CN106481343B - A kind of Soft Rock Tunnel Excavation and preliminary bracing method - Google Patents

A kind of Soft Rock Tunnel Excavation and preliminary bracing method Download PDF

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Publication number
CN106481343B
CN106481343B CN201611001276.7A CN201611001276A CN106481343B CN 106481343 B CN106481343 B CN 106481343B CN 201611001276 A CN201611001276 A CN 201611001276A CN 106481343 B CN106481343 B CN 106481343B
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tunnel
segment
rock
current
preliminary bracing
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CN201611001276.7A
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Chinese (zh)
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CN106481343A (en
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于远祥
陈宝平
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西安科技大学
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    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D9/00Tunnels or galleries, with or without linings; Methods or apparatus for making thereof; Layout of tunnels or galleries
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/003Linings or provisions thereon, specially adapted for traffic tunnels, e.g. with built-in cleaning devices
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04Lining with building materials
    • E21D11/10Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D11/00Lining tunnels, galleries or other underground cavities, e.g. large underground chambers; Linings therefor; Making such linings in situ, e.g. by assembling
    • E21D11/04Lining with building materials
    • E21D11/10Lining with building materials with concrete cast in situ; Shuttering also lost shutterings, e.g. made of blocks, of metal plates or other equipment adapted therefor
    • E21D11/107Reinforcing elements therefor; Holders for the reinforcing elements
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D20/00Setting anchoring-bolts
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21DSHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
    • E21D21/00Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
    • E21D21/0026Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection characterised by constructional features of the bolts

Abstract

The invention discloses a kind of Soft Rock Tunnel Excavation and preliminary bracing method, multiple segments is divided to be excavated to soft rock tunnel and preliminary bracing construction from the front to the back, any segment is excavated and when preliminary bracing is constructed, including step:First, country rock basic mechanical parameter determines;2nd, tunnel is reserved excavated volume and is determined:The reserved excavated volume of current segment of constructing is determined according to the country rock inward displacement theoretical value of soft rock tunnel after the completion of supporting;3rd, tunnel excavation;4th, Tunnel structure determination;5th, Tunnel is constructed;6th, next segment is excavated and preliminary bracing is constructed;7th, step 6 is repeated several times, until completing whole excavations of soft rock tunnel and preliminary bracing work progress.The method of the present invention step is simple, reasonable design and realization are convenient, using effect is good, and reserved excavated volume is determined according to the surrouding rock deformation situation of soft rock tunnel, and uses steel bracket with Bolt net and jet preliminary bracing respective outer side edges to tunnel progress tunneling boring preliminary bracing.

Description

A kind of Soft Rock Tunnel Excavation and preliminary bracing method
Technical field
The invention belongs to technical field of tunnel construction, more particularly, to a kind of Soft Rock Tunnel Excavation and preliminary bracing method.
Background technology
In recent years, it as highway in China, railway construction are developed by leaps and bounds, is carried out under great burying, large ground pressure soft Rock constructing tunnel becomes one of inexorable trend of field of traffic development, such as prominent domestic Nanning Kunming Railway Jiazuqing Tunnel, Wushao Ling Tunnel, Zhongnanshan Mountain Tunnel and mouth of a gorge tunnel etc..Since engineering geological condition is severe, self is poor, and soft rock tunnel becomes Shape is violent, if supporting not in time or scheme is unreasonable, country rock large deformation and the destruction of liner structure easily occurs.It is for this purpose, a large amount of Experts and scholars and field engineering technical staff have made intensive studies the construction and its support technology of soft rock tunnel.Li Xiao Red grade, according to the analytic solutions of tunnel surrounding rock displacement and live displacement monitoring, analyzes initial stage branch using Shi Long tunnels as engineering background Protect the influence to soft rock tunnel stability and displacement;Li Dan etc. will be with the corresponding physical model of Soft Rock Engineering support design method Large-scale real triaxial model test machine is placed in, has studied the method for protecting support of soft rock tunnel under model boundary the same terms;Li Hongbo etc. By on-the-spot test, mouth of a gorge high stressed soft rock Highway Tunnel Wall Rock deformation rule and the loading characteristic of structure are analyzed, it is proposed that The design of its support countermeasure of high stressed soft rock serious deformation;Zhang Dehua etc. analyzes shape steel bracket and grid steel frame in high-ground stress Supporting mechanism and its adaptability in soft rock tunnel explore the mechanical response process of supporting construction under the conditions of different-stiffness;King Tree benevolence etc. analyzes the deformation mechanical mechanism of Wuqiaoling tunnel country rock, it is proposed that the soft layer support technology of firm gap;The analyses such as Chen Weizhong Foam concrete absorbs soft rock tunnel deformation energy and improves the stressed effect of secondary liner structure;Tian Hongming etc. optimizes Yichang To the fracture morphology and its supporting scheme in the east of Sichuan mouth of a gorge high ground stress soft rock stress tunnel;Yang Jianhui etc. has inquired into anchor pole based on finite element And influence of the steelframe to Analyses of Tunnel Wall Rock Stability.
In conclusion although achieving more achievement in research currently for soft rock tunnel surrouding rock deformation and support technology, And emphasize to need to reserve the deflection of 80mm~120mm in related specifications between supporting and secondary lining in the early stage, to avoid Tunnel is caused to invade limit after soft-rock slope.In fact, for the large deformation soft rock tunnel under the conditions of specific geology, even specification institute The 120mm upper limits deformation allowance of permission can not meet the requirement of soft rock continuous deformation after preliminary bracing, and country rock strain energy is not It can fully be discharged, eventually lead to steel arch-shelf destruction and wall rock destabilization.And so far, still lack to large deformation soft rock tunnel Excavate the comprehensive theoretical research of deformation allowance system.
