NB/T 35082-2016Technical code for eco-restoration of vegetation concrete on steep slope of hydropower projects (English PDF)

Foreword

This document was issued on 16 August 2016 by the National Energy Administration of the PRC and takes effect on 1 December 2016.

It is a NB/T standard: recommended rather than compulsory, but it is the text a Chinese reviewer applies when assessing a submission.

It is classified under ICS 27.140, Chinese classification P59.

This code was formulated in accordance with the requirements of the Notice of the National Energy Administration on Issuing the First Batch of Energy Sector Standard Formulation (Revision) Plans for 2014 (Guo Neng Ke Ji [2014] No. 298). The drafting group carried out extensive investigation and research, carefully summarized practical experience, referred to relevant domestic standards and advanced foreign standards, and formulated this code on the basis of widely soliciting opinions.

The main technical contents of this code are: basic data, drainage, irrigation, reinforcement, vegetation, vegetation concrete, construction, maintenance and management, and inspection.

The National Energy Administration is in charge of the administration of this code. China Renewable Energy Engineering Institute proposed it and is responsible for its routine management, and the Energy Sector Standardization Technical Committee for Hydropower Planning, Reservoir and Environmental Protection is responsible for the interpretation of its specific technical contents. Comments and suggestions arising during implementation should be sent to China Renewable Energy Engineering Institute (Address: No. 2 Liupukang Beixiaojie, Xicheng District, Beijing; Postcode: 100120).

Chief development organizations of this code: China Three Gorges University; China Renewable Energy Engineering Institute.

Participating development organizations: Soil and Water Conservation Plant Development and Management Center of the Ministry of Water Resources; Sinohydro Bureau 7 Co., Ltd.; PowerChina Kunming Engineering Corporation Limited; China Gezhouba Group Three Gorges Construction Engineering Co., Ltd.; China Gezhouba Group Survey and Design Co., Ltd.; China Gezhouba Group No. 6 Engineering Co., Ltd.; China Gezhouba Group Foundation Engineering Co., Ltd.

Announcement of the National Energy Administration

Announcement 2016 No. 6: In accordance with the relevant provisions of the Notice of the National Energy Administration on Issuing the Administrative Measures for Standardization of the Energy Sector (Trial) and the Implementation Rules (Guo Neng Ke Ji [2009] No. 52), and upon review, the National Energy Administration approved 144 sector standards, of which 75 are energy standards (NB) and 69 are electric power standards (DL), and hereby issues them.

In the attached list of sector standards, NB/T 35082-2016 appears as item 32, with no standard superseded, approved on 2016-08-16 and implemented from 2016-12-01.

1 Scope

NB/T 35082-2016 is the Chinese technical code for eco-restoration of steep slopes on hydropower projects using vegetation concrete. Hydropower construction leaves behind large bare rock and soil faces - cut slopes at dam abutments, spillway and powerhouse excavations, quarry faces and road cuttings - that are often between 45 and 85 degrees, too steep for ordinary soil to stay on and too exposed for plants to establish. Vegetation concrete is the answer the code describes: a sprayed mixture of planting soil, a small proportion of cement, organic matter, a green additive that corrects the alkalinity the cement introduces, and seed, anchored to the slope with mesh so that a growing medium stays in place long enough for roots to bind it. The code sets the general provisions and defined terms, then the site investigation of slope geometry, rock type, stability, climate and native plant species. It covers the design of the treatment: the classification of slopes into hard rock and soft rock, the thickness of the base and surface layers, the mix proportions with their formulas and coefficients, the anchoring and mesh system, and the selection of plant species. Materials and their quality requirements follow, then construction - surface preparation, anchor installation, mixing, spraying, seeding and curing - and the maintenance and monitoring of the vegetation. Acceptance criteria and evaluation of the restored slope close the code.

1.0.1 This code is formulated with a view to standardizing the design and construction of eco-restoration works using vegetation concrete on steep slopes of hydropower projects.

1.0.2 This code is applicable to stable slopes of hydropower projects with a slope gradient of 45 degrees to 85 degrees, and may also be used for similar slopes of other projects.

