CN105672378A - Foundation pit excavation model testing device simulating lifting of artesian head - Google Patents
Foundation pit excavation model testing device simulating lifting of artesian head Download PDFInfo
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- CN105672378A CN105672378A CN201610205917.4A CN201610205917A CN105672378A CN 105672378 A CN105672378 A CN 105672378A CN 201610205917 A CN201610205917 A CN 201610205917A CN 105672378 A CN105672378 A CN 105672378A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
Abstract
The invention discloses a foundation pit excavation model testing device simulating lifting of an artesian head. The foundation pit excavation module testing device comprises a model box, a pressure-bearing superterranean layer, symmetrical surface soil baffle units, a foundation pit support structure, an artesian head adjustment system and a measurement system; the model box consists of a model box framework, tempered glass, a model box bottom plate, a reaction plate, a top frame and a model box base; the bottom of the model box is provided with the pressure-bearing superterranean layer which is connected with the artesian head adjustment system; the symmetrical surface soil baffle units are fixed on the model box framework through bolts; and the artesian head adjustment system consists of a water manometer, a Mariotte flask and a support. The foundation pit excavation model testing device can simulate lifting of the artesian head in a foundation pit excavation process, measures the water and soil pressure and deformation of the foundation pit under different artesian heads, and sorts relevant testing data and determines the foundation pit stress, the deformation development rule and the like; effective testing data support is provided for foundation pit problem research caused by the lifting of the artesian head; and a basis is provided for a subsequent theory analysis model.
Description
Technical field
The present invention relates to a kind of excavation models testing apparatus, particularly relate to the excavation of foundation pit model test apparatus under pressure-bearing head jacking conditions, when can be used for simulation pressure-bearing head lifting pressure bearing layer and on cover the interaction between weak water-permeable soil mass of foundation pit, the water and soil pressure response of Ji Keng and problem on deformation under the different pressure-bearing head of research.
Background technology
In strand, riparian area rich groundwater, engineering often faces below aquitard at the bottom of Deep Foundation Pit and remains the situation at pressure bearing layer, owing to the seasonal variation etc. of seasonal drought, river or lake level line will cause the raw lifting of the piestic water hair of pressure bearing layer, thus affect base hole water and soil pressure further, one of material risk source that distortion and stability, the foundation pit deformation that piestic water effect causes and destabilization problems are such area deep-foundation pit engineering.
Adopting set soil constitutive model compared to the research of economics analysis method and finite element numerical method, choosing of calculating parameter is had very big dependency by the soil mass water earth pressure that the pressure-bearing change of water level calculated causes and distortion size; The more difficult water and soil pressure Real-Time Monitoring carrying out being cheated by Ji Keng the end (being positioned at excavation of foundation pit region) in actual engineering, carries out engineering monitoring data statistic analysis similar in a large number and is also difficult to realization with the method for the deformation rule of aquitard at the bottom of the hole that obtains pressure-bearing change of water level and cause; In view of geotechnical model test under Chang Chongli, do not affect soil body microtexture, between soil particle size and soil particle, interaction relationship is consistent with practical situation, the interaction between piestic water and hole end aquitard soil particle can be objectively responded, it is widely used in considering the microexamination of resistance to shear of soil strain relation.
At present, the relevant geotechnical model test research of traditional piestic water effect, does not consider that in water, gas enters the unsaturated soil problem tested the soil body and may cause; Consider the excavation models test of constant phreatic table effect, have research (Peng Shuquan. sand barricade failure mechanisms grand thin sight research [D]. Tongji University, 2007.) film is adopted to connect retaining wall and mold box by smearing the method for epoxy resin after corona, the method can obtain excess pore water pressure, earth pressure and foundation pit deformation data in the test soil body, but film corona technique is comparatively complicated, when lateral diaphragm wall displacement is bigger, film may be torn in moving process or cause breakage due to soil particle friction, cannot complete test smoothly or carry out revision test.Consider the excavation models test of WATER LEVEL CHANGES impact, have research (Sun Wei. the strand area test of deep basal pit proterties and theoretical investigation [D]. Zhejiang University, 2015.) method of fixed stop cob wall is adopted, the method can only obtain the changing conditions of excess pore water pressure in the soil body, earth pressure change accurately and foundation pit deformation data cannot be obtained, still there is larger difference with the response condition of actual base pit engineering under pressure-bearing head lift action.