Invention content
In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is that provide a kind of soft rock tunnel Excavation and preliminary bracing method, method and step is simple, reasonable design and realization are convenient, using effect is good, according to soft rock tunnel Surrouding rock deformation situation reserved excavated volume is determined, and using steel bracket with Bolt net and jet preliminary bracing respective outer side edges to tunnel Carry out tunneling boring preliminary bracing.
In order to solve the above technical problems, the technical solution adopted by the present invention is:A kind of Soft Rock Tunnel Excavation and preliminary bracing Method, it is characterised in that:Be longitudinally extended direction along tunnel divides multiple segments to excavate constructed soft rock tunnel from the front to the back And preliminary bracing construction, the excavation of multiple segments and preliminary bracing construction method all same;To any section of soft rock tunnel When Duan Jinhang is excavated and preliminary bracing is constructed, include the following steps:
Step 1: country rock basic mechanical parameter determines:Laboratory test is carried out by boring sample to scene, to currently being applied The country rock basic mechanical parameter of work segment is tested, and record is synchronized to test result;
It is determined Step 2: excavated volume is reserved in tunnel:According to country rock basic mechanical parameter identified in step 1, to current The reserved excavated volume of constructed segment is determined;
When being determined to the reserved excavated volume of current segment of constructing, according to the country rock of soft rock tunnel after the completion of supporting to Intrinsic displacement theoretical value S is determined;Wherein, S=S1+S2(1);
In formula (1), S1For the plastic displacement amount of soft rock tunnel surface country rock,In formula (2), P0By currently the tunnel of construction segment encloses before excavation The stress of primary rock of rock rock mass;ξ by current construction segment tunnel surrounding intensive parameter and Currently to be applied The internal friction angle of the tunnel surrounding rock mass of work segment;σcThe uniaxial compressive of tunnel surrounding rock mass by current construction segment is strong Degree;r0By the equivalent excavation radius in tunnel of current institute construction segment, E by currently construction segment tunnel surrounding rock mass synthesis Elasticity modulus, Poisson's ratios of the μ by the tunnel surrounding rock mass of current construction segment,By construction segment current after the completion of supporting Tunnel surrounding plastic zone equivalent redius, P0、σcUnit with E is Pa, r0WithUnit be m;In formula (3), PiAnchor pole is used during to carry out preliminary bracing to soft rock tunnel (2) Support Resistance and its unit is Pa;C is by the cohesive strength of the tunnel surrounding rock mass of current construction segment and its unit Pa, A and t are coefficient, In formula (4), G is The rock mass modulus of shearing and its unit of the tunnel surrounding rock mass of current segment of constructing are Pa,EaFor anchor pole Elasticity modulus and its unit are Pa, AsIt is m for the cross-sectional area of anchor pole and its unit2, rbIt is constructed by the inner end of anchor pole to current The distance of the tunnel central point of segment and its unit m, k are supporting coefficient and k=0.8,By segment of currently constructing before supporting Tunnel surface country rock shift value and its unit be m;PmaxIt is N for the axial tension maximum value on anchor rod body and its unit;
In formula (1), S2For the displacement after the country rock bulking deformation of soft rock tunnel surface,In formula (5), KpTunnel surrounding rock mass by current construction segment Broken swollen coefficient,By the tunnel surrounding relaxation zone equivalent redius for segment of currently constructing after the completion of supporting,
Step 3: tunnel excavation:According to the reserved excavated volume of current constructed segment identified in step 2, by backward It is preceding that current segment of constructing is excavated, obtain the Tunnel for excavating and completing;
Step 4: Tunnel structure determination:Used Tunnel structure include it is multiple from the front to the back At the beginning of laying and the tunneling boring steel bracket of tunneling boring supporting being carried out to Tunnel and carries out the Bolt net and jet of tunneling boring supporting to Tunnel Phase supporting construction, the structure snd size all same of multiple tunneling boring steel brackets and its be in uniformly distributed, the tunneling boring steel The shape of stent is identical with the transverse shape of Tunnel;The Bolt net and jet preliminary bracing structure is using bolt-mesh-spurting supporting method The preliminary bracing structure of construction molding, the Bolt net and jet preliminary bracing structure include multiple suspension roof support lists laid from the front to the back Member, multiple suspension roof support units are in the laying with multiple tunneling boring steel brackets respectively of uniformly distributed and its installation position Position corresponds, and a suspension roof support unit is laid on the outside of each tunneling boring steel bracket, each anchor Bar supporting unit includes the anchor pole that multiple excavation contour lines along Tunnel are laid from front to back, each suspension roof support list Member is laid in the tunneling boring steel bracket on its inside on the same cross section of Tunnel;The suspension roof support list The length all same of multiple anchor poles in member, the length l'=l of the anchor pole1'+l+l2', wherein l1'=10cm~20cm, l2'=30cm~50cm, l are the effective length of anchor pole and its unit is m, And l >=1.5m;
Step 5: Tunnel is constructed:According to Tunnel structure identified in step 4, from the front to the back Tunnel construction is carried out to current segment of constructing;
Step 6: next segment is excavated and preliminary bracing construction:Step 1 is repeated to step 5, next segment is opened It digs and preliminary bracing is constructed;
Step 7: step 6 is repeated several times, until completing whole excavations of soft rock tunnel and preliminary bracing work progress.
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:The longitudinal length of multiple segments is equal For 10m~50m.
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:Worked as after the completion according to excavation in step 2 The country rock inward displacement theoretical value S of preceding constructed segment, when being determined to the reserved excavated volume of current segment of constructing, according to Formula Δ d=S+ Δs d1 (7) is determined;In formula (7), reserved excavated volumes of the Δ d by current construction segment, Δ d1=0 ~0.2m.
