Excavation construction method for ultra-deep foundation

Abstract

The invention provides an ultra-deep foundation excavation construction method, which relates to the technical field of building construction, and comprises the following steps: step 1, leveling a site, and arranging a drainage ditch; step 2, surveying and setting out; thirdly, a rainproof shed is built in the foundation pit, and a well ring is built; fourthly, lifting equipment is installed; 5, excavation of a foundation pit; 6, construction of a retaining wall; seventhly, coring is conducted through a water mill drill, air pick crushing is matched with excavation, and segmentation is conducted; 8, hole cleaning and foundation pit inspection are conducted; ninthly, the reinforcement cage is hoisted and fixed; and tenthly, concrete is poured. The problem that potential safety hazards exist when manual digging is adopted is solved.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a method for excavating and constructing ultra-deep foundations. Background Technology

[0002] According to design specifications, when there is a height difference between the bottom elevations of two adjacent foundations, the angle between the line connecting the bottoms of the two foundations and the horizontal plane is called the rigid angle. The design specifications require that the rigid angle not exceed 45 degrees. When the site conditions do not meet the requirements, the depth of the foundation needs to be adjusted to meet the rigid angle requirements.

[0003] When there are steps in the excavation of the foundation pit, there are a few isolated foundations on the outer slope or walkway of the foundation pit. In cases where the rigidity angle is not met, the foundation needs to be over-excavated to a depth of 2 to 7 meters. When the construction site for these isolated foundations is narrow, it is not suitable to use mechanical operations. Therefore, manual excavation of the foundation is carried out using water-cooled drills. For deep foundations with a height of more than 5 meters, due to geological uncertainties, such as when the soil is not hard enough or there is groundwater, once excavation begins, the original soil balance will be broken, the inner wall soil will become unstable and slip, and it is easy to collapse, which cannot guarantee the safety of personnel in the pit and poses a safety hazard. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for excavating ultra-deep foundations, which solves the safety hazards associated with manual excavation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for excavating ultra-deep foundations includes the following steps:

[0007] Step 1: Level the site and set up drainage ditches;

[0008] Step 2: Measure and lay out the lines;

[0009] Step 3: Erect a rain shelter and build the well ring;

[0010] Step 4: Install the lifting equipment;

[0011] Step 5: Excavation of the foundation pit;

[0012] Step Six: Wall Protection Construction;

[0013] Step 7: Core extraction with water-jet drilling and excavation with pneumatic hammer breaking, carried out in sections;

[0014] Step 8: Hole cleaning and foundation pit inspection;

[0015] Step Nine: Hoisting and securing the steel reinforcement cage;

[0016] Step 10: Pour concrete.

[0017] Preferably, in step three, each foundation pit frame is equipped with 4 upright poles and 4 diagonal poles, with a pole spacing of 1.2m and a total height of 2.0m for the rain shelter. Safety nets are installed around the frame, extending 1.5m from the ground upwards, and the top is covered with felt.

[0018] Preferably, in step three, the well ring is at least 30cm above the ground.

[0019] Preferably, in step five, the excavation is carried out layer by layer from top to bottom, and the excavation sequence is to excavate the middle first and then the perimeter, and the cross-section size is controlled by adding 30cm to the designed foundation pit cross-section.

[0020] Preferably, in step six, wooden formwork is used for construction. The thickness of the wooden formwork panel shall not be less than 9mm. When pouring concrete, the upper section is removed and the lower section is supported, and the formwork is reused from top to bottom.

[0021] Preferably, the top layer of the retaining wall is made of 20mm diameter round steel with 2 to 4 lifting lugs, and fixed to the ground wooden stakes with steel wire ropes.

[0022] Preferably, step seven mainly includes the following construction sequence: drilling the rock around the ultra-deep foundation; drilling the rock in the middle; drilling holes with a pneumatic pick; inserting steel wedges and striking the steel wedges to split the rock; manually loading slag and using an electric lifting frame to remove slag; correcting the foundation pit and proceeding to the next cycle of construction.

