Annex 3 Soil Erosion Control Plan
1.Overall Arrangement for Soil Erosion Control
The overall erosion control measures shall be determined for each protection zone according to the principles of the arrangement of erosion control. The overall layout of erosion control measures for the full line is shown in Table 1.
Table 1 Overall Layout of Soil Erosion Control Measures along the New Rapid Railway from Zhangjiakou to Hohhot
Control zones / Control objects / Conservation and prevention measuresHilly area / Subgrade works / Subgrade slope / Retaining wall shall be located by using frame bolt and shaller to protect the deep cutting. Frame slope protection and vegetation measures shall be combined to protect subgrade slope, with vegetation measures mainly being slope shrubs, planting shrubs and grasses within the frame, etc.; and engineering measures are frame slope protection with water cut-off and drainage channels, mortar rubble slope protection and subgrade drainage works, etc.
Both sides of subgrade / Mainly plant-based measures, with shrubs inside and trees outside, and natural recovery of both sides of the subgrade shall be paid attention to.
Subgrade stripped topsoil / Temporary protective measures shall be taken on the temporary stockpiling field of the stripped topsoil in the subgrade.
Station / Station / Engineering measures are mainly station slope protection and drainage works; plant measures are landscaping design combining trees, shrubs, flowers and grass to beautify the environment and improve soil and water conservation.
Stripped topsoil in the station / Temporary protective measures shall be taken on the temporary stockpiling field of stripped topsoil in the station site.
Bridge and culvert works / Bridge and culvert / Mortar rubble slope shall be used for the bridge cone slope and river bank; cofferdam shall be set up and removed, and temporary protective measures shall be strengthened.
Tunnel / Tunnel / Mortar rubble masonry shall be used for the side invert slope and gutter in the tunnel entrance, and water cut-off and drainage measures shall be taken.
Earth-fetching field / Earth-fetching field / When the construction is completed, protection measures to spread grass seed and plant shrubs shall be taken, and temporary protective measures shall be strengthened for the stripped topsoil on the earth-fetching field.
Spoil (ballast) field / Spoil (ballast) field / Engineering measures and plant measures shall be combined. Retaining walls and drains shall be installed, and topsoil cover measures shall be taken; grass seed shall be spread or shrubs be planted for natural recovery of spoil (ballast) body; and temporary protective measures shall be enhanced for spoil, and stripped topsoil in the disposable ballast.
Construction sidewalk / Construction sidewalk / It shall be remained for local use or maintenance of roads according to the actual situation. The sidewalk which is not used shall be cleaned up and leveled when the construction is finished, and grass seeds shall be spread for natural recovery.
Production and living area in construction / Construction site, camp / After the construction, the garbage site and hardening space shall be cleaned, and the surface shall be leveled; plant recovery measures shall be taken according to the actual situation.
Plain area / Subgrade works / Subgrade slope / Frame slope protection and plant measures shall be combined for the slope protection of the subgrade, with plant measures being shrubs planted at the slope, shrubs planted in the frame and seeding grass, etc. and engineering measures being frame slope protection with water cut-off and drainage channels, mortar rubble slope protection and subgrade drainage works.
Both sides of subgrade / Mainly plant-based measures, with shrubs inside and trees outside, and natural recovery of both sides of the subgrade shall be paid attention to.
Subgrade stripped topsoil / Temporary protective measures shall be taken on the temporary stockpiling field of the stripped topsoil in the subgrade.
Station / Station / Engineering measures are mainly station slope protection and drainage works; plant measures are landscaping design combining trees, shrubs, flowers and grass to beautify the environment and improve soil and water conservation.
Stripped topsoil in the station / Temporary protective measures shall be taken on the temporary stockpiling field of stripped topsoil in the station site.
Bridge and culvert works / Bridge and culvert / Mortar rubble slope shall be used for the bridge cone slope and river bank; cofferdam shall be set up and removed, and temporary protective measures shall be strengthened.
Tunnel / Tunnel / Mortar rubble masonry shall be used for the side invert slope and gutter in the tunnel entrance, and water cut-off and drainage measures shall be taken.
Earth-fetching field / Earth-fetching field / When the construction is completed, protection measures to spread grass seed and plant shrubs shall be taken, and temporary protective measures shall be strengthened for the stripped topsoil on the earth-fetching field.
Spoil (ballast) field / Spoil (ballast) field / Engineering measures and plant measures shall be combined. Retaining walls and drains shall be installed, and topsoil cover measures shall be taken; grass seed shall be spread or shrubs be planted for natural recovery of spoil (ballast) body; and temporary protective measures shall be enhanced for spoil, and stripped topsoil in the disposable ballast.
Construction sidewalk / Construction sidewalk / It shall be remained for local use or maintenance of roads according to the actual situation. The sidewalk which is not used shall be cleaned up and leveled when the construction is finished, and grass seeds shall be spread for natural recovery.
Production and living area in construction / Production and living area in construction / After the construction, the garbage site and hardening space shall be cleaned, and the surface shall be leveled; plant recovery measures shall be taken according to the actual situation.