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:Before tunnel excavation being carried out in step 3, First according to the reserved excavated volume of current constructed segment identified in step 2, and the design for combining segment of currently constructing is opened Contour line is dug, the practical excavation contour line of current segment of constructing is determined;
The practical excavation contour line of current segment of constructing is located on the outside of the design excavation contour line of current segment of constructing And spacing therebetween is Δ d;
When being excavated from the front to the back to current segment of constructing in step 3, according to identified current constructed segment Practical excavation contour line excavated.
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:From the front to the back to current institute in step 3 When construction segment is excavated, excavated using full face tunneling method or benching tunnelling method.
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:Tunneling boring steel bracket described in step 4 For shape steel bracket, the tunneling boring steel bracket include the steel arch-shelf that supporting is carried out to the arch wall of Tunnel and to Tunnel bottom into The arc steelframe of row supporting, the arc steelframe are located at the underface of the steel arch-shelf, the both ends of the arc steelframe respectively with Two side bottoms of the steel arch-shelf are fixedly connected;
The Bolt net and jet preliminary bracing structure further includes one layer of bar-mat reinforcement mated formation on multiple tunneling boring steel brackets The concrete layer being injected on Tunnel inner wall with one layer, it is the inner end of all anchor poles in multiple suspension roof support units, multiple The tunneling boring steel bracket and the bar-mat reinforcement are both secured in the concrete layer;The concrete layer is steel fiber reinforced concrete Layer and its thickness are 20cm~30cm;
When Tunnel construction is carried out in step 5, first using multiple tunneling boring steel brackets from the front to the back to tunnel Road hole carries out supporting, then carries out preliminary bracing using bolt-mesh-spurting supporting method, obtains the Tunnel of construction molding Structure.
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:Described in step 2In formula (8), K is that the shearing in anchor rod body unit length is firm It is Pa/m to spend coefficient and its unit, and D is the section girth of anchor pole and its unit is m,The unit of B is m2;rmNeutral point for anchor pole is to current The distance between tunnel central point of constructed segment and its unit are m, For The tunnel surrounding plastic zone equivalent redius of current segment of constructing and its unit are m during non-supporting,
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:Anchor pole described in step 2 is mortar anchor Bar, shear stiffness coefficient K=2MPa/m=2 × 106Pa/m;
P described in step 2maxFor the axial tension after the completion of supporting at anchor pole neutral point position.
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:Described in step 2lsFor The outer edge line length of the tunnel cross section of current segment of constructing being pre-designed;
Described in step 2
The tunnel central point of current segment of constructing by currently construction segment tunnel cross section equivalent circular the center of circle, rb =l+r0
A kind of above-mentioned Soft Rock Tunnel Excavation and preliminary bracing method, it is characterized in that:It is front and rear two neighboring described in step 4 Anchor pole in suspension roof support unit in being laid staggeredly, in each suspension roof support unit between the two neighboring anchor pole between Away from for a, between the front and rear two neighboring suspension roof support unit and between the front and rear two neighboring tunneling boring steel bracket Spacing is a;The Tunnel structure is that the built-up arch of supporting is carried out to Tunnel;
In step 4 carry out Tunnel structure determination when, also need according to formula b=l-acot θ (11), to a into Row determines;In formula (11), b be the built-up arch thickness andθ is anchor pole to tunnel surrounding rupture zone rock The angle of action of body compression and θ=45 °.
Compared with the prior art, the present invention has the following advantages:
1st, method and step is simple, realizes that convenient and input cost is low.
2nd, used tunnel excavation method reasonable design and realization convenience, to ensure excavation effect, longitudinally prolong along tunnel Stretch direction divides multiple segments to excavate soft rock tunnel from the front to the back;Also, when being excavated to any one segment of soft rock, It first determines country rock basic mechanical parameter, current the reserved of segment of constructing is opened further according to identified country rock basic mechanical parameter Digging amount is determined, finally according to the reserved excavated volume of identified current construction segment from the front to the back to current segment of constructing It is excavated, easy construction and work progress is easily controllable can have strong operability.
3rd, the characteristics of just tending towards stability for surrouding rock deformation after Soft Rock Tunnel Excavation supporting for a period of time, from tunnel initial-stage branch The force analysis of Bolt used in shield construction is started with, by determining the neutral point radius of anchor pole (i.e. in anchor pole Property point is to the distance between the tunnel central point of current constructed segment rm) and its maximum axle power (i.e. after the completion of supporting in anchor pole Axial tension P at property point positionmax), derive that the plastic zone range after tunnel wall rock deformation stabilization (is worked as after the completion of supporting The tunnel surrounding plastic zone equivalent redius of preceding constructed segment) and rupture zone range (section of currently constructing after the completion of supporting The tunnel surrounding rupture zone equivalent redius of section), and consider the broken swollen characteristic of dilatation of rupture zone rock mass, derive that tunnel surface encloses The displacement (the country rock inward displacement theoretical value S of soft rock tunnel i.e. after the completion of supporting) occurred in rock tunnel space, and according to S to tunnel It reserves excavated volume and is determined in road.
4th, the reserved excavation method for determination of amount of used current constructed segment is simple, realizes easy and using effect Good, rationally, accurately, can be effectively ensured ensures that tunnel internal space after molding meets design and wants to identified reserved excavated volume It asks, and ensures the structural stability and supporting effect of Tunnel structure and Tunnel Second Lining.It is identified reserved Excavated volume is determined according to the country rock inward displacement theoretical value S of soft rock tunnel after the completion of supporting, and wherein S is soft rock tunnel surface The plastic displacement amount S of country rock1With displacement S after tunnel surface country rock bulking deformation2The sum of, and in view of soft in practice of construction The complex deformation factor in rock tunnel is superimposed the country rock inward displacement theoretical value S of soft rock tunnel after the completion of the supporting that is calculated Certain adjustment amount (i.e. Δ d1).Meanwhile the plastic displacement amount S of soft rock tunnel surface country rock that the present invention uses1With tunnel table Displacement S after the country rock bulking deformation of face2Determine that method is simple, reasonable and precision is high, according to predetermined country rock basic mechanical Parameter, and integrating tunnel actual structure parameters, can it is easy, quickly and accurately to S1And S2It is determined.