In excavation models is tested, great majority research completes the hole of the base under operating mode force and deformation situation for every one-level excavation and propping and launches, and does not consider the force and deformation situation of Ji Keng Ji Keng in excavation or propping process. in the model trial considering Excavation Process, research is had to adopt native bag (the AzevedoRF.CentrifugeandAnalyticalModellingofExcavationin Sand.PhDthesis of the weight such as unloading equal-volume, UniversityofColorado, Boulder, CO, USA, 1983.) or discharge generation soil liquid (BoltonMDandPowrieW.Thecollapseofdiaphragmwallsretainingc lay.G é otechnique, 1987, 37 (3): 335-353.) the method simulation soil excavation unloading such as, this type of method can not the change of stress field in the soil body that causes of accurate simulation excavation of foundation pit, still there is certain difference in the base hole force and deformation situation caused with actual excavation of foundation pit. the model trial employing pre-plugged of a large amount of simulating excavation installs the method for the retaining wall of support, the direct excavation pit soil body, do not need to carry out again propping operation, the method is comparatively simple, but preset all inner supports all will be subject to power in whole digging process, obviously cheat stressing conditions with the base of actual engineering not to be consistent, also cannot the force and deformation situation of Ji Keng in non-propping situation in accurate simulation Excavation Process. the method having research to adopt whisky jack to apply power to retaining wall support at present simulates the installation supported, and the method adopts hydraulic efficiency plant more complicated, and when excavation of foundation pit width is bigger, the method is not suitable for. the excavation plane of symmetry of most excavation of foundation pit model is vertical fixing baffle plate in addition, realizes excavation of foundation pit by grabbing soil or soil digging downwards, and the method can not excavate soil layer by clear definition, the soil body that meeting disturbance is not excavated, the method is loaded down with trivial details, not easily operates, and when particularly the size of the excavation of foundation pit model soil body that is relatively big or needs excavation is more, the workload of test operation is quite big. therefore, how realizing accurately soil excavation and support installation is the emphasis problem needing in excavation of foundation pit model trial to solve.
Summary of the invention
In order to overcome above-mentioned the deficiencies in the prior art, the present invention provides the excavation of foundation pit model test apparatus of simulation pressure-bearing head lifting, solve the simulation problem of pressure-bearing head lifting in test, can simulate pressure-bearing head lifting time pressure bearing layer and on cover the interaction between weak water-permeable soil mass of foundation pit, measure water and soil pressure and the distortion of Ji Keng under different pressure-bearing head, arrange correlation test data and the problem such as the force and deformation rule of development of Ji Keng under determining pressure-bearing head lifting, the base hole Study on Problems caused for the lifting of pressure-bearing head provides effective testing data support, and be the foundation of theoretical analysis model offer afterwards.
The technical solution adopted for the present invention to solve the technical problems is: a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting, comprises mold box, pressure-bearing Stilt layer, some planes of symmetry gear soil unit, foundation pit supporting construction, pressure-bearing head regulation system and measurement system six parts;Described mold box is made up of mold box framework, toughened glass, mold box base plate, top frame, reaction plate and mold box base; The bottom fixed mould molding box base plate of described mold box framework, toughened glass is fixed in former and later two sides; Described mold box framework and reaction plate are all fixed on mold box base, and top is connected by top frame; The bottom right side of described mold box installs the valve being connected pressure-bearing Stilt layer, for connection mode molding box and pressure-bearing head regulation system;
Described pressure-bearing Stilt layer is made up of the stainless steel plate in band water flowing hole, stainless steel short column and anti-filter geotextile; Fix stainless steel short column bottom the stainless steel plate in described band water flowing hole, it is positioned on the mold box base plate in mold box, and is tightly connected with mold box framework, toughened glass; Anti-filter geotextile is pasted on the stainless steel plate surface in described band water flowing hole, prevents the loss testing the soil body in pressure-bearing head change procedure;
Described plane of symmetry gear soil unit is U-shaped stainless steel strip, is bolted on mold box framework; Being connected by H type watertight rubber bar between described U-shaped stainless steel strip, U-shaped stainless steel strip is connected by S type watertight rubber bar with mold box framework;
Described foundation pit supporting construction comprises retaining wall, retaining wall support and some support unit; Described retaining wall top is by support standing bolt fixed stop cob wall support, and middle part has threaded hole, the support standing bolt being threaded and being installed by threaded hole and support needed for unit, the fixing watertight rubber bar of both sides fluting; Described watertight rubber bar ensures not leak with mold box contact surface in retaining wall moving process; One end of described support unit has inner thread mouth, and inner thread mouth is threaded with support standing bolt, it is achieved support the installation of unit;
Described pressure-bearing head regulation system is made up of hydraulic gage, Marriot bottle and support; Described hydraulic gage is by Y-tube connection mode molding box and Marriot bottle; Fixed pulley is installed on the top of described support, and wireline one end connects hand-operated device, and the other end is walked around fixed pulley and connected Marriot bottle, is controlled the size of the lift adjustment pressure-bearing head of Marriot bottle by hand-operated device; Described Marriot bottle is made up of plexiglass cylinder, air intake valve, water flowing valve, the gentle capsule of valve of giving vent to anger; Arranging air intake valve and water flowing valve bottom described plexiglass cylinder, top sets out air valve; Described air intake valve is connected with air bag;
Described measurement system comprises miniature pore water pressure sensor, miniature earth pressure cell, displacement sensor, multi-channel data acquisition instrument and digital photographing machine; Described miniature pore water pressure sensor, miniature earth pressure cell, displacement sensor are by signal transmission line connecting multi-channel data collecting instrument; Described digital photographing machine is positioned over mold box right on.
