A kind of grid encloses the anti-liquefied foundation reinforcement means of hoop
The invention belongs to building field, it is applied to the ground anti-liquefying treatment of the engineering field building such as building construction, municipal administration, water conservancy and hydropower, petroleum and petrochemical industry, road and rail, specifically a kind of solve thick-layer saturated sand and silt foundation produces liquefaction under seismic loading, intensity be close to completely lose and cause the subsidence of foundations, side direction expand or slide a kind of new method for processing foundation.
According to the mechanism that foundation soil liquefaction produces, being used for the specific practice of building foundation liquefaction injury survey mainly contains two kinds of thinkings:
(1) liquefying soil soil property is improved: by strengthening to the improvement of liquefying soil grogs, raising compactness, cementation solidifying, reduction saturation ratio the ability that liquefaction resisted early stage by foundation soil.
(2) ess-strain condition is improved: by reducing water level, setting up catch pit, supercharging, the measure dissipation hole pressure such as to seal, improve effective stress, stop hole Hair Fixer exhibition, suppressing shear strain, thus control the increase accumulation of hole water stress and the increase of shearing strain, the large deformation that restriction post liquefaction produces.
When liquefaction soil layers more smooth and evenly time, by current specifications, corresponding ground anti-liquefaction measure can be selected to carry out the depression of all or part of elimination foundation liquefaction according to building the provide fortification against earthquakes grade of liquefaction of classification and ground of (structure) thing.Anti-liquefied foundation reinforcement means conventional at present mainly contains following several:
(1) excavate to change and fill out or densification: liquefying soil is excavated and is replaced into non-liquefying soil or densification.
(2) enciphered method: adopt punching of shaking, vibration encryption, compacted effect, strong rammer or blasting procedure to carry out deep layer encryption, to improve sand and silt relative compaction.
(3) other method for processing foundation: suppress shear strain as agitation pile, high-pressure rotary jet grouting pile, CFG stake method etc. form reinforcement in ground, and soil around pile increases with consolidation intensity because of compacted, thus strengthen ground Anti-liquefying asility, and slip casting is solidified, is set the thickness etc. catch pit, surcharge preloading, reinforcement, increase being covered non-liquefaction soil layers.
(4) method is sealed: the generation together with building basis, foundation soil being surrounded restriction liquefaction large deformation by continuous piling wall structure.
(5) deep foundation: generally adopt pile foundation, penetrates liquefaction soil layers, and stake end stretches into the following steady soil of liquefaction depth.
Below often kind for the treatment of measures have its scope of application, advantage and deficiency, steel sheet pile and diaphragm wall etc. is often adopted to seal at present as sealed method, when the mass-type foundation of employing large scale is (as raft foundation, case base, oil tank mass-type foundation) or liquefied foundation on have time ballast (as highway subgrade) and ground can be surrounded, the basis liquescent impact in outside is controlled, and limit ground beneath saturated sand and silt and produce sandblasting and emit water or lateral flow etc. to liquefy macroscopic appearance and cause foundation soil to be escaped running off, thus avoid ground to occur obvious depression, tilt, reach certain anti-liquefaction effect, but cost is relatively high, when sealing area and being larger, the center that seals still there will be higher excess pore water pressure, the shrinkage strain of cutting that geological process produces also be can not ignore, the situation of inapplicable employing bar base or single footing, ground integral rigidity is not high yet, to the lateral displacement limited use that the gentle slope territorial restrictions liquefaction closing on riverbank etc. produces.