5th, used Tunnel structure is reasonable in design and supporting effect is good, including multiple cloth from the front to the back And if the tunneling boring steel bracket of tunneling boring supporting is carried out to Tunnel and Tunnel is carried out the Bolt net and jet initial stage of tunneling boring supporting Supporting construction, can easy, the quick split molding Tunnel progress preliminary bracing of digging.Bolt net and jet preliminary bracing structure includes more A suspension roof support unit, multiple suspension roof support units are longitudinally extended direction along tunnel and lay from the front to the back, easy construction and construction It is easy to control the quality.Also, suspension roof support unit includes multiple anchor poles that tunneling boring supporting is carried out to Tunnel, in the arch of Tunnel Anchor pole is respectively provided on portion, bottom and left and right sides abutment wall, and the length of anchor pole and line space design are reasonable, can further improved soft The preliminary bracing effect in rock tunnel.Used Tunnel structure can not only carry out effectively initial stage branch to Tunnel Shield, occurs safety accident after avoiding preliminary bracing, it is ensured that the stability of Tunnel structure, and surrouding rock deformation demand is adapted to, After soft mould supporting construction is set between Tunnel structure and Tunnel Second Lining, surrouding rock deformation can be effectively solved Damage to Tunnel Second Lining, the thickness of the soft mould supporting construction is S and the cross section shape of its cross-sectional shape and Tunnel Shape is identical, and practice of construction is easy.
6th, the simple determining method of Tunnel structure structure, reasonable design are used and is realized conveniently, using effect Fruit is good, and energy is easy, quickly the effective length of anchor pole employed in suspension roof support unit is determined, and mutually reply uses anchor The length of bar is determined, and the Design of length of anchor pole is reasonable, can be to the entire rupture zone of soft rock tunnel by suspension roof support unit It is effectively reinforced, and labor and material saving is time saving.Using country rock of the invention after theoretically analyzing soft rock tunnel preliminary bracing Plastic zone and the size of rupture zone, and total displacement (the i.e. soft rock tunnel after the completion of supporting after surrouding rock deformation is stablized has been calculated Country rock inward displacement theoretical value S), and then optimize preliminary bracing scheme and supporting parameter.The tunnel initial-stage branch of construction molding Protection structure can carry out compatible deformation with surrouding rock deformation, it is ensured that the safety and stability of Tunnel Second Lining structure.Used soft mould branch Injection steel fiber reinforced concrete in protection structure, the soft mould supporting construction is with its intrinsic rigidity and intensity and Tunnel structure Compatible deformation not only can largely absorb the broken swollen strain energy of country rock, improve structure stress, but also have certain residual strength, really Protect the safety and stability of Tunnel Second Lining structure.Soft mould supporting construction forms crushable backpacking, Tunnel structure with it is soft On the basis of mould supporting construction, Tunnel Second Lining is set according to original design, to increase substantially the whole of tunnel support structure Body intensity and rigidity prevent the excessive deformation of Tunnel structure and soft mould supporting construction, it is ensured that soft rock tunnel it is long-term Stablize.
7th, using effect is good and practical value is high, just tends to for surrouding rock deformation after Soft Rock Tunnel Excavation supporting for a period of time The characteristics of stablizing, be first calculated the country rock inward displacement theoretical value S of soft rock tunnel after the completion of supporting, and according to being calculated Country rock inward displacement theoretical value S reserves excavated volume to tunnel and is determined, and can effectively solve because the practical reserved excavated volume in tunnel is small Tunnel structure is caused seriously to crack, seriously affect with circumferential appearance in longitudinal direction in country rock inward displacement theoretical value S The supporting effect of tunnel support structure need to reprocess soft rock tunnel, input cost height, construction risk headlight problem, and energy It effectively solves the problems, such as to invade tunnel clearance in soft rock tunnel after surrouding rock deformation and influences tunnel normal use.It can by the above Know, the present invention is directed to because surrouding rock deformation this feature that just tends towards stability directly affects tunnel after Soft Rock Tunnel Excavation supporting for a period of time The problem of road excavation plan and its supporting effect, and for the plastic zone range after existing soft rock tunnel stabilization and rupture zone Range determines the deficiency of aspect theoretical research and the objective difficulties of field measurement, after rational soft rock tunnel stabilization Plastic zone range and rupture zone range determining method carry out the country rock inward displacement theoretical value S of soft rock tunnel after the completion of supporting It calculates, and mutually should determine that excavated volume is reserved in reasonable, accurate tunnel.
Meanwhile molding Tunnel progress simplicity, quickly and efficiently supporting are dug using Tunnel structure is split, Meet that supporting is stable, under the premise of reliable and safety, achieve the purpose that it is cost-effective, have economical, input construction cost is relatively low, The advantages that safe and reliable, thus can be that soft rock tunnel normal construction provides a strong guarantee, it can effectively solve the change of soft rock tunnel country rock Tunnel clearance is invaded after shape and the problem of influence tunnel normal use, when tunnel excavation reserves rational excavated volume, it is ensured that molding Tunnel internal space afterwards meets design requirement;Meanwhile using the firm supporting of compressible tunneling boring and Bolt net and jet preliminary bracing knot Structure carries out soft rock tunnel effectively reinforcing, supporting, avoids the reclamation work of soft rock tunnel, and construction cost is low.
In addition, the present invention can effectively reinforce, and energy soft rock tunnel by the way of excavation section by section and sectional supporting The preliminary bracing effect of long distance tunnel is effectively ensured, and construction cost is relatively low.
