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MindMap Gallery Road subgrade construction
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Road subgrade construction
This is a mind map about road subgrade construction, including groundwater control, special subgrade treatment, subgrade construction technology, etc. This mind map will help you familiarize yourself with the key points of knowledge and enhance your memory. Students in need can save it.
Edited at 2024-12-09 16:11:32
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- 稲盛和夫氏 私の今世の経験は、全部をまとめると、この36つだけです！
これは稲盛和夫に関するマインドマップです。私のこれまでの人生のすべての経験は、ビジネスの明確な目的と意味、強い意志、売上の最大化、業務の最小化、そして運営は強い意志に依存することを主な内容としています。
- 計画テンプレート - 月次計画ボード
かんばんボードのデザインはシンプルかつ明確で、計画が一目で明確になります。毎日の進捗状況を簡単に記録し、月末に要約を作成して成長と成果を確認することができます。 実用性が高い：読書、早起き、運動など、さまざまなプランをカバーします。 操作簡単：シンプルなデザイン、便利な記録、いつでも進捗状況を確認できます。 明確な概要: 毎月の概要により、成長を明確に確認できます。 小さい まとめ、今月の振り返り掲示板、今月の習慣掲示板、今月のまとめ掲示板。
Road subgrade construction
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Find a streamlined guide created using EdrawMind, showcasing the Lemon 8 registration and login flow chart. This visual tool facilitates an effortless journey for American users to switch from TikTok to Lemon 8, making the transition both intuitive and rapid. Ideal for those looking for a user-centric route to Lemon 8's offerings, our flow chart demystifies the registration procedure and emphasizes crucial steps for a hassle-free login.
- 稲盛和夫氏 私の今世の経験は、全部をまとめると、この36つだけです！
これは稲盛和夫に関するマインドマップです。私のこれまでの人生のすべての経験は、ビジネスの明確な目的と意味、強い意志、売上の最大化、業務の最小化、そして運営は強い意志に依存することを主な内容としています。
- 計画テンプレート - 月次計画ボード
かんばんボードのデザインはシンプルかつ明確で、計画が一目で明確になります。毎日の進捗状況を簡単に記録し、月末に要約を作成して成長と成果を確認することができます。 実用性が高い：読書、早起き、運動など、さまざまなプランをカバーします。 操作簡単：シンプルなデザイン、便利な記録、いつでも進捗状況を確認できます。 明確な概要: 毎月の概要により、成長を明確に確認できます。 小さい まとめ、今月の振り返り掲示板、今月の習慣掲示板、今月のまとめ掲示板。
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- Outline
Road subgrade construction
groundwater control
Classification and soil and water interaction
Groundwater classification
Forms of water in soil: solid, liquid, gaseous
Groundwater burial conditions
The distribution range of stagnant water in the upper layer is limited and close to the surface. The water level is greatly affected by climate and season.
Diving is widely distributed and closely related to municipal projects such as roads. In arid and semi-arid plain areas, if the mineralization is high and the burial is shallow, attention should be paid to salinization.
Pressurized water There is a certain water head height between two water-isolating layers. It excretes upwards and emerges in the form of rising springs.
soil and water interaction
The factor causing the greatest and most lasting impact is groundwater. Hazard: Reduce the strength and stability of the soil, causing the soil around the roadbed or underground structures to soften, and may cause landslides and subsidence. subsidence, submerged erosion, piping, frost heave, mud turning, etc.
Surface water accumulation and drainage methods along the road, as well as changes in flood levels and normal water levels in adjacent rivers, can also cause hazards such as landslides, subsidence, frost heaving, and muddying of the roadbed.
The groundwater level and movement patterns of groundwater, other forms of hydrology and hydrogeology factors have an impact on the stability of the roadbed or other structure foundations, and are also important factors affecting the safety of the main structure and operation safety.
Groundwater and Surface Water Control
Subgrade drainage: general conditions: pipes, canals, underground drainage structures; groundwater or surface water that harms the stability of the subgrade slope: seepage ditches or intercepting ditches; steep slopes or may be washed away by running water: slope protection, retaining walls.
Roadbed separates (intercepts) water:
If the groundwater level is close to or higher than the road bed elevation: set up underground ditches, seepage ditches or other facilities.
The groundwater level or ground water level is high, and the roadbed is too wet or wet: an isolation layer can be set up or measures such as drying can be taken; geotextiles, plastic boards and other materials can be dried or overloaded and preloaded
Base and road drainage
Base layer: Strictly control the fine particle content, have good water stability and permeability, and prevent frost heaving and muddying;
Surface layer: surface water discharge to meet the requirements of antifreeze layer thickness.
Waterproofing of accessory structures
Sealing measures should be taken at the joint between the street branch pipe and the inspection well to prevent early collapse of the road surface caused by water leakage.
The backfilling and compaction around pipelines, inspection wells, and rainwater inlets must meet the relevant requirements of the design and specifications to prevent surface water from infiltrating and causing damage to the roads.