Summary of the invention
A kind of cement-soil grid is the object of the present invention is to provide to enclose hoop anti-liquefaction ground reinforcement means, it makes cement-soil pile by the technique such as deep-layer stirring, high-pressure rotary-spray and seals foundation soil under basis in ground, and utilizes cement earth pile can cut splicing processes construction flexible combination to become the feature of various cell structure to arrange cement-soil pile in length and breadth with certain reasonably spacing in district and form grid to the ground fortifield village hoop sealed in district sealing.Ground is divided into several grids closed by cement-soil grid piling wall, the bulk strength of ground and rigidity are improved significantly, cement fortifield village hoop piling wall has shared the shear stress that most seismic load produces simultaneously, also stronger restriction is had to foundation deformation, saturated sand and silt excess pore water pressure in grid are effectively suppressed, thus plays good anti-liquefaction; Supporting capacity and the slide ability of ground can be strengthened on the other hand.When needing, also can enclose hoop grid in catch pit is set, form drainage system dissipation hole with the mattress layer of tool water filtering function and press, stop hole Hair Fixer exhibition.
This method can be widely used in in the ground anti-liquefying treatment of bearing capacity of foundation soil and all higher building of settlement request on thick-layer liquefiable saturated sand and silt foundation, particularly to the bulk strength of ground and rigidity requirement is higher, antagonism liquefaction side direction extended capability require strong and surrounding edge environment to construction noise require tight (as conventional enciphered method construction noise and vibration large) and be positioned at the ground of building in the area, gentle slope closing on riverbank etc.
For reaching above object, the technical solution adopted in the present invention is:
A kind of grid encloses the anti-liquefied foundation reinforcement means of hoop, comprising:
(1) in ground, make cement-soil pile seal the following foundation soil in basis, and seal in district arrange in length and breadth cement-soil pile formed grid ground fortifield village is bound round, ground is divided into the grid that several are closed, to improve bulk strength and the rigidity of ground, reach the object suppressing pore water pressure to rise.
(2) cement-soil pile can select the technique of deep-layer stirring, high-pressure rotary-spray to adopt cutting splicing processes (or with Small Distance arrangement) construction to make, thick 0.5 ~ the 2.5m of piling wall body of wall, can be solid shape or grid-like, when adopting cell structure, replacement ratio is generally not less than 0.7; Its Specific construction technique and parameter can design by current specifications according to geological conditions and construction equipment.
(3) the grid-like anti-liquefaction of cement-soil pile is enclosed cuff structure and can only be arranged within the scope of basic plane; To large scale mass-type foundation (as raft foundation, case base, oil tank mass-type foundation), grid encloses hoop body of wall and can be arranged symmetrically with in grid under the foundation, single footing grid encloses hoop body of wall and can arrange under mast axis, and enclosing hoop body of wall to strip foundation grid can arrange under strip foundation wall; Grid lattice area desirable 100 ~ 250m when seismic fortification intensity is 7 degree
2, desirable 60 ~ 150m when 8 degree
2.Cement-soil pile grille plane is arranged also should in conjunction with building superstructure feature and to ground bearing capacity, determine the method calculating design that the requirement of the anti-extended capability of side direction advise by current specifications.
(4), when all eliminating foundation liquefaction depression, cement-soil pile extends the following steady soil of liquefaction depth; When part eliminates foundation liquefaction depression, the foundation liquefaction index below the cement-soil pile degree of depth should not be greater than 5, and to single footing and strip foundation, the cement-soil pile degree of depth still should not be less than the higher value of liquefying soil depths of features and foundation width under foundation bed.The cement-soil pile degree of depth also should be determined according to the requirement of superstructure to ground bearing capacity, and should penetrate soft layer to reaching the relatively high soil layer of bearing capacity.When be positioned at gentle slope area time, piling wall stretch into liquefaction depth following steady soil length should by national earthquake resistant code carry out slide checking computations determine.
(5) after adopting grid to enclose the design of hoop anti-liquefying treatment, when Bearing Capacity of Composite Foundation and distortion do not meet design requirement, can in conjunction with conventional basement process in lattice district, method for processing foundation can adopt Deep Mixing Method, high-pressure rotary spraying method, Sand Pile Method, CFG method, settlement Control compound scattering pile method etc.