In conclusion the method for the present invention step is simple, reasonable design and realization are convenient, using effect is good, according to soft rock tunnel The surrouding rock deformation situation in road is determined reserved excavated volume, and using steel bracket and Bolt net and jet preliminary bracing respective outer side edges to tunnel Road carries out tunneling boring preliminary bracing.
Below by drawings and examples, technical scheme of the present invention is described in further detail.
Description of the drawings
Fig. 1 is the method flow block diagram of the present invention.
Fig. 2 is the structure diagram of suspension roof support unit of the present invention.
Reference sign:
1-soft rock tunnel;2-anchor pole.
Specific embodiment
A kind of Soft Rock Tunnel Excavation as shown in Figure 1 and preliminary bracing method, direction is longitudinally extended from the front to the back along tunnel Multiple segments is divided to excavate constructed soft rock tunnel 1 and preliminary bracing is constructed, the excavation of multiple segments and initial stage branch Protect construction method all same;Any segment of soft rock tunnel 1 is excavated and preliminary bracing construct when, include the following steps:
Step 1: country rock basic mechanical parameter determines:Laboratory test is carried out by boring sample to scene, to currently being applied The country rock basic mechanical parameter of work segment is tested, and record is synchronized to test result;
It is determined Step 2: excavated volume is reserved in tunnel:According to country rock basic mechanical parameter identified in step 1, to current The reserved excavated volume of constructed segment is determined;
When being determined to the reserved excavated volume of current segment of constructing, according to the country rock of soft rock tunnel after the completion of supporting to Intrinsic displacement theoretical value S is determined;Wherein, S=S1+S2(1);
In formula (1), S1For the plastic displacement amount of soft rock tunnel surface country rock,In formula (2), P0By currently the tunnel of construction segment encloses before excavation The stress of primary rock of rock rock mass;ξ by current construction segment tunnel surrounding intensive parameter and Currently to be applied The internal friction angle of the tunnel surrounding rock mass of work segment;σcThe uniaxial compressive of tunnel surrounding rock mass by current construction segment is strong Degree;r0By the equivalent excavation radius in tunnel of current institute construction segment, E by currently construction segment tunnel surrounding rock mass synthesis Elasticity modulus, Poisson's ratios of the μ by the tunnel surrounding rock mass of current construction segment,By construction segment current after the completion of supporting Tunnel surrounding plastic zone equivalent redius, P0、σcUnit with E is Pa, r0WithUnit be m;In formula (3), PiAnchor is used during to carry out preliminary bracing to soft rock tunnel 1 The Support Resistance of bar 2 and its unit are Pa;C is by the cohesive strength of the tunnel surrounding rock mass of current construction segment and its unit Pa, A and t are coefficient, In formula (4), G is The rock mass modulus of shearing and its unit of the tunnel surrounding rock mass of current segment of constructing are Pa,EaFor anchor pole 2 Elasticity modulus and its unit are Pa, AsIt is m for the cross-sectional area of anchor pole 2 and its unit2, rbBy the inner end of anchor pole 2 to currently applying The distance of the tunnel central point of work segment and its unit m, k are supporting coefficient and k=0.8,By construction section current before supporting The shift value of the tunnel surface country rock of section and its unit are m;PmaxFor the axial tension maximum value and its unit on 2 body of rod of anchor pole For N;
In formula (1), S2For the displacement after the country rock bulking deformation of soft rock tunnel surface,In formula (5), KpTunnel surrounding rock by current construction segment The broken swollen coefficient of body,By the tunnel surrounding relaxation zone equivalent redius for segment of currently constructing after the completion of supporting,
Step 3: tunnel excavation:According to the reserved excavated volume of current constructed segment identified in step 2, by backward It is preceding that current segment of constructing is excavated, obtain the Tunnel for excavating and completing;
Step 4: Tunnel structure determination:Used Tunnel structure include it is multiple from the front to the back At the beginning of laying and the tunneling boring steel bracket of tunneling boring supporting being carried out to Tunnel and carries out the Bolt net and jet of tunneling boring supporting to Tunnel Phase supporting construction, the structure snd size all same of multiple tunneling boring steel brackets and its be in uniformly distributed, the tunneling boring steel The shape of stent is identical with the transverse shape of Tunnel;The Bolt net and jet preliminary bracing structure is using bolt-mesh-spurting supporting method The preliminary bracing structure of construction molding, the Bolt net and jet preliminary bracing structure include multiple suspension roof support lists laid from the front to the back Member, multiple suspension roof support units are in the laying with multiple tunneling boring steel brackets respectively of uniformly distributed and its installation position Position corresponds, and a suspension roof support unit is laid on the outside of each tunneling boring steel bracket, each anchor Bar supporting unit includes the anchor pole 2 that multiple excavation contour lines along Tunnel are laid from front to back, each suspension roof support Unit is laid in the tunneling boring steel bracket on its inside on the same cross section of Tunnel, refers to Fig. 2;It is described The length all same of multiple anchor poles 2, the length l'=l of the anchor pole 2 in suspension roof support unit1'+l+l2', wherein l1'= 10cm~20cm, l2'=30cm~50cm, l are the effective length of anchor pole 2 and its unit is m,And l >=1.5m;
Step 5: Tunnel is constructed:According to Tunnel structure identified in step 4, from the front to the back Tunnel construction is carried out to current segment of constructing;
Step 6: next segment is excavated and preliminary bracing construction:Step 1 is repeated to step 5, next segment is opened It digs and preliminary bracing is constructed;
Step 7: step 6 is repeated several times, until completing whole excavations of soft rock tunnel 1 and preliminary bracing work progress.
Wherein, S, S1、S2WithUnit be m.
