CN102787608A - Gravity type foundation pit supporting system under vacuum effect and construction method - Google Patents

Gravity type foundation pit supporting system under vacuum effect and construction method Download PDF

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Publication number
CN102787608A
CN102787608A CN2012102958139A CN201210295813A CN102787608A CN 102787608 A CN102787608 A CN 102787608A CN 2012102958139 A CN2012102958139 A CN 2012102958139A CN 201210295813 A CN201210295813 A CN 201210295813A CN 102787608 A CN102787608 A CN 102787608A
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hole
vertical
vacuum
domatic
vertical drainage
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CN102787608B (en
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刘远锋
刘敬
林葵
张尔伽
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China Civil Engineering Construction Corp
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China Civil Engineering Construction Corp
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Abstract

The invention discloses a gravity type foundation pit supporting system under a vacuum effect and a construction method. The system comprises a peripheral vertical sealed curtain, a pit top horizontal sealing layer, a transverse drainage body, a slope surface sealing layer, a slope bottom vertical sealed curtain, a pit top vertical drainage body and a slope surface vertical drainage body. The peripheral vertical sealed curtain is downward vertically installed from an outside boundary of a setting range of the pit top horizontal sealing layer; the pit top vertical drainage body is arranged in foundation soil of the setting range of the pit top horizontal sealing layer; the transverse drainage body is arranged on the surface of the foundation soil at a top end of the pit top vertical drainage body; the pit top horizontal sealing layer is formed on the surface of the transverse drainage body; the slope surface vertical drainage body is arranged in the foundation soil inside the pit top vertical drainage body; the slope surface sealing layer is formed on the slope surface vertical drainage body; the slope bottom vertical sealed curtain is formed in a slope foot of a pit bottom. In the gravity type foundation pit supporting system under the vacuum effect and the construction method provided by the invention, a side wall is not arranged to solidify a wall body and a curtain shielding body, a greater cutting depth requirement can be met, construction cost is low and construction period is shorter.

Description

Vacuum action gravity foundation pit supporting system and job practices
Technical field
The invention belongs to civil construction Base hole supporting technology field, particularly relate to a kind of vacuum action gravity foundation pit supporting system and job practices.
Background technology
A kind of vacuum curtain water stop and atmospheric pressure support deep pit digging method (hereinafter referred " vacuum curtain method ") are disclosed in the Chinese invention patent the 200810236142.3rd; This method is to utilize vacuum curtain to carry out sealing; And the performance atmospheric pressure be used for carrying out pattern foundation pit supporting structure, it is safer to construct, and need not the foundation ditch inner supporting structure; Need not the inside and outside precipitation well point of foundation ditch, have comparatively remarkable advantages at aspects such as safe and reliable, saving duration, saving investments.
The vacuum curtain method mainly may further comprise the steps:
The first step, carry out the leveling of the required place of excavation of foundation pit, around foundation ditch, plan the vacuum curtain zone, the zone that promptly will lay diaphragm seal;
Second step, in the soil body in vacuum curtain zone, squeeze into vertical drainage body according to the degree of depth of excavation of foundation pit, the degree of depth that said vertical drainage body is squeezed into is greater than the degree of depth of excavation of foundation pit; And carry out foundation ditch border body of wall and solidify construction, sidewall promptly is set on the foundation ditch boundary line solidifies body of wall;
Need based on actual conditions, can solidify wall outer side at foundation pit side-wall the window shade body is set, the setting of window shade body realizes through the method for solidifying wall outer side driven pile or on-the-spot pile, on-the-spot one-tenth wall at foundation pit side-wall.The window shade body can be single stake or wall, also can be multiline pile or wall.Whether the window shade body is set, and its type, layout and quantity when the window shade body is set, need to come comprehensive definite with formation condition according to the degree of depth of excavation of foundation pit;
The 3rd step, lay diaphragm seal in vacuum curtain zone, the border of said diaphragm seal is imbedded in the soil body, thereby forms vacuum curtain;
The 4th goes on foot, vacuum source is connected with vertical drainage body, and through the mode that vacuum source vacuumizes, the air pressure in the said vacuum curtain is descended;
The 5th step, when the negative pressure of vacuum in the vacuum curtain reach and remain on-40kPa~-85kPa after, in keeping vacuum curtain, carry out excavation of foundation pit under the prerequisite of vacuum, adopt the mode of stage excavation to carry out in the digging process; Behind the intact layer soil body of every excavation; Expose the new foundation ditch external boundary sidewall of a circle, carry out the vertical seal isolation processing, promptly on new hole external boundary sidewall, lay barrier film along this foundation ditch external boundary sidewall; This barrier film is connected with the diaphragm seal sealing that constitutes vacuum curtain; With atmospheric pressure balance lateral soil pressure, and then carry out next layer soil body excavation and this layer foundation ditch external boundary sidewall vertical seal isolation processing, finish until excavation;
The 6th goes on foot, carries out the construction of base plate of foundation pit and sidewall.