(6) grid encloses the anti-liquefaction reinforced composite ground of hoop and should arrange under the foundation and be not less than the thick medium sand of 20cm or coarse sand or graded sand and stone mattress layer, and concrete thickness is determined according to wall soil relative rigidity.When foundation liquefaction layer is between permeability lower level, when design needs, also can enclose in hoop grid at grid and catch pit is set, catch pit blossom type or arranged in squares, spacing 1.5 ~ 4.0m, in order to improve anti-liquefaction effect, catch pit must punch under easy liquidized layer and basis between the soil layer of all poor permeability, and form drainage system dissipation hole with the mattress layer of tool water filtering function and press, stop hole Hair Fixer exhibition.
(7) method for designing principle of the present invention:
First anti-liquefaction Design is carried out according to the provide fortification against earthquakes grade of liquefaction of classification and ground of place seismic fortification intensity, building by technique scheme, and determine that cement-soil grid encloses hoop piling wall layout pattern, grid area, reinforcement depth, piling wall thickness and unit tectonic type in conjunction with the interaction of superstructure feature, basis and ground, select suitable curing compound and additive ratio, construction technology, construction technical requirement, and routinely composite foundation method checking computations grid enclose hoop anti-liquefied foundation bearing capacity and distortion whether meet design requirement.
When adopting large scale mass-type foundation, grid encloses the anti-liquefaction Bearing Capacity of Composite Foundation characteristic value of hoop and should determine according to load test and regional experience.
During preliminary design, Bearing Capacity of Composite Foundation characteristic value f
spkestimate by following formula: f
sk.In above formula: ζ is bearing power increase coefficient, generally gets 1.1 ~ 2.0, the desirable low value when the native mud for normal consolidation of substrate and mucky soil, stream mould soft plasticviscosity soil, Saturated loess soil, plain fill; The desirable high level when substrate soil is silt, sand, gravelly soil, plastic hard plastic cohesive soil or replacement ratio height; f
skfor natural foundation bearing capacity characteristic value.Have regulation in " Code for design of building " (GB-50007-2012), composite foundation distortion can calculate by the pertinent regulations of current specifications to be determined.
When employing bar base and single footing, when arranging piling wall under wall or under mast axis, the modulus of compressibility enclosing the anti-liquefaction Bearing Capacity of Composite Foundation characteristic value of hoop and composite earth layer can calculate by current specifications to be determined.
When being positioned at area, gentle slope, composite foundation still should carry out slide checking computations, takes anti-soil body slip measure.
When grid enclose the checking computations of hoop anti-liquefaction composite foundation treatment cannot meet bearing capacity or settlement request time, can in conjunction with conventional basement process in grid, processing method can adopt Deep Mixing Method, high-pressure rotary spraying method, Sand Pile Method, CFG method, settlement Control compound scattering pile method etc.
Composite foundation arranges under the foundation and is not less than the thick mattress layer of 20cm, and its material can select medium sand, coarse sand, graded sand and stone etc.When foundation liquefaction layer is between permeability lower level, when design needs, also catch pit can be set in grid, catch pit blossom type or arranged in squares, spacing 1.5 ~ 4.0m.
(8) anti-liquefied foundation reinforcement means implementation step of the present invention comprises:
1, data collection, comprises the bad border situation etc. in place detailed geotechnical investigation data, superstructure and basic design information, regional basement process experience and execution conditions, place.
2, according to design basis type, load and instructions for use, in conjunction with sitework geological conditions, the method for processing foundation etc. that cement-soil grid encloses hoop piling wall layout pattern, grid area, reinforcement depth, piling wall thickness and unit tectonic type, combines is determined in design, select suitable curing compound and additive ratio, construction technology, specify construction technical requirement, draw working drawing.And carry out technical economic analysis and contrast with other method, reach the object of prioritization scheme.
3, before formal construction, representational place is carried out corresponding field trial or tentative construction, and carries out necessary test, with test design parameter and treatment effect.