As shown in Fig. 2, each suspension roof support unit includes multiple excavation contour lines along Tunnel from front to back The anchor pole 2 of laying, thus the suspension roof support unit include the arch to Tunnel, left and right sides abutment wall and bottom respectively into The anchor pole 2 of row supporting.
In the present embodiment, the tunneling boring steel bracket be compressible steel bracket, also referred to as scalable steel bracket.Also, institute The country rock inward displacement demand of soft rock tunnel after the completion of supporting can be met by stating the decrement of tunneling boring steel bracket.
The rock mass not influenced in the earth's crust by Human dried bloodstains (tunnel is dug in such as mine) is known as in situ rock mass, letter Claim protolith.The stress of primary rock described in step 2 refers to be present in stratum not by the natural stress of Engineering Disturbance, also referred to as rock Body primary stress, absolute stress or crustal stress.
Wherein, broken swollen coefficient, the also referred to as coefficient of volumetric expansion refer to the ratio of volume and broken front volume after catalase.
According to general knowledge known in this field, after soft rock tunnel (i.e. Support System in Soft Rock Tunnels) excavates, due to surrouding rock stress redistribution And its significant rheological behavior, it just tends towards stability, is studied under supporting state after failure and deformation of surrounding rocks supporting for a period of time in the early stage Surrouding rock deformation range and its displacement will be reasonably to determine that great burying soft rock tunnel deformation allowance and its supporting scheme provide Important theoretical foundation.To give full play to country rock self-supporting, preliminary bracing and country rock is allowed to have certain deformation, and will design Excavation line makees appropriate widened pre- allowance, referred to as tunnel deformation allowance.Deformation allowance refers to apply from Tunnel Work starts, to tunnel perimeter deflection it is basicly stable when, the aggregate-value of periphery displacement.
To soft rock tunnel surrounding rock displacement after the completion of supporting, (i.e. country rock inward displacement theoretical value S refers to and considers the broken swollen tunnel of dilatation Road surrounding rock displacement) when being analyzed, it is assumed that plastic zone of surrounding rock constancy of volume, by circular reservoir country rock diameter buried under elastic-plastic behavior Geometric equation and plastic stress strain stress relation to displacement are understood:The plastic displacement of tunnel surface country rock is S1;Engineering in practice, When tunnel surrounding intensity is less than surrouding rock stress, tunnel perimeter surface country rock is inevitable to enter broken state by plastic deformation, goes out Existing dilatation bulking deformation, country rock further will generate displacement on the basis of original plastic displacement to tunnel space,And then it can obtain:WhereinFor tunnel table Equivalent redius after the country rock bulking deformation of face, it can thus be concluded that the displacement after tunnel surface country rock bulking deformationIt can thus be seen that for a determining tunnel cross-section, caused by surrouding rock deformation Displacement depends on its equivalent excavation radius, country rock modulus of shearing and country rock after stress difference on elastic plastic interphase and preliminary bracing Plastic zone and radius of fractured zone.
Wherein, after the completion of Tunnel construction is referred to after the completion of supporting, Tunnel is referred to before supporting Before.
For a long time, Bolt is widely adopted in Highway Tunnel Wall Rock supporting.If tunnel excavation initial stage encloses Rock is in elastic-plastic behavior, and surface country rock forms rupture zone into tunnel space under pressure at right angle effect after continuous deformation.For Convenient for discussing, it is assumed that:Firstth, tunnel cross-section is equivalent to circle, longitudinal length is much larger than transverse width, belongs to plane strain Problem;Secondth, anchor pole surrounding rock body is reduced to homogeneous, continuous and isotropic elasticoplastic body;Third, anchor surface are any It is not produced relative sliding between point and its surrounding rock body;4th, anchor pole tensile strength is much larger than the tensile strength of surrounding rock body, Length is country rock surface to elastic region outer boundary.By the way that tunnel surrounding is reduced to ideal elastic-plastic medium in the present invention, in tunnel Bolt is laid in road country rock.
After Soft Rock Tunnel Excavation, it is followed successively by rock crusher area, plastic zone and elasticity from the inside to the outside along 2 length direction of anchor pole Area, since each area's rock mass has different radial-deformations, closer to tunnel surface, country rock radial displacement rate is bigger.It is close One section of body of rod of tunnel surface has the trend that fracture area rock mass is prevented to be deformed into tunnel, and surface, which generates, is directed toward tunnel Interior positive friction;Since the rate of displacement of elasto-plastic range (elasto-plastic region) rock mass is less than normal compared with fracture area, remaining one section of body of rod is then close to tunnel The drawing effect of the surface body of rod is lower to generate the negative friction for being directed toward deep wall rock.The interface of positive negative friction is suffered by the body of rod The neutral point of anchor pole, relative displacement and swimming cloths power of the body of rod with its surrounding rock body are zero, but its axial tension reaches To maximum value.Thus, opposite separation is directed toward on the anchor pole 2 there are a swimming cloths power, which is the anchor The neutral point that bar 2 is zero with its surrounding rock body relative displacement, which is zero.But at the separation, the axis of the anchor pole 2 Reach maximum to pulling force and gradually decreased and gone to zero from the both ends axial tension of the separation to the anchor pole 2.