Further, described support unit comprises solid aluminum bar, expansion link and support and connection bolt; Having some grooves on described solid aluminum bar, one end has inner thread mouth; Described expansion link is hollow aluminum pipe, and expansion link has some threaded holes; The threaded hole of described support and connection bolt on expansion link supports the groove of solid aluminum bar.
Further, described support unit comprises the first support bar, the 2nd support bar and sleeve; One end of described first support bar has outside screw; One end of described 2nd support bar has inner thread mouth, and the other end has outside screw; Described sleeve has internal thread passage, and one end is threaded the first support bar, and the other end is threaded the 2nd support bar.
Further, exclusive PCR answered by described digital photographing machine in process of the test, and its position can not be moved; Can need to set up light source according to shooting.
Further, described mold box framework is welded by the thick stainless steel steel bar of 10mm and stainless-steel sheet; Described toughened glass is arranged on inside mold box framework by building glue; Described mold box base plate and reaction plate are the stainless-steel sheet that 10mm is thick; Described top frame is welded by the stainless steel steel bar that 20mm is thick; Described mold box main body and reaction plate are fixed on mold box base by surrounding spot welding; Described retaining wall is aluminium sheet, and its thickness is obtained by the retaining wall Rigidity Calculation of test simulation; Described retaining wall support is the strip aluminium sheet that 20mm is thick; Described retaining wall keeps vertical with toughened glass all the time in moving process; Described valve, air intake valve, water flowing valve, valve of giving vent to anger are copper core valve.
Further, the diameter of the wall thickness of the diameter of described solid aluminum bar, expansion link, the first support bar, the diameter of the 2nd support bar and the wall thickness of sleeve obtain by the Rigidity Calculation of the inner support of test simulation.
Further, described air bag is built with the nitrogen of 1atm.
Further, the bottom test soil body in mold box is gravel sand, to simulate pressure-bearing soil layer; On cover test the soil body be the weak water-permeable soil body, adopt air free water saturated.
Further, the described weak water-permeable soil body is cement powder soil.
Further, described plexiglass cylinder is built with air free water.
Further, described hand-operated device has from lock function.
Compared with prior art, the invention has the beneficial effects as follows:
1, the present invention adopts the saturated test soil body of air free water before the test, process of the test provides without gas piestic water environment, the hole testing the soil body is made to be full of air free water, as above operation has 2 benefits: one is avoid underwater bubble to enter unsaturation problem (compared with saturated soil, the mechanical characteristic of unsaturated soil exists larger difference and uncertainty) that weak water-permeable soil layer causes the soil body; Two is avoid underwater bubble to disturb miniature pore water pressure sensor to affect its measuring accuracy.
2, the pressure-bearing Stilt layer in the present invention can realize on the one hand from bottom to top the test soil body in abundant saturated model case, is conducive to gas purging in the test soil body; It is connected the pressure-bearing head of pressure-bearing head regulation system to provide pressure-bearing gravel layer different on the other hand, close with the mode of occurence of natural piestic water; Pressure-bearing gravel layer with on cover weak water-permeable soil layer directly contact by pressure bearing layer in objective simulation pressure-bearing head lifting process and on cover the interaction between weak water-permeable soil layer, be conducive to further disclose pressure-bearing head lifting cause soil mass of foundation pit water and soil pressure response and soil mass of foundation pit deformation rule; Research experiment under normal gravity condition, does not affect the microtexture of soil mass of foundation pit so that between soil particle size and soil particle, interaction relationship is consistent with practical situation, is conducive to carrying out the microexamination relating between soil particle and interacting.
3, the present invention adopts dismountable plane of symmetry gear soil unit, the soil body that interim gear passive zone of pit does not excavate, plane of symmetry gear soil unit can be removed in advance before the every layer soil body of excavation, excavation of foundation pit is carried out by unloading native method to the excavation of foundation pit plane of symmetry, compare the method that downward soil digging is fetched earth with tradition, the present invention can specify each layer of excavation soil layer not to be affected and not to excavate, easy to operate, greatly reduces the workload that excavation of foundation pit unloads soil.
