Requirements for the construction of the operating conditions conditions:
1. Earth excavation should be based on the requirements of the construction program before the construction of the area of the underground, aboveground obstacles to be removed and processed.
2. The location of buildings or structures or the site's positioning control lines (piles), standard horizontal piles and the gray line dimensions of the trenching must be inspected and qualified; and pre-inspection procedures must be completed.
3. When working at night, there should be enough lighting facilities; obvious signs should be set up in dangerous areas, and the excavation sequence should be reasonably arranged to prevent wrong digging or over-digging.
4. When excavating pit trench and pipe trench with groundwater level, measures should be taken to reduce the groundwater level according to local engineering geological data. Generally, it should be reduced to 0.5m below the excavation surface before excavation.
5. Roads, bridges and unloading facilities through which construction machinery enters the site should be inspected beforehand, and preparatory work such as reinforcement or widening should be carried out if necessary.
6. Selection of earthmoving machinery should be determined according to the topography and operating conditions of the construction area, the type and thickness of soil, the total volume of work and the duration of the work in order to give full play to the efficiency of the construction machinery, and compile a good construction program.
7. The layout of the running route in the construction area should be determined according to the size of the project in the operation area, the performance of the machinery, the transportation distance and the topography of the undulation.
8. In the mechanical construction can not work in the parts and repair the slope gradient, clean the bottom of the slot, etc., should be equipped with manual.
9. Familiarize yourself with the drawings, and make a good technical handover.
Process:
Determine the sequence and slope of excavation → average excavation in sections and layers → trimming and clearing the bottom
Determination of the slope: according to the project site soil for the geology of miscellaneous reclamation and slope proximity to meet the conditions of motorized trucks passing through the project to determine the -2.45 meters above the use of 1: 0.67 sloping excavation to -2.45 meters after. According to the specific circumstances of the artificial individual excavation of the pit is determined separately. 1.00 1:1.25
3 Rigidly molded light subclay 1:0.67 1:0.75 1:1.00
4 Medium-dense gravelly soil (filled with clay) 1:0.50 1:0.67 1:0.75
5 Rigidly molded subclay, clay 1:0.33 1:0.50 1:0.67
6 Old Loess 1:0.10 1:0.25 1:0.33
7 Soft soil (after well point precipitation) 1:1.00 ?
Table 1-4
Types of soil Slope gradient (height:width)
1 Sandy soil (excluding fine sand and silt) 1∶1.25～1∶1.15
Firm 1∶0.75～1∶1.00
Rigid 1∶1.0～1∶1.25
Filled with hard, hard plastic clay 1∶0.5～1∶1.00
Filled with hard, hard plastic clay 1∶0.5～1∶1.00
Filled with hard, hard plastic clay 1∶0.5～1∶1.00
Filled with soft soil 1∶0.10 1∶0.25 1∶0.33 1:1.00
Filling sandy soil 1:1.00～1:1.50
When the excavation passes through different kinds of soil (rock) layers or the depth is more than 10m, the slope can be made into folding line or step shape.
When excavating pit (trench) or pipe trench, the excavation sequence, route and depth of excavation should be reasonably determined.
When bulldozers are used to excavate large pits (trench), the soil should generally be pushed from the two ends or the top (longitudinal), push the soil to the middle or the top, temporarily stacked, and then pushed the soil horizontally away from the pit (trench) on both sides.
When large foundation pit (trench) is excavated by shoveling machine, it should be shoveled downward in longitudinal rows and layers in accordance with the slope line, but the centerline lot of each layer should be a little higher than the two sides in order to prevent accumulation of water.
Backhoe, pull shovel excavator excavation pit (slot) or pipe trench, there are two kinds of construction methods;
End digging method: excavator from the pit (slot) or pipe trench at the end of the backward traveling method of excavation. Dump trucks are configured to load and transport soil on both sides of the excavator.
Lateral excavation method: the excavator moves along one side of the pit (trench) or pipe trench, and the dump truck loads and transports the soil on the other side.
When the excavator moves along the edge of the excavation, the width of the machinery from the upper edge of the slope shall not be less than 1/2 of the depth of the pit (trench) or pipe trench, such as excavation depth of more than 5m, it should be determined in accordance with the professional construction program.
The earth excavation should be carried out sequentially from top to bottom in layers and segments. Make a certain slope at any time to facilitate water drainage.
In the excavation process, the status of the slot wall and slope should be checked at any time. When the depth is more than 1.5m, according to the change of soil quality, the pit (slot) or pipe trench should be prepared for support to prevent collapse.
Excavation pit (slot) and pipe trench, shall not be dug below the design elevation, such as can not be accurately dug to the design of the base elevation, can be above the design elevation of a layer of soil temporarily left unexcavated, so that in the leveling of the leveling, dug by hand.
The temporary layer of soil: general shovel, bulldozer digging, for about 20cm; excavator with backhoe, shovel and pull shovel digging, for about 30cm is appropriate.
In the mechanical construction of the earth can not be dug, should be with the manual at any time to excavate, and wheelbarrows to transport the soil to the place of mechanical digging, in order to timely use the machinery to dig away.
