CN118207884B - Existing building dismantling and newly-built building foundation pit supporting cross comprehensive construction method - Google Patents
Existing building dismantling and newly-built building foundation pit supporting cross comprehensive construction method Download PDFInfo
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Abstract
The invention relates to a construction method for constructing foundation pit support cross of existing building, which comprises the steps of designing and dividing construction area, dismantling structure of wall outside first dismantling, carrying out in-situ earthwork backfill, constructing backfill slope protection structure, forming construction operation surface of new underground continuous wall in the area, constructing new underground continuous wall, dismantling old underground structure, connecting construction wall section and first construction wall section into a whole at this time after backfilling area, forming waterproof curtain for dismantling structure of wall inside later dismantling, and continuing dismantling structure of wall inside later dismantling. The invention designs that the underground structure of the existing building in the crossing area is firstly locally dismantled, then in-situ backfilling is carried out to form stress connection, a construction working surface for a new underground diaphragm wall is formed, then the new underground diaphragm wall is constructed, and then the other structures are dismantled.
Description
Technical Field
The invention belongs to the technical field of urban updating green demolition construction, and particularly relates to a construction method for the intersection of existing building demolition and newly-built building foundation pit support.
Background
With urban development and population growth, old and existing buildings may be difficult to meet the requirements of modern society due to design outages, functional limitations or structural aging. The existing buildings do not meet the standard of modern city planning, and the beauty and the overall image of the city are affected, so that the land resource is wasted. Meanwhile, the old building can have potential safety hazards, and the life and property safety of residents is threatened. Therefore, the construction of newly built buildings on the land of the existing buildings becomes the new generation of urban updated green construction selection, and has the following advantages: 1. the existing land resources can be fully utilized, and environmental damage and ecological influence caused by newly developed land are avoided; 2. the in-situ construction can be better integrated with the urban texture, coordinate with the surrounding environment, promote the integral appearance of the city, and meet the functional requirements of the modern society; 3. is beneficial to reducing traffic pressure and population migration and provides more convenient living environment for urban residents.
In the construction of demolishing of existing building and the construction of the support of newly-built building in the city, existing building and newly-built building often all have underground structure simultaneously, and the underground structure of both is unavoidable to take place alternately in underground construction position, will produce following problem to the construction this moment:
1. the dismantling construction of the existing building and the supporting construction of the newly built building are required to carry out precipitation steps, particularly when groundwater resources are rich, the whole-area precipitation can lead to groundwater resource waste, and meanwhile, urban groundwater also has no condition of field drainage of the whole area, so that groundwater control is difficult;
2. The underground structure is crossed, the existing drilling equipment cannot directly drill through the underground structure of the existing building, and the construction of the newly built building supporting structure can be performed only by dismantling the underground structure of the existing building in the crossed area; however, the construction period is short, the demolition of the existing building and the support of the newly built building cannot be constructed successively, and synchronous construction is needed; the construction scheme contradicts the construction period requirement.
Disclosure of Invention
The invention aims to provide a construction method for the cross and comprehensive construction of foundation pit support of an existing building and a newly built building, which aims to solve the technical problem that in the existing construction method, the whole-area on-site drainage scheme of the existing building and the newly built building causes difficult groundwater control; and solves the problem that the construction scheme and the construction period requirement are contradictory when the underground structure is crossed.
In order to achieve the above purpose, the invention adopts the following technical scheme:
The construction method for the existing building demolition and newly-built building foundation pit support intersection comprehensive construction comprises the following construction steps:
Step one, designing and dividing a construction area:
the underground structure to be dismantled of the existing building is an old underground structure, which comprises a top plate, a beam, a column, a bottom plate and a side wall,
The foundation pit support to be constructed of the newly built building is a new underground continuous wall,
The underground structure to be constructed of the newly built building is a new underground structure,
The new underground diaphragm wall is enclosed on the periphery of the foundation pit of the new underground structure, a fertilizer groove width is reserved between the new underground diaphragm wall and the new underground structure,
Construction working conditions: a part of wall sections of the new underground continuous wall continuously cross a part of old underground structure;
Dividing a construction area of the new underground continuous wall: the part of the wall sections which are traversed is set as the back construction wall sections of the backfill area, the rest wall sections are the first construction wall sections,
Construction area division of old underground structure: dividing an old underground structure into a first-dismantling structure outside the wall and a second-dismantling structure inside the wall by taking a contour line of the new underground structure in a corresponding range inside a backfill area rear construction wall section as a boundary, wherein the second-dismantling structure inside the wall is enclosed inside the new underground continuous wall and is also used as a waterproof curtain when the second-dismantling structure inside the wall is dismantled, and the other old underground structures are first-dismantling structures outside the wall;
step two, dismantling the structure which is firstly dismantled outside the wall:
Local precipitation before demolition: adopting dewatering wells to ensure that the dewatering wells are uniformly distributed around the structure which is firstly disassembled outside the wall; the construction range of the dewatering well is the inner periphery of a new underground structure contour line of a corresponding range from the periphery of the structure to the inner side of the construction wall section after the backfilling area is firstly disassembled along the outer part of the wall;
and (3) construction slope protection: the underground water is lowered to 1m below the bottom plate of the old underground structure, and slope protection is constructed along the peripheral range of the contour line of the structure which is firstly disassembled outside the wall: firstly removing earthwork outside the structure outside the slope excavation wall, and then constructing and removing the soil slope protection structure to form a removing operation surface;
and (3) removing the structure: the method comprises the steps of carrying out static force demolishing on a demolishing operation surface to demolish a structure outside a wall, wherein demolishing members are all members in the range and comprise a top plate, a beam, a column, a bottom plate and a side wall;
thirdly, after the structure in the second step is dismantled, in-situ earth backfilling is carried out, and a backfill slope protection structure is constructed, so that a construction working surface of the new underground continuous wall in the range is formed;
step four, constructing a new underground continuous wall:
the construction time of the first construction wall section is as follows: the construction stage of the third step is started,
Construction time for constructing wall sections after backfilling areas: after the earth backfilling in the third step is completed;
Step five, dismantling the old underground structure:
the dismantling time is as follows: starting a construction stage of the fourth step;
and (3) removing the structure: removing top plates, beams and columns in the old underground structure, wherein the removing members are the top plates, the beams and the columns in the range of the rear removing structure in the wall;
Dismantling sequence: synchronously dismantling the top plate and the beams from the center of the structure to the periphery, and then dismantling the columns;
step six, the back construction wall section of the backfill area and the first construction wall section are connected into a whole at the moment to form a waterproof curtain with a back dismantling structure inside the wall;
Step seven, continuously dismantling the rear dismantling structure inside the wall:
and (3) removing the structure: and dismantling the side wall and the bottom plate in the structure after the interior of the wall is dismantled, and finishing the dismantling of the old underground structure.
The outer contour of the old underground structure is in a flower shape and comprises petal parts and non-petal parts, the side walls of the petal parts are slope protection retaining walls and serve as structural supports, and the side walls of the non-petal parts are directly used as structural supports.
In the fifth step, the slope protection retaining wall of the span beam range at the outermost side is reserved at the petal position and is not dismantled, the rear dismantling structure of the wall inner part of the span beam range at the outermost side is reserved at the non-petal position, and the reserved components of the rear dismantling structure in the wall inner part are all components in the range, and the reserved components comprise a top plate, a beam, a column, a bottom plate and a side wall; the two parts remain the structure to be removed integrally with the structure in step seven.
When the wall outside first-dismantling structure comprises at least one petal part, the slope protection of the petal part is firstly constructed in the second step of construction, and then the slope protection of the rest part is constructed.
In the second step, the dewatering well avoids the position right above the existing building facilities, a reverse circulation well is adopted, a sand-free concrete water filtering pipe is put into the whole hole in the well, a layer of nylon net is wrapped on the outer side of the sand-free concrete water filtering pipe, a filter material is backfilled in the sand-free concrete water filtering pipe, and the wellhead of the dewatering well is sealed by clay to prevent surface water from flowing in.
In the third step, the original position earth backfill is two-stage backfill, the backfill comprises a first-stage backfill and a second-stage backfill, the top height position of the first-stage backfill is 4m below the ground surface position, the part of backfill is the first-stage backfill, the top height position of the second-stage backfill is the ground surface position, the part of backfill is the second-stage backfill, the maximum height of the second-stage backfill is 5.9m,
Backfilling the two sides of the new underground diaphragm wall to the first-stage backfill top elevation position within the range of 8m respectively, backfilling the other ranges to the second-stage backfill top elevation position, and connecting the two-stage backfill soil by adopting a 1:0.3 slope; wherein the secondary backfill soil part in the range of 8m on the inner side of the new underground diaphragm wall covers the inner part of the wall and then the structure is disassembled for stress connection.
And thirdly, mixing cement into backfill soil within the range of 2m on both sides of the new underground diaphragm wall to form a reinforced cement soil layer, wherein the reinforced cement soil layer is a stressed soil layer for constructing the new underground diaphragm wall, which is formed after the strength of the backfill soil is improved.
Before the construction of the third backfill, the optimal cement mixing amount of the backfill soil needs to be determined, and the determination steps are as follows:
step a, taking a soil sample of site backfill soil to perform compaction test on the filling material, and obtaining the optimal water content and the maximum dry density of the original soil sample;
B, performing geotechnical tests of the soil samples under the condition of mixing amounts of 0%, 4%, 7% and 9% of four mass ratios, and controlling the dry densities of the soil samples with different cement mixing amounts to be the maximum dry density of the original soil samples;
step c, drawing a change condition diagram of a cement doping amount soil sample and each physical and mechanical index, wherein the physical and mechanical indexes comprise compression modulus, cohesion and internal friction angle;
According to the change condition diagram of the physical and mechanical indexes, the improvement of the mechanical property of the soil body is nonlinear increase and the increase speed tends to be gentle along with the increase of the cement doping amount, so that the cement doping amount of 7% is selected for backfilling.
