Construction method of integrated basement ramp combining permanent and temporary structures

Abstract

This invention relates to a construction method for a combined permanent and temporary basement ramp. Before excavation, the location of the permanent ramp on the first basement level is measured and marked on the ground according to the engineering design. Along the location line, cast-in-place piles, pipe piles, and row piles are driven every 2 meters on the outside of the permanent ramp to complete the positioning and support structure of the permanent ramp. During the excavation phase, earthwork is reserved according to the slope of the permanent ramp. Concrete is laid on the slope surface of the permanent ramp, anchor cables are installed on the sides, steel mesh is arranged, and fine aggregate concrete is sprayed. The lower temporary ramp connects to the permanent ramp. During the excavation of the second basement level, earthwork is reserved, and steel mesh is laid on the sides of the reserved temporary ramp earthwork, and fine aggregate concrete is sprayed. Graded crushed stone is laid on the slope surface and steel plates are fully laid. After the overall excavation of the foundation pit is completed, the temporary ramp is dismantled, and the permanent ramp is formally poured using the support structure of the permanent ramp constructed in the first step.

Description

Technical Field

[0001] This invention belongs to the field of deep foundation pit excavation construction, specifically a construction method for a permanent and temporary integrated basement ramp. Background Technology

[0002] With the increasing number of urban building complexes and the decreasing land resources, various types of buildings are beginning to expand underground, resulting in increasingly deeper foundation pits. Deep foundation pit construction requires a large number of heavy machinery vehicles for earthmoving operations, necessitating the construction of ramps for transporting soil and facilitating the movement of heavy machinery. Currently, the main methods for removing soil from deep foundation pits include natural slope excavation and the construction of specialized steel or concrete trestle bridges. However, due to the considerable depth of deep foundation pits, internal supports are often installed to ensure the structural safety of the pit itself. Whether concrete or steel, the horizontal and vertical structural members of these internal supports vary widely in form and distribution, leading to high construction costs for deep foundation pit excavation ramps.

[0003] A Chinese invention patent, patent number CN201410176143.8, published on June 22, 2016, discloses a construction method for reverse-construction earthwork excavation. Specifically, it discloses "in the first stage, a temporary ramp is excavated to 2.5 meters below the beams and slabs of the first basement level, and the beams and slabs of the first basement level and the permanent driveway of the first basement level are constructed." This scheme completes the permanent driveway construction in one go, using the completed ramp as a slope for transporting excavated soil during the foundation pit excavation process. The permanent ramp is a regular building structure, and various large equipment are involved in the passage during the foundation pit construction. After the basement is completed, the permanent ramp is usually severely damaged, which not only increases construction investment but may also affect the construction quality. Summary of the Invention

[0004] The present invention aims to solve the above problems, thereby providing a construction method that saves construction costs and ensures the quality of completed building ramps.

[0005] The technical solution adopted by the present invention to solve the aforementioned problem is as follows:

[0006] A construction method for a combined permanent and temporary basement ramp is carried out according to the following steps:

[0007] Step 1: Based on the ramp design drawings and the route of the municipal roads outside the site, select the best transportation route and plan the location and slope of the permanent and temporary ramps in the foundation pit.

[0008] Step 2: The elevation of the top of the permanent ramp is the same as the elevation of the top of the foundation pit, and extends to the outside of the foundation pit to form an internal and external connection; according to the positioning of the permanent ramp on the first basement level in the engineering design, the ground is measured and the positioning line is drawn; along the positioning line, cast-in-place piles, pipe piles and pile rows are driven every 2 meters on the outside of the permanent ramp.