But there is following weak point in above-mentioned vacuum curtain method:
Though one of advantage of 1 this vacuum curtain method is uprightly to excavate, and need not to put the slope, opens amount of excavation thereby practiced thrift; And can reduce the taking of peripheral place, but upright excavation also becomes one of its limitation, because upright excavation can make the stability of hole wall reduce; Thereby the excavation of foundation pit degree of depth that makes this law use is restricted; Be that the excavation of foundation pit degree of depth surpasses after a certain value, the hole wall can't keep stable, and need keep the stability of hole wall by means of ancillary methods such as interior supports; And so just having lost the cost advantage of vacuum curtain method, the duration also can prolong greatly.
2, according to the narration of this patent document content; The setting and the foundation pit side-wall that main effect that sidewall solidifies body of wall is set is air water flow rate, assisted vacuum curtain and the foundation ditch SEQUENCING VERTICAL seal film of exterior domain in fixedly excavation of foundation pit boundary shape, the reduction foundation ditch border are built exterior sheathing, in particular cases can also play the effect of subduing few part foundation ditch lateral earth pressure.But be not difficult to find out that sidewall solidifies still fixing excavation of foundation pit boundary shape this point of the topmost effect of body of wall.Why the vacuum curtain method need be provided with sidewall curing body of wall fixes the excavation of foundation pit boundary shape, also is because way of its upright excavation causes.The natural soil body; Especially weak soil as being excavated into upright side slope, very easily occurs collapsing; At least be to occur the part easily to collapse; Sidewall is set to solidify body of wall be essential in order to prevent to cheat collapsing of wall, but will increase like this engineering quantity that sidewall solidifies body of wall is set, cost is unfavorable for reducing.
3, in some cases, the vacuum curtain method need be solidified wall outer side at sidewall the window shade body is set, and the setting of window shade body realizes through the method for solidifying wall outer side driven pile or on-the-spot pile, on-the-spot one-tenth wall at foundation pit side-wall.Purpose and the actual role that the window shade body is set is not described in this patent document; But through analyzing; The window shade body roughly has following two effects: the one, when the window shade body is the sealing body of wall; It can play the sealing function that auxiliary sidewall is solidified the body of wall and the vertical seal barrier film oppose side wall deep soil body, prevents that the vacuum pressure in the vacuum curtain from leaking; The 2nd, utilize the window shade body deeply to cheat the wedge action of end ground and the stability that self bending resistance, shear structure intensity directly strengthen the hole wall, promptly the hole wall is stablized the auxiliary effect of strengthening of playing.In this case, the window shade body is a kind of auxiliary strengthening measure, if take other measure, lets vacuum seal be guaranteed with the hole wall is stable, then the window shade body can be set, and the cost of this part engineering of window shade body is set with saving.
4, it is similar that the method for processing foundation of mode and traditional vacuum preloading of diaphragm seal is laid on vacuum curtain method hole top; The outer boundaries of diaphragm seal is that shallow embedding is simply gone in the soil body; Thereby be prone to make the vacuum pressure in the vacuum curtain to spread laterally; And the diffusion of vacuum pressure can reduce the vacuum in the curtain scope on the one hand; Thereby reduce the buckling safety factor of hole wall, can make on the one hand in addition that ground in the adjacent domain certain limit shrinks, cracking and depression, surrounding environment is caused harmful effect.And because this method sealing effect realizes that through the vacuum pumping action effect of precipitation can be arranged the ground of foundation ditch periphery in fact, when surrounding environment was responsive for ground precipitation, then this method was inapplicable.
Summary of the invention
In order to address the above problem, the object of the present invention is to provide a kind of sidewall that need not be provided with to solidify body of wall and window shade body, can satisfy the vacuum action gravity foundation pit supporting system that bigger cutting depth requires, cost is lower, the duration is shorter.
Another object of the present invention is to provide a kind of job practices of above-mentioned vacuum action gravity foundation pit supporting system.
In order to achieve the above object, vacuum action gravity foundation pit supporting system provided by the invention comprises peripheral vertical airtight curtain, the horizontal confined layer in top, hole, transverse row water body, domatic confined layer, the vertical airtight curtain in the end, slope, top, hole vertical drainage body and domatic vertical drainage body; Wherein peripheral vertical airtight curtain is that top horizontal confined layer is provided with the scope outer boundaries original ground is provided with downward vertically and forms from the top, hole from the hole; Top, hole vertical drainage body is that horizontal confined layer is provided with evenly setting in the foundation soil in the scope on the top, hole, and the bottom elevation of top, hole vertical drainage body is lower than the elevation on ground, the end, maximum dredging depth hole; The transverse row water body is arranged on the foundation soil surface on vertical drainage body top, top, hole; And inner horizontal is laid with the vacuum chimney filter of distributed in grid; The vacuum chimney filter passes the horizontal confined layer in top, hole through pipeline membrane device, is connected on the vacuum pump via outside vacuum-pumping pipeline; The horizontal confined layer in top, hole is to lay one or more layers geotextiles and one or more layers geomembrane on the surface of transverse row water body; Perhaps directly lay one or more layers composite geo-membrane and form; And outer ledge and peripheral vertical airtight curtain upper end are tightly connected, and the inboard is then imbedded underground through the sealing ditch; Domatic vertical drainage body is arranged in the inboard foundation soil of top, hole vertical drainage body, and its bottom elevation is identical with the bottom elevation of top, hole vertical drainage body, and the top elevation is then with domatic consistent when locating excavation; Domatic confined layer is to form from sealing ditch and tripping out and cover on the domatic vertical drainage body that newly sets being positioned at inboard geotextiles and geomembrane or composite geo-membrane on the top horizontal confined layer of hole; The vertical airtight curtain in the end, slope is that base slope pin place vertically sets a circle steel plate for sealing water stake and forms in the hole; Steel plate for sealing water stake upper end is tightly connected with the lower edge of domatic confined layer, and the top elevation of the vertical airtight curtain in the end, slope is higher than the elevation on ground, the end, maximum dredging depth hole.