[0023] Preferably, when drilling the rock around the ultra-deep foundation, core sampling points are arranged along the wall of the pile hole, with the center of the core sampling point located on the designed inner diameter baseline. The core sampling diameter is 170mm. Core samples are then drilled downwards at an outward inclination angle of 15°. The extracted core samples are 600mm high. After the outer core samples are extracted, the middle rock mass forms a free surface.

[0024] Preferably, when drilling the intermediate rock, the rock core is drilled along the pile radius, and the pile core rock body is divided into three equal parts, each part accounting for 1 / 3 of the pile core rock body.

[0025] Preferably, when drilling with a pneumatic pick, a hole is drilled in the rock mass, and then the pile rock is divided into six equal parts.

[0026] The present invention has the following beneficial effects:

[0027] Before excavation, the site is leveled and drainage ditches are set up to prevent safety hazards caused by soil conditions and water accumulation, so as to facilitate subsequent excavation. At the same time, rain shelters are erected and well rings are built to block water and prevent rainwater from flowing into the foundation pit on rainy days. After excavation, retaining wall construction is carried out to maintain the stability of the pit wall, prevent collapse, isolate groundwater, control seepage, and provide a safe space and working surface for subsequent construction, so as to jointly ensure the safety of subsequent manual drilling.

[0028] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the construction process of the present invention. Detailed Implementation

[0030] To make the technical means, creative features, objectives and effects of the present invention clearer and easier to understand, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] Please see Figure 1 As shown, a method for excavating ultra-deep foundations includes the following steps:

[0032] Step 1: Level the site and set up drainage ditches;

[0033] Step 2: Measure and lay out the lines;

[0034] Step 3: Erect a rain shelter and build the well ring;

[0035] Step 4: Install the lifting equipment;

[0036] Step 5: Excavation of the foundation pit;

[0037] Step Six: Wall Protection Construction;

[0038] Step 7: Core extraction with water-jet drilling and excavation with pneumatic hammer breaking, carried out in sections;

[0039] Step 8: Hole cleaning and foundation pit inspection;

[0040] Step Nine: Hoisting and securing the steel reinforcement cage;

[0041] Step 10: Pour concrete.

[0042] Before excavation, the site is leveled and drainage ditches are set up to prevent safety hazards caused by soil conditions and water accumulation, facilitating subsequent excavation. At the same time, rain shelters are erected and well rings are built to block water and prevent rainwater from flowing into the foundation pit on rainy days. After excavation, retaining wall construction is carried out to maintain the stability of the pit wall, prevent collapse, isolate groundwater, control seepage, and provide a safe space and working surface for subsequent construction, jointly ensuring the safety of subsequent manual drilling. Then, excavation is carried out in sections, the holes are cleaned, the foundation pit is inspected, and finally, the steel cage is placed and concrete is poured.

[0043] Specifically, in step one above, site leveling requires removing loose rocks and soil from the slope. Slopes with cracks or signs of collapse should be reinforced with necessary protection. Loose soil layers should be removed and compacted before constructing the construction platform. During filling, ensure the distance between the pile edge and the platform edge is at least 1.5m. This distance can be reduced appropriately if filling is difficult, but should not be less than 1.0m. A balance between excavation and filling should be achieved as much as possible, avoiding unnecessary borrowing or disposal. Site leveling prevents accidents such as rockfalls, landslides, and collapses during subsequent construction, ensuring the safety of construction personnel and equipment. Removing and compacting loose soil layers provides a solid and stable working surface. It provides a platform for equipment placement and operation, creating necessary working space for construction. It ensures the quality of pile foundation construction. A level site facilitates the passage of construction vehicles and the movement of equipment, avoiding delays caused by site issues, greatly improving work efficiency. Furthermore, achieving a balance between excavation and filling reduces the transportation costs of waste soil and the cost of purchasing fill soil, lowering project costs and being more environmentally friendly. In addition, when there is a large amount of water flowing into the slope, a 30cm x 30cm drainage ditch can be set up at the toe of the slope to divert the drainage to the original drainage network.

