It is necessary to pay attention to the strength of the joint surface of the old and new foundation.
Executive standard of architectural communication media ID: jianzhong001: Code for design of foundation reinforcement of existing buildings jgj123-2016 design steps: 1.
For compaction grouting, when cement mortar slurry is used, the slump should be 25-75mm and the pressure should be 1-7mpa; If the slump is small, take the upper limit value.
Steel can be used, and the reinforced concrete pile should be square with side length of 200 ~ 300mm; The pile length of each section should be 1.0 ~ 2.5m2.
for the original rigid foundation, it is necessary to consider whether the rigid angle still meets the requirements, otherwise it should be widened and raised.
Reinforcement effect of lime pile method: 1.
Its consolidated body is generally distributed like a sphere or block in the soil.
Under the action of high pressure, the slurry will produce splitting flow along the structural plane of the formation, forming veins and network distribution in the formation.
Pore forming compaction – in miscellaneous fill, there are more coarse particles and good compaction effect; In cohesive soil, the one with small permeability coefficient has poor compaction effect.
The distance between grouting holes is 1.0-2.0m, and the pressure of splitting grouting should be 0.2-0.5mpa in sandy soil; Clay, preferably 0.2-0.3mpa.
4 heating and dehydration – 1kg calcium oxide generates 280 calories, and the pile body temperature is 200 ~ 300 ℃.
infiltration grouting: the slurry expels the free water and gas in the soil and cements the surrounding soil by filling cracks or voids to form a dense solidified body, so as to improve the compressive strength and impermeability of the soil layer.
Increasing the foundation bottom area method A.
Grouting reinforcement method A.
The tree root pile method A.
Select the reinforcement scheme, combine the current situation of the structure and consider the joint action of the three, and preliminarily select the scheme of strengthening the foundation, strengthening the foundation or strengthening the stiffness of the superstructure and strengthening the foundation.
It can be used to chisel, treat the interface, brush the interface agent or increase the mechanical connection strength.
According to the expected effect, construction difficulty Material source and transportation conditions, construction safety, impact on adjacent buildings and environment, equipment conditions, construction period and cost, and select the best scheme.
Irregular veins, network consolidation and soil compacted due to slurry pressure form a composite stratum, which has a certain bearing capacity and water stop capacity.
Lime pile method A.
It is composed of quicklime and fly ash (pozzolanic ash or other admixtures).
When the bearing capacity of the original bearing platform is insufficient, it shall be reinforced.
2 water absorption – 1kg pure calcium oxide absorbs 0.32kg water, and lime pile absorbs 65% – 70%.
It is suitable for foundation reinforcement when the bearing capacity of existing building foundation or the size of foundation area does not meet the design requirements.
Brief description of various methods of foundation reinforcement 1.
Anchor static pressure pile method a, applicable to sludge, mucky soil, cohesive soil Reinforcement of foundation soil such as silt and artificial fill B.
Compaction grouting: the slurry with certain consistency or quick setting type is used to produce the compaction effect on the soil through pressure, so as to improve the physical and mechanical properties of the soil.
Splitting grouting: the slurry is injected into the stratum with small porosity under high pressure.
It is divided into infiltration grouting, splitting grouting and compaction grouting C.
It is applicable to the repair and layer addition of existing buildings on foundation soil such as silt, mucky soil, cohesive soil, silt, sand, gravel soil and artificial fill, the repair of ancient buildings, the crossing of subway, etc.
In the design, it can be widened asymmetrically according to the repair requirements.
The original rubble rigid foundation shall be widened with reinforced concrete.
It is applicable to the foundation reinforcement of sandy soil, silt, cohesive soil and artificial fill B.
Infiltration grouting will not cause large changes in soil volume.
When the local layer is cohesive soil layer with large buried depth and small permeability coefficient (less than 10-5cm / s), split grouting should be adopted.
The increase range is related to the pile strength and displacement rate.
Under the pressure of 50-100kpa, the expansion amount is 20% ~ 30%.
6 displacement – the soft soil is replaced by lime piles with high strength, which increases the bearing capacity of the composite foundation.
The common ratio is 1:1, 1:1.5 or 1:2 to improve the strength of the pile body.
anchor static pressure pile is to statically press prefabricated pile or steel pipe into the soil by using the pull-out resistance of anchor bolt, and improve the bearing capacity of the original foundation through the pile bearing capacity.
The calcium oxide content of quickstone ash shall not be less than 70%, the powder content shall not exceed 10%, and the water content shall not be more than 5%, The maximum block diameter shall not be greater than 50mm.
5 ion exchange – sodium ions in soft soil are exchanged with calcium ions in lime, which improves the properties of soil between piles and forms a hard layer with high strength on the surface of pile body.
It is applicable to the treatment of cohesive soil, silt, loose silty fine sand, silt, mucky soil, miscellaneous fill or saturated loess below the groundwater level and the reinforcement of soil around the foundation B.
Cantilever beam or bearing platform as pressure pile can also be set.
Cement, sand and stone chips can also be added.
3 expansion and compaction – water absorption and expansion.
When the local stratum is quaternary stratum such as sand layer, pebble layer and gravelly soil (the permeability coefficient is greater than 10-4cm / s), the infiltration grouting method should be adopted.
The layout can adopt straight pile type or network structure inclined pile type 3 Pit static pressure pile method A.
The original flexible foundation is upgraded to rigid foundation..
Reinforcement method: foundation reinforcement: anchor static pressure pile method, root pile method, pit static pressure pile method, lime pile method, grouting reinforcement method, foundation reinforcement: foundation grouting reinforcement method (crack repair), increasing foundation bottom area method, deepening foundation method, foundation deviation correction and unloading method, brief description of various methods of foundation reinforcement 1.
the straight diameter of tree root pile should be 150 ~ 300mm, and the pile length should not exceed 30m.
open steel pipe with pile body diameter of 150 ~ 300mm or reinforced concrete square pile with side length of 150 ~ 250mm.
It is applicable to foundation soil such as silt, mucky soil, cohesive soil, silt and artificial fill, and the groundwater level is low.