Special roadbed treatment
Engineering use classification
Type I soil (soft soil): sand, powder, impact sand, loose planting, silt (peat) 0.5~0.6
Category II soil (ordinary soil): silty clay, moist loess, sand mixed with gravel and pebbles, silt mixed with pebbles (gravel), planting soil, and fill soil 0.6 to 0.8
Type 3 soil (firm soil): soft and medium dense clay, heavy silty clay, gravel, dry loess, loess containing gravel pebbles, silty clay, compacted fill soil 0.8 ~ 1.0
Type 4 soil (gravel and hard soil): solid and dense clay soil or loess, containing gravel and pebbles, medium dense clay or loess, coarse pebbles, naturally graded sand and gravel, soft marl 1.0~1.5
Type 5 soil ~ Type 8 soil Rock types: 5-soft rock, 6-hard rock, 7-hard rock, 8-extremely hard rock 1.5~4.0
Main performance parameters of subgrade soil
Moisture content ω: the ratio of the mass of water in the soil to the mass of dry soil particles,
Natural density ρ: mass per unit volume of soil
Porosity ratio e: the ratio of soil pore volume to soil particle volume
Porosity n: the ratio of the pore volume of the soil to the volume of the soil
Plastic limit ωp: The lower plastic limit of the moisture content of soil when it changes from a plastic state to a semi-solid state, which is called the plastic limit, or plastic limit for short.
Liquid limit ωL: The upper liquid limit of the moisture content of soil when it changes from a plastic state to a fluid state, which is called the liquid limit, or liquid limit for short.
Plasticity index Ip: the difference between the liquid limit and the plastic limit of the soil,
Liquid index IL: The ratio of the difference between the natural moisture content of the soil and the plastic limit to the plasticity index
Poor soil roadbed treatment
Classification of bad soil subgrade treatment
Soil improvement: using mechanical (mechanics), chemical, electrical, thermal and other means to increase density;
Replacement of soil: replacement and filling;
Soil reinforcement: Use membranes, rope nets, sheet piles, etc. to restrain the soil, or put in reinforcing materials with high tensile strength to form a composite subgrade to strengthen and improve the shear characteristics of the subgrade soil.
Roadbed treatment methods
Rolling and tamping: heavy hammer tamping, mechanical rolling, vibration compaction, strong tamping (dynamic consolidation) gravel soil, sand, silt, low saturation clay soil, miscellaneous fill soil, etc., saturated viscosity Treat soil with caution
Soil replacement cushion: gravel, plain soil, lime soil, slag cushion, shallow treatment of soft soil such as underground ditches and underground ponds
Drainage consolidation, natural foundation preloading, sand well preloading, plastic drainage board preloading, vacuum preloading, precipitation preloading treatment of saturated soft soil layers. Peat soil with extremely low permeability must be treated with caution.
Vibration and compaction Vibration and compaction, lime soil compaction piles, sand piles, gravel piles, gravel piles, lime piles, blasting and compaction, dynamic compaction replacement, processing of loose sand, silt, miscellaneous fill soil and collapsible loess
Vibration displacement and mixing of vibratory displacement, deep stirring, high-pressure jet grouting, lime piles, CFG piles and other clay soils, fill soil, silt sand, fine sand, etc.; vibratory displacement method when the undrained shear strength is < Use with caution at 20kPa
Reinforcement: Geopolymer reinforcement, anchorage, tree root piles, reinforced soil, soft soil foundation, fill soil and steep slope fill soil, sandy soil
Roadbed construction technology
Filling roadbed treatment
Urban road subgrade construction technology
Construction characteristics: Open-air operations are greatly affected by natural conditions; there are many types of professions, many structures, and pipelines of various professions are crisscrossed; there is a lot of cooperation between professions and society, there is a lot of interference, and there are many changes in construction. The old road reconstruction project brings great traffic pressure, complex underground pipelines, and high requirements for driving safety, pedestrian safety, and protection of trees and structures. Mainly mechanical operations, supplemented by manual cooperation; when manual coordination with earthwork operations, special personnel must be assigned to direct; flow or segmented parallel operations should be adopted.
Construction projects: earth (stone) work for roadbed (roadbed, embankment), related projects include culverts, retaining walls, shoulders, slope protection, drainage ditches, rapids, various pipelines, etc.
Basic process
Preparation
Set up enclosures in accordance with the traffic guidance plan approved by the traffic management department to guide temporary traffic.
Before the start of construction, the technical person in charge of the construction project should make a technical and safety briefing to the construction personnel based on the approved construction plan.
Close and encrypt the known measurement control points, establish a measurement control network, lay out control piles, restore the center line, and patch corner piles and exterior piles on both sides of the road.
Before construction, the natural moisture content, liquid limit, plastic limit, standard compaction and CBR test of the subgrade soil should be carried out according to the engineering geological survey report. If necessary, particle analysis, organic matter content, soluble salt content, freeze expansion and expansion should be carried out. Quantity testing.
Construction and protection of underground pipelines and ancillary structures:
Culverts (pipes) and other structures can be constructed at the same time as roadbed (earthwork). The construction of new underground pipelines must follow the principles of "first underground, then above ground" and "first deep, then shallow".
Demolition, modification, reinforcement and protection of existing underground pipelines and other structures.
