A, subgrade engineering construction scheme
(1) Overview of subgrade engineering
The overall subgrade width of the main line in this contract section is 24.5m, the carriageway width is 2× 2× 3.75m, and the separated subgrade width is 2 *12.25m..
(2) Construction team arrangement
It is planned to equip two subgrade engineering construction teams to complete subgrade construction in this contract section. For details of the tasks, please refer to the aforementioned "Division Table of Regional Tasks".
(3) Construction machines and tools
See the technical proposal "Equipment" in the bidding documents for the main construction machinery and equipment.
(4) Subgrade construction scheme
The construction of subgrade engineering should be combined with the construction of structures, and the construction of passages and culverts should be coordinated with subgrade engineering, so as to carry out large-scale subgrade earthwork construction as soon as possible.
Subgrade earthwork construction adopts mechanized operation. When the transportation distance is within 65,438+000 meters, bulldozers should be used for excavation, and when the transportation distance is between 65,438+000 meters and 700 meters, scrapers should be used for excavation. The road section with a transportation distance of more than 700 meters is excavated and transported by excavators and loaders, and the filled road section is filled and compacted by layers according to the full width of the cross section.
Subgrade protection and drainage engineering and subgrade engineering cross construction, coordination and arrangement. The excavated slope shall be leveled and protected in time. The drainage project adopts mechanical cooperation with manual trench digging and manual masonry construction.
Cutting earthwork excavation adopts mechanical direct excavation and artificial auxiliary slope repair. Rock that cannot be directly excavated by machinery is excavated by blasting.
(5) Progress Plan of Subgrade Engineering
Construction progress plan: subgrade construction will be completed from February 1 day, 2008 to May 3 1 day, 2009 (excluding construction preparation), and 16 months.
(6) earthwork allocation scheme
Except for users, subgrade earthwork is abandoned in the spoil ground designated by the design.
Second, the subgrade engineering construction method
(1) Cutting excavation construction
1, cutting construction method
(1) Key points of earthwork excavation: Earthwork is directly excavated by excavators and transported by dump trucks.
(1) Do a good job of intercepting ditch before subgrade excavation, and build temporary drainage facilities during construction to achieve permanent combination.
(2) Earthwork excavation should be carried out from top to bottom, and it is forbidden to dig indiscriminately and overbreak, and it is forbidden to use blasting method for construction and dig holes to borrow soil. The slope surface should be leveled by manual scraping.
(3) In the process of excavation, in case of soil change, if it is necessary to modify the construction scheme and slope gradient, it shall be submitted for approval in time.
(4) The settlement caused by compaction should be considered in the construction elevation of excavation subgrade, and its value is determined by experiment. After excavation to subgrade construction elevation, drainage ditch must be built immediately.
⑤ If the excavated earthwork meets the subgrade filling standards, it will be transported to the filling area as subgrade filling, otherwise it will be transported to the spoil ground as spoil.
⑥ During the construction of deep cutting, slope construction shall be carried out in strict accordance with the drawing slope, and adequate drainage facilities shall be provided. Slope protection construction shall be carried out in time after excavation.
⑦ When the excavated materials cannot be used for subgrade filling and compaction due to climatic conditions, the excavation shall be stopped until the climatic conditions improve.
(2) Key points of stone excavation construction: DTH drilling rig with rock drill, loose controlled blasting, and smooth blasting for slope forming.
(1) Rock excavation method is determined according to rock type, weathering degree and joint development degree. For soft rocks and strongly weathered rocks, mechanical excavation can be used, and rocks that cannot be directly excavated by machinery can be excavated by blasting.
(2) Pre-splitting, smooth blasting and controlled blasting technology should be adopted in rock blasting, and the section should be effectively controlled, and excessive blasting is not allowed; Otherwise, all materials loosened by blasting outside the design section shall be cleaned at their own expense to make up for environmental damage until the supervision engineer is satisfied.
