Safety technology of the hottest manual hole diggi

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Safety technology for hole forming of manual hole digging pile

because the hole digging personnel are working underground, there is little room for movement, the working environment is poor, and the maximum depth can reach 50m, the situation is complex, so personal injury and death accidents occur from time to time

1. Accident type

(1) hole wall collapse: when the underground water level is high, the foundation soil is sandy soil layers such as silt and silty fine sand with large permeability coefficient or deep saturated muddy clay, there is no retaining wall or retaining wall, but it does not have effective stiffness and strength, and cannot bear the lateral pressure of water and soil, and no precipitation measures are taken, water seepage, quicksand and mud inflow are very easy to occur, resulting in hole wall collapse. (2) Falling objects at the orifice: there are deposits near the pile hole that are not cleaned in time, and objects fall into the hole under human or rain washing, resulting in casualties. (3) Suffocation and poisoning: when the pile is deep, a large amount of harmful and combustible gases may accumulate in the hole; If the pile position was originally the burial place of harmful substances and was not treated, it will cause injury to personnel. (4) Electric shock casualties: the construction surface in the pile hole is narrow and wet, and the safety voltage and safety lamp lower than 36V are not used. (5) In the falling hole: there is no cover plate, guardrail and other protective measures or obvious signs at the orifice, and there is insufficient lighting at night, so people are easy to fall into the hole. (6) The construction personnel use hemp rope and nylon rope to hang or pedal the hole wall up and down; The electric hoist (winch) has no automatic clamping safety device to avoid product appearance problems; (2) Material selection: senior material engineers can develop colors and materials according to customer requirements; (3) Mold design: professional mold engineers provide gate structure, location and waterway layout design to ensure product appearance; (4) Process design: professional mold testing engineers provide professional mold adjustment services, and many fields are in the starting or chasing state, realizing the transformation from single enterprise to industrial cluster in the park, from manual process control to intelligent, and from production-oriented manufacturing to service-oriented manufacturing. (7) Pedestal collapse: pile 3. Indication accuracy: ± 1% after the completion of the enlarged head, concrete will not be poured for a long time, and the soil will lose stability

2. Countermeasures

2.1 precautions for foundation investigation: (1) strength, thickness and permeability of geological layers; Adverse effects such as groundwater type, water level change, supplementary source and erosion; (2) Whether there are buried objects (cables, gas pipelines, sewers, etc.) and obstacles (original structure foundation, waste steel, etc.) underground; (3) Whether there are harmful landslides, fault damage zones, debris flows, collapses, and strongly developed karst, soil caves and other adverse geological phenomena; (4) Whether there is anoxia, harmful gases, etc., the types of harmful gases and their causes; (5) The height, structural form, foundation form, buried depth and other data of adjacent buildings

2.2 design considerations (1) selection of hole forming process: manual hole digging pile is more suitable for cohesive soil, fill, seasonal expansive soil, self weight and non self weight collapsible loess above the groundwater level, with hard interlayer, soft and weathered rock layer in the middle, and can be used for silt and muddy soil, silt, sand interlayer and gravel layer in the middle. When the underground water level is high, especially in the sandy soil layer with confined water, stagnant water layer, high-pressure compressible silt layer with large thickness and fluid plastic muddy soil layer, reliable technical and safety measures must be taken, such as using high-pressure jet grouting method, deep mixing method, rotary jet grouting pile, etc. to form a water cut-off curtain. (2) The minimum center distance of manually dug piles must be greater than 3D  D is the diameter; The diameter of the expanded bottom of the Manually Excavated Pile should not be greater than 3D  the slope is 1/381/2, and the minimum center distance of the expanded bottom end must be greater than 1.5D or D + 1.0m  D is the design diameter of the expanded end, so as to prevent the soil wall between adjacent piles from collapsing due to inability to stand upright. (3) The hole diameter (excluding the retaining wall) of the manually dug pile shall not be less than 800mm, and the pile length shall not be greater than 40m  to prevent the construction operation from being impossible. (4) The retaining wall is usually concrete retaining wall, and the thickness should not be less than 100mm. The concrete strength grade should not be lower than the pile strength. 8 φ 688 straight steel bars are tied between the upper and lower retaining walls with steel bars. When the hole is not too deep and the soil is dense, brick wall protection can be used, but when the soil layer is loose or quicksand layer, steel casing or reinforced concrete caisson should be used. (5) When the groundwater is rich and shallow, the well point precipitation should be considered. At this time, the impact on the environment should be analyzed to avoid the ground subsidence caused by groundwater overexploitation, which endangers the safety of surrounding buildings

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