In this way, the present invention is based on the compatible deformation principle of anchor pole and country rock, and by establishing 2 body of rod of anchor pole and rock around it The mechanical model of body interaction, analyzes the regularity of distribution of 2 swimming cloths power of anchor pole and axle power, and put down according to the static(al) of the body of rod Weighing apparatus condition derives neutral point position and its maximum axial value of thrust that 2 body of rod of anchor pole is zero with rock mass relative displacement, and analyzes Go out the plastic zone of tunnel surrounding and the equivalent redius calculation formula of rupture zone under the conditions of preliminary bracing, refer to formula (3) and formula (6).According to formula (3) and formula (6) energy simplicity, directly find out:(i.e. anchor pole 2 acts on surface to the Support Resistance of the anchor pole 2 Resistance on country rock, specifically anchor pole 2 act on the resistance on the country rock unit area of soft rock tunnel surface, and also referred to as suspension roof support is anti- Power) influence to tunnel surrounding plastic zone and rupture zone range is little, show that surrouding rock deformation is one kind when Surrounding Rock Strength is less than The physical state of tunnel perimeter objective reality during surrouding rock stress, artificial supporting can not thoroughly avoid country rock from deforming destruction. Meanwhile can directly find out, tunnel is equivalent to excavate radius r0Influence to tunnel surrounding plastic zone and rupture zone range is notable, supporting The tunnel surrounding plastic zone equivalent redius of current segment of constructing after the completionWith the tunnel of segment of constructing current after the completion of supporting Road broken rock zone equivalent rediusRadius r is excavated with tunnel is equivalent0Increase and it is approximate linear increase, andIt is excavated The influence of radius is more significant.
According to formula (3) and formula (6), the deformation thickness of tunnel surrounding after the completion of supporting easy, quick can be obtained, i.e.,With
As shown in the above, after tunnel wall enters broken state by mecystasis, hole wall rock mass unloads, suffered by country rock The peak value of pressure is concentrated to be shifted to deep rock mass, the country rock elasto-plastic range (elasto-plastic region) that excavation initial stage is formed will further expand, country rock branch Plastic zone equivalent redius after shieldRefer to formula (3);When vertical support pressure suffered by tunnel surface country rock is more than its intensity Plastic flow to occur and destroy, and form rupture zone, range and plastic zone equivalent rediusThere are certain association, country rock branch Rupture zone equivalent redius after shieldRefer to formula (6).
Due toThus the anchor pole 2 effective length according toAnd r0It carries out Determine, the effective length of the anchor pole 2 determine that method is simple and the effective length l of the determining anchor pole 2 of institute rationally and accurately, can be effective Ensure the supporting effect of anchor pole 2.
In the present embodiment, the longitudinal length of multiple segments is 10m~50m.
During practice of construction, the longitudinal length of multiple segments can be adjusted accordingly respectively according to specific needs.
According to the country rock inward displacement theoretical value S for excavating current segment of constructing after the completion in step 2, to currently being applied When the reserved excavated volume of work segment is determined, it is determined according to formula Δ d=S+ Δs d1 (7);In formula (7), Δ d is works as The reserved excavated volume of preceding constructed segment, Δ d1=0~0.2m.
In the present embodiment, Δ d1=0.Thus, Δ d=S.
In the present embodiment, before carrying out tunnel excavation in step 3, first current constructed according to identified in step 2 The reserved excavated volume of segment, and the design excavation contour line for segment of currently constructing is combined, to the reality of current segment of constructing Excavation contour line is determined;
The practical excavation contour line of current segment of constructing is located on the outside of the design excavation contour line of current segment of constructing And spacing therebetween is Δ d;
When being excavated from the front to the back to current segment of constructing in step 3, according to identified current constructed segment Practical excavation contour line excavated.
In the present embodiment, before progress country rock basic mechanical parameter determines in step 1, first from current constructed segment A segment is chosen as test section, the test section is located at current construct segment rear end and the length of 1m.
When progress country rock basic mechanical parameter determines in step 1, bore sample from the test section and carry out laboratory test, and The result of the test obtained is by the country rock basic mechanical parameter for segment of currently constructing after excavation.
Also, in view of the characteristics such as heterogeneous, discontinuous and anisotropy of the tunnel surrounding of soft rock tunnel 1, mechanics ginseng Number must determine on the basis of experiment, to ensure data accurately and reliably, reduce and calculate error.
In the present embodiment, when being excavated from the front to the back to current segment of constructing in step 3, using full face tunneling Method or benching tunnelling method are excavated.
Also, used full face tunneling method or benching tunnelling method are conventional tunnel excavation method.
In the present embodiment, tunneling boring steel bracket described in step 4 be shape steel bracket, the tunneling boring steel bracket include pair The arch wall of Tunnel carries out the steel arch-shelf of supporting and the arc steelframe of supporting is carried out to Tunnel bottom, and the arc steelframe is located at The underface of the steel arch-shelf, the both ends of the arc steelframe are fixedly connected respectively with two side bottoms of the steel arch-shelf.
The Bolt net and jet preliminary bracing structure further includes one layer of bar-mat reinforcement mated formation on multiple tunneling boring steel brackets The concrete layer being injected on Tunnel inner wall with one layer, it is the inner end of all anchor poles 2 in multiple suspension roof support units, multiple The tunneling boring steel bracket and the bar-mat reinforcement are both secured in the concrete layer.In the present embodiment, the concrete layer is Steel fiber concrete layer and its thickness are 20cm~30cm.
When Tunnel construction is carried out in step 5, first using multiple tunneling boring steel brackets from the front to the back to tunnel Road hole carries out supporting, then carries out preliminary bracing using bolt-mesh-spurting supporting method, obtains the Tunnel of construction molding Structure.
In the present embodiment, described in step 2In formula (8), K is Shear stiffness coefficient and its unit in 2 body of rod unit length of anchor pole are Pa/m, and D is the section girth and its unit of anchor pole 2 For m,The unit of B is m2;rmNeutral point for anchor pole 2 is extremely worked as The distance between tunnel central point of preceding constructed segment and its unit are m, The tunnel surrounding plastic zone equivalent redius of current construction segment and its unit is m during by non-supporting,
In the present embodiment, anchor pole 2 described in step 2 be grouting rock bolt, shear stiffness coefficient K=2MPa/m=2 × 106Pa/m。
Wherein, shear stiffness coefficient refers to that rock sample under certain normal stress and shear stress effect, is cut accordingly The ratio of stress and shear displacemant.