(3) Blasting operation should prevent damage to subgrade. The subgrade shall be leveled with materials with the same strength, rolled by impact vibratory roller, rolled by protruding part, and backfilled and compacted by concave part to improve the uniformity of subgrade.
(4) In the process of construction, the excavated stones should be used to the maximum extent. In addition to embankment filling, qualified stones should be processed into blocks, blocks and crushed stones for building masonry, pavement subbase and concrete aggregate. It is not allowed to throw away stones at will.
⑤ The elevation of the top surface of the roadbed of the stone cutting shall meet the requirements of the drawings, the higher part shall be leveled manually, and the overbreak part shall be backfilled and compacted with materials approved by the supervision engineer.
For the construction technology of subgrade excavation, see the construction technology block diagram of main sub-projects in Chapter 12.
2, construction control and detection
Drainage should be done well before cutting excavation to prevent the slope from being washed by flood in rainy season, and the drainage system should be kept unblocked during construction.
When the cutting excavation is close to the design elevation, it should be supplemented by small mechanical operations to prevent over-excavation. The excavation shall be carried out from top to bottom, and no underexcavation shall be allowed.
The slope that needs protection shall be supported in time according to the design requirements, and shall not be exposed for a long time, so as not to cause the slope to collapse.
Cutting excavation should not only control slope ratio, shoulder elevation and width, but also strictly control subgrade filling and compaction.
For landslides caused by non-construction reasons, excavation should be carried out according to the boundary or slope specified by the supervision engineer, and then used for embankment filling or other treatment.
3. Rock blasting construction
Before rock blasting operation, the technical design scheme for blasting construction shall be prepared according to the topography, geology, excavation section and construction machinery and equipment, and submitted to the supervision engineer for approval, and the instructions of the supervision engineer shall be strictly implemented.
In this contract section, DTH drilling rig is proposed to be used for hole arrangement, layered, segmented, smooth and controlled blasting technology with small dosage. In the process of subgrade stone construction, the slope with excavation height less than 5 meters is drilled by pneumatic rock drill and blasted by shallow hole; If the excavation height is more than 5 meters, DTH drilling rig will be used for drilling, and deep-hole controlled blasting will be used; 10 meters above is bench blasting. The blasting is connected by millisecond delay blasting network of electric detonator, and the pre-splitting blasting, interval charging and bottom reinforcement charging technology are used for both sides of slope. The whole blasting adopts the techniques of row delay in the hole, group delay outside the hole and instantaneous initiation in the same group, which ensures the stability of the slope after blasting and the safety of nearby communication, power lines and residents. After blasting, the fragmentation should be moderate, and the fragmentation rate should be controlled within 7%, which can not only meet the mechanical loading operation, but also meet the requirements of subgrade filling.
In order to further improve the efficiency of one-stop operation of mechanical equipment, DTH drilling rig, 7 ~ 9m3 internal combustion air compressor, bulldozer, excavator and dump truck are equipped for drilling and blasting operation, and one-stop operation of drilling and blasting is implemented.
Two-sided slope kerbs and one-sided slope kerbs that cannot be excavated transversely shall be excavated longitudinally step by step. In order to increase the excavation surface, the shallow section is dug first, and then the deep section is dug.
The stonework blasting in this contract section adopts the construction scheme of combining deep hole controlled blasting with smooth blasting.
According to the experience of stone excavation construction, DTH drilling rig is proposed to be used for deep hole controlled blasting technology construction. Deep-hole controlled blasting is blasting by dispersing a columnar charge in rock mass, which can achieve "two controls": controlling flying stones and controlling blasting vibration waves, so as to eliminate the influence of blasting vibration on the stability of cutting slopes and landslide areas to the maximum extent. The blasting method adopts millisecond millisecond blasting technology, which squeezes the free surface that can be opened by millisecond blasting, and the compression wave and reflection wave are superimposed on each other, so that the stone particle size is controllable, the crushing effect is good, and it is convenient for shipment and filling.