[0009] Step 3: Excavate the foundation pit using engineering vehicles; reserve earthwork for the permanent ramp according to its slope; excavate the permanent ramp to the bottom elevation of the first basement level, lay a 100mm thick graded crushed stone or 0.5m steel slag base course on the slope, and fully cover it with steel plates. Spend 5-7 days having vehicles roll back and forth to allow the slope soil to fully settle and compact, then remove the steel plates and pour a 0.6m concrete pavement; use foundation pit guardrails on both sides of the ramp to separate people and machinery; clear and transport the earthwork from the first basement level using engineering vehicles; anchor cables are installed on the sides of the reserved permanent ramp earthwork, but the anchor cables cannot be placed entirely outside the ramp, so the anchor cables are interrupted to leave the sides exposed;

[0010] Step 4: Lay steel mesh on the side of the permanent slope earthwork; fix it with U-shaped clips made of ∮6.5 steel bars, and spray 60mm to 100mm thick fine stone concrete on the surface of the steel mesh.

[0011] Step 5: Set up groundwater level monitoring wells on both sides of the upper opening of the permanent slope to observe the groundwater level. When the water level exceeds or approaches the height of the earthwork excavation foundation, set up vacuum lightweight wellpoint dewatering in the foundation trench.

[0012] Step 6: Based on the site structure of the foundation pit, determine the location and slope of the temporary ramp. The upper part of the temporary ramp should connect with the lower part of the permanent ramp on the first basement level. During the excavation of the second basement level, reserve earthwork. For every 2 meters of excavation depth in the second basement level, lay a portion of steel mesh on the side of the reserved temporary ramp earthwork. The end of the temporary ramp should extend to the bottom of the foundation pit, with the last 50 meters constructed as an arc-shaped ramp. After the temporary ramp reaches the bottom platform of the second basement level and all steel mesh is laid, spray a 60mm-100mm thick layer of fine aggregate concrete onto the steel mesh. Lay a 100mm thick layer of graded crushed stone on the surface of the temporary ramp, and fully cover it with steel plates. Lay a single piece of steel plate at the junction of the temporary ramp and the permanent ramp.

[0013] Step 7: After the overall construction of the foundation pit is completed, the temporary ramp is removed, including the concrete layer and steel mesh used for the temporary ramp support, as well as the reserved earthwork for the temporary ramp.

[0014] Step 8: Design the permanent ramp segments. First, remove the anchor cables, concrete layer, and steel mesh from the first basement level to the second basement level of the first segment. Clear the excavated soil from the second basement level slab to the top of the pit. Construct a concrete foundation for the permanent ramp on the second basement level. Then, control the elevation of this segment and tie the permanent ramp reinforcement with HRB400 steel bars according to the slope. Finally, pour C35 concrete to form the first segment, and simultaneously construct the hidden columns. Remove the anchor cables, concrete layer, and steel mesh from the second segment. Clear the excavated soil from the second basement level slab to the top of the pit. Similarly, complete the concrete pouring of the second permanent ramp segment, leaving a construction joint between the second and first segments. Construct the remaining segments of the permanent ramp in the same manner.

[0015] Compared with the prior art, the present invention, which adopts the above technical solution, has the following beneficial effects:

[0016] This invention positions and supports the permanent ramp during the foundation pit excavation phase to ensure its stability; facilitates the construction of the temporary ramp; and controls and pours the permanent ramp at its official elevation during the basement construction phase, thereby ensuring the construction quality of the permanent ramp upon completion.

[0017] As a preferred embodiment, a further technical solution of the present invention is:

[0018] Permanent and temporary ramps must lie on undisturbed undisturbed soil. If the undisturbed soil is disturbed, the disturbed soil must be excavated.

[0019] The temporary ramp is sloped in two stages: the first stage is a 45-degree slope and the second stage is a 60-degree slope, with the slope locally increased to form a small platform 0.6 meters from the top of the slope.

[0020] The monitoring of the ramp is incorporated into the overall foundation pit monitoring system. According to the ramp design drawings, monitoring points are set up and initial data is collected before construction. For the first three days after the ramp is put into use, its elevation and position are monitored three times a day, in the morning, noon and evening. From the third to the fourteenth day, it is monitored once a day. After two weeks, it is monitored once every three days until the temporary ramp is dismantled.