The vertical airtight curtain in described periphery adopts vertical laying geomembrane, water jetting to make diaphragm wall, slotting becomes wall method, kerf to become wall method, catheter reverse circulation method, grab bucket method to become wall, vibration grooving method to become wall, sheet pile wall worker method to become wall, deep layer Beater operator method to become wall, slip casting method Cheng Qiang, high spray Fa Chengqiang, native fixed worker's method to become wall, self-solidifying mortar method to become wall, SMW worker's method to become wall to become a kind of method setting in the wall with TRD worker's method.
Described hole top vertical drainage body and domatic vertical drainage body are made up of a kind of in plastic draining board, sand wick and the plastic drain-pipe.
The sand cushion that described transverse row water body constitutes for the medium coarse sand by 0.4~0.6 meter thickness.
Be evenly distributed with filter opening on the described vacuum chimney filter tube wall, and external surface is coated with layer of non-woven fabric, the PVC filter pipe of vacuum chimney filter employing φ 50mm, chimney filter spacing 8m.
The upper end of described steel plate for sealing water stake has is convenient to the device that is tightly connected with domatic confined layer.
The job practices of vacuum action gravity foundation pit supporting system provided by the invention comprises the following step that carries out in order:
1) horizontal confined layer is provided with scope outer boundaries place and from cheating the top original ground peripheral vertical airtight curtain is set downward vertically on the top, hole;
2) horizontal confined layer is provided with top, hole vertical drainage body is set in the foundation soil in the scope on the top, hole, and the bottom elevation of top, hole vertical drainage body is lower than the elevation on ground, the end, maximum dredging depth hole;
3) on the foundation soil surface on the vertical drainage body top, top, hole that sets completion the transverse row water body is set, lays the vacuum chimney filter of distributed in grid in transverse row water body inner horizontal;
4) lay one or more layers geotextiles and one or more layers geomembrane on the surface of transverse row water body; Perhaps directly lay one or more layers composite geo-membrane; Form the horizontal confined layer in top, hole thus; And with being tightly connected on the vertical airtight curtain in its outer ledge and periphery, the inboard is then imbedded underground through the sealing ditch;
5) above-mentioned vacuum chimney filter is passed the horizontal confined layer in top, hole through pipeline membrane device, be connected on the vacuum pump via outside vacuum-pumping pipeline;
6) open vacuum pump treats that the foundation soil degree of consolidation of foundation pit side-wall reaches after 10%~80%, excavation pit under the condition that constantly vacuumizes;
7) whenever dig dark 1m; In the foundation soil of vertical drainage body inboard, top, hole, progressively carry out the construction of domatic vertical drainage body; Its spacing, arrangement are all identical with top, hole vertical drainage body; Domatic vertical drainage body bottom elevation is identical with the bottom elevation of top, hole vertical drainage body, and domatic vertical drainage body top elevation is then with domatic consistent when locating excavation;
8) will cheat and be positioned at inboard geotextiles and geomembrane or composite geo-membrane on the horizontal confined layer in top and trip out and cover on the domatic vertical drainage body that newly sets part, form the domatic confined layer of part thus, imbed the hole sealing ditch at the end then again from the sealing ditch;
9) repeating step 7) and 8), until the projected depth of excavating foundation ditch;
10) base slope pin place vertically sets a circle steel plate for sealing water stake in the hole; Form the vertical airtight curtain in the end, slope thus; And the steel plate for sealing water stake upper end lower edge with domatic confined layer is tightly connected, the top elevation of the vertical airtight curtain in the end, slope is higher than the elevation on ground, the end, maximum dredging depth hole;
11) build base plate of foundation pit, build the construction of under ground portion structure;
12) stop to vacuumize, remove the vertical airtight curtain in the end, slope, domatic confined layer, the hole horizontal confined layer in top and the peripheral vertical airtight curtain of part then, and to the in addition recycling of wherein steel plate for sealing water stake and geomembrane;
13) foundation soil is backfilling into the space between foundation pit walls and the building under ground portion structure, until reaching natural ground level, pattern foundation pit supporting structure and excavation work are so far all accomplished.