In the construction of deep-hole controlled blasting, according to the design requirements, the site should be leveled by sections, the hole arrangement operation and hole location selection should be standardized, the charge quantity should be strictly controlled, the charging and filling quality should be paid attention to, the network connection and initiation should be paid attention to, and the construction interval should be selected as the safe blasting time to avoid operation interference and improve the work efficiency.
Smooth blasting is to accurately cut the reserved smooth blasting layer from the reserved rock mass by using smooth blasting holes arranged on the designed excavation contour line after the main charge blasting, and form a flat excavation slope.
(2) Subgrade filling construction
1, process test
Before subgrade filling construction, select road sections with representative geological conditions and cross-section forms (full-width subgrade with length not less than100m) for subgrade filling, and select the best scheme, process parameters and detection methods to guide the construction. Records shall be made during the test, and the test report shall be submitted to the engineer for approval, including the type of compaction equipment, the best combination mode, the times and speed of rolling, the working procedure, the loose laying thickness of each layer of material, etc. Strict implementation of construction technology, clear detection methods, to ensure the construction quality. If the site filler changes during construction, it shall be tested in time and reported to the supervision engineer for approval.
2. Key points of subgrade filling construction
Key points of the scheme: when the earth-rock transportation distance is within 100 meters, bulldozers will be used for construction; When the earthwork distance 100 ~ 700 meters, the scraper will be used for construction; When the earthwork transportation distance is more than 700 meters, the mechanized combined construction method of excavator, loader and dump truck is adopted.
All subgrade construction in this contract section adopts mechanized operation, bulldozers and graders are used for leveling and preloading, filling subgrade is rolled by road rollers with excitation force greater than 40 tons, rock-filled subgrade is rolled by sheep feet first, and then by road rollers with excitation force greater than 50 tons. For special sections and special parts, impact rollers are used for rolling. Narrow parts such as both sides of culvert passage and behind abutment should be tamped by small mechanical vibration.
(1) substrate treatment
Within the scope of general embankment filling, the original ground surface should be cleaned, and the roots of crops should be completely removed according to the depth required by the design and specifications. After site cleaning, the basement shall be fully compacted to the specified degree of compaction before filling.
When the original ground cross slope is steeper than 1∶5, the excavation width of subgrade base is 2m, and the slope is 4%.
Sections with zero fill and zero excavation and filling height < < 80cm (excluding pavement thickness) shall be treated according to the requirements of the tender documents.
For soft soil sections and flooded subgrade, silt should be removed first and reinforced as designed.
(2) Earthwork filling
Fill subgrade should be filled in parallel layers according to the design line of pavement, and each layer of filling surface should be made into a cross slope of not less than 3% to facilitate drainage.
Paving and compacting in parallel in layers, accurately lofting every three layers, leveling and shaping with grader, so that the filling surface can meet the design requirements of longitudinal and transverse slopes. Each layer of construction should be marked with soil and controlled by benchmarking. The loose laying thickness of each layer shall be determined through on-site process test, and the maximum loose laying thickness of each layer shall be controlled to be no more than 30cm, and the minimum compacted thickness shall be no less than 10cm.
In the process of filling soil, fill soil according to the selected optimal water content, or sprinkle water or turn over the sun, and the water content is controlled within 2% of the optimal water content. Before each layer is filled, the working face must be wet. The width of each side of each layer of filler is 30cm wider than the design width of the filler layer, and the wheel tracks of rolling should overlap by 20 ~ 30cm.
When filling subgrade in sections, the slope at the end of the first construction section shall not be steeper than 1:5, and it must be leveled and compacted to facilitate the construction machinery to open steps when going up and down the subgrade.
(3) Rock filling
The strength, particle size and paving layer thickness of stone used for embankment filling meet the requirements of design and technical specifications of bidding documents.
Rock-filled embankments should be filled horizontally in layers, and the construction should be organized by the method of jacking and leveling, and the method of stacking and paving is not suitable. High-power bulldozers and heavy vibratory rollers are paved and compacted in layers.