[0021] The temporary ramp was dismantled in sections. The engineering vehicles were parked on the upper side of the temporary ramp. First, the outer protective structure of the first section was dismantled, and then the soil in that section was excavated. Then the engineering vehicles moved to the next section, and the outer support of the second section was dismantled and the soil in the second section was excavated until the soil of the reserved temporary ramp was completely removed. Attached Figure Description

[0022] Figure 1 A schematic diagram of the ramp for the foundation pit designed for this invention;

[0023] Figure 2 This is a schematic diagram of the positioning line and pile driving for the permanent ramp of this invention;

[0024] Figure 3 The foundation pit of this invention is excavated to the bottom platform of the permanent ramp;

[0025] Figure 4 The foundation pit of this invention is excavated to the bottom platform of the temporary ramp;

[0026] Figure 5 This is a schematic diagram of the segmented demolition and pouring of permanent ramps.

[0027] In the diagram: 1. Positioning line; 2. Cast-in-place pile; 3. Pipe pile; 4. Permanent ramp; 5. Temporary ramp; 6. Steel mesh. Detailed Implementation

[0028] The present invention will be further described below with reference to embodiments, which are intended only to provide a better understanding of the invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0029] See Figures 1 to 5 The present invention provides a construction method for a permanent and temporary integrated basement ramp, which is constructed according to the following steps:

[0030] I. Design of Excavation Pit Ramp

[0031] Step 1: During the excavation of the foundation pit, the construction of the ramps within the pit should be planned simultaneously, and the division of the excavation work area should be fully integrated with the ramp design. Based on the ramp design drawings and the route of the municipal roads outside the site, the location and slope of the permanent ramp 4 and temporary ramp 5 within the foundation pit should be planned according to the optimal transportation route.

[0032] The construction sections are carried out in parallel, and the construction schedule of the ramps is determined in conjunction with the progress of the foundation pit excavation. Due to the long earthwork excavation operation, in order to improve the speed of earthwork transportation vehicles and separate personnel and vehicles, the earthwork transportation routes are planned and arranged on the construction site, and the location of each ramp is fully considered to ensure the safety of earthwork transportation.

[0033] II. Ramp Construction and Support

[0034] The construction of the foundation pit adopts the following methods: on-site dredging, support piles, capping beams, and earthwork excavation (in conjunction with anchor cables).

[0035] Step 2: The elevation of the top of the permanent ramp 4 is the same as the elevation of the top of the foundation pit, and extends to the outside of the foundation pit to form an internal and external connection; according to the positioning of the permanent ramp 4 on the first basement level in the engineering design, the ground is measured and the positioning line 1 is drawn; along the positioning line 1, cast-in-place piles 2, pipe piles 3, and rows of piles are driven every 2 meters on the outside of the permanent ramp 4. The top of the ramp is located at the top line of the foundation pit, the slope ratio is 1:6, and the width of the ramp is 7 meters.

[0036] Excavation of the foundation pit was carried out using engineering vehicles; earthwork was reserved for section 4 of the permanent ramp according to its slope; the permanent ramp 4 was excavated to the elevation of the first basement level, and a 100mm thick graded crushed stone or 0.5m steel slag base course was laid on the slope, followed by a full layer of steel plates. Vehicles were allowed to compact the soil for 5-7 days, after which the steel plates were removed and a 0.6m concrete pavement was poured; protective railings were installed on both sides of the ramp to separate personnel and machinery, meeting both construction transportation requirements and dust control requirements. The excavated earthwork from the first basement level was cleared and transported away using engineering vehicles; anchor cables were installed on the sides of the reserved permanent ramp 4 earthwork. Since the anchor cables could not be fully placed outside the ramp, they were interrupted to leave the sides exposed.

[0037] The ramp bottom slab must be placed on undisturbed original soil. If the original soil is disturbed, it must be excavated and backfilled with graded sand and gravel to the design elevation. The compaction coefficient of the graded sand and gravel shall not be less than 0.97.

[0038] When the side slope of the ramp is connected to the cast-in-place pile, in order to avoid lateral pressure caused by the difference in soil height on both sides of the pile, it is necessary to increase the slope locally on three sides around the pile to improve the stability of the ramp and prevent unsafe conditions caused by temporary heavy machinery transportation.

