m, the filler should be laid evenly and densely, and the overfilling height should be 1-2cm.

(4) In accordance with the requirements of the relevant construction specifications, each process should be closely linked, and the moulded slope should be avoided to be exposed for a long time to produce damage. Construction should be avoided in the rainy season to prevent the slope and guest soil from being washed by rainwater and causing accidents.

(5) According to the local climate and requirements, choose the vegetation and tree species suitable for the growth of local slopes, and at the same time, do a good job of protection, drainage and later maintenance work.