Traditional foundation pit supporting system is divided into cement soil deep agitation pile barricade formula, sheet pile formula (steel sheet pile, steel pipe pile etc.), campshed formula (bored pile, digging hole filling pile etc.), diaphragm wall, reinforced cement cob wall supporting (SMW worker's method), stability of slope formula (bolt-spary supports, plate brad supporting), the contrary types such as arch wall formula, open caisson (case) method of doing by its operating principle and material behavior.The supporting of cement soil deep agitation pile barricade formula belongs to gravity retaining wall, and it relies on weight of body of wall own and rigidity to keep off soil, keeps it and stablizes, and simultaneously again as water-stop curtain, has the double action of retaining soil and sealing.Vacuum action gravity foundation pit supporting system provided by the invention belongs to gravity retaining wall in essence, and body of wall has the double action of retaining soil and sealing.
Vacuum action gravity foundation pit supporting system provided by the invention belongs to the gravity retaining structure; Itself and the topmost difference of cement soil deep agitation pile barricade be that its method that adds vertical drainage body with vacuum reinforces the soil body in the scope of design of the wall outside, hole, replaced cement mixing method that the physical chemistry solidification of the soil body in the scope of design of the wall outside, hole is formed the gravity barricade.
Gravity retaining wall as all is the same; Hole wall gravity retaining wall in the vacuum action gravity foundation pit supporting system mainly need be resisted three types destruction; Be that antiskid moves destruction, the anti-shearing destruction in wall body cross section at the bottom of wall body overturning or slip resistance analysis destruction, the wall, but the composition in drag source that its opposing destroys is but different with the gravity retaining wall of common employing barnacle body, sheet stone concrete or concrete material.The drag source that its opposing destroys is formed as follows:
1, the overturning or slip resistance analysis of wall body destroys drag source composition:
Soil body deadweight and top, hole atmospheric pressure.
2, antiskid moves and destroys drag source composition:
The anti-shearing force of the substrate soil strength performance after effective stress obtains strengthening under the negative pressure of vacuum effect.
3, the anti-shearing destruction drag in wall body cross section source is formed:
The anti-shearing force that wall body cross section soil strength after effective stress obtains strengthening under the negative pressure of vacuum effect produces.
The present invention is through cheap vacuum consolidation draining effect; Make the intensity of slope soil self obtain than leap ahead; Generally can be in 2~3 months time the intensity of foundation soil be improved 2~3 times; Utilize simultaneously negative pressure of vacuum effect moment to improve the effective stress of the soil body fully, thereby greatly improve the intensity of foundation soil once again, and utilize vacuum to draw water to reach the dual purpose of sealing and stability of slope with domatic confined layer sealing function; Interior support can be set, and cost and speed of application all have remarkable advantages.Vacuum action gravity foundation pit supporting system provided by the invention has following advantage:
1, can supporting the foundation ditch of the heavy excavation degree of depth more.In theory; If do not consider the maximum of vertical drainage body the degree of depth is not set; As long as enough plane spaces are arranged on every side for arranging supporting and protection structure; The excavation of foundation pit degree of depth of vacuum action gravity foundation pit supporting system provided by the invention institute supporting can be unrestricted, because it can guarantee the stability of deep foundation ditch through putting the enough mild side slope in slope.Certainly, in the actual engineering, dark excessively foundation ditch, for example the degree of depth surpasses 50m, and is basically also unrealistic, because the excavation of foundation pit degree of depth is genuine so big, the mode of underground excavations such as employing shield structure should be more convenient and economical than open cut.
2, need not to be provided with sidewall and solidify body of wall, can reduce construction costs.Vacuum action gravity foundation pit supporting system provided by the invention; Because in conjunction with putting slope excavation; Itself relatively helps keeping homeostasis the shape of foundation pit side-wall, and the inside and outside foundation soil body of foundation ditch improved intensity by the vacuum consolidation effect, and the excavation of foundation pit border is that the shape of foundation pit side-wall is easy to be maintained; Solidify body of wall thereby need not to be provided with sidewall, reduced construction costs.
3, need not to solidify wall outer side the window shade body is set, can reduce construction costs at sidewall.Vacuum action gravity foundation pit supporting system provided by the invention; Because in conjunction with putting slope excavation; The buckling safety factor of foundation pit side-wall is very high, and the obturation effect of domatic confined layer is because be in favourable installation site, and obturation effect also is guaranteed; So need not to solidify wall outer side at sidewall again the window shade body is set, has further reduced construction costs.
4, owing to be provided with peripheral vertical airtight curtain, the diffusion of vacuum pressure is by big limitations.Can come to guarantee well to be provided with the vacuum in the vertical drainage body scope with the less power that vacuumizes so on the one hand; Thereby also guaranteed the stability and safety property of hole wall; On the one hand peripheral in addition vertical airtight curtain to the iris action of vacuum pressure avoided also that the adjacent domain ground shrinks, cracking and depression, the harmful effect of surrounding environment is reduced greatly.Equally, the present invention has also farthest been limited the precipitation effect of the ground of foundation ditch periphery, has further reduced the influence to surrounding environment.