[0039] III. Slope Protection and Drainage

[0040] Step 4: Slope protection involves laying steel mesh 6 on the side of the permanent slope 4 earthwork and spraying 60mm-100mm thick C20 fine aggregate concrete. The steel mesh is fixed with U-shaped clips made of ∮6.5 steel bars, spaced 1.0m apart, in a quincunx pattern. Before spraying concrete, the steel mesh in the surface layer should be firmly fixed to the side wall and meet the specified protective layer thickness requirements, and should not vibrate under concrete spraying. The overlap length on each side of the steel mesh should not be less than 250mm. The strength grade of the sprayed concrete is C20, the maximum particle size of the coarse aggregate should not exceed 12mm, the mix proportion should be based on the mix proportion sheet issued by the laboratory, and the spraying thickness is 60mm. All spraying operators should hold a training certificate, and the spraying distance should be within the range of 0.8-1.5m. To facilitate construction overlap, the bottom 0.2m of each layer is temporarily left unsprayed and made into a 45° slope shape, and the contact area of ​​the sprayed layer is cleaned with air or water. The air pressure for shotcreting should be adjusted appropriately according to the shotcreting distance. The water-cement ratio should be controlled during shotcreting to maintain a smooth concrete surface free of dry spots, slippage, and flow. The thickness error of the shotcrete should not exceed ±5mm. The rebound rate of the shotcrete should be controlled within 15%. The shotcrete should be cured for at least seven days after completion.

[0041] Step 5: Set up groundwater level monitoring wells on both sides of the upper opening of the permanent slope 4, with a spacing of 50m, a diameter of 300mm, and a depth of 20-25m. Observe the groundwater level through these monitoring wells. When the water level exceeds or approaches the height of the earthwork excavation base, set up vacuum lightweight wellpoint dewatering in the foundation trench to ensure a safe water level in the foundation trench.

[0042] IV. Temporary ramp

[0043] Step 6: After the excavation of the foundation pit descends to the first basement level, construction of temporary ramp 5 begins. Based on the site structure of the foundation pit, the location and slope of temporary ramp 5 are determined. The upper end of temporary ramp 5 connects to the lower end of permanent ramp 4 on the first basement level. During the excavation of the second basement level, earthwork is reserved. For every 2 meters of excavation depth in the second basement level, a portion of steel mesh 6 is laid on the side of the reserved earthwork for temporary ramp 5. The end of temporary ramp 5 extends to the bottom of the foundation pit, with the last 50 meters constructed as an arc-shaped ramp. After temporary ramp 5 is excavated to the bottom platform of the second basement level and all steel mesh 6 is laid, a 60mm-100mm thick layer of fine aggregate concrete is sprayed onto the steel mesh 6. The steel mesh fixing and concrete spraying are the same as in step 4. The front slope ratio of temporary ramp 5 is 1:7, and its width is 7 meters. At the last 50 meters, the ramp width changes to a 6-meter arc-shaped ramp, continuing until the bottom of the foundation pit. A 100mm thick layer of graded crushed stone is laid on the surface of temporary ramp 5, and then fully covered with steel plates. The joint between temporary ramp 5 and permanent ramp 4 is covered with a single piece of steel plate, without any joints.

[0044] To avoid lateral pressure caused by the difference in soil elevation on both sides, the slope of the ramp needs to be treated in two stages. The first stage is a 45-degree slope, and the second stage is a 60-degree slope. The slope is increased locally to form a small platform 0.6 meters from the top of the slope.

[0045] The ramp floor must be placed on undisturbed undisturbed soil. If the undisturbed soil is disturbed, it must be excavated and backfilled with graded sand and gravel.