Frame slope protection and plant measures shall be combined for the slope protection of the subgrade, with plant measures being shrubs planted at the slope, shrubs planted in the frame and seeding grass, etc. and engineering measures being frame slope protection with water cut-off and drainage channels, mortar rubble slope protection and subgrade drainage works.
2.Subgrade Protection Measures
2.1 Subgrade Protection
To reduce soil erosion resulted from subgrade filling and excavation and to ensure the safety of the subgrade project, the line of subgrade has been reinforced and appropriate measures such as retaining wall protection, slope protection by framework or mortar rubble revetment, arched or square slope, planted tank, and new soil grass have been take based on the characteristics of subgrade in different segments. In addition, appropriate drainage system has been designed.
(1)General subgrade slope protection
If the height of the subgrade slope <3.0m, hollow bricks with new soil grass and planted shrubs shall be used; if the height of the slope≥ 3.0m, a layer of two-way geogrid with a limit tensile strength of not less than 25.0kN/m shall be laid every a filling of 0.6m within the width of 3.0m at the outer section of the slope, C25 concrete hollow brick with new soil grass + planted shrubs in water disconnection framework shall be used for slope protection. The main frame shall be 0.6m thick, and C25 concrete masonry shall be used for the water disconnection tank. The interface between the subgrade surface drainage and slope drainage shall be paid attention to. Three-dimensional ecological bags may be considered for the protection of city road segments, scenic areas and ecologically sensitive areas. If the slope of the subgrade height is greater than 8.0m, a different slope rate shall be taken according to the filling height. It is 1:1.5 for the slope of 0 ~ 8.0m, 1:1.75 for the slope of 8.0 ~ 12.0m, and 1:2.0 for the slope below 12 m; and a 2.0m wide platform will be located at 12.0m for the slope. New soil grass and planted shrubs in the hollow bricks in C25 concrete arch water disconnection frame will be used for the slope of 0 ~ 12.0m under the shaller, and dry stone revetment or prefabricated solid block revetment will be used for the side slope below 12.0m.
(2)High subgrade slope protection
If the slope height exceeds 12m, the slope rate is 1:1.5 for 0 ~ 8.0m, 1:1.75 for 8.0 ~12.0m, 1:2.0 for the height below 12 m. A 2.0m-wide platform will be located at 12.0m for the slope. New soil grass and planted shrubs in the hollow bricks in C25 concrete arch water disconnection frame will be used for the slope of 0 ~ 12.0m under the shaller, and dry stone revetment or prefabricated solid block revetment will be used for the side slope below 12.0m. C25 concrete or rubble foot wall of concrete will be positioned at the slope. Gravity retaining wall may be located at some high-fill subgrades with less arable land to reduce the use of farmland.
(3)General graben slope protection
1）For the cutting slope of general clay and all-weathered layer, if the height of the slope is less than 3.0m, hollow bricks with new soil grass and planted shrubs shall be used for protection; if the height is equal to or greater than 3.0m, hollow bricks with new soil grass and planted shrubs in C25 concrete water disconnection frame shall be used for protection.
2）For gravel soil, sandy soil cutting slope, hollow bricks with new soil grass and planted shrubs in C25 concrete arched or square grass window shall be used for protection.
3）For strong-weak weathered soft rock cutting slope whose height is less than 8.0m, hollow bricks with new soil grass and planted shrubs in C25 concrete water disconnection frame shall be used for protection; if the height is greater than 8.0m, hollow bricks with new soil grass and planted shrubs in C25 concrete arch or square grass window shall be used for the lower side slope for protection, hollow bricks with new soil grass and planted shrubs in C25 concrete water disconnection frame shall be used for the most upper side slope for protection.
4）For strong-weak weathered hard rock cutting slope, if the slope height is less than 8.0m, hollow bricks with new soil grass and planted shrubs in C25 concrete arch or square grass window shall be used for protection; if the height is greater than 8.0m, hollow bricks with new soil grass and planted shrubs in the retaining wall of C25 concrete hollow window shall be used at the bottom, while hollow bricks with new soil grass + planted shrubs in C25 concrete arched or square grass window shall be used at the upper slope for protection.
Weakly- sligthly hard rock cutting: in general, the height of the slope is controlled within 30.0m, and M10 mortar rubbles will be embedded for the slope. Hollow bricks with new soil grass will be used for the protection in the concrete grass window or anchor rod and cable within the framework.
5）In the lots with absence of A, B group packing, if the cutting soil is sand gravel, hard rock, large platform shall be reserved for the foot and side slope of cutting slope, with one level every 8.0 ~ 10.0m, and the slope rate shall be reduced accordingly. C25 concrete grass window shall be used for the slope protection.
6）The types of water disconnection frame slope protection are arch, herringbone and box types. They shall be used based on the soil quality of the slope and the requirement for erosion prevention combined with landscape demand. The spacing between the main frame and the arch shall be 3.0m. For the general soil and soft rock cutting, the main frame is 0.65m thick, and the supporting frame is 0.4m thick; for very soft rock, red clay, swelling (rock) soil cutting, the main frame is 0.8m thick, and the supporting frame is 0.6m thick.