Compared with the prior art, the invention has the following characteristics and beneficial effects:
The water stopping scheme of the invention is to match the construction sequence of the existing structure dismantling and newly built building support, firstly, a dewatering well is adopted to carry out local dewatering of the structure which is firstly dismantled outside the wall, then, the bottom plate and the side wall of the structure which is firstly dismantled outside the wall are backfilled in earth after being dismantled, and then, the whole new underground continuous wall is constructed, the structure which is secondly dismantled inside the wall is enclosed inside the new underground continuous wall, and at the moment, the new underground continuous wall is also used as a water stopping curtain when the structure which is secondly dismantled inside the wall is dismantled.
The water stopping scheme of the invention is that the partial precipitation well of the external structure of the wall and the new underground continuous wall are matched for precipitation, the precipitation construction range is greatly reduced, the water quantity is controllable, and the new underground continuous wall is also a water stopping curtain and a supporting structure of a newly built building, thereby realizing the precipitation target of the whole project.
Aiming at the characteristic that the underground structures of new and old buildings are crossed, the existing drilling equipment cannot directly drill through the underground structures of the existing buildings, so that the creative design firstly partially removes the underground structures of the existing buildings in the crossed area, then carries out in-situ backfill to form stressed connection to form a construction working face for a new underground continuous wall, then constructs the new underground continuous wall, then carries out the removal of the rest structures, realizes the simultaneous alternate construction of the underground structure removal of the existing buildings and the support of the new buildings, establishes a foundation for the project underground structure node construction period through reasonable procedure arrangement,
The earth retaining of the retaining wall with the original structure is fully utilized when the existing building is dismantled, and the dismantling sequence of the top plate, the columns, the bottom plate, the middle part and the periphery is determined, so that the construction safety is ensured; in particular, during in-situ backfilling, the optimal cement blending amount is designed, so that the grooving quality of the position is ensured.
The invention provides a reference for similar projects for the synchronous construction of the demolishing of the underground structure and the construction of the newly built underground continuous wall, solves the technical problems of excessively high underground water level, large-area backfilling of earthwork and the like in the implementation process.
Drawings
The invention is described in further detail below with reference to the accompanying drawings.
Fig. 1 is a schematic plan view of an old underground structure and a new underground diaphragm wall of the present invention.
Fig. 2 is a schematic plan view of an old underground structure, a new underground diaphragm wall and a new underground structure of the present invention.
FIG. 3 is a schematic view of a precipitation well layout of the exterior pre-dismantling structure of the wall of the present invention.
Fig. 4 is a view showing the arrangement of the soil removing slope protection structure of the wall exterior pre-dismantling structure of the present invention.
Fig. 5 is a schematic view of section A-A of fig. 4.
Fig. 6 is a schematic view of section B-B of fig. 4.
Fig. 7 is a schematic view of section C-C of fig. 4.
Fig. 8 is a schematic view of reinforcement of the removed soil slope protection structure of fig. 4.
Fig. 9 is a block diagram of the backfill slope protection structure, the two-stage backfill, and the position where a new underground diaphragm wall is to be installed according to the present invention.
Fig. 10 is a schematic view of section D-D of fig. 9.
Fig. 11 is a steel pipe reinforcing schematic diagram of the backfill slope protection structure in fig. 10.
Fig. 12 is an enlarged schematic view of a portion of the backfill slope protection structure of fig. 10.
Fig. 13 is a schematic view of the position of the retaining structure in the fifth step and the side wall in the seventh step.
Fig. 14 is a schematic view of a double-catwalk construction at a construction site.
FIG. 15 is a graph showing the change of compression modulus of soil samples with different cement contents.
FIG. 16 is a graph showing the change of cohesion of soil samples with different cement contents.
FIG. 17 is a graph showing the change of internal friction angle of soil samples with different cement contents.
Reference numerals:
1-old underground structure, 11-wall external pre-dismantling structure, 12-wall internal post-dismantling structure, 13-petal part, 14-non-petal part, 15-slope protection retaining wall, 16-non-petal side wall,
2-New underground continuous wall, 21-first construction wall section, 22-backfill area and then construction wall section,
3-New underground structure, 4-fertilizer groove width, 5-dewatering well,
6-Backfill, 61-first-stage backfill, 62-second-stage backfill,
7-Reinforced cement soil layer, 8-driving ramp,
9-Removing soil slope protection structure, 91-removing soil slope protection steel bar, 92-removing soil slope protection steel bar net sheet, 93-removing soil slope protection concrete surface layer, 94-removing soil slope protection vertical reinforcing rib, 95-removing soil slope protection horizontal reinforcing rib, 96-burying rib at bottom of slope protection steel bar,
10-Backfill slope protection structure, 101-backfill slope protection steel pipe, 102-backfill slope protection steel bar net sheet, 103-backfill slope protection concrete surface layer, 104-backfill slope protection vertical reinforcing rib, 105-backfill slope protection horizontal reinforcing rib, 106-slope protection steel pipe bottom buried rib, 107-slope protection steel pipe top buried rib, 108-slope protection steel pipe backfill soil layer, and,
17-A first horse way, 18-a second horse way, 19-a construction parting line, 20-an existing subway line, 23-a petal position retaining structure and 24-a non-petal position retaining structure.