5, the speed of application of set vertical drainage body among the present invention, laying horizontal rows water body and diaphragm seal etc. is all very fast; And, because need not to be provided with interior support, reduced the cost that supports the engineering time of this procedure in being provided with and practiced thrift interior support on the one hand; In addition on the one hand because the interference of supporting in the space of excavation, not having; The scope of operation is open, can also accelerate the speed of cutting the earth greatly, practices thrift the cost of cutting the earth; So the construction of vacuum action gravity foundation pit supporting system provided by the invention is very convenient, has also practiced thrift the valuable duration.
Because vacuum adds the relative cement mixing method of vertical drainage body, has tangible cost and duration advantage, so the relative cement soil deep agitation pile of vacuum action gravity foundation pit supporting system barricade support system has tangible cost and duration advantage.In addition; Because the present invention have can supporting more the heavy excavation degree of depth foundation ditch, need not to be provided with sidewall and solidify body of wall, need not to solidify wall outer side window shade body, the big limitations of peripheral vertical airtight curtain the have been set diffusion of vacuum pressure at sidewall; Therefore thereby advantages such as harmful effect have been reduced greatly, in technology with all be superior to prior art vacuum curtain method aspect economical two to surrounding environment.
Description of drawings
Fig. 1 is a vacuum action gravity foundation pit supporting system cross-sectional configuration sketch map provided by the invention.
Fig. 2 is a vacuum action gravity foundation pit supporting system floor map provided by the invention.
Among the figure:
Top, 1-hole original ground
The peripheral vertical airtight curtain of 2-
The horizontal confined layer in top, 3-hole
4-transverse row water body
The domatic confined layer of 5-
Ground, the end, 6-maximum dredging depth hole
The vertical airtight curtain in the 7-end, slope
Top, 8-hole vertical drainage body
The domatic vertical drainage body of 9-
The specific embodiment
Below in conjunction with accompanying drawing and embodiment vacuum action gravity foundation pit supporting system provided by the invention and job practices are elaborated.
Certain base pit engineering digs dark 20m, and the planar dimension of excavation is 20m * 150m.
The situation of three layers of foundation soil is respectively:
1. silty clay, 28 meters of thickness, grayish green, grey is to Dark grey, and stream is moulded soft moulding, and is saturated, is master's silty clay with glutinous grain with powder, contains 10% black organic matter and a large amount of solubility salt crystals.Natural unit weight γ=16.0kN/m 3, moisture content 61%, void ratio 1.6, index of plasticity I p=22.1, C u=10.0kPa, φ u=3.0 °, basic bearing capacity σ 0=80kPa, osmotic coefficient k≤1 * 10 -7M/s belongs to low-intensity, high-compressibility soil, and engineering properties is relatively poor.
2. opaque fine sand~medium sand, 7 meters of thickness, light brown to Dark grey, closely knit, wet, composition is the sand of particulate to middle grain.The classification of rock construction engineering belongs to the common soil of II level.Natural unit weight γ=18.0kN/m 3, moisture content 15%, void ratio 0.4, C u=5.0kPa, φ u=30.0 °, basic bearing capacity σ 0=180kPa, osmotic coefficient k≤1 * 10 -4M/s.
3. sandy gravel, thickness is greater than 10 meters, and dark-brown, closely knit particulate contain the solubility salt of adularescent to middle coarse grain sandy gravel.The classification of rock construction engineering belongs to the common soil of II level.Natural unit weight γ=22.0kN/m 3, void ratio 0.5, C u=0kPa, φ u=40.0 °, basic bearing capacity σ 0=300kPa, osmotic coefficient k≤1 * 10 -3M/s.
Like Fig. 1, shown in Figure 2, vacuum action gravity foundation pit supporting system provided by the invention comprises the vertical airtight curtain of the horizontal confined layer of peripheral vertical airtight curtain 2, top, hole 3, transverse row water body 4, domatic confined layer 5, the end, slope 7, hole top vertical drainage body 8 and domatic vertical drainage body 9; Wherein peripheral vertical airtight curtain 2 is that top horizontal confined layer 3 is provided with the scope outer boundaries original ground 1 is provided with downward vertically and forms from the top, hole from the hole; Top, hole vertical drainage body 8 is that horizontal confined layer 3 is provided with evenly setting in the foundation soil in the scope on the top, hole, and the bottom elevation of top, hole vertical drainage body 8 is lower than the elevation on ground, the end 6, maximum dredging depth hole; Transverse row water body 4 is arranged on the foundation soil surface on vertical drainage body 8 tops, top, hole; And inner horizontal is laid with the vacuum chimney filter of distributed in grid; The vacuum chimney filter passes the horizontal confined layer 3 in top, hole through pipeline membrane device, is connected on the vacuum pump via outside vacuum-pumping pipeline; The horizontal confined layer 3 in top, hole is to lay one or more layers geotextiles and one or more layers geomembrane on the surface of transverse row water body 4; Perhaps directly lay one or more layers composite geo-membrane and form; And outer ledge and peripheral vertical airtight curtain 2 upper ends are tightly connected, and the inboard is then imbedded underground through the sealing ditch; Domatic vertical drainage body 9 is arranged in the foundation soil of vertical drainage body 8 inboards, top, hole, and its bottom elevation is identical with the bottom elevation of top, hole vertical drainage body 8, and the top elevation is then with domatic consistent when locating excavation; Domatic confined layer 5 is to form from sealing ditch and tripping out and cover on the domatic vertical drainage body 9 that newly sets being positioned at inboard geotextiles and geomembrane or composite geo-membrane on the top horizontal confined layer 3 of hole; The vertical airtight curtain 7 in the end, slope is that base slope pin place vertically sets a circle steel plate for sealing water stake and forms in the hole; Steel plate for sealing water stake upper end is tightly connected with the lower edge of domatic confined layer 5, and the top elevation of the vertical airtight curtain 7 in the end, slope is higher than the elevation on ground, the end 6, maximum dredging depth hole.