4, the present invention can simultaneously simulating excavation and propping operation, obtain excavation of foundation pit and support the change of base hole stress field caused in installation process, compare to test with tradition excavation models and only consider that the specific state that excavation of foundation pit completes to a certain degree of depth or propping carries out research, more comprehensively, accurately reflect excavation of foundation pit and support Ji Keng in installation process being subject to the response condition of power and foundation pit deformation; The soil body that Ji Keng can not do not excavated by the present invention in inner support installation process has disturbing influence; It is connected by being screwed between inner support with retaining wall, than the test of traditional excavation models, inner support frame is located on retaining wall or directly supports the method that retaining wall realizes propping, more can reflect propping situation when actual base pit engineering excavates objectively; Realized the simulation of internal support of foundation pit rigidity by the wall thickness of control solid aluminum bar diameter, expansion link wall thickness, the first support bar diameter, the 2nd support bar diameter and sleeve, reflecting inner support more objectively affects the engineering of excavation of foundation pit; Can according to the demand of geotechnical model test, the quantity of adjustment inner support element, and the position of inner support standing bolt on retaining wall and quantity, the excavation situation of the different Ji Keng of simulation.
5, the present invention adopts retractable supports element, the excavation of foundation pit test of different in width can be simulated, compare and adopt with traditional excavation of foundation pit model trial the support of regular length or retractable supports only to support, for realizing, the experimental considerations installed, same set of testing apparatus can be adopted to carry out the excavation of foundation pit test of many group different in width, decreasing the repacking to testing apparatus, saved experimentation cost and Modelling time, principle of work is simple, easy to operate, there is very big practicality.
6, the present invention adopts the Marriot bottle of improvement, by the air pressure inside and outside the nitrogen balance Marriot bottle in air bag, nitrogen is utilized to be insoluble in the characteristic of water, for the test soil body is built without gas piestic water environment, the soil body unsaturated soil problem that the bubble being dissolved in water when effectively avoiding conventional Marriot bottle to supply water causes; Utilize the pressure-bearing head pressure that the height from lock function fixing Marriot bottle of hand-operated device ensures to provide stable; Hydraulic gage connection mode molding box and pressure-bearing head regulation system, can accurately read the size of the pressure-bearing head pressure of applying.
Accompanying drawing explanation
The excavation of foundation pit model test apparatus side-view of the simulation pressure-bearing head lifting that Fig. 1 (a) supports for adopting the first kind.
The excavation of foundation pit model test apparatus side-view of the simulation pressure-bearing head lifting that Fig. 1 (b) supports for adopting the 2nd class.
The mold box vertical view that Fig. 2 (a) supports for adopting the first kind.
The mold box vertical view that Fig. 2 (b) supports for adopting the 2nd class.
Fig. 3 is excavation of foundation pit plane of symmetry schematic diagram.
Fig. 4 (a) is the orthographic plan of pressure-bearing Stilt layer structure.
Fig. 4 (b) is the side-view of pressure-bearing Stilt layer structure.
Fig. 5 is retaining wall schematic diagram.
The foundation pit supporting construction schematic diagram that Fig. 6 (a) supports for the first kind.
Fig. 6 (b) is the foundation pit supporting construction schematic diagram that the 2nd class supports.
In figure: mold box 1; Mold box framework 1-1; Toughened glass 1-2; Mold box base plate 1-3; Top frame 1-4; Reaction plate 1-5; Mold box base 1-6; Pressure-bearing Stilt layer 2; Stainless steel plate 2-1 with water flowing hole; Stainless steel short column 2-2; Anti-filter geotextile 2-3; Plane of symmetry gear soil unit 3; The bolt 4 of fixed symmetrical face gear soil unit; Retaining wall 5; Watertight rubber bar 5-1;Retaining wall support 6; Support standing bolt 7; Support unit 8; Solid aluminum bar 8-1; Hollow aluminum bar 8-2; Support and connection bolt 8-3; First support bar 8-4; 2nd support bar 8-5; Sleeve 8-6; Support standing bolt 8-7; Valve 9; Gravel sand 10-1; Cement powder soil 10-2; Hydraulic gage 11; Marriot bottle 12; Plexiglass cylinder 12-1; Air intake valve 12-2; Water flowing valve 12-3; Give vent to anger valve 12-4; Air bag 12-5; Support 13; Fixed pulley 13-1; Wireline 13-2; Hand-operated device 13-3; Air free water 14.