Detailed Description
1-3, The demolition project of the existing building of a permanent meeting place project of a new forum is mainly an overground underground supermarket, the number of underground layers is one, and the layer height is 8.1m, and the underground layers are close to the existing subway line 20. The underground supermarket is old underground structure 1, and its outline is including flower shape, including petal portion 13 and non-petal portion 14, and petal portion 13 includes five, and non-petal portion 14 still includes a driving ramp 8, and this supermarket outer wall divide into two parts that have the bank protection and do not have the bank protection, specifically does: the side walls of the petal parts 13 are slope protection retaining walls 15 and serve as structural supports, and the side walls 16 of the non-petal parts are directly used as structural supports. In this embodiment, the slope protection part is a reinforced concrete retaining wall with a thickness of 250mm, the slope protection height of the slope protection part is 6m, and the slope protection gradient is 1:0.125. The revetment-free section is directly supported by the building exterior wall structure, i.e., the side wall 16. Meanwhile, two layers of groundwater are present in the basement dismantling depth range of the old underground structure 1, the ground groundwater level is high, and the water quantity is rich. The foundation pit supporting structure of the newly built building is intersected with the basement bottom plate of the old underground structure 1 at the left upper corner, and the construction condition of the newly built foundation pit supporting structure is required to be provided after backfilling is removed. Meanwhile, the project construction period is tight, and the underground structure is dismantled for only more than 40 days.
The old underground structure 1 exists in the site of the newly built building project, and the underground structure of the project can be constructed after the old underground structure is dismantled. The difficulties of the project include:
1. The ground water level of the field is very high, the water quantity is rich, and the failure of the whole project can be caused by the insufficient control of the ground water; because of the depth of field diving, groundwater control is one of the keys of success and failure of projects. If the precipitation scheme is adopted, the water-bearing layer has large thickness, good permeability, rich water quantity, estimated water pumping quantity of more than 5000 m/d, large water discharge, unsatisfied on-site drainage conditions of urban projects and serious waste of underground water resources, so the whole-area precipitation scheme is not feasible.
2. The foundation pit supporting structure of the newly built building is intersected with the basement bottom plate of the old underground structure 1 at the left upper corner, the existing drilling equipment cannot directly drill through, and the supporting structure cannot be constructed without dismantling the area bottom plate.
3. The construction period is tension, and the dismantling and the construction of the supporting structure are required to be synchronously carried out, so that the construction period requirement can be met.
Therefore, aiming at the technical problems, research is carried out from the aspect of groundwater control and earthwork backfilling, and the construction method for comprehensively constructing foundation pit support intersection of the existing building and the newly built building is provided, wherein the construction steps are as follows:
step one, referring to fig. 1-2, designing and dividing a construction area:
The underground structure to be dismantled of the existing building is an old underground structure 1, which comprises a top plate, a beam, a column, a bottom plate and a side wall,
The foundation pit support to be constructed of the newly built building is a new underground continuous wall 2,
The underground structure to be constructed of the newly built building is a new underground structure 3,
The new underground diaphragm wall 2 is enclosed on the periphery of the foundation pit of the new underground structure 3, a fertilizer groove width 4 is reserved between the new underground diaphragm wall 2 and the new underground structure 3,
Construction working conditions: a part of wall sections of the new underground diaphragm wall 2 continuously cross a part of the old underground structure 1;
construction area division of the new underground diaphragm wall 2: the part of the wall sections which are traversed is set as a backfill area and then the wall sections 22 are constructed, the rest of the wall sections are first constructed wall sections 21,
Construction area division of the old underground structure 1: the contour line of the new underground structure 3 in the corresponding range inside the backfill area rear construction wall section 22 is taken as a boundary, the old underground structure 1 is divided into a wall outer first-dismantling structure 11 and a wall inner second-dismantling structure 12, specifically, for convenience of construction, the two corner position pulling construction dividing lines 19 of the old underground structure 1 near the new underground structure 3 can be set as boundaries of the successively-dismantling structures, the wall inner second-dismantling structure 12 is enclosed inside the new underground continuous wall 2, and the new underground continuous wall 2 also serves as a waterproof curtain when the wall inner second-dismantling structure 12 is dismantled, and the rest of the old underground structures 1 are the wall outer first-dismantling structures 11.
In this embodiment, the first-dismantling structure 11 outside the wall in the upper left corner includes a petal portion 13 and a non-petal portion 14 near the petal portion 13, and further includes a driving ramp 8 of the non-petal portion 14, and in the second step, the slope protection of the petal portion 13 is constructed first, and then the slope protection of the rest is constructed.
Step two, dismantling the wall external pre-dismantling structure 11:
Local precipitation before demolition: 1-3, adopting dewatering wells 5 to ensure that dewatering wells 5 are uniformly distributed around a pre-dismantling structure 11 outside the wall; the construction range of the dewatering well 5 is the inner periphery of the contour line of the new underground structure 3 along the periphery of the pre-detached structure 11 outside the wall until the corresponding range of the inner side of the backfill area post-construction wall section 22.