The job practices of vacuum action gravity foundation pit supporting system provided by the invention comprises the following step that carries out in order:
1) top horizontal confined layer 3 is provided with scope outer boundaries place and adopts downwards and vertically lay that geomembrane, water jetting are made diaphragm wall, slotting becomes wall method, kerf to become wall method, catheter reverse circulation method, grab bucket method to become wall, vibration grooving method to become wall, sheet pile wall worker method to become wall, deep layer Beater operator method to become wall, slip casting method Cheng Qiang, high spray Fa Chengqiang, native fixed worker's method to become wall, self-solidifying mortar method to become wall, SMW worker's method to become wall to become a kind of method in the wall that peripheral vertical airtight curtain 2 is set with TRD worker's method from cheating top original ground 1 in the hole, and this engineering is that the method that adopts fluting to lay the dark composite geo-membrane of 10m is provided with peripheral vertical airtight curtain 2;
2) horizontal confined layer 3 is provided with top, hole vertical drainage body 8 evenly is set in the foundation soil in the scope on the top, hole; Hole top vertical drainage body 8 is made up of a kind of in plastic draining board, sand wick and the plastic drain-pipe, and the bottom elevation of top, hole vertical drainage body 8 is lower than the elevation on ground, the end 6, maximum dredging depth hole; Top, hole vertical drainage body 8 adopts plastic draining board in this engineering, and the degree of depth is 25m, and arranged in squares, spacing are 1m, and plastic draining board bottom elevation is lower than the elevation 5m on ground, the end 6, maximum dredging depth hole;
3) on the foundation soil surface on vertical drainage body 8 tops, top, hole that set completion transverse row water body 4 is set; Lay the vacuum chimney filter of distributed in grid in transverse row water body 4 inner horizontal; The sand cushion that transverse row water body 4 constitutes for the medium coarse sand by 0.4~0.6 meter thickness, this engineering are to lay the thick medium coarse sand bottom of one deck 0.3m sand mat of subgrade on the foundation soil surface on vertical drainage body 8 tops, top, hole earlier, and level is laid the vacuum chimney filter of distributed in grid on the bottom sand mat of subgrade then; Be evenly distributed with filter opening on the vacuum chimney filter tube wall; And external surface is coated with layer of non-woven fabric, can allow water, gas to get in the vacuum chimney filter like this, prevents that simultaneously sand grains from getting into the vacuum chimney filter; The vacuum chimney filter adopts the PVC filter pipe of φ 50mm, and chimney filter spacing 8m re-lays the thick medium coarse sand top layer of one deck 0.2m sand mat of subgrade then on vacuum chimney filter top, and constituting thickness by bottom sand mat of subgrade and top layer sand mat of subgrade is 0.5 meter transverse row water body 4;
4) lay one or more layers geotextiles and one or more layers geomembrane on the surface of transverse row water body 4; Perhaps directly lay one or more layers composite geo-membrane; Form the horizontal confined layer 3 in top, hole thus; And its outer ledge and peripheral vertical airtight curtain 2 upper ends are tightly connected, the inboard is then imbedded underground through the sealing ditch; The horizontal confined layer 3 in top, hole is the composite geo-membrane of 20m for one deck width in this engineering;
5) above-mentioned vacuum chimney filter is passed the horizontal confined layer 3 in top, hole through pipeline membrane device, be connected on the vacuum pump via outside vacuum-pumping pipeline; The way of pipeline membrane device is consistent with common vacuum prepressing ground foundation treatment method.Vacuum pump adopts jet pump, and separate unit power is 7.5kW, and vacuum pressure surpasses 96kPa under the no-load condition, and the area of plane of every vacuum pump reinforcing is not more than 800m 2, this engineering disposes 30 vacuum pumps altogether;
6) open vacuum pump treats that the foundation soil degree of consolidation of foundation pit side-wall reaches 10-80% excavation pit later on; Excavation carries out according to the gradient that designs; The excavation gradient is set at 1: 1 in this engineering; The controlling value of the foundation soil degree of consolidation before the excavation is main to be confirmed according to design excavation speed; Excavation speed is fast more, and then the requirement of the foundation soil degree of consolidation before the excavation is high more, and the foundation soil degree of consolidation before this engineering excavation is 30%;
7) whenever dig dark 1m; In the foundation soil of vertical drainage body 8 inboards, top, hole, progressively carry out the construction of domatic vertical drainage body 9; Its spacing, arrangement are all identical with top, hole vertical drainage body 8; Domatic vertical drainage body 9 bottom elevations are identical with the bottom elevation of top, hole vertical drainage body 8, and domatic vertical drainage body 9 top elevations are then with domatic consistent when locating excavation; Domatic vertical drainage body 9 adopts plastic draining board in this engineering, and the degree of depth is that 4.5m~23.5m does not wait, and arranged in squares, spacing are 1m;