Build surface water and groundwater drainage facilities to create conditions for subsequent earth and stone construction.
Roadbed (earth and stone) construction: excavation of road cuttings, filling of embankments, leveling of roadbed, compaction of roadbed, roadbed repair, construction of protection projects, etc.
Key points for roadbed construction
Original ground treatment:
Remove accumulated water from the original site and remove tree roots, weeds, silt, etc.
Grave pits and wells should be properly treated and filled in layers to the original base level.
When the ground slope of the fill section is steeper than 1:5, it should be built in the form of steps. The height of each step should not be greater than 300mm and the width should not be less than 1.0m.
Test section:
(1) The main purposes of the test are: ① Determine the pre-settlement value of the roadbed; ② Reasonably select compaction equipment; ③ Determine the number of compaction passes; ④ Determine the thickness of each layer of virtual paving; ⑤ Select the compaction method
The height of the subgrade fill should be increased by the pre-settlement value according to the design elevation.
Marking, transporting and unloading soil:
Transportation combined with environmental protection dust control measures (tarpa covering, etc.)
Filling construction:
According to the measured centerline piles and downhill foot piles, fill and compact the soil in layers.
Filling materials with different properties should be classified, filled in layers, and compacted; a special construction plan should be formulated for the construction of high roadbed slopes.
Filling should be carried out in layers. Only after the lower filling is qualified can the upper layer be filled. The subgrade fill width should be 500mm wider on each side than the design width.
When filling to the last layer, the filling thickness should be controlled according to the designed section and elevation and should be rolled and trimmed in time.
It should be made into a two-way cross slope. The cross slope of general soil filling should be 2% to 3%, and the cross slope of soil filling with low water permeability should be 4%.
The maximum compacted thickness of each layer should be no more than 300mm, and the compacted thickness of the last layer on the top surface should be no less than 100mm.
Leveling work
Bulldozer rough leveling
Grader precision leveling
Inspection before compaction
Before rolling, check the width, thickness and moisture content of the paved soil layer. Loosen and dry the soil that is too wet, or add water evenly to the soil that is too dry. The moisture content should be close to the optimal moisture content range (2%).
Compaction work
Compaction methods: gravity compaction (static pressure) and vibration compaction.
Light first and then heavy, first static and then vibrating, first low and then high, first slow and then fast, wheel tracks overlap, and the maximum speed of the roller should not exceed 4km/h.
Rolling should be carried out from the edge of the roadbed to the center, and the outer edge of the roller should be kept at a safe distance from the edge of the roadbed.
The final rolling should be carried out with a grade roller of not less than 12t.
Parts that cannot be compacted (road edges, inspection wells, around rainwater outlets and backfill in trenches) should be compacted using a small compactor to prevent leakage, and the compaction area should overlap by 1/4 to 1/3.
During compaction, check at any time whether there is soft elasticity, peeling, pushing, waves, cracks, etc.; after compaction, there must be no looseness, soft elasticity, slurry, or uneven surface.
Backfilling and compaction of pipeline trenches under roadbed
Light compaction equipment should be used within 50cm above the top of the pipe.
The thickness of the soil covering from the top surface of the structure to the road bed: no more than 50cm - the pipeline structure should be reinforced; 50 ~ 80cm - the pipeline structure should be protected or reinforced during compaction.
Quality inspection and refurbishing:
The compaction degree and deflection value of the earthwork subgrade should be 100% qualified, and the longitudinal section elevation, center line offset, flatness, width, cross slope and embankment slope should meet the requirements.
Excavating cuttings
Before construction, the existing water on the ground should be removed and dried, and tree root pits, grave pits, well holes and other parts should be treated.
Excavate according to measured centerline and side piles.
Excavation should be carried out in layers from top to bottom, and digging holes is strictly prohibited. When mechanical excavation, structures and pipelines must be avoided, and manual excavation must be used within 1m from the edge of the pipeline; manual excavation must be used within 2m from directly buried cables. The excavation section must not be overexcavated, and a compaction amount should be left for rolling to the design elevation.
The roller should be no smaller than 12t. Rolling should be carried out from both sides of the road to the center of the road until there are no obvious wheel marks on the surface.
During rolling, measures such as watering, soil replacement, and drying should be taken depending on the degree of dryness and moisture of the soil.
The trenches of cross-street rainwater branch pipes and the areas around inspection wells should be filled with lime soil or lime fly ash gravel or materials required by the design.
stone roadbed
The surface should be cleaned, the edges should be laid first, and then stones should be filled horizontally layer by layer.
A test section is built first to determine construction parameters such as loose paving thickness, compaction machine tool combination, number of compaction passes, and settlement difference.
Vibratory rollers above 12t, tire rollers above 25t, tamper hammers above 2.5t
The trenches around pipelines and structures within the subgrade should be backfilled with soil.
The particle size of embankment filler should not be larger than 500mm, and should not exceed 2/3 of the layer thickness. Within 400mm below the bottom of the road bed, the filler particle size shall not be larger than 150mm, and the content of fine materials smaller than 5mm shall be not less than 30%.