4, when in grid during the process of combining encryption method, first basement process in construction grid, when combining basement process such as adopting cement earth pile method, CFG stake method, settlement Control compound scattering pile method in grid, can construct according to physical condition and anti-liquefaction cement-soil pile and synchronous interting carry out or can construct in two steps, sequence of construction can adjust according to actual conditions, and construction technical requirement and quality inspection are undertaken by current art standard and designing requirement.
5, Foundation Treatment complete after, during as being designed with vertical drainage system, then construction drainage well.Also first can to have constructed all or part of vertical drain well according to designing requirement.
6, last excavation pit is to design elevation, carries out top mattress layer construction, completes after construction detects and pays, carry out top foundation construction.
Owing to have employed such scheme, the present invention has following characteristics: reinforcement mechanism is clear and definite, and applicability is strong, the scope of application is wide, and anti-liquefaction effect is remarkable, reaches the object eliminated foundation liquefaction depression, suppress side direction expansion or slide, and few on the impact of bad border, construction experience is ripe, and cost is relatively economized.
Accompanying drawing explanation
Fig. 1 is that the anti-liquefied foundation of the embodiment of the present invention one reinforces layout schematic diagram;
Fig. 2 is the generalized section of embodiment one in Fig. 1;
Fig. 3 is the cement-soil pile unit tectonic type of embodiment one in Fig. 1;
Fig. 4 is that the anti-liquefied foundation of the embodiment of the present invention two reinforces layout schematic diagram;
Fig. 5 is that the anti-liquefied foundation of the embodiment of the present invention three reinforces layout schematic diagram;
Fig. 6 is the generalized section of embodiment three in Fig. 5.
In figure: 1--cement-soil pile 2--cement earth pile 3--commonly uses vertical reinforcement 4--large scale mass-type foundation 5--mattress layer 6--liquefaction soil layers 7--non-liquefaction steady soil 8--bar base.
Detailed description of the invention
Below in conjunction with accompanying drawing illustrated embodiment, the present invention is further illustrated:
Fig. 1 ~ Fig. 6 is that grid of the present invention encloses hoop method anti-liquefied foundation Scheme of Strengthening design diagram.When specific design is implemented, according to foundation pattern and other engineering specifications, can different cement-soil pile grid layout patterns be adopted by mentality of designing of the present invention or combine with other and carry out basement process design.
The arrangement of Fig. 1 can be adopted raft foundation, case base, oil tank mass-type foundation cement-soil pile grid, be arranged symmetrically with in grid; The arrangement of Fig. 4 can be adopted single footing cement-soil pile grid, arrange under mast axis; The arrangement of Fig. 5 can be adopted strip foundation cement-soil pile grid, arrange under strip foundation wall.
Embodiment one: see Fig. 1, Fig. 2, Fig. 3, place is positioned at area, gentle slope, earth grade about 12 °, and basis is large scale mass-type foundation 4(raft foundation), cement-soil pile 1 is arranged symmetrically with the grid being separated into by ground and closing one by one 4 times on basis in grid; Cement-soil pile 1 adopts grid construction as shown in Figure 2, adopts cutting splicing processes to construct make by cement earth pile 2; Cement-soil pile 1 stretches into the following steady soil 7 of liquefaction depth through liquefaction soil layers 6; In lattice in conjunction with conventional method for processing foundation to improve anti-liquefaction Bearing Capacity of Composite Foundation and to reduce sedimentation and deformation, conventional vertical reinforcement 3 is by arranged in squares; Composite foundation is arranged the graded sand and stone mattress layer 5 that 30cm is thick.
Embodiment two: see Fig. 4, basis is single footing, arranges under cement-soil pile 1 mast axis, ground is separated into the grid closed one by one; Carry out basement process according to a conventional method under single footing, Bearing Capacity of Composite Foundation and sedimentation and deformation are met design requirement, and unifies with cement-soil pile 1, improve bulk strength and the rigidity of ground.