[0044] In step two, the allowable elevation benchmark is determined, and the center of the pile position is identified. Using the midpoint as the center, a circle is drawn with the pile radius plus the retaining wall thickness as the radius. Lime lines are then used as the excavation dimensions for the foundation pit. After verification, the construction team installs four cross-shaped retaining piles around the pile foundation. These piles must be reinforced and protected with mortar or concrete to facilitate pile position inspection during excavation.

[0045] In step three, the rain shelter is constructed using steel pipes. Each foundation pit is supported by four uprights and four diagonal supports, with a spacing of 1.2m between the uprights. The total height of the rain shelter is 2.0m. Safety netting is installed around the scaffolding, extending 1.5m upwards from the ground. The top is covered with tarpaulin for rain protection, and safety warning signs must be placed on the rain shelter. The purpose of the rain shelter is to prevent rainwater from flowing into the foundation pit during rainy weather.

[0046] In step three, the well ring should be at least 30cm above the ground to facilitate water blocking and positioning. The center line of the well ring should coincide with the axis of the foundation pit, and its deviation from the axis should not exceed 50mm.

[0047] In step four, a standard material hoisting frame is used for the lifting equipment. Before erecting the foundation pit scaffold, the foundation where the scaffold is located must be treated and compacted using small machinery. If the ground soil is poor, it can be replaced or the foundation area can be hardened with concrete to prevent the scaffold from collapsing due to foundation issues. The capacity of the bucket should not exceed 200 kg at a time, and should not exceed 2 / 3 of the slag bucket's height. The lifting safety factor should be greater than 3. The hooks and bucket gates must be both secure and safe. The winch should be approximately 60-80 cm above the wellhead.

[0048] In step five, the foundation pit excavation is carried out layer by layer from top to bottom using picks and shovels. Within the upper 2m range, hard soil or ordinary low-strength rock layers are broken using hammers, chisels, and pneumatic picks. The excavation sequence is to excavate the center first, then the perimeter, controlling the cross-sectional size by adding 30cm to the designed pit cross-section. The excavated soil and rocks are loaded into buckets and transported vertically to the ground using lifting equipment, where they are piled at a designated location to prevent environmental pollution. Note that during the excavation process, the hole walls do not need to be smoothed; they should be slightly uneven to increase the friction of the pile.

[0049] In step six, the construction of the retaining wall concrete involves using wooden formwork. Cross lines are marked on the well ring, the first foundation pit is excavated, the first section of retaining wall formwork is constructed, and the retaining wall concrete is poured. The thickness of the wooden formwork panels must not be less than 9mm. When pouring concrete, the upper section is removed and the lower section is supported, allowing for reuse from top to bottom. The formwork is interlocked, with two sets of 6-8 gauge steel rings tightened at the top and bottom. Each steel ring consists of two semicircles connected by bolts, without additional supports, to facilitate concrete pouring and excavation of the next section. The top layer of the retaining wall uses 20mm diameter round steel with 2-4 lifting lugs, fixed to wooden piles on the ground with wire ropes. Retaining wall construction is carried out after excavation to prevent collapse, eliminate safety accidents, control soil erosion, minimize impact on the surrounding area, and create a stable, dry, and safe construction environment for subsequent operations.

[0050] Step seven mainly includes the following construction sequence: drilling the rock around the ultra-deep foundation; drilling the rock in the middle; drilling holes with a pneumatic drill; inserting steel wedges and striking them to split the rock; manually loading slag and using an electric hoist to remove slag; correcting the foundation pit and proceeding to the next cycle of construction. Specifically:

[0051] When drilling the rock around the ultra-deep foundation, core sampling points are arranged along the wall of the pile hole. The center of the core sampling point is located on the design inner diameter baseline. The core sampling diameter is 170mm. Core samples are drilled downwards at an outward inclination angle of 15°. The core samples are 600mm high. After the core samples are taken from the outer perimeter, the middle rock mass forms a free surface.