8) will cheat and be positioned at inboard geotextiles on the horizontal confined layer 3 in top and trip out and cover on the domatic vertical drainage body 9 that newly sets part from the sealing ditch, form the domatic confined layer 5 of part thus, imbed the sealing ditch of cheating the end then again with geomembrane or composite geo-membrane;
9) repeating step 7) and 8), until the projected depth of excavating foundation ditch;
10) base slope pin place vertically sets a circle steel plate for sealing water stake in the hole; Form the vertical airtight curtain 7 in the end, slope thus; And the steel plate for sealing water stake upper end lower edge with domatic confined layer 5 is tightly connected; The top elevation of the vertical airtight curtain 7 in the end, slope is higher than the elevation on ground, the end 6, maximum dredging depth hole, and the upper end of steel plate for sealing water stake has and is convenient to the device that is tightly connected with domatic confined layer 5; The length of sealing steel sheet pile is 3m in this engineering, and the top elevation is than the high 0.5m of elevation on ground, the end 6, maximum dredging depth hole;
11) build base plate of foundation pit, build the construction of under ground portion structure;
12) stop to vacuumize, remove the vertical airtight curtain in the end, slope 7, domatic confined layer 5, the hole horizontal confined layer 3 in top and the peripheral vertical airtight curtain 2 of part then, and to the in addition recycling of wherein steel plate for sealing water stake and composite geo-membrane;
13) foundation soil is backfilling into the space between foundation pit walls and the building under ground portion structure, until reaching natural ground level, pattern foundation pit supporting structure and excavation work are so far all accomplished.
If this engineering adopts bored pile, collar tie beam and Guan Liang to add the interior supporting of supporting, the supporting scheme of cement mixing method and high-pressure rotary jet grouting pile sealing, total cost will be 4,080,000 yuan; 11 months durations; And adopt the cost of this programme to have only 2,300,000 yuan, 6 months durations, this shows that cost reduces by one times nearly; Duration shortens half simultaneously, so economic benefit very significantly.

Claims (7)

1. vacuum action gravity foundation pit supporting system is characterized in that: described vacuum action gravity foundation pit supporting system comprises peripheral vertical airtight curtain (2), top, hole horizontal confined layer (3), transverse row water body (4), domatic confined layer (5), the slope vertical airtight curtain in the end (7), hole top vertical drainage body (8) and domatic vertical drainage body (9); Wherein peripheral vertical airtight curtain (2) is from the hole horizontal confined layer in top (3) the scope outer boundaries to be set to be provided with downward vertically and to form from cheating top original ground (1); Hole top vertical drainage body (8) is to be provided with in the foundation soil in the scope at the hole horizontal confined layer in top (3) evenly to be provided with, and the bottom elevation of hole top vertical drainage body (8) is lower than the elevation on maximum dredging depth ground, the end, hole (6); Transverse row water body (4) is arranged on the foundation soil surface on top vertical drainage body (8) top, hole; And inner horizontal is laid with the vacuum chimney filter of distributed in grid; The vacuum chimney filter passes the hole horizontal confined layer in top (3) through pipeline membrane device, is connected on the vacuum pump via outside vacuum-pumping pipeline; The hole horizontal confined layer in top (3) is to lay one or more layers geotextiles and one or more layers geomembrane on the surface of transverse row water body (4); Perhaps directly lay one or more layers composite geo-membrane and form; And outer ledge and peripheral vertical airtight curtain (2) upper end are tightly connected, and the inboard is then imbedded underground through the sealing ditch; Domatic vertical drainage body (9) is arranged in the inboard foundation soil of hole top vertical drainage body (8), and its bottom elevation is identical with the bottom elevation of hole top vertical drainage body (8), and the top elevation is then with domatic consistent when locating excavation; Domatic confined layer (5) is to trip out and cover on the domatic vertical drainage body (9) that newly sets and form from the sealing ditch being positioned at inboard geotextiles and geomembrane or composite geo-membrane on the hole horizontal confined layer in top (3); The slope vertical airtight curtain in the end (7) is that base slope pin place vertically sets a circle steel plate for sealing water stake and forms in the hole; Steel plate for sealing water stake upper end is tightly connected with the lower edge of domatic confined layer (5), and the top elevation of the slope vertical airtight curtain in the end (7) is higher than the elevation on maximum dredging depth ground, the end, hole (6).