[0046] V. Construction of Permanent Ramp

[0047] Step 7: After the overall construction of the foundation pit is completed, the trench is excavated, and the temporary ramp 5 is dismantled. This includes the concrete layer and steel mesh 6 used for the support of the temporary ramp 5, as well as the reserved earthwork for the temporary ramp 5. The dismantling of the temporary ramp 5 is carried out in sections. The engineering vehicles are parked on the upper side of the temporary ramp 5. First, the outer protective structure of the first section is dismantled, and then the earthwork of that section is excavated. Then, the engineering vehicles retreat to the upper section, and the outer support of the second section is dismantled, and the earthwork of the second section is excavated, until the reserved earthwork for the temporary ramp 5 is completely removed.

[0048] Step 8: Design and construct the permanent ramp in four sections. 1) First, remove the anchor cables, concrete layer, and steel mesh 6 from the first basement level to the second basement level of the first section, and clear the excavated soil from the second basement level slab to the top of the pit for the permanent ramp 4. 2) Construct the concrete foundation layer for the permanent ramp 4 on the second basement level. 3) Then, control the elevation of this section and tie the steel reinforcement of the permanent ramp 4 with HRB400 steel bars according to the slope. 4) Then, pour the first section with C35 concrete and construct the hidden columns simultaneously. 5) Remove the anchor cables, concrete layer, and steel mesh 6 from the second section, and clear the excavated soil from the second basement level slab to the top of the pit for the permanent ramp 4. Similarly, complete the concrete pouring of the second section of the permanent ramp 4, leaving a construction joint between the second section and the first section. Similarly, complete the pouring of the other sections of the permanent ramp 4.

[0049] VI. Slope Monitoring: Slope monitoring is incorporated into the overall foundation pit monitoring system. Based on the slope design drawings, monitoring points are set up and initial data is collected before construction. For the first three days after the slope is put into use, its elevation and position are monitored three times a day, in the morning, noon and evening. From the third to the fourteenth day, it is monitored once a day. After two weeks, it is monitored once every three days until the temporary slope 5 is dismantled.

[0050] This invention relates to a construction method for temporary ramps in deep foundation pit construction. It employs a combined permanent and temporary construction method, fully utilizing existing structural components of the deep foundation pit support structure to reduce construction difficulty. Compared to construction using only temporary ramps 5, it reduces the workload of dismantling temporary ramps 5, achieving cost reduction and efficiency improvement. During the foundation pit excavation phase, the permanent ramp 4 is positioned and supported to ensure structural stability when used as a temporary ramp 5, facilitating construction. During the basement construction phase, the permanent ramp 4's final elevation is controlled and poured, ensuring the construction quality of the permanent ramp 4 upon completion.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