In the embodiment, a 28-hole dewatering well 5 is arranged at the upper left corner of the dewatering well 5, the dewatering well 5 avoids the position right above the existing building facilities, reverse circulation well formation is adopted, the depth of the dewatering well 5 is 12-15 m, the pore forming aperture is 600mm, the diameter of a whole hole in the well is 400mm, and a sand-free concrete filter pipe with the wall thickness of 50mm is arranged. The outside of the sand concrete water filtering pipe is wrapped with a layer of 80 mesh nylon net, the filter material is backfilled in the sand-free concrete water filtering pipe, the diameter of the backfilled filter material is 3mm-7mm, and the wellhead of the dewatering well 5 is sealed by clay to prevent the inflow of surface water.
And (3) construction slope protection: after the precipitation operation starts a week, the groundwater is lowered to 1m below the bottom plate of the old underground structure 1, and the slope protection is constructed along the peripheral range of the contour line of the external pre-dismantling structure 11: referring to fig. 4, the outside of the slope excavation wall is firstly dismantled from the earthwork outside the structure 11, and then the soil slope protection structure 9 is constructed and dismantled.
Referring to FIGS. 5-8, the demolishing soil slope protection structure 9 is a soil nail wall, a slope with the diameter of 1:0.3 is adopted, soil nails are arranged in a quincuncial manner by adopting demolishing soil slope protection steel bars 91 with the diameter of 22mm, the intervals of the quincuncial patterns are 1.2m, the buried slope protection length of the soil nails is 6m-9m, the inclined surface of the slope protection structure is 8mm in diameter, the mesh size of the demolishing soil slope protection steel bar meshes 92 is 200mm, and the demolishing soil slope protection concrete surface layer 93 with the thickness of 100mm is sprayed in a matched manner.
In the specific embodiment, demolish the outside of native bank protection reinforcing bar net piece 92 and be equipped with 16mm strengthening rib, for logical long demolish the vertical strengthening rib 94 of native bank protection and demolish the horizontal strengthening rib 95 of native bank protection respectively, demolish the tip of native bank protection reinforcing bar 91 and throw away the outside of strengthening rib, the bending end that throws away with demolish the vertical strengthening rib 94 single face welding of native bank protection, demolish native bank protection reinforcing bar 91 downside and be equipped with bank protection reinforcing bar bottom and bury the muscle 96, the tip that the strengthening rib was buried in bank protection reinforcing bar bottom is thrown away the outside of strengthening rib, the bending end that throws away also with demolish the vertical strengthening rib 94 single face welding of native bank protection, demolish the also single face welding between native bank protection reinforcing bar 91 and the bank protection reinforcing bar bottom and bury the muscle 96.
And (3) removing the structure: the outer pre-dismantling structure 11 of the wall is dismantled on the dismantling working surface by static force, and the dismantling components are all components in the range, including a top plate, a beam, a column, a bottom plate and side walls.
And thirdly, after the structure in the second step is dismantled, determining the optimal cement doping amount of the backfill soil, and then carrying out in-situ earthwork backfill, wherein the construction of the backfill soil slope protection structure 10 is shown in fig. 9-10, so as to form a construction operation surface of the new underground diaphragm wall 2 in the range. The wall thickness of the new underground diaphragm wall 2 in this embodiment is 600mm.
The original position earthwork backfill is two-stage backfill, the backfill 6 comprises a first-stage backfill 61 and a second-stage backfill 62, the top standard height position of the first-stage backfill is 4m below the ground surface position, the part of backfill is the first-stage backfill 61, the top standard height position of the second-stage backfill is the ground surface position, the part of backfill is the second-stage backfill 62, and the maximum height of the first-stage backfill 62 is a=5.9m.
Backfilling the two sides of the new underground diaphragm wall 2 to a first-stage backfill top elevation position within the range of c=8m, and backfilling the other ranges to a second-stage backfill top elevation position, wherein the two-stage backfill soil is connected by adopting a 1:0.3 slope; the secondary backfill 62 in the range of c=8m inside the new diaphragm wall 2 partially covers the wall interior and the post-dismantling structure 12 is connected by force.
In the third step, referring to fig. 10-13, the first-stage backfilling is needed to be made into a backfill slope protection structure 10, the backfill slope protection structure 10 is a soil nail wall, a 1:0.5 slope is adopted, soil nails are embedded into a pre-buried DN48 backfill slope protection steel pipe 101, the soil nails are arranged in a plum blossom shape, each plum blossom shape interval is 1.2m, the soil nails are embedded into the slope protection length is 2m-4m, and the soil nails are backfilled with 7% cement soil at the soil nails, namely, the backfill soil layer 108 of the slope protection steel pipe is formed, the dimension of the backfill soil layer 108 of the slope protection steel pipe is larger than the deepest position of the soil nails, the horizontal direction is larger than d=1000 mm, the vertical direction is larger than e=200mm, the slope protection structure inclined surface adopts a backfill slope protection steel bar mesh 102 with the diameter of 8mm, the mesh dimension of 200mm, and the backfill slope protection steel layer 103 is matched with the injection of 100mm thickness and C20 is formed into a demolition operation surface.