When filling in layers, arrange the transportation route, assign special personnel to command, fill in layers horizontally, first low and then high, then discharge to both sides, then discharge to the middle, and level it with a large bulldozer. Individual uneven places are manually filled with fine stones and leveled with stone chips. Other requirements shall be strictly in accordance with the design, bidding documents and current construction specifications.
(4) subgrade detection
After each layer of subgrade is rolled, one layer shall be detected in time. The density of subgrade fill can be detected by nuclear density meter, ring cutter method or sand filling method, and the strength of fill can be detected by K30 bearing plate, CBR value strength detection and Beckmann beam method. Through different testing methods, find out the correlation between different methods, ensure the reliability of testing data, and meet the requirements of controlling compactness, mechanical properties and quality. In the high-fill section, the final cumulative deformation of the filler layer can be calculated through indoor tests and shear and compression tests of the filler with different compaction coefficients in the remolded state. At the same time, the settlement of subgrade can be observed for a long time by embedding settlement cups, flexible settlement sensors and other test components in the base.
(5) Subgrade renovation
(1) According to the requirements of design drawings, restore the pile position, and check the position, width, longitudinal slope, transverse slope, slope and corresponding elevation of subgrade centerline. According to the inspection results, the rectification plan can be prepared and submitted to the supervision engineer for approval before construction.
(2) The soil subgrade is trimmed from top to bottom manually or mechanically. When filling 2m high, trim the fill slope and brush the slope according to the design requirements. When the depth is 3m, the slope will be trimmed.
(3) The rocky slope should be trimmed accurately and meet the design requirements, and the loose or prominent stones on the slope should be removed in time.
(4) When repairing the slope to be reinforced, reserve the reinforcement position; When the fill is insufficient or the slope is washed away by rain, the original slope will be dug into steps and compacted by layers. If the thickness of the fill is very small (10-20cm) and it is not a slope reinforcement area, it will be filled with planting soil.
⑤ After the subgrade surface reaches the design elevation, level it with grader or bulldozer. When the shoveled soil is not enough to fill the depression, it should be leveled and compacted with the same soil as the subgrade surface.
⑥ The renovation of side ditches should be carried out by hanging lines, and the longitudinal slopes of various ditches should be detected by instruments until the renovation meets the design and specification requirements.
⑦ Overfill width on both sides of fill subgrade should be removed.
⑧ After the subgrade is renovated, remove the spoil within the subgrade.
For the construction technology of subgrade filling, see the construction technology block diagram of main sub-projects in Chapter 12.
3, high fill subgrade filling construction
In addition to meeting the requirements of general embankment filling, the following points should also be paid attention to:
(1) The high fill embankment shall be filled in strict accordance with the design gradient, and the design gradient shall not be changed at will.
(2) The base of high fill embankment shall be cleaned and compacted according to the design and specification requirements.
(3) The loose laying thickness of layered compaction of high-fill embankment is the same as that of ordinary road sections, which should be determined by tests according to the types of fillers and mechanical properties of compaction. If the filler comes from different sources and its performance is quite different, it should be filled in layers, and it should not be filled in sections or vertically.
(4) Fillers with good water stability or water permeability should be used for the flooded part of high fill embankment, and the slope ratio should meet the requirements of the drawings.
(5) When the basement on one side of half-dug and half-filled is a slope, horizontal steps shall be dug as required, and loose spoil other than the designed slope shall be removed after embankment filling.
(6) The settlement and displacement of high fill embankment must be observed, and the observation method should be handled according to the relevant provisions of technical specifications or other methods approved by the supervision engineer.
Construction scheme and method of subgrade and its ancillary works
A, subgrade engineering construction scheme
(1) Overview of subgrade engineering
The main line of this contract section includes: integral subgrade with a width of 24.5m, driveway with a width of 2× 2× 3.75m, and concealed subgrade with a width of 2 *12.25m..