Claims

1. A construction method of a permanent and temporary combined integral basement ramp, characterized in that: Step 1, according to the ramp design drawings, combined with the municipal road route outside the site, the best transportation route is selected to plan the position, slope, structure and construction procedure of the permanent and temporary ramp in the foundation pit; Step 2, the upper opening elevation of the permanent ramp is the same as the upper opening elevation of the foundation pit, and extends to the outside of the foundation pit to form an internal and external connection; according to the positioning of the permanent ramp of the negative one floor in the engineering design, the positioning line is drawn on the ground; along the positioning line, every 2 meters outside the permanent ramp, cast-in-place piles, pipe piles and row piles are punched; Step 3, the foundation pit is excavated by using engineering vehicles; the permanent ramp part is reserved according to its slope; the permanent ramp is excavated to the negative one floor bottom plate elevation, 100mm thick graded gravel or 0.5m steel slag base is laid on the slope surface, and steel plate is fully laid; it takes 5-7 days for vehicles to come and go to roll, so that the ramp soil body is fully deposited and compacted, then the steel plate is removed, and 0.6m concrete pavement is poured; the foundation pit guardrails are used on both sides of the ramp to separate people and machines; the negative one floor earthwork is excavated and transported out by engineering vehicles; the reserved permanent ramp earthwork side is pulled anchor cable, the anchor cable cannot be placed in all positions outside the ramp, the anchor cable is interrupted to make its side empty; Step 4, the steel mesh is arranged on the side of the permanent ramp earthwork; the U-shaped clamp made of ∮6.5 steel is used to fix the steel mesh, the surface of the steel mesh is sprayed with 60-100mm thick fine stone concrete; Step 5, underground water level monitoring wells are arranged on both sides of the upper opening of the permanent ramp, the underground water level is observed through the monitoring wells, when the water level height exceeds the earthwork excavation base height or approaches, the vacuum light well point dewatering is arranged in the foundation trench; Step 6, according to the foundation pit structure on site, the position and slope of the temporary ramp are determined, the upper opening of the temporary ramp is connected with the lower opening of the negative one floor permanent ramp; the earthwork is reserved during the excavation of the negative two floor; every 2 meters deep to the negative two floor, a part of the steel mesh is laid on the reserved temporary ramp earthwork side; the temporary ramp extends to the bottom of the foundation pit at the end, and the end 50 meters is constructed as an arc-shaped ramp; the temporary ramp is excavated to the negative two floor bottom platform, after the whole steel mesh is arranged, 60-100mm thick fine stone concrete is sprayed on the steel mesh; 100mm thick graded gravel is laid on the surface of the temporary ramp, and steel plate is fully laid; the temporary ramp and the permanent ramp connection part are paved with whole steel plate; Step 7, after the whole foundation pit construction is completed, the temporary ramp is removed, including the concrete layer and steel mesh for supporting the temporary ramp and the reserved temporary ramp earthwork; Step 8, design permanent ramp section, first segment side from negative one layer to negative two layer anchor cable, concrete layer and mesh sheet removal, clear the first segment of negative two layer floor to the top of the foundation pit permanent ramp earthwork, in the negative two layer construction of permanent ramp concrete cushion, then in the segment elevation control, according to the slope with HRB400 reinforcement permanent ramp reinforcement binding, then with C35 concrete pouring into the first segment, synchronous construction of hidden column; the second segment of anchor cable, concrete layer and mesh sheet removal, clear the second segment of negative two layer floor to the top of the foundation pit permanent ramp earthwork, also complete the second segment of the concrete pouring, the second segment and the first segment reserved construction joint; similarly, the other segments of the permanent ramp pouring is completed. Permanent ramp and temporary ramp must be placed on undisturbed in-situ soil, if the in-situ soil is disturbed, the disturbed earthwork must be removed.

2. The method of installing a permanent- temporary integrated basement ramp of claim 1, wherein: The slurry of shotcrete uses C20 concrete with maximum coarse aggregate size not more than 12mm; the shooting distance is in the range of 0.8m-1.5m, the lower 0.2m of each layer is left empty and shaped into 45° slope, then clean the contact part of the spray layer; the shotcrete air pressure is adjusted according to the shotcrete distance; the rebound rate of shotcrete is controlled within 15%; 3. The method of installing a permanent- temporary integrated basement ramp as claimed in claim 1, wherein: After the completion of shotcrete, it should be maintained for at least seven days. The side slope of temporary ramp is treated by two-stage slope, the first stage is 45 degree slope, the second stage is 60 degree slope, and the slope is increased locally.

4. The method of installing a permanent- temporary integrated basement ramp of claim 1, wherein: The slope monitoring is included in the overall foundation pit monitoring system, according to the slope design drawing, the monitoring points are set before construction and the initial data is collected; three days before the slope is put into use, the elevation and position are monitored three times a day; the third to fourteenth days, the slope is monitored once a day; two weeks later, it is monitored once every three days until the temporary ramp is removed.

5. The method of installing a permanent- temporary integrated basement ramp of claim 1, wherein: When the temporary ramp is removed, it is removed in sections, the engineering vehicle stops on the side of the temporary ramp, the outer support structure of the first segment is removed first, then the earthwork of the segment is excavated; then the engineering vehicle retreats to the previous segment, the outer support of the second segment is removed, and the earthwork of the second segment is excavated, until the reserved temporary ramp earthwork is completely removed.

6. The method of installing a permanent- temporary integrated underground basement ramp of claim 1, wherein: ​

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