The length of the pile extending into the pit bottom shall be greater than 5 times the pile diameter and greater than 1m.
(7) The thickness of protective layer of soil nailing reinforcement shall not be less than 25mm..
Single soil nailing wall is used for non soft soil foundation pit above groundwater level or precipitation, with depth ≤ 12m; Prestressed anchor composite soil nailing wall is used for non soft soil foundation pit above groundwater level or precipitation, with depth ≤ 15m; When cement soil pile composite soil nailing wall is used for mucky soil foundation pit, the depth is ≤ 6m.
Vi.
When it reaches a certain depth and the soil layer is relatively stable, it can be drilled at a normal speed.
III.
The grouting pressure should be 0.4 ~ 0.6MPa; (6) The maximum particle size of aggregate for shotcrete shall not be greater than 15mm; The operation shall be carried out in sections and pieces at one time, from bottom to top in the same section, and the thickness of one shot shall not be greater than 120mm.
Shotcrete construction shall be started after the acceptance of reinforcement mesh and soil nail, and the nozzle shall be vertical to the sprayed surface.
(4) The lower earthwork can be excavated only 48 hours after the grouting of the upper layer of soil nails is completed.
IV.
The inclination angle shall be 5 ~ 20 ° and the hole diameter shall be 70 ~ 120mm.
The distance between the nozzle and the sprayed surface should be controlled in the range of 0.8 ~ 1.5m.
(5) The hole grouting soil nail shall be constructed by twice grouting process.
The main reinforcement shall be welded with the centering support every 1 ~ 2m to prevent the main reinforcement from deviating from the center of the soil nail.
The reinforcement mesh shall extend to the ground surface and extend 0.5m beyond the slope line.
applicable conditions: the safety level of the side wall of the foundation pit is level II and level III.
VIII.
The reinforcement mesh shall be constructed in layers and set layer by layer with the soil nail.
Three construction requirements (1) the construction of soil nailing wall must follow the principle of “advance support, layered and segmented construction, layer by layer construction, limited time closure and no over excavation”.
During grouting, the conduit shall be pulled out slowly and evenly, and the slurry outlet shall always be buried under the slurry surface in the hole to ensure that all the gas in the hole can be discharged.
The soil nailing reinforcement shall be HRB400 and HRB500 reinforcement.
Soil nailing wall is a commonly used support method in foundation pit engineering.
(3) After excavation, the placement of soil nails and shotcrete surface shall be completed within 24h, and the placement of soil nails and shotcrete surface shall be completed within 12h for muddy soil.
The slurry mix proportion and grouting pressure shall be controlled according to the design requirements.
The spraying sequence of primary spraying bottom concrete shall be from top to bottom.
The first grouting should be cement mortar, and the grouting amount should not be less than 1.2 times of the drilling volume.
The thickness of the protective layer shall not be less than 20mm, the overlapping length shall not be less than 30d, and the length of single-sided welding shall not be less than 10d.
The concrete shall be cured by spraying water within 2h after final setting to keep the concrete surface moist.
The conduit shall be inserted to 250 ~ 500mm from the hole bottom, and the grout stop plug shall be set at the hole opening.
Construction process flow 1: the earthwork for trimming the slope surface shall be excavated in layers and sections, the excavation depth of each layer shall be consistent with the vertical spacing of soil nails, and the excavation elevation shall be 200mm below the position of soil nails.
The thickness of one-time spraying should not be less than 40mm.
pressure grouting shall be adopted for grouting.
When the soil nail is drilled, it shall be drilled slowly according to the hole position.
The reinforcement mesh shall be 6 ~ 10mm in diameter with a spacing of 150 ~ 250mm.
The horizontal spacing and vertical spacing of soil nailing shall be 1 ~ 2m.
place the soil nail reinforcement.
After filling, the pressure shall be maintained for 1 ~ 2min.
After each layer of soil is excavated, it shall be trimmed to remove the protruding soil and compact the loose soil on the surface, so as to ensure the flatness of the shotcrete surface.
The structure of the support shall not hinder the free flow of slurry during grouting.
I.
The drilling shall not disturb the surrounding strata, and high-pressure air or water shall be used for hole cleaning after drilling.
Key points of construction technology soil nailing wall can be divided into single soil nailing wall, prestressed anchor composite soil nailing wall, cement soil pile composite soil nailing wall, micro pile composite soil nailing wall and so on.
Accelerator should be added to the sprayed concrete to improve the setting speed of concrete and prevent concrete collapse.
After the final setting of the previous layer of concrete, the next layer of concrete can be sprayed.
The grouting material with diameter of 16 ~ 32mm can be cement slurry or cement mortar, and the strength shall not be less than 20MPa.
Structural requirements: the slope ratio of soil nailing wall shall not be greater than 1:0.2.
II.
The stiffener shall be micro pile composite soil nailing wall with a diameter of 14 ~ 20mm.
The main reinforcement shall be cut according to the design length plus 20cm.
Install drain holes and insert horizontal (slightly downward) drain pipes with a length of 400 ~ 600mm and a diameter of no less than 40mm at the back of the support surface layer.
When the thickness of the surface layer exceeds 100mm, the concrete shall be sprayed in layers, and the thickness of the first layer shall not be less than 40mm.
before the positioning drilling and hole cleaning of soil nails, the hole position shall be determined and marked and numbered according to the design requirements.
The overlapping width shall not be less than twice the thickness, and the joints shall be staggered.
binding the reinforcement mesh.
The length of the cement soil composite soil nailing wall pile extending into the pit bottom shall be greater than 2 times the pile diameter and greater than or equal to 1m; The 28d unconfined compressive strength of the pile body should not be less than 1MPa.
The outer end extends out of the support surface layer, and the spacing of drain pipes can be 1.5 ~ 2m, so as to discharge the accumulated water in the soil layer after the shotcrete surface layer.
VII.
The second grouting can be carried out after the initial setting of the first grouting; For the second time, pure water slurry is injected, and the grouting amount is 30% – 40% of the first grouting amount.
II.
V.
The thickness of concrete surface shall be 80 ~ 100mm, The design strength grade shall not be lower than C20.
Click the blue word attention above to send you a high-quality material for free.
When placing the main reinforcement, bind the grouting pipe with the main reinforcement, the grouting pipe is about 0.5m away from the hole bottom, and the end of the soil nail is connected with the reinforcement and reinforcement mesh in the surface layer through the reinforcement.
(2) After the construction of each layer of soil nails, spot check the pull-out resistance of soil nails as required.
The spraying direction should be vertical to the spraying surface.
It is a slope reinforcement support construction method that strengthens the foundation pit slope through soil nails made of steel bars, paves a steel mesh on the slope surface, and then sprays a layer of concrete surface layer and earth slope.
The outer end shall be provided with a 90 degree 20cm hook.