(2) the arrangement of the construction team
We plan to arrange two subgrade construction teams to complete the subgrade construction of this contract section. You can find the detailed division of tasks in the List of Division of Tasks in the Administrative Region.
(3) Layout of construction machinery
The main construction machinery is suggested as "equipment" in the technical treatment of procurement documents.
(4) the underground engineering construction scheme
The subgrade construction is generally arranged in combination with the structure. Tunnel and culvert construction should cooperate with each other, and subgrade earthwork construction should be started as soon as possible.
Subgrade earthwork construction adopts mechanical construction. If the transportation distance from excavation to fill is less than 100 meters, we mainly use bulldozers. 100-700m, using loading-transportation-unloading. More than 700 meters, using grab, loader and dump truck. Fill in the fill, and gradually flatten it according to the cross section.
Subgrade protection and drainage works cross. When digging a step, we should protect it in time. We use manpower and machines to complete drainage works and build fortifications manually.
High cutting earthwork mainly adopts mechanical direct excavation and artificial slope repair. Stones that cannot be directly excavated can be blasted.
(5) Progress Plan of Subgrade Project
Construction plan: from February 1 day, 2008 to May 3 1 day, 2009, the project will be completed within 16 months (except preparation time).
(6) Arrangement of earthwork and stonework
Except for the earthwork used for subgrade, the rest earthwork will be put into the designated spoil ground.
Two. Construction method of subgrade engineering
(1) Cutting excavation construction
1. Cutting excavation construction method
(1) Earthwork excavation elements: directly excavate the earth with grab bucket, and then transport it with dump truck.
(1) in order to successfully complete the project, we need to prepare the intercepting ditch before digging the subgrade. During the construction period, we must build temporary drainage facilities.
(2) the earthwork excavation should be carried out from top to bottom, shall not be arbitrarily overbreak. Blasting operations and hollowing out earthwork are prohibited. Artificial auxiliary trimming of slope plane.
(3) in the process of excavation, if it is necessary to change the construction scheme and slope gradient due to the change of soil quality, the relevant personnel should be reported to obtain the modification scheme.
(4) When the excavation surface has elevation, the subsidence caused by pressure should be considered. Its value is determined by experiment. After digging to the elevation, the drainage ditch should be done immediately.
⑤ If the excavated earthwork meets the fill standard, it will be transported to the fill as fill. Otherwise, they will be transported to the wasteland.
⑥ When digging deep into high cutting, the slope gradient should be consistent with the design, and drainage instruments should be prepared.
⑦ When the excavated earthwork is not suitable for filling due to the weather, stop digging and wait for the weather to improve.
(2) Elements of rock excavation: DTH drill is used to assist hammer drilling. Loose controlled blasting and slope forming smooth wall blasting.
(1) stone excavation according to the type of stone, weathering degree and joint development degree. If possible, soft and hard weathered rocks will be excavated by machines. If not, we can use blasting.
② Rock blasting mainly adopts presplitting, trimming and controlled blasting to effectively control the section. Excessive blasting is prohibited. Otherwise, they should be responsible for removing all loose objects except road sections and making up for environmental damage until the supervision engineer is satisfied.
(3) blasting should prevent damage to the road. The pavement should be filled with the same material and compacted by vibratory roller. In this way, the road will be smooth and its equality will be improved.
We should make full use of the excavated soil. In addition to fillers, stones that meet the requirements can be made into block stones, rubble and rubble, which can be used as building stones, floors and concrete materials. Do not abandon them.
⑤ The elevation value of the top of stone cutting subgrade should comply with the design. The excess part shall be cut manually, and the sunken part shall be filled up according to the requirements of the supervision engineer.
See "Chapter 12 Construction Flowchart of Subdivisional Works" for details of subgrade excavation construction technology.
2. Construction control and inspection
We should make good preparations for drainage before digging high cutting. To prevent the rainy season floods from scouring the slope. In the process of construction, we should ensure that the drainage equipment is always unblocked.