1.0.3 Eco-restoration with vegetation concrete shall be carried out on the basis of the safety and stability of the slope, and the slope stability shall take into account the additional loads and effects imposed on the slope body by the vegetation concrete eco-restoration works.

1.0.4 Eco-restoration with vegetation concrete on steep slopes of hydropower projects shall follow the principle of sustainability.

1.0.5 Eco-restoration with vegetation concrete on steep slopes of hydropower projects shall comprehensively consider factors such as hydrological and meteorological conditions, slope conditions, vegetation, construction conditions and project investment, adapt measures to local conditions, and ensure rational design, careful construction and strengthened maintenance and management.

1.0.6 Slopes are classified into four types, namely hard slopes, soft slopes, soil-rock mixed slopes and infertile thin soil slopes, and different types of slopes shall be treated differently.

1.0.7 In addition to this code, eco-restoration with vegetation concrete on steep slopes of hydropower projects shall also comply with the relevant current national standards.

2 Terms

2.0.1 vegetation concrete: A mixture made by mixing planting soil, cement, organism of habitat material, amendment of habitat material, plant seeds and water. It features strong resistance to scouring, high fertility and a rational distribution of the solid, liquid and gas phases, and is a typical habitat material.

2.0.2 organism of habitat material: A granular substance used as an ingredient of vegetation concrete, made from several kinds of natural organic materials such as farmyard manure, straw, rice husk, sawdust and distillers' grains, after processing by crushing, blending, stacking and fermentation.

2.0.3 amendment of habitat material: A fine granular substance used to improve the physical and chemical properties of vegetation concrete, such as its microbial environment and pH value, fertility, water retention and structure.

2.0.4 watershed of slope crest: A water collection area set between the intercepting ditch at the slope crest and the upper edge of the restored slope surface, in order to supply ecological water for the slope plants.

3 Basic data

3.0.1 Before project design, the basic data of the project area shall be investigated to obtain information on meteorology, geology, water sources, topsoil resources, natural organic materials and plants.

3.0.2 The investigation of meteorological data shall mainly cover the zone type, climate type, multi-year average annual sunshine hours, multi-year average air temperature, extreme maximum temperature, extreme minimum temperature, multi-year average annual precipitation, multi-year average annual evaporation, frost-free period, freezing period, effective accumulated temperature of not less than 10 degrees C, and wind speed; it should be based mainly on the collection and analysis of data, supplemented by necessary field investigation.

3.0.3 The investigation of geological data shall mainly cover the rock and soil type of the slope, slope area, slope aspect, maximum slope gradient, maximum vertical height, groundwater conditions, seepage on the slope surface, stability of the slope body and slope shape; it should be based mainly on the collection and analysis of data, supplemented by necessary field investigation.

3.0.4 The investigation of water source data shall mainly cover the types of water sources such as tap water, well water and river or lake water, together with their water supply capacity, distance, head difference and cost of use; it should be based mainly on field investigation, supplemented by data analysis.

3.0.5 The investigation of topsoil resource data shall mainly cover the type, texture, structure, cost of use and available quantity, with priority given to the cultivated soil in areas occupied or disturbed by the project; it should be based mainly on field investigation, supplemented by data analysis.

3.0.6 The investigation of natural organic material data shall mainly cover the types of natural organic materials such as farmyard manure, straw, rice husk, sawdust and distillers' grains, their obtainable quantity and cost of use; it should be based mainly on field investigation, supplemented by data analysis.

3.0.7 The investigation of plant data shall mainly cover the zonal vegetation types around the slope surface and the native plant species; it should be based mainly on field investigation, supplemented by quadrat survey when necessary.

3.0.8 The contents and record formats of the basic data investigation shall comply with Appendix A of this code.

4 Drainage

4.0.1 In the design of drainage, for slopes where conditions permit, a watershed of slope crest (see Figure 4.0.1) shall be set between the upper edge of the restored slope surface and the intercepting ditch at the slope crest, to supply the ecological water demand of the plants on the slope surface. In Figure 4.0.1, 1 is the intercepting ditch at the slope crest, 2 the upper edge of the slope surface and 3 the drainage ditch at the slope toe; alpha is the slope gradient, beta the gradient of the watershed of slope crest, A the natural slope, B the watershed of slope crest, C the slope, H the vertical height of the slope and D the distance from the lower edge of the intercepting ditch to the upper edge of the slope surface.