2. vacuum action gravity foundation pit supporting system according to claim 1 is characterized in that: the vertical airtight curtain in described periphery (2) adopts vertical laying geomembrane, water jetting to make diaphragm wall, slotting becomes wall method, kerf to become wall method, catheter reverse circulation method, grab bucket method to become wall, vibration grooving method to become wall, sheet pile wall worker method to become wall, deep layer Beater operator method to become wall, slip casting method Cheng Qiang, high spray Fa Chengqiang, native fixed worker's method to become wall, self-solidifying mortar method to become wall, SMW worker's method to become wall to become a kind of method setting in the wall with TRD worker's method.
3. vacuum action gravity foundation pit supporting system according to claim 1 is characterized in that: top, described hole vertical drainage body (8) and domatic vertical drainage body (9) are made up of a kind of in plastic draining board, sand wick and the plastic drain-pipe.
4. vacuum action gravity foundation pit supporting system according to claim 1 is characterized in that: the sand cushion that described transverse row water body (4) constitutes for the medium coarse sand by 0.4~0.6 meter thickness.
5. vacuum action gravity foundation pit supporting system according to claim 1; It is characterized in that: be evenly distributed with filter opening on the described vacuum chimney filter tube wall; And external surface is coated with layer of non-woven fabric, and the vacuum chimney filter adopts the PVC filter pipe of φ 50mm, chimney filter spacing 8m.
6. vacuum action gravity foundation pit supporting system according to claim 1 is characterized in that: the upper end of described steel plate for sealing water stake has is convenient to the device that is tightly connected with domatic confined layer (5).
7. the job practices of a vacuum action gravity foundation pit supporting system as claimed in claim 1, it is characterized in that: described job practices comprises the following step that carries out in order:
1) at the hole horizontal confined layer in top (3) scope outer boundaries place is set and peripheral vertical airtight curtain (2) is set downward vertically from cheating top original ground (1);
2) horizontal confined layer (3) is provided with hole top vertical drainage body (8) is set in the foundation soil scope on hole top, and the bottom elevation of hole top vertical drainage body (8) is lower than the elevation that maximum dredging depth is cheated ground, the end (6);
3) on the foundation soil surface on top, hole vertical drainage body (8) top that sets completion transverse row water body (4) is set, at the inner vacuum chimney filter of laying distributed in grid of transverse row water body (4);
4) lay one or more layers geotextiles and one or more layers geomembrane on the surface of transverse row water body (4); Perhaps directly lay one or more layers composite geo-membrane; Form top, hole horizontal confined layer (3) thus; And with being tightly connected on its outer ledge and the peripheral vertical airtight curtain (2), the inboard is then imbedded underground through the sealing ditch;
5) above-mentioned vacuum chimney filter is passed the hole horizontal confined layer in top (3) through pipeline membrane device, be connected on the vacuum pump via outside vacuum-pumping pipeline;
6) open vacuum pump treats that the foundation soil degree of consolidation of foundation pit side-wall reaches after 10%~80%, excavation pit under the condition that constantly vacuumizes;
7) whenever dig dark 1m; In the foundation soil of hole top vertical drainage body (8) inboard, progressively carry out the construction of domatic vertical drainage body (9); Its spacing, arrangement are all identical with hole top vertical drainage body (8); Domatic vertical drainage body (9) bottom elevation is identical with the bottom elevation of hole top vertical drainage body (8), and domatic vertical drainage body (9) top elevation is then with domatic consistent when locating excavation;
8) will cheat and be positioned at inboard geotextiles and geomembrane or composite geo-membrane on the top horizontal confined layer (3) and trip out and cover on the domatic vertical drainage body (9) that newly sets part from the sealing ditch; Form the domatic confined layer of part (5) thus, imbed the hole sealing ditch at the end then again;
9) repeating step 7) and 8), until the projected depth of excavating foundation ditch;
10) base slope pin place vertically sets a circle steel plate for sealing water stake in the hole; Form the slope vertical airtight curtain in the end (7) thus; And the steel plate for sealing water stake upper end lower edge with domatic confined layer (5) is tightly connected, the top elevation of the slope vertical airtight curtain in the end (7) is higher than the elevation on maximum dredging depth ground, the end, hole (6);
11) build base plate of foundation pit, build the construction of under ground portion structure;
12) stop to vacuumize, remove the slope vertical airtight curtain in the end (7), domatic confined layer (5), top, hole horizontal confined layer (3) and part periphery vertical airtight curtain (2) then, and to the in addition recycling of wherein steel plate for sealing water stake and geomembrane;
13) foundation soil is backfilling into the space between foundation pit walls and the building under ground portion structure, until reaching natural ground level, pattern foundation pit supporting structure and excavation work are so far all accomplished.
CN201210295813.9A 2012-08-17 2012-08-17 Gravity type foundation pit supporting system under vacuum effect and construction method Active CN102787608B (en)

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