When the excavation height is close to the design elevation, micro-machinery should be used to prevent over-excavation. Excavation should be carried out from top to bottom, and bottom-up excavation is prohibited.
If the slope needs to be protected, it should be protected according to the design. In case it is squeezed, don't expose it for a long time
When digging high cutting, in addition to controlling the elevation and width of slope angle and shoulder (road). The filling and compactness of subgrade should also be controlled.
For rolling caused by other reasons, excavation shall be carried out according to the side or slope specified by the supervision engineer, and the excavated materials can be used for filling or other purposes.
3. Rock blasting construction
Before rock blasting, we should make a feasible blasting construction plan. According to the topography, geology, section and construction machinery, etc. The plan shall be approved by the supervision engineer and executed in strict accordance with the instructions of the supervision engineer.
We use the layered, separated, smooth and small-dose blasting technology of in-hole drilling rig. During the construction of rock subgrade, the excavation slope is less than 5 m, and pneumatic rock drill is used for drilling and shallow hole blasting. When the excavation slope is more than 5 m, a down-the-hole drill is used to drill holes, and deep-hole controlled blasting is used. Over 10 m, bench blasting is adopted. The electric detonator is connected by millisecond blasting network. Pre-splitting blasting, interval charging and strengthening bottom charging technology are adopted on both sides of slope. The whole blasting adopts blasting delay in the hole and delay in the group outside the hole, and the same group is the technology. This can stabilize the slope and nearby telecommunications and power lines, and ensure the safety of residents after blasting. After blasting, the fragmentation must be moderate, and the fragmentation rate must be within 7%, which can meet the requirements of loading machinery and subgrade filling.
In order to improve the mechanical efficiency, blasting down-the-hole drilling rig, 7-9 m3 internal combustion air compressor, bulldozer, excavator and dump truck are used for drilling. Drilling, blasting and transportation are carried out simultaneously.
Bilateral high cutting and unilateral high cutting cannot be excavated, and excavation shall be carried out step by step. In order to increase the excavation scale, shallow sections are dug first, and then deep sections are dug.
The stonework blasting in this contract section adopts the construction scheme of combining deep hole blasting with smooth blasting.
According to the experience of rock excavation, we plan to use down-the-hole drilling rig for deep-hole controlled blasting technology. Deep-hole controlled blasting is to distribute the grain in the rock for blasting, which can have "two controls". Control flying rocks and blasting vibration waves, and eliminate the influence of blasting vibration on the stability of cut excavation slope and landslide section to the maximum extent. The blasting method adopts millisecond technology. The free surface can be opened by millisecond blasting, and the compression wave and reflection wave are superimposed with each other. The particle size of the stone can be controlled, and the crushing effect is good, and it is convenient to transport to the filling site.
In the construction of deep-hole controlled blasting, first of all, it is necessary to level off in sections, standardize the operation, and select the hole position according to the design requirements. Strictly control the quantity of drugs. Pay attention to drug installation, packaging quality, network connection and detonation process. The construction interval is selected as the safe blasting time. Avoid interfering with operation and improve efficiency.
After the main blasting, the smooth wall blasting uses the excavation contour line to adopt the gun position-blasting hole in the design, and accurately cuts the reserved smooth surface from the reserved stone blasting to form the excavation slope.
(2) Subgrade filling construction
1. Process test
Before subgrade filling construction, the geological conditions of various types of construction subgrade should be tested as a whole, and a representative section form (the overall length is less than 100 m) should be selected. Then choose the best subgrade construction scheme, process parameters and inspection methods to guide the construction. During the test, records should be made, such as the type of compaction equipment, optimal combination, rolling times and speed, working procedure and material thickness of each step. Then submit it to the engineer for confirmation. Therefore, we can strictly enforce the construction technology, make the detection methods clean, and ensure the construction quality. If the fill changes, we need to test it immediately and submit it to the supervision engineer for review and approval.