Embodiment
Below in conjunction with drawings and Examples, the present invention is further described.
As shown in Figure 1 and Figure 2, the present invention simulates the excavation of foundation pit model test apparatus of pressure-bearing head lifting, comprises mold box 1, pressure-bearing Stilt layer 2, some planes of symmetry gear soil unit 3, foundation pit supporting construction, pressure-bearing head regulation system and measurement system six parts.
Described mold box 1 is made up of mold box framework 1-1, toughened glass 1-2, mold box base plate 1-3, top frame 1-4, reaction plate 1-5 and mold box base 1-6; The bottom fixed mould molding box base plate 1-3 of described mold box framework 1-1, toughened glass 1-2 is fixed in former and later two sides; Described mold box framework 1-1 and reaction plate 1-5 is fixed on the mold box base 1-6 that joist steel is welded by surrounding spot welding, and top is connected by surrounding spot welding by stainless steel top frame 1-4; Described mold box framework 1-1 is welded by the thick stainless steel steel bar of 10mm and stainless-steel sheet; Described toughened glass 1-2 is arranged on inside mold box framework 1-1 by building glue; Described mold box base plate 1-3 and reaction plate 1-5 is the stainless-steel sheet that 10mm is thick; Described top frame 1-4 is welded by the stainless steel steel bar that 20mm is thick;
Described pressure-bearing Stilt layer 2 is made up of the stainless steel plate 2-1 in band water flowing hole, stainless steel short column 2-2 and anti-filter geotextile 2-3; Fix stainless steel short column 2-2 bottom the stainless steel plate 2-1 in described band water flowing hole, it is positioned on the mold box base plate 1-3 in mold box 1, and is tightly connected with mold box framework 1-1, toughened glass 1-2; Anti-filter geotextile 2-3 is pasted on the stainless steel plate 2-1 surface in described band water flowing hole, prevents the loss testing the soil body in pressure-bearing head change procedure;
Described plane of symmetry gear soil unit 3 is U-shaped stainless steel strip, is fixed on mold box framework 1-1 by bolt 4; Being connected by H type watertight rubber bar between described U-shaped stainless steel strip, U-shaped stainless steel strip is connected by S type watertight rubber bar with mold box framework 1-1;
Described foundation pit supporting construction comprises retaining wall 5, retaining wall support 6 and some support unit 8; Described retaining wall 3 keeps vertical with toughened glass 1-2 all the time in moving process; One end of described support unit 8 has inner thread mouth, and inner thread mouth is threaded with support standing bolt 8-7, it is achieved support the installation of unit 8;
The bottom right side of described mold box 1 installs the valve 9 being connected pressure-bearing Stilt layer 2, for connection mode molding box 1 and pressure-bearing head regulation system; The bottom test soil body in mold box 1 is gravel sand 10-1, to simulate pressure-bearing soil layer; On cover test the soil body be the weak water-permeable soil body, can adopt cement powder soil 10-2, adopt air free water saturated;
Described pressure-bearing head regulation system is made up of hydraulic gage 11, Marriot bottle 12 and support 13; Described hydraulic gage 11 is by Y-tube connection mode molding box 1 and Marriot bottle 12; Fixed pulley 13-1 is installed on the top of described support 13, and wireline 13-2 one end connects hand-operated device 13-3, and the other end is walked around fixed pulley 13-1 and connected Marriot bottle 12, is controlled the size of the lift adjustment pressure-bearing head of Marriot bottle 12 by hand-operated device 13-3;Described Marriot bottle 12 is made up of plexiglass cylinder 12-1, air intake valve 12-2, water flowing valve 12-3, the valve 12-4 and air bag 12-5 that gives vent to anger; Arranging air intake valve 12-2 and water flowing valve 12-3 bottom described plexiglass cylinder 12-1, top sets out air valve 12-4; Described air intake valve 12-2 is connected with air bag 12-5; Described air bag 12-5 is built with the nitrogen of 1atm; Described valve 9, air intake valve 12-2, water flowing valve 12-3, the valve 12-4 that gives vent to anger are copper core valve;
Described measurement system comprises miniature pore water pressure sensor, miniature earth pressure cell, displacement sensor, multi-channel data acquisition instrument and digital photographing machine; Described miniature pore water pressure sensor, miniature earth pressure cell, displacement sensor are by signal transmission line connecting multi-channel data collecting instrument; Described digital photographing machine is positioned over mold box right on, can need to set up light source according to shooting; Exclusive PCR answered by described digital photographing machine in process of the test, and its position can not be moved;
As shown in Figure 3, the thickness of described plane of symmetry gear soil unit 3 is 10mm, and the spoil layer thickness that its width can be simulated as required adjusts; The bolt 4 of described fixed symmetrical face gear soil unit 3 is of a size of M8, is fixedly welded on mold box framework 1-1.