In the specific embodiment, the outside of backfill slope protection reinforcing bar net piece 102 is equipped with 16mm strengthening rib, is the vertical strengthening rib 104 of the backfill slope protection of logical length and the horizontal strengthening rib 105 of backfill slope protection respectively, and the back-up slope protection steel pipe 101 is equipped with the tip around the body of backfill slope protection concrete face layer 103 and throws away the slope protection steel pipe bottom of strengthening rib outside and buries muscle 106 and slope protection steel pipe top and buries muscle 107, and the bending end that throws away and the vertical strengthening rib 104 single face welding of backfill slope protection, and slope protection steel pipe bottom buries muscle 106 and slope protection steel pipe top buries muscle 107 and also all welds with the outer wall single face of back-up slope protection steel pipe 101.
The slope-releasing excavation in the second step and the in-situ earthwork backfill in the third step are recommended to be carried out by sectional running water, and the backfill compaction is carried out immediately after excavation to the substrate as much as possible by 10m-20m of a single running water section.
In the third step, referring to fig. 10, after the side wall and the bottom plate of the structure 11 are removed, the earth with the thickness of a=5.9m needs to be backfilled to form the construction surface of the new underground continuous wall 2, and in view of the fact that the dead weights of the equipment such as the underground continuous wall grooving machine, the crawler crane and the like are large, the requirement on the bearing capacity of the foundation is high, and therefore the backfilling quality of the earth has a great influence on the construction safety. For soil layers in a wide range of b=2m on both sides of the new underground diaphragm wall 2, as main stress points of a grooving machine during construction, the problems of safety quality such as collapse, local hole collapse and the like are very easy to occur, a certain amount of cement is required to be doped into earthwork in the range to form cement soil, and the backfill soil strength is improved. Therefore, cement is doped into the backfill soil 6 within the range of b=2m at the two sides of the new underground diaphragm wall 2 to form a reinforced cement soil layer 7, and the reinforced cement soil layer 7 is a stressed soil layer formed after the strength of the backfill soil 6 is improved to construct the new underground diaphragm wall 2.
Before the construction of the third backfill, the optimal cement mixing amount of the backfill soil needs to be determined, and the determination steps are as follows:
Step a, taking a soil sample of site backfill soil to perform compaction test on the filling material, and obtaining the optimal water content and the maximum dry density of the original soil sample; in this example, the optimum moisture content and maximum dry density of the obtained soil sample were 16.3% and 1.80g/cm, respectively.
And b, performing geotechnical tests of the soil samples under the condition of mixing amounts of 0%, 4%, 7% and 9% of four mass ratios, and controlling the dry densities of the soil samples with different cement mixing amounts to be 1.80g/cm of the maximum dry density of the original soil sample.
And c, drawing a graph of the change condition of the cement doping amount soil sample and each physical and mechanical index, wherein the physical and mechanical indexes comprise compression modulus Es, cohesion c and internal friction angle phi, as shown in figures 15-17, in order to obtain the improvement condition of the physical and mechanical properties of backfill soil under the condition of different cement doping amounts.
According to the change condition diagram of the physical and mechanical indexes, the compression modulus, the cohesion and the internal friction angle of the soil sample are obviously improved after the cement is doped, the mechanical property of the soil body is obviously improved, the improvement of the mechanical property of the soil body is nonlinear growth and the growth speed tends to be gentle along with the increase of the doping amount, and the situation that the mixing in a laboratory cannot be uniform when the cement is mixed in site is considered, so that 7% of the optimal cement doping amount is selected for backfilling. Practice shows that 7% of cement soil meets the construction requirement.
Step four, constructing a new underground continuous wall 2, and constructing the whole frame by frame:
The construction time of the first construction wall section 21 is as follows: the construction stage of the third step is started,
Construction timing of the construction wall section 22 after backfilling the area: and D, after the earthwork backfilling in the third step is completed.
Step five, dismantling the old underground structure 1:
the dismantling time is as follows: starting a construction stage of the fourth step;
And (3) removing the structure: removing the top plate, the beam and the column in the old underground structure 1, wherein the removing members are the top plate, the beam and the column in the structure range of the back removing inside the wall;
dismantling sequence: the roof and beams are removed synchronously from the center of the structure to the periphery, and then the columns are removed.
Step six, the back construction wall section 22 of the backfill area and the first construction wall section 21 are connected into a whole at the moment to form the waterproof curtain of which the back dismantling structure 12 is dismantled inside the wall.
Step seven, continuing to dismantle the rear dismantling structure 12 inside the wall:
and (3) removing the structure: and removing the side wall and the bottom plate in the structure 12 after removing the inside of the wall, and finishing the removal of the old underground structure 1.
In order to ensure construction safety, the slope protection retaining wall 15 with the outermost span beam range is reserved at the petal part 13 in the fifth step and is not removed, the wall inner rear dismantling structure 12 with the outermost span beam range is reserved at the non-petal part, and reserved components of the wall inner rear dismantling structure 12 are all components in the range, including a top plate, a beam, a column, a bottom plate and a side wall; the two parts remain the structure to be removed integrally with the structure in step seven.