[0052] When drilling the middle rock, drill the rock core along the pile radius and divide the pile core rock body into three equal parts, each part accounting for 1 / 3 of the pile core rock body;

[0053] When drilling with a pneumatic pick, a hole is drilled in the rock mass, and then the rock for the pile is divided into six equal parts;

[0054] Insert steel wedges and strike the steel wedges to split the rock. Drive steel wedges into the pit drilled by the pneumatic pick along the radial direction of the pile foundation. Use a sledgehammer to strike the steel wedges to give the rock mass a horizontal impact force. Under the action of the horizontal impact force, the rock is pulled and cracked along the vertical surface. Horizontal shear fracture will occur at the bottom. The rock mass is split in sequence until the entire rock mass of that layer is fractured.

[0055] Manual loading of slag and electric lifting frame for slag removal. After one single cycle of construction, the rock core drilled by the water-powered drill is removed in sequence. Slag removal is carried out from one side of the foundation pit. Then, steel wedges are inserted and struck to split the rock before another slag removal is performed.

[0056] Finally, because the pile hole wall becomes serrated after core drilling with a water-jet drill, the rock serrations that encroach on the pile foundation space must be knocked off to ensure the effective pile diameter. The design pile center is marked in the foundation pit using a well ring to protect the pile, the deviation of the pile bottom is checked and corrected in time, and the position for core drilling on the outer perimeter of the next cycle is marked, thus entering the next cycle of ultra-deep foundation excavation.

[0057] In step eight, before the hole is closed, an inspection should be conducted to clean up any loose stones and mud at the bottom of the hole, level the bottom of the hole, and then inspect the foundation pit.

[0058] The reinforcing cage is used to bear loads, provide structural strength, and enhance overall integrity and stability. After hoisting and securing the reinforcing cage, concrete is poured. When the concrete surface rises to the bottom of the reinforcing cage, the following measures can be taken to prevent the cage from being pushed up by the concrete: Minimize the total concrete pouring time to prevent the concrete from having insufficient fluidity when the top layer of concrete enters the reinforcing cage; when the concrete surface approaches and initially enters the reinforcing cage, the bottom of the tremie pipe should be positioned 3m below and 1m above the bottom of the reinforcing cage, and the concrete should be poured slowly to reduce the impact on the cage. The upward impact force after the concrete exits the bottom of the guide pipe; when the concrete in the pit has penetrated 2m to 3m into the reinforcing cage, the guide pipe should be raised appropriately to reduce its embedment length, thereby increasing the embedment depth of the cage below the guide pipe opening and thus increasing the bond force of the concrete to the reinforcing cage; a steel pipe should be inserted into the main reinforcement at the top of the reinforcing cage, and sleepers and soil bags should be placed on the steel pipe. 15 to 30 soil bags should be kept in the foundation pit; the first, second, and third truckloads of concrete should not remain on site for more than 30 minutes to prevent excessive slump loss; the position of the guide pipe should be carefully controlled to prevent it from catching on the reinforcing cage.

[0059] When the reinforcing cage floats, pouring should be stopped immediately. A steel pipe should be fitted over the main reinforcement bars at the cage opening to hold the cage in place. The steel pipe should be secured in the foundation pit with sleepers and sandbags. The depth of the guide pipe should be measured. If the depth is too great, remove one section of the guide pipe and continue pouring concrete slowly. If it is not enough, remove one section and slow down the concrete pouring speed until the reinforcing cage reaches a depth of 6m or more and stops floating before resuming the normal pouring speed.

[0060] In addition, foundation pits with a depth exceeding 5m need to be equipped with ventilation devices. Ventilation should be provided 5 minutes before each start of work, with a ventilation time of no less than 5 minutes. The diameter of the ventilation pipe should be no less than 10cm, and the air volume should be no less than 25L / S. The distance between the outlet of the ventilation pipe and the operator should be no more than 2m. The presence of toxic gases and oxygen deficiency should be checked in advance. If toxic or harmful gases are detected, the gas must be purged before wearing a gas mask before entering the well for work. During the construction process, an air quality detector should be used to monitor the air quality at all times.