As shown in Fig. 4 (a), Fig. 4 (b), the stainless steel plate 2-1 in described band water flowing hole makes the air free water in pressure-bearing Stilt layer 2 and gravel sand 10-1 pressure bearing layer hydraulic communication, it is provided that the pressure-bearing head pressure of gravel sand 10-1 pressure bearing layer; The arrangement of the thickness of stainless steel plate 2-1 in described band water flowing hole, the arrangement in water flowing hole and stainless steel short column 2-2 should meet Force Calculation requirement so that pressure-bearing Stilt layer 2 is enough to bear the weight of the test soil body.
As shown in Figure 5, described retaining wall 5 is aluminium sheet, and its thickness is obtained by the retaining wall Rigidity Calculation of test simulation; Described retaining wall support 6 is the strip aluminium sheet that 20mm is thick; Described retaining wall 5 top is by support standing bolt 7 fixed stop cob wall support 6, and middle part has threaded hole, the support standing bolt 8-7 being threaded and being installed by threaded hole and support needed for unit 8, the fixing watertight rubber bar 5-1 of both sides fluting; Described watertight rubber bar 5-1 ensures not leak with mold box 1 contact surface in retaining wall 5 moving process; Described support standing bolt 7 and support standing bolt 8-7 are of a size of M8.
As shown in Fig. 6 (a), Fig. 6 (b), described support standing bolt 8-7, by the threaded hole on retaining wall 5, tightens and is fixed on retaining wall 5. Described support unit 8 can adopt following two kinds of forms:
One, described support unit 8 comprises solid aluminum bar 8-1, expansion link 8-2 and support and connection bolt 8-3; Having some grooves on described solid aluminum bar 8-1, one end has inner thread mouth; Described expansion link 8-2 is hollow aluminum pipe, and expansion link 8-2 has some threaded holes; The threaded hole of described support and connection bolt 8-3 on expansion link 8-2 supports the groove of solid aluminum bar 8-1 so that solid aluminum bar 8-1 and expansion link 8-2 compact siro spinning technology, does not slide in process of the test. The diameter of described solid aluminum bar 8-1 and the thickness of hollow aluminum bar 8-2 are calculated by the support stiffness of test simulation; The size of described support and connection bolt 8-3 can select M6.
Two, described support unit 8 comprises the first support bar 8-4, the 2nd support bar 8-5 and sleeve 8-6; One end of described first support bar 8-4 has outside screw; One end of described 2nd support bar 8-5 has inner thread mouth, and the other end has outside screw; Described sleeve 8-6 has internal thread passage, and one end is threaded the first support bar 8-4, and the other end is threaded the 2nd support bar 8-5.The diameter of described first support bar 8-4, the diameter of the 2nd support bar 8-5 and the wall thickness of sleeve 8-6 are obtained by the Rigidity Calculation of the inner support of test simulation.
The working process of the present invention is as follows: first retaining wall 5 and retaining wall support 6 are assembled by support standing bolt 7; Then installing earth pressure cell on retaining wall 5, both sides notch embeds watertight rubber bar 5-1, and smears epoxy resin in the gap of notch and watertight rubber bar 5-1; The retaining wall 5 assembled is erected in mold box 1 by retaining wall support 6, ensures that retaining wall 5 is vertical with the toughened glass 1-2 of mold box 1 both sides; Plane of symmetry gear soil unit 3 is installed at the plane of symmetry place of excavation of foundation pit model, is fixed on mold box framework 1-1 by the bolt 4 of fixed symmetrical face gear soil unit; In mold box 1, layering filling gravel sand 10-1 tamps, and fills to appointment height; Layering filling cement powder soil 10-2 compacting, until having banketed, being led to air free water saturated test soil body gravel sand 10-1 and cement powder soil 10-2, treating that the soil body closes water flowing valve 9 after completely saturated by water flowing valve 9 with the speed of 50L/ days to mold box 1; Pore water pressure sensor is buried in boring underground, the backfill boring soil body; At retaining wall 5 and base hole inside and outside soil body surface installation position displacement sensor, monitor displacement and the soil mass of foundation pit distortion situation of retaining wall 5 respectively;
Opening water flowing valve 12-3 and the valve 12-4 that gives vent to anger, inject air free water 14 by water flowing valve 12-3 in the plexiglass cylinder 12-1 of Marriot bottle 12, by giving vent to anger, valve 12-4 discharges the gas in plexiglass cylinder 12-1; Treat to fill air free water in plexiglass cylinder 12-1, close water flowing valve 12-3 and the valve 12-4 that gives vent to anger; The air bag 12-5 that 1atm nitrogen is housed is connected by air intake valve 12-2; Then by water flowing valve 9 connection mode molding box 1 and pressure-bearing head regulation system.