The petal-position retaining structures 23 are shown with reference to the shaded portions in fig. 13, as non-petal-position retaining structures 24.
In the seventh step, after the new underground diaphragm wall 2 is closed, when the side wall and the bottom plate in the wall inside rear dismantling structure 12 begin to be dismantled, the earthwork excavation operation is carried out outside the old underground structure 1. At this time, the construction waste is transported by the double-horse way, as shown in fig. 14, the starting end of the first horse way 17 is arranged at the right upper corner of the rear dismantling structure 12 inside the wall of the old underground structure 1, extends to the new underground continuous wall 2 and is transported out of the ground, and is transported out of the ground by the right upper door. The second catwalk 18 is arranged in the new underground diaphragm wall 2 outside the old underground structure 1 at the lower right corner, extends to the new underground diaphragm wall 2 and then is transported out of the ground, and is transported out of the ground by the lower right door. Through the arrangement, the working surfaces of all areas are fully utilized, the construction efficiency is improved, and the construction waste and earthwork are respectively transported and consumed by arranging double horse roads.
Claims (8)
1. The construction method for the cross comprehensive construction of the foundation pit support of the existing building and the newly-built building is characterized by comprising the following construction steps:
Step one, designing and dividing a construction area:
The underground structure to be dismantled of the existing building is an old underground structure (1) and comprises a top plate, a beam, a column, a bottom plate and a side wall,
The foundation pit support to be constructed of the newly built building is a new underground continuous wall (2),
The underground structure to be constructed of the newly built building is a new underground structure (3),
The new underground diaphragm wall (2) is enclosed on the periphery of the foundation pit of the new underground structure (3), a fertilizer groove width (4) is reserved between the new underground diaphragm wall (2) and the new underground structure (3),
Construction working conditions: a part of wall sections of the new underground diaphragm wall (2) continuously cross a part of the old underground structure (1);
Dividing a construction area of the new underground continuous wall (2): the part of the wall sections which are traversed is set as a backfill area and then the wall sections (22) are constructed, the rest wall sections are firstly constructed wall sections (21),
Construction area division of an old underground structure (1): dividing an old underground structure (1) into a wall external pre-dismantling structure (11) and a wall internal post-dismantling structure (12) by taking the contour line of a new underground structure (3) in a corresponding range inside a backfill area post-construction wall section (22) as a boundary, wherein the wall internal post-dismantling structure (12) is enclosed inside the new underground structure by a new underground continuous wall (2), the new underground continuous wall (2) is also used as a waterproof curtain when the wall internal post-dismantling structure (12) is dismantled, and the rest of the old underground structures (1) are the wall external pre-dismantling structures (11);
step two, dismantling the structure (11) which is firstly dismantled outside the wall:
Local precipitation before demolition: adopting a dewatering well (5) to ensure that the dewatering well (5) is uniformly distributed around the pre-dismantling structure (11) outside the wall; the construction range of the dewatering well (5) is the inner periphery of the contour line of the new underground structure (3) in the corresponding range along the periphery of the structure (11) which is firstly disassembled outside the wall until the inner side of the backfill area is constructed;
and (3) construction slope protection: the underground water is lowered to 1m below the bottom plate of the old underground structure (1), and slope protection is constructed along the peripheral range of the contour line of the externally detached structure (11) of the wall: firstly removing earthwork outside the structure (11) outside the slope-releasing excavation wall, and then constructing and removing the soil slope protection structure (9) to form a removing operation surface;
And (3) removing the structure: the method comprises the steps of (1) carrying out static force dismantling on a dismantling operation surface to obtain a wall external dismantling structure (11), wherein dismantling components are all components in the range and comprise a top plate, a beam, a column, a bottom plate and a side wall;
thirdly, after the structure in the second step is dismantled, in-situ earth backfilling is carried out, and a backfill slope protection structure (10) is constructed, so that a construction working surface of a new underground continuous wall (2) in the range is formed;
step four, constructing a new underground continuous wall (2):
Construction time of firstly constructing a wall section (21): the construction stage of the third step is started,
Construction time for constructing the wall section (22) after backfilling the area: after the earth backfilling in the third step is completed;
Step five, dismantling the old underground structure (1):
the dismantling time is as follows: starting a construction stage of the fourth step;
And (3) removing the structure: removing top plates, beams and columns in the old underground structure (1), wherein the removing members are the top plates, the beams and the columns in the range of the rear removing structure (12) in the wall;
Dismantling sequence: synchronously dismantling the top plate and the beams from the center of the structure to the periphery, and then dismantling the columns;
Step six, the back construction wall section (22) of the backfill area and the first construction wall section (21) are connected into a whole at the moment to form a waterproof curtain of which the back dismantling structure (12) in the wall is dismantled;
Step seven, continuously dismantling the rear dismantling structure (12) in the wall:
and (3) removing the structure: and (3) dismantling the side wall and the bottom plate in the structure (12) after the interior of the wall is dismantled, and finishing the dismantling of the old underground structure (1).