In the present embodiment, the P described in step 2maxFor the axial tension at 2 neutral point position of anchor pole after the completion of supporting, Thus PmaxIt can also be obtained by experimental test.
In the present embodiment, described in step 2lsBy the tunnel horizontal stroke of current institute construction segment being pre-designed The outer edge line length of section.
Also, described in step 2In actual use, σcIt can also use what experimental test obtained Test value.
In the present embodiment, the tunnel central point of current segment of constructing by currently construction segment tunnel cross section it is equivalent The round center of circle, rb=l+r0.Thus, the tunnel central point of current segment of constructing by currently construction segment tunnel cross section The center of circle of equivalent circular, rbBy the equivalent length l of the anchor pole 2 and the tunnel cross section radius of equivalent circle of current construction segment (the equivalent excavation radius in tunnel of i.e. current segment of constructing) r0The sum of.
In the present embodiment, in step 2 the tunnel surrounding of current segment of constructing by currently construction segment tunnel arch Or the country rock of left and right sides abutment wall present position.
In the present embodiment,lsThe outer edge line of current by what is be pre-designed the tunnel cross section of construction segment Length.
In the present embodiment, the anchor pole 2 in step 4 in the front and rear two neighboring suspension roof support unit is in being laid staggeredly, often Spacing in a suspension roof support unit between the two neighboring anchor pole 2 is a, the front and rear two neighboring suspension roof support list Spacing between member and between the front and rear two neighboring tunneling boring steel bracket is a;The Tunnel structure is The built-up arch of supporting is carried out to Tunnel.
In step 4 carry out Tunnel structure determination when, also need according to formula b=l-acot θ (11), to a into Row determines;In formula (11), b be the built-up arch thickness andθ is anchor pole 2 to tunnel surrounding rupture zone The angle of action of rock mass compression and θ=45 °.
In the present embodiment,And b is not less than 2m.
Wherein, the spacing in each suspension roof support unit between the two neighboring anchor pole 2 refers to two neighboring The distance between described 2 inner end of anchor pole, the inner end of the anchor pole 2 refer to one end that anchor pole 2 is located in the Tunnel.
In the present embodiment, the soft rock tunnel 1 constructed is positioned at the Liu Tong stockaded villages tunnel of Mao County to Long Tang sections, is to create into All to the key control engineering of Lanzhou railway line, left line overall length 16262m, maximum buried depth about 1400m, right line overall length 16257.5m, maximum buried depth about 1410m, left and right line spacing 30m~40m.Tunnel surrounding is with carbonaceous phyllite, phyllite horsestone English Based on rock, limestone, sandstone and quartzite.Sui Zhi areas are located at plate margin structural belt, and there is landform to cut extremely strong, construction item Part is extremely complex actively, lithology condition extremely weak broken, Wenchuan earthquake effect is extremely notable and high crustal stress, high earthquake Earthquake intensity, high geological disaster risk " quadrupole three is high " distinguishing feature, soft rock large deformation problem is very prominent, the big change of left tunnel line Shape prediction paragraph adds up 6850m, and Tunnel Right Line Prediction of large deformation paragraph adds up 6810m.Tunnel Design excavation height 7.65m, Maximum span 8.0m, original design preliminary bracing use the overall length adhesive mortar anchor pole of a diameter of Φ 22mm, the grouting rock bolt Between array pitch 1.2m × 1.2m and the length of 3.0m.Bolt net and jet and steel arch-shelf combined supporting are used in poor section of geological conditions, two Secondary lining cutting is form concrete, and deformation allowance involved in digging process is 15cm.
In the present embodiment, when progress country rock basic mechanical parameter determines in step 1, identified country rock basic mechanical ginseng Number should at least include the stress of primary rock P of the tunnel surrounding rock mass of current segment of constructing in soft rock tunnel 1 of constructing before excavating0、 The internal friction angle of the tunnel surrounding rock mass of current segment of constructingThe synthesis bullet of the tunnel surrounding rock mass of current segment of constructing Property modulus E, current segment of constructing tunnel surrounding rock mass Poisson's ratio μ, to being used during the progress preliminary bracing of soft rock tunnel 1 The Support Resistance P of anchor polei, the cohesive strength c of tunnel surrounding rock mass of current segment of constructing, segment of currently constructing before supporting The shift value of tunnel surface country rock
Also, also need excavation radius r equivalent to the tunnel of current segment of constructing0, the anchor pole 2 elastic modulus Ea, institute State the cross-sectional area A of anchor pole 2s, the anchor pole 2 tunnel central point of the inner end to current constructed segment distance rbWith it is described Axial tension maximum value P on 2 body of rod of anchor polemaxIt is determined respectively.
In the present embodiment, the buried depth H=912m for soft rock tunnel 1 of constructing, overlying rock volume-weighted average γ=25kN/m3, The vertical crustal stress of protolith (i.e. the stress of primary rock) P0=22.8MPa=22.8 × 106Pa, tunnel excavation half high a=3.5m, half-breadth b= 4.0m, tunnel is equivalent to excavate radius r0=5.3m, cohesive strength c=8.0MPa=8.0 × 106Pa, internal friction angleT= 1.464, Poisson's ratio μ=0.25, synthetical elastic modulus (also referred to as deformation modulus) E=9.8GPa=9.8 × 109Pa, rock mass are cut Shear modulu G=3.92GPa=3.92 × 109Pa (is referred specifically to after the completion of excavating and before Tunnel) current before supporting The shift value of the tunnel surface country rock of constructed segmentEffective length l=3m, a diameter of Φ of original design anchor pole 2 Array pitch is 0.8m, the shear stiffness coefficient K=2MPa/m in 2 body of rod surface unit length of anchor pole between 22mm and anchor pole 2 =2 × 106Pa/m, the elastic modulus E of the anchor pole 2a