| Nowadays retaining and protecting of pile-anchor with dewatering is widely usedin the building foundation pit engineering. But it has problems such as waste ofresources, environmental pollution or destruction and affecting subsequent undergroundengineering construction, etc. In order to solve these problems, a green constructiontechnology of pile-anchor supporting for building foundation pit engineering wasdeveloped through investigation, theoretical analysis, laboratory experiments andengineering tests. In the green construction technology, long auger boringpress-grouting cement-soil slurry forms antiseepage pile wall, foundation pit has nodewatering, and the cement-soil slurry is made of soils from construction site andcement on the ground. Recyclable H-shaped steel is inserted into the pile wall to retainand protect foundation pit with recyclable anchor ropes together, and the H-shapedsteels and steel cables of anchor rope are recycled after the foundation pit completes.Through experiments, the optimizing formula of cement-soil slurry was obtained, asfollows: cement300+soil2000+gravel600+water (which is controlled by the slump),cement mixing ratio15%. Compressive strength of slurry stone was greater than orequal to0.8MPa, and the permeation coefficient was less than or equal to1×10-6cm/safter28days. The thickness of the lap joint between piles was more than100mm to200mm according to the different foundation pit depth. Theoretically, factors thatinfluences the pull-out force of shaped steel are bond force between shaped steel andcement-soil, static frictional force, drag from deformation and weight of shaped steeletc., And effect of inserting technology of the shaped steel, bond force and the staticfrictional force is strongest. The results of modeling and engineering tests show thatdecreasing the bond force and the static frictional force helps recycling shaped steels. Itcan be achieved either by inserting the shaped steels after initial setting time of pileslurry, or by inserting after initial setting time, then pulling out and inserting again.Theoretical analysis and engineering tests show that the bearing stand structure is thekey of the recyclable anchor ropes. Unbonded steel cables must be used. In theengineering test with U-shape structure anchor ropes the steel cables has been recycledsmoothly. It is proved that although recycling pulling force is relatively large, theU-shaped structure anchor ropes have advantages of simple structure, low cost, easy toimplement. The green construction technology of pile-anchor supporting was used forthe design of practical foundation pit. Deformation and settlement of the foundation pitin three typical working conditions in excavation process are simulated and analyzedwith FlAC3D software. It was proved that the design was safe and reliable. Overall thegreen construction technology of pile-anchor supporting can avoid destruction due to dewatering to buildings and structures around the foundation pit. It prevents waste of alot of steel materials used in reinforced concrete pile and anchor, and helps to conserveresources, reducing costs and protecting the environment. |