2. The method for comprehensively constructing foundation pit support intersections of the existing building and the newly built building according to claim 1, wherein the method comprises the following steps: the outer contour of the old underground structure (1) is in a flower shape and comprises petal parts (13) and non-petal parts (14), the side walls of the petal parts (13) are slope protection retaining walls (15) and serve as structural supports, and the side walls (16) of the non-petal parts are directly and concurrently serve as structural supports.
3. The method for comprehensively constructing foundation pit support intersections of the existing building and the newly built building according to claim 2, which is characterized in that: in the fifth step, the slope protection retaining wall (15) of the span beam range at the outermost side is reserved at the petal part (13) and is not dismantled, the wall inside rear dismantling structure (12) of the span beam range at the outermost side is reserved at the non-petal part, and reserved components of the wall inside rear dismantling structure (12) are all components in the range, and the reserved components comprise a top plate, a beam, a column, a bottom plate and a side wall; the two parts remain the structure to be removed integrally with the structure in step seven.
4. The method for comprehensively constructing foundation pit support intersections of the existing building and the newly built building according to claim 2, which is characterized in that: when the structure (11) is detached firstly outside the wall and comprises at least one petal part (13), the slope protection of the petal part (13) is firstly constructed in the second construction step, and then the slope protection of the rest part is constructed.
5. The method for comprehensively constructing foundation pit support intersections of the existing building and the newly built building according to claim 1, wherein the method comprises the following steps: in the second step, the dewatering well (5) avoids the position right above the existing building facilities, a reverse circulation well is adopted, a sand-free concrete water filtering pipe is put into the whole hole in the well, a layer of nylon net is wrapped on the outer side of the sand-free concrete water filtering pipe, a filter material is backfilled in the sand-free concrete water filtering pipe, and the wellhead of the dewatering well (5) is sealed by clay to prevent surface water from flowing in.
6. The method for comprehensively constructing foundation pit support intersections of the existing building and the newly built building according to claim 1, wherein the method comprises the following steps: in the third step, the original position earth backfill is two-stage backfill, the backfill (6) comprises a first-stage backfill (61) and a second-stage backfill (62), the top height position of the first-stage backfill is 4m below the ground surface position, the part of the backfill is the first-stage backfill (61), the top height position of the second-stage backfill is the ground surface position, the part of the backfill is the second-stage backfill (62), the maximum height of the second-stage backfill (62) is 5.9m,
Backfilling the two sides of the new underground diaphragm wall (2) to the first-stage backfill top elevation position within the range of 8m respectively, and backfilling the other ranges to the second-stage backfill top elevation position, wherein the two-stage backfill soil is connected by adopting a 1:0.3 slope; wherein, the secondary backfill soil (62) in the range of 8m inside the new underground diaphragm wall (2) partially covers the rear dismantling structure (12) inside the wall for carrying out force connection.
7. The method for comprehensively constructing foundation pit support intersections of the existing building and the newly built building according to claim 6, wherein the method comprises the following steps: and thirdly, cement is doped into backfill soil (6) within the range of 2m at the two sides of the new underground diaphragm wall (2) to form a reinforced cement soil layer (7), and the reinforced cement soil layer (7) is a stressed soil layer for constructing the new underground diaphragm wall (2) formed after the strength of the backfill soil (6) is improved.
8. The method for comprehensively constructing foundation pit support intersections of the existing building and the newly built building according to claim 7, wherein the method comprises the following steps: before the construction of the third backfill, the optimal cement mixing amount of the backfill soil needs to be determined, and the determination steps are as follows:
step a, taking a soil sample of site backfill soil to perform compaction test on the filling material, and obtaining the optimal water content and the maximum dry density of the original soil sample;
B, performing geotechnical tests of the soil samples under the condition of mixing amounts of 0%, 4%, 7% and 9% of four mass ratios, and controlling the dry densities of the soil samples with different cement mixing amounts to be the maximum dry density of the original soil samples;
step c, drawing a change condition diagram of a cement doping amount soil sample and each physical and mechanical index, wherein the physical and mechanical indexes comprise compression modulus, cohesion and internal friction angle;
and d, according to a physical and mechanical index change condition diagram, along with the increase of the cement doping amount, the improvement of the mechanical property of the soil body is nonlinear increase, the increase speed is gradually flattened, and 7% of the cement doping amount is selected as the optimal cement doping amount for backfilling.
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| CN109680678A (en) * | 2018-12-27 | 2019-04-26 | 广州市住宅建设发展有限公司 | Diaphram wall meets the low disturbance forming construction method thereof of old supporting construction |
| CN110486019A (en) * | 2019-07-22 | 2019-11-22 | 上海建工一建集团有限公司 | The excavating construction method in subterranean communication road is added between new and old building |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109680678A (en) * | 2018-12-27 | 2019-04-26 | 广州市住宅建设发展有限公司 | Diaphram wall meets the low disturbance forming construction method thereof of old supporting construction |
| CN110486019A (en) * | 2019-07-22 | 2019-11-22 | 上海建工一建集团有限公司 | The excavating construction method in subterranean communication road is added between new and old building |
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