4.0.2 Where a watershed of slope crest is set, the distance from the lower edge of the intercepting ditch at the slope crest to the upper edge of the restored slope surface should be calculated as D = 2.94 x eta x psi x H^0.32 / [(cos alpha)^0.06 x cos beta] (Formula 4.0.2), where D is this distance in m; if the calculated value is less than 5 m, 5 m is taken, and if it is greater than 15 m, 15 m is taken.

In Formula 4.0.2, eta is the correlation coefficient of multi-year average annual precipitation: 1.15 to 1.10 for 400 mm to 600 mm, 1.10 to 1.05 for 600 mm to 800 mm, 1.05 to 1.00 for 800 mm to 1200 mm, 1.00 to 0.95 for 1200 mm to 1600 mm, 0.95 to 0.90 for 1600 mm to 2000 mm, and 0.90 to 0.85 for more than 2000 mm.

In Formula 4.0.2, psi is the correlation coefficient of the target slope vegetation, taken as 0.8 for a pure herbaceous community, 1.0 for a grass-shrub community and 1.2 for a pure shrub community.

In Formula 4.0.2, H is the vertical height of the slope in m, taken as the vertical height of the highest bench for multi-stage slopes; alpha is the slope gradient in degrees; beta is the gradient of the watershed of slope crest in degrees.

4.0.3 Slope drainage design shall be carried out in accordance with the relevant provisions of the current sector standard Code for slope design of hydropower and water conservancy projects DL/T 5353.

4.0.4 The interception and drainage design of the slope surface shall comply with the relevant provisions of the current national standards Technical code for comprehensive control of soil and water conservation - Small-scale water storage, drainage and diversion works GB/T 16453.4 and Code for design of soil and water conservation engineering GB 51018.

5 Irrigation

5.0.1 An irrigation system shall be provided for vegetation concrete eco-restoration works, and the irrigation system should adopt fixed sprinkler irrigation or drip irrigation.

5.0.2 The quality of irrigation water shall comply with the relevant provisions of the current national standard Standard for irrigation water quality GB 5084, and filtration treatment shall be carried out when necessary.

5.0.3 Watering, fertilization and the spraying of chemicals for pest and disease control should be combined into integrated irrigation.

5.0.4 The material selection and layout of the irrigation system shall comply with the relevant provisions of the current national standard Technical specification for low pressure pipe conveyance irrigation engineering in farmland GB/T 20203.

5.0.5 The basic irrigation parameters shall comply with Table 5.0.5, which specifies the measuring method and the required index for each parameter.

Table 5.0.5, item 1: irrigation intensity, measured by the water collection method, index 12 mm/h to 18 mm/h.

Table 5.0.5, item 2: irrigation uniformity, measured by visual inspection, index not less than 0.85.

Table 5.0.5, item 3: irrigation coverage rate, measured by visual inspection, index not less than 0.98.

Table 5.0.5, item 4: water droplet diameter, measured by the filter paper method, index 1.0 mm to 3.0 mm.

5.0.6 Irrigation shall meet the following requirements: 1 The irrigation time and water quantity shall be determined in combination with natural precipitation and evaporation from the slope surface, so as to meet the needs of plant growth.

2 Irrigation shall follow the principle of appropriate quantity, repeated application and uniformity.

3 In summer and early autumn, irrigation under strong afternoon sunlight shall be avoided; to prevent pests and diseases, irrigation in the evening shall be avoided in summer.

6 Reinforcement

6.0.1 Anchor nails and hanging nets shall be set in the vegetation concrete so as to fix the vegetation concrete on the slope surface.

6.0.2 The setting of anchor nails shall meet the safety and stability requirements of the vegetation concrete and comply with the following provisions: 1 Anchor nails should be made of hot-rolled ribbed steel bars.

2 The diameter of the anchor nails shall not be less than 18 mm.

3 The maximum spacing of anchor nails on the slope surface should be calculated as d = 30 x [K + 1/sin(alpha - 30 degrees)] - 20 (Formula 6.0.2-1), where d is the spacing of anchor nails on the slope surface in cm.