[0061] If significant seepage occurs in the pit, a deeper sump can be dug within the foundation pit, and a submersible pump can be installed in each pit to drain the water out of the foundation pit. The drained groundwater should be discharged at a distance from the foundation pit to avoid creating new seepage sources. If the inflow is very large, one pile can be excavated ahead of schedule to lower the groundwater level in the nearby foundation pit. In addition to digging intercepting ditches around the surface pile locations, to prevent muddy water seeping from the pit from polluting the environment, the water from the drainage hole should first be drained into an excavated sedimentation tank for sedimentation and filtration before being discharged into the existing drainage ditch on the nearby site. If a confined aquifer with a large inflow is encountered during excavation, the aquifer can be sealed by grouting a ring of gravel with cement mortar. To facilitate drainage within the well, drainage holes (with the same diameter as the water pipe's outer diameter) should be pre-reserved in the retaining wall of the permeable layer section to facilitate pipe connection and drainage, and these holes should be plugged before pouring concrete.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for excavating and constructing ultra-deep foundations, characterized in that, Includes the following steps: Step 1: Level the site and set up drainage ditches; Step 2: Measure and lay out the lines; Step 3: Erect a rain shelter and build the well ring; Step 4: Install the lifting equipment; Step 5: Excavation of the foundation pit; Step Six: Wall Protection Construction; Step 7: Core extraction with water-jet drilling and excavation with pneumatic hammer breaking, carried out in sections; Step 8: Hole cleaning and foundation pit inspection; Step Nine: Hoisting and securing the steel reinforcement cage; Step 10: Pour concrete.

2. The ultra-deep foundation excavation construction method as described in claim 1, characterized in that, In step three, each foundation pit frame is equipped with 4 upright poles and 4 diagonal poles, with a pole spacing of 1.2m. The total height of the rain shelter is 2.0m. Safety nets are installed around the frame, extending 1.5m from the ground upwards, and the top is covered with felt.

3. The ultra-deep foundation excavation construction method as described in claim 1, characterized in that, In step three, the well ring should be at least 30cm above the ground.

4. The ultra-deep foundation excavation construction method as described in claim 1, characterized in that, In step five, the excavation is carried out layer by layer from top to bottom. The excavation sequence is to excavate the middle first and then the perimeter. The cross-sectional size is controlled by adding 30cm to the designed foundation pit cross-section.

5. The ultra-deep foundation excavation construction method as described in claim 1, characterized in that, In step six, wooden formwork is used for construction. The thickness of the wooden formwork panels shall not be less than 9mm. When pouring concrete, the upper section is removed and the lower section is supported, and the formwork is reused from top to bottom.

6. The ultra-deep foundation excavation construction method as described in claim 5, characterized in that, The top layer of the retaining wall is made of 20mm diameter round steel with 2 to 4 lifting lugs, which are fixed to the ground wooden piles with steel wire ropes.

7. The ultra-deep foundation excavation construction method as described in claim 1, characterized in that, Step seven mainly includes the following construction sequence: drilling the rock around the ultra-deep foundation; drilling the rock in the middle; drilling holes with a pneumatic pick; inserting steel wedges and striking the steel wedges to split the rock; manually loading slag and using an electric lifting frame to remove slag; correcting the foundation pit and proceeding to the next cycle of construction.

8. The ultra-deep foundation excavation construction method as described in claim 7, characterized in that, When drilling the rock around the ultra-deep foundation, core sampling points are arranged along the wall of the pile hole. The center of the core sampling point is located on the design inner diameter baseline, and the core sampling diameter is 170mm. Core samples are drilled downwards at an outward inclination angle of 15°. The core samples taken are 600mm high. After the core samples are taken from the outer perimeter, the middle rock mass forms a free surface.

9. The ultra-deep foundation excavation construction method as described in claim 7, characterized in that, When drilling the middle rock, drill the rock core along the pile radius and divide the pile core rock body into three equal parts, each part accounting for 1 / 3 of the pile core rock body.

10. The ultra-deep foundation excavation construction method as described in claim 7, characterized in that, When drilling with a pneumatic pick, a hole is drilled in the rock mass, and then the rock for the pile is divided into six equal parts.

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