Digital photographing machine being placed in mold box right on (cannot move in process of the test), regulates camera parameter, the automatic shooting timed interval arranging digital photographing machine is 20s; If laboratory insufficient light, Led light source can be set up in digital photographing machine both sides; Utilize the reading of miniature pore water pressure sensor under data collecting instrument acquisition and recording test original state, miniature earth pressure cell and displacement sensor, utilize the test soil body photo under digital photographing machine shooting test original state; Open water flowing valve 9, water flowing valve 12-3 and air intake valve 12-2, and it is held open state in whole soil mass of foundation pit excavation and support installation process; Regulated the height of Marriot bottle 12 by hand-operated device 13-3, utilize the height from lock function fixing Marriot bottle 12 of hand-operated device 13-3, read pressure-bearing head size by hydraulic gage 11.
After treating that above-mentioned test preparation work completes, remove first segment plane of symmetry gear soil unit, slowly excavate the soil body on the left of retaining wall 5 by unloading native method to the excavation of foundation pit plane of symmetry; When being excavated to below first supported design position, installing first and support, be connected with the support standing bolt 8-7 on retaining wall 5 by supporting the internal thread of 8 one end, the length being supported 8 by adjustment makes it to hold out against counter-force frame 1-5, completes the installation supporting 8. Complete to continue after first supports installation the excavation soil body, adopt identical method to install and support, until excavation of foundation pit completes. In whole excavation of foundation pit process of the test, apply the corresponding pressure-bearing head of each operating mode of excavation of foundation pit by pressure-bearing head regulation system;By the reading of miniature pore water pressure sensor, miniature earth pressure cell and displacement sensor in data collecting instrument continuous acquisition record process of the test, take, by triggering digital photographic camera, the photo testing soil deformation in whole process of the test.
By the reading of the miniature pore water pressure sensor of analytical data Acquisition Instrument acquisition and recording and miniature earth pressure cell, show that the water and soil pressure response pattern that in whole digging process, the lifting of pressure-bearing head causes cheated by base; By the reading of the displacement sensor of analytical data Acquisition Instrument record, and the photo captured by digital photographic camera is carried out PIV image analysis, draw the displacement field of the soil body, thus learn the deformation rule of soil mass of foundation pit with pressure-bearing head lifting.
Claims (10)
1. simulate the excavation of foundation pit model test apparatus of pressure-bearing head lifting for one kind, it is characterized in that, comprise mold box (1), pressure-bearing Stilt layer (2), some planes of symmetry gear soil unit (3), foundation pit supporting construction, pressure-bearing head regulation system and measurement system six parts; Described mold box (1) is made up of mold box framework (1-1), toughened glass (1-2), mold box base plate (1-3), top frame (1-4), reaction plate (1-5) and mold box base (1-6); Bottom fixed mould molding box base plate (1-3) of described mold box framework (1-1), toughened glass (1-2) is fixed in former and later two sides; Described mold box framework (1-1) and reaction plate (1-5) are all fixed on mold box base (1-6), and top is connected by top frame (1-4); The bottom right side of described mold box (1) installs the valve (9) being connected pressure-bearing Stilt layer (2), for connection mode molding box (1) and pressure-bearing head regulation system;
Described pressure-bearing Stilt layer (2) is made up of the stainless steel plate (2-1) in band water flowing hole, stainless steel short column (2-2) and anti-filter geotextile (2-3); The fixing stainless steel short column (2-2) in stainless steel plate (2-1) bottom in described band water flowing hole, it is positioned on the mold box base plate (1-3) in mold box (1), and it is tightly connected with mold box framework (1-1), toughened glass (1-2); Anti-filter geotextile (2-3) is pasted on stainless steel plate (2-1) surface in described band water flowing hole, prevents the loss testing the soil body in pressure-bearing head change procedure;
Described plane of symmetry gear soil unit (3) is U-shaped stainless steel strip, is fixed on mold box framework (1-1) by bolt (4); Being connected by H type watertight rubber bar between described U-shaped stainless steel strip, U-shaped stainless steel strip is connected by S type watertight rubber bar with mold box framework (1-1);
Described foundation pit supporting construction comprises retaining wall (5), retaining wall support (6) and some support unit (8); Described retaining wall (5) top is by support standing bolt (7) fixed stop cob wall support (6), middle part has threaded hole, the support standing bolt (8-7) being threaded and installing by threaded hole and support needed for unit (8), the fixing watertight rubber bar (5-1) of both sides fluting; Described watertight rubber bar (5-1) ensures not leak with mold box (1) contact surface in retaining wall (5) moving process; One end of described support unit (8) has inner thread mouth, and inner thread mouth is threaded with support standing bolt (8-7), it is achieved support the installation of unit (8);