Repair the gang and clear the bottom. In the bottom of the slot from the design elevation of 50cm slot gang, copied out the horizontal line, nailed on the small wooden pout, and then manually dig away the temporary soil layer. At the same time by both ends of the axis (center line) lead pile pull through line (with a small line or lead wire), check the size from the edge of the slot, determine the slot width standard, so as to repair the edge of the slot. Finally remove the bottom of the slot earth.
After repairing and leveling the bottom of the slot, quality inspection and acceptance.
Excavation pit (slot) of the earth, in the site has the condition of stacking, be sure to leave enough backfill required for good soil; excess earth, should be transported away, to avoid the second handling.
Rain, winter construction:
Earth excavation is generally not suitable for the rainy season, otherwise the working surface should not be too large, should be completed section by section, piece by piece in stages.
Rainy season construction in the excavation pit (slot) or pipe trench, should pay attention to slope stability. If necessary, the slope gradient can be appropriately slowed down, or set up support. At the same time should be in the pit (trench) outside the earth dike or ditch, to prevent the inflow of surface water. Frequent inspection of the slope, support, earth embankment, found problems should be dealt with promptly.
Earth excavation should not be constructed in winter. If it must be constructed in winter, its construction method should be carried out according to the winter construction program.
When the earth excavation is carried out by preventing freezing method, it can be covered with insulating material or tilled and raked the top layer of soil before freezing, and the depth of tilling should be determined according to the local temperature conditions. Generally not less than 30cm.
Excavation pit (trench) or pipe trench, must prevent the foundation of the subsoil frozen. An appropriate thickness of loose soil should be reserved above the base elevation. Or covered with other insulating materials. In case of earth excavation caused by the exposure of foundations and bases of neighboring buildings or structures, anti-freezing measures should be taken to prevent freezing damage.
4.1 Guaranteed items:
The soil quality of the subsoil of the column foundation, foundation pit, foundation trench, pipe trench and site must comply with the design requirements and is strictly forbidden to be disturbed.
Allowable deviation items, see Table l-5.
Allowable deviation values for excavation and site leveling of earthworks Table 1-5
No. Item Allowable deviation (mm) Inspection method
1 2 3 Surface elevation length, width Side slopes are steeper than the steepest +0 -50 -0 Not permitted Inspection with a level meter Checking with the latitude and longitude meter, pulling the line and the footage Inspection Observation or with the slope scale Check.
5.1 For positioning standard piles, axial guide piles, standard leveling points, gantry boards, etc., they shall not be bumped or rested on the gantry boards when digging and transporting soil. And should often measure and check its plane position, horizontal elevation and slope gradient whether it meets the design requirements. Positioning standard piles and standard level points should also be regularly re-tested and checked for correctness.
5.2 Earth excavation should prevent sinking and deformation of neighboring buildings or structures, roads and pipelines. If necessary, it should consult with the design unit or construction unit to take protective measures and conduct settlement or displacement observation during construction.
5.3 If there are cultural relics or ancient tombs found during construction, they should be properly protected and should be reported to the local authorities in a timely manner before continuing construction. If found with the measurement of permanent stakes or geological, seismic departments set up long-term observation points, etc., should be protected. In the laying of ground or underground pipelines, cables in the lot of earthwork, should obtain the written consent of the relevant management department, the construction should take measures to prevent damage to the pipeline, resulting in serious accidents.
6.l base over-excavation: excavation pit (trench) pipe trench shall not exceed the base elevation. If individual places over-excavation, the treatment method should obtain the consent of the design unit, and shall not be handled privately.
6.2 The base is not protected: the excavation of the foundation pit (slot) should minimize the disturbance of the subsoil. In case the foundation can not be constructed in time, 30cm of soil layer can be reserved above the elevation of the foundation without digging, to be dug again when doing foundation.
6.3 Construction order is unreasonable: the construction program should be strictly in accordance with the provisions of the construction sequence of earth excavation construction, it should be noted that it is desirable to start from the low side of the excavation, layer by layer, section by section, to form a certain slope, in order to facilitate drainage.
6.4 Construction machinery sinking: construction must be aware of the soil quality and water table conditions. Bulldozer, shoveling machine generally need to push shoveling soil above the water table 0.5m; excavator generally need to dig above the water table 0.8m to prevent machinery sinking under its own weight. Positive shovel excavator digging step height, shall not exceed the maximum digging height of 1.2 times.
6.5 Insufficient excavation size and too steep side slopes: the excavation width and slope at the bottom of the foundation pit (trench) or pipe trench, in addition to the structural size requirements should be taken into account, the width of the working surface should be increased according to the needs of construction, such as the width required for drainage facilities, support structures and so on.
6.6 During rainy season construction, 30cm of soil layer should be reserved at the bottom of foundation trench and pit, and then excavated to the design elevation before concrete bedding.
This process standard shall have the following quality records:
7.1 Engineering geological survey report.
7.2 Record of engineering positioning survey.
Answer hopefully satisfied