Embodiment three: see Fig. 5, Fig. 6, basis is strip foundation 8, and cement-soil pile 1 is arranged under strip foundation wall, takes the construction of cutting splicing processes, ground is separated into the grid closed one by one; Under bar base, composite foundation is arranged the thick broken stone cushion layer 5 of 30cm.
Certain engineering is the complex building on beach, nearly Fenhe River, Taiyuan City, high 10 floor in building, frame construction, and design adopts raft lamination foundation, higher to ground requirement for bearing capacity, more responsive to sedimentation and deformation.Place is positioned at area, gentle slope, earth grade about 12 °, and seismic fortification intensity is 8 degree, and foundation liquefaction grade is serious, and foundation soil forms distribution situation and is: top is saturated sand and silt, and the sense of silt sand is strong, loose ~ slightly close, thickness 7.5 ~ 10.0m; Bottom is silty clay, cobble, clay and medium coarse sand, and cohesive soil plastic state is close in sand; Another surrounding enviroment to vibration and noise requirements tight, vibration enciphered method should not be taked to carry out anti-liquefying treatment.
In this engineering, the emphasis of basement process eliminates foundation liquefaction depression, limit lateral expansion or slides, and improves bearing capacity of foundation soil on the other hand, reduce sedimentation and deformation, make foundation settlement deformation meet the average settlement amount of complex building and integral inclined requirement.
For reaching above-mentioned processing intent well, avoid producing large impact to surrounding enviroment, through designing and calculating such as anti-liquefaction, bearing capacity and settlement distortion and slide checking computations, this engineering adopts grid to enclose the anti-liquefaction consolidation process of hoop method, and in conjunction with conventional basement process in grid.Concrete implementation step is as follows:
(1) cement-soil pile grid symmetry is arranged in quadrangle, and grid size is 10m × 9.6m, only arranges in raft foundation planar range; Cement earth pile wall thickness 1300mm, takes cutting splicing processes to construct by three row's cement earth piles and makes, lap width 100mm, in grid-like structure, and the replacement ratio 0.899 of cement-soil; Cement earth pile adopts deep mixing method, wet construction, stake footpath 500mm, every meter of water mixing mud 50kg; Cement-soil pile dark 12.5, stake end stretches into the following steady soil of liquefaction depth through liquefaction soil layers and is no less than 2.5m.
(2) cement-soil mixing pile process is carried out in grid area, to meet the requirement of complex building antagonism liquefaction Bearing Capacity of Composite Foundation and sedimentation and deformation, cement-soil mixing pile stake footpath 500mm, pile spacing 1.2m, by arranged in squares, every meter of water mixing mud 55kg, composite foundation is arranged the graded sand and stone mattress layer that 30cm is thick.
(3) Farm Planning, agitation pile synchronous construction in anti-liquefaction cement-soil pile and grid, construction technical requirement and quality inspection are undertaken by current art standard and designing requirement.
(4) excavation pit is to design elevation, carries out top mattress layer construction, detects qualified rear payment, carries out top foundation construction.
The mechanism that the present invention produces according to liquefaction, the method of being enclosed hoop ground by cement-soil pile grid improves foundation soil ess-strain condition, reach dissipation hole pressure, improve effective stress, stop hole Hair Fixer exhibition, suppress shear strain object, thus control the increase accumulation of hole water stress and the increase of shearing strain, the large deformation that restriction post liquefaction produces.Anti-liquefaction reinforcement mechanism is clear and definite, and applicability is strong, simultaneously can with other method for processing foundation conbined usage, play respective advantage, make effect better, the scope of application is wider.
Above-mentioned is can understand and apply the invention for the ease of those skilled in the art to the description of embodiment.Person skilled in the art obviously easily can make various amendment to these embodiments, and General Principle described herein is applied in other embodiments without performing creative labour.Therefore, the invention is not restricted to embodiment here, those skilled in the art are according to announcement of the present invention, and the improvement make the present invention and amendment all should within protection scope of the present invention.