In Formula 6.0.2-1, K is the correlation coefficient of the slope type, taken as 2.0 for hard rock slopes, 1.5 for soft rock slopes, 1.3 for soil-rock mixed slopes and 1.1 for infertile thin soil slopes.

Slopes of basic quality grades I, II and III under the current national standard Standard for engineering classification of rock masses GB 50218, as well as concrete slopes and grouted block masonry slopes, are classified as hard rock slopes; slopes of basic quality grades IV and V under GB 50218 are classified as soft rock slopes.

Slopes composed of hard rock fragments and sandy soil particles or gravelly soil are classified as soil-rock mixed slopes; cohesive soil slopes, sandy soil slopes, loess slopes and the like are classified as infertile thin soil slopes.

4 The spacing of anchor nails at the periphery of the slope shall be taken as 1/2 of the value calculated by Formula 6.0.2-1.

5 The minimum length of anchor nails on the slope surface should be calculated as L = 35/(K - 0.2)^2 + 45 sin(alpha - 30 degrees) + 10 (Formula 6.0.2-2), where L is the length of anchor nails on the slope surface in cm.

6 The length of anchor nails at the periphery of the slope shall be increased by 20 cm over the value calculated by Formula 6.0.2-2.

7 Anchor nails shall be subjected to anti-corrosion treatment.

8 Anchor nails shall be installed firmly, the length exposed above the slope surface shall be controlled at 8 cm to 12 cm, and the inclination angle should be 5 degrees to 20 degrees.

6.0.3 The setting of hanging nets shall comply with the following provisions: 1 A machine-woven chain-link wire mesh with a wire diameter of not less than 2.0 mm, or a flexible plastic net with a maximum tensile force of not less than 6.0 kN/m and an anti-aging life of not less than 15 years, shall be selected.

2 The mesh opening diameter of the hanging net should be 50 mm to 75 mm.

3 Machine-woven chain-link wire mesh shall be plastic-coated or galvanized for corrosion protection.

4 The lap width between adjacent hanging nets should be 100 mm to 150 mm.

6.0.4 Hanging nets shall be firmly bound to the anchor nails and to each other, and the distance between the hanging net and the slope surface should be 2/3 of the total spraying thickness.

7 Vegetation

7.0.1 Plant screening shall follow the following principles: 1 Native slope protection plants shall be preferred, and invasive alien plants shall not be used.

2 Plants with strong stress resistance, reproductive capacity, soil improvement and soil consolidation capacity shall be selected in combination with the investigated basic data.

3 Plant selection shall conform to the principles of biodiversity and sustainability.

4 Plants with good ornamental value may be selected in combination with landscape requirements.

7.0.2 Plant seeds and seedlings shall comply with the following provisions: 1 Plant seeds shall be labeled with the variety, place of origin, producer, year of harvest, purity, germination rate and thousand-seed weight.

2 Nursery stock shall have a well-developed root system and a sturdy plant form, with no damaged seedlings, no contamination of stems and leaves, and no pests or diseases.

3 Purchased plant seeds and seedlings shall hold a domestic inspection and quarantine certificate.

7.0.3 Plant configuration shall follow the following principles: 1 It should be in harmony with the surrounding environment, with a rational combination of grasses, shrubs and vines; hard rock slopes and soft rock slopes should be dominated by herbaceous plants, while soil-rock mixed slopes and infertile thin soil slopes should be dominated by shrubs.

2 Cool-season and warm-season plants should be combined in the configuration according to the investigated basic data.

3 Mutually exclusive plant species shall be avoided in the selection.

7.0.4 The pretreatment of plant seeds and seedlings shall meet the following requirements: 1 The purity, germination rate and thousand-seed weight of the plant seeds shall be rechecked.

2 Plant seeds shall be disinfected and soaked, and shell-breaking treatment shall be carried out when necessary.

3 Before non-container nursery stock is transplanted on site, it shall be heeled in in accordance with the current sector standard Code for construction and acceptance of garden and landscape engineering CJJ 82.