7）Planting tanks in which japanesecreepers and evergreen low shrubs are planted shall be located at the platform of the side trenches in the cutting where retaining wall, pile wall and protection wall are located and the platform from the flooding closed slope lot to the drainage.
(4)Deep cutting slope protection
If the height of soil and soft rock cutting slope exceeds 12.0m, and of hard rock slope exceeds 20.0m, the deep cutting shall be designed, and reinforced protection works shall be set.
1）Gravity retaining wall shall be used in the close of the slope for soil and completely weathered rock cutting, and the height of the retaining wall shall not exceed 4.0m. The measures of slope protection refer to slope subgrade. If the slope height is greater than 15.0m, stratified excavation shall be considered for hierarchical reinforcement or pre- strengthening of the lowest part of the slope.
2）In the lots where the slope height of soft rock cutting and hard weathered rock cutting is not more than 18.0m and there is no adverse impact on the structure surface, retaining wall, concrete window grass slope and framework anchored rod shall be used for protection. The height of the retaining wall shall not be greater than 6.0m. In the lots where the slope height is greater than 18.0m or there is adverse impact of the structure surface or broken lithology, stratified excavation shall be considered for hierarchy reinforcement or pre- reinforcement of the lowest part of the slope, such as prestressed cables, pre-reinforced piles and sheet pile walls. In general, the height of the slope shall be controlled within 25.0m. As the strata of the hard rock along this line is old, the joints are developed and the rocks are crushing, grass window wall shall be used for the slope or the slope shall be closed.
3）The slope rate for excavation of the cutting slope of weakly–slightly weathered hard rock shall be determined based on rock lithology, degree of weathering, level, geological structure, groundwater and required allocation of earth and stone. If the slope height is not greater than 24.0m and there are no lots with adverse impact on the structure surface, retaining wall, concrete grass window slope, wall and frame anchored rod shall be used for protection, with the height of the retaining wall not greater than 8.0m. If the height of the wall exceeds 6.0m, temporary shotcrete shall be taken for the excavated slope of the back of the wall. If the slope height is greater than 24.0m or there are lots with adverse side effects of structure and broken lithology, stratified excavation shall be considered for hierarchical reinforcement or pre-strengthening of the foot of the slope. The slope height of weak–slight weathered hard rock cutting shall, in general, be controlled within 30.0m. Finishing or pre-split blasting shall be used for the slope within the thickness of 3.0m, and M10 mortar rubbles shall be embedded. Hollow bricks with new soil grass shall be used inside the concrete grass windows or frame anchored rods and cables.
4）Planting tanks in which japanesecreepers and evergreen low shrubs are planted shall be located at the platform of the side trenches in the cutting where retaining wall, pile wall and protection wall are located and the platform from the foot of the flooding closed slope lot to the drainage.
5）In the lots with absence of A, B group packing, if the cutting soil is sand gravel or hard rock, depressed road's extension shall be designed and large platform shall be reserved for the foot and side slope of cutting slope, with one level every 8.0 ~ 10.0m, and the slope rate shall be reduced accordingly. C25 concrete grass window shall be used for the slope protection.
(5)Expansion rock (soil) cutting slope protection
1）The slope design of expansion rock (soil) excavation shall follow the principle of "reduced slope rate, wide platform, reinforced toe, enhanced drainage and appropriate slope protection". The excavation height shall be generally controlled within 15.0m. The rating of the slope height shall not be more than 6.0m. If the slope height of the cutting is less than 10.0m, the slope rate is generally 1:1.75 for weak swelling rock (soil), 1:2.0 for moderate swelling rock (soil), and 1:2.25 - 1:2.5 for strong expansion rock (soil). The width of the slope platform shall not be less than 2.0m for weak expansion rock (soil), and not less than 3.0m for medium and strong expansion rock (soil).
2）If the slope height of the cutting is less than 3.0m, the use of hollow bricks with new soil grass + planted shrubs shall be made for protection; if the slope height is greater than 3.0m but less than 10.0m, the use of hollow bricks with new soil grass and planted shrubs in C25 concrete water disconnection frame (expansion soil) or C25 concrete grass window (expansion rock) shall be made for protection; if the slope height is equal to or greater than 10.0m, a platform in a width of 3.0 ~ 6.0m shall be located at the slope of expansive soil cutting, hollow bricks with new soil grass and planted shrubs in C25 concrete water disconnection frame combined with supporting sewer shall be used for protection; if the slope is equal to or greater than 10.0m, hollow bricks with new soil grass and planted shrubs in framework anchoring rod (or anchoring cable) combined with supporting sewer shall be used for the protection of the slope of expansion rock. The thickness of the main frame of the C25 concrete water disconnection framework shall not be less than 0.8m, and that of the supporting frame shall be 0.6m. The main frame spacing and the spacing between arches is 3.0m.