Described pressure-bearing head regulation system is made up of hydraulic gage (11), Marriot bottle (12) and support (13); Described hydraulic gage (11) is by Y-tube connection mode molding box (1) and Marriot bottle (12); Fixed pulley (13-1) is installed on the top of described support (13), wireline (13-2) one end connects hand-operated device (13-3), the other end is walked around fixed pulley (13-1) and is connected Marriot bottle (12), is controlled the size of the lift adjustment pressure-bearing head of Marriot bottle (12) by hand-operated device (13-3);Described Marriot bottle (12) is made up of plexiglass cylinder (12-1), air intake valve (12-2), water flowing valve (12-3), valve of giving vent to anger (12-4) and air bag (12-5); Described plexiglass cylinder (12-1) bottom arranges air intake valve (12-2) and water flowing valve (12-3), and top sets out air valve (12-4); Described air intake valve (12-2) is connected with air bag (12-5);
Described measurement system comprises miniature pore water pressure sensor, miniature earth pressure cell, displacement sensor, multi-channel data acquisition instrument and digital photographing machine; Described miniature pore water pressure sensor, miniature earth pressure cell, displacement sensor are by signal transmission line connecting multi-channel data collecting instrument; Described digital photographing machine is positioned over mold box right on.
2. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 1, it is characterized in that, described support unit (8) comprises solid aluminum bar (8-1), expansion link (8-2) and support and connection bolt (8-3); Having some grooves on described solid aluminum bar (8-1), one end has inner thread mouth; Described expansion link (8-2) is hollow aluminum pipe, and expansion link (8-2) has some threaded holes; Described support and connection bolt (8-3) supports the groove of solid aluminum bar (8-1) through the threaded hole on expansion link (8-2).
3. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 1, it is characterized in that, described support unit (8) comprises the first support bar (8-4), the 2nd support bar (8-5) and sleeve (8-6); One end of described first support bar (8-4) has outside screw; One end of described 2nd support bar (8-5) has inner thread mouth, and the other end has outside screw; Described sleeve (8-6) has internal thread passage, and one end is threaded the first support bar (8-4), and the other end is threaded the 2nd support bar (8-5).
4. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 1, it is characterised in that, exclusive PCR answered by described digital photographing machine in process of the test, and its position can not be moved; Can need to set up light source according to shooting.
5. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 1, it is characterised in that, described mold box framework (1-1) is welded by the thick stainless steel steel bar of 10mm and stainless-steel sheet; Described toughened glass (1-2) is arranged on mold box framework (1-1) inner side by building glue; Described mold box base plate (1-3) and reaction plate (1-4) are the thick stainless-steel sheet of 10mm; Described top frame (1-5) is welded by the stainless steel steel bar that 20mm is thick; Described mold box main body and reaction plate (1-4) are fixed on mold box base (1-6) by surrounding spot welding; Described retaining wall (5) is aluminium sheet, and its thickness is obtained by the retaining wall Rigidity Calculation of test simulation; Described retaining wall support (6) is the thick strip aluminium sheet of 20mm; Described retaining wall (5) keeps vertical with toughened glass (1-2) all the time in moving process; Described valve (9), air intake valve (12-2), water flowing valve (12-3), valve of giving vent to anger (12-4) are copper core valve.
6. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 1, it is characterized in that, the diameter of the diameter of described solid aluminum bar (8-1), the wall thickness of expansion link (8-2), the first support bar (8-4), the diameter of the 2nd support bar (8-5) and the wall thickness of sleeve (8-6) obtain by the Rigidity Calculation of the inner support of test simulation.
7. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 1, it is characterised in that, described air bag (12-5) is built with the nitrogen of 1atm.
8. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 1, it is characterised in that, the bottom test soil body in mold box (1) is gravel sand (10-1), to simulate pressure-bearing soil layer; On cover test the soil body be the weak water-permeable soil body, adopt air free water saturated.
9. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 8, it is characterised in that, the described weak water-permeable soil body is cement powder soil (10-2).
10. a kind of excavation of foundation pit model test apparatus simulating pressure-bearing head lifting according to claim 1, it is characterised in that, described plexiglass cylinder (12-1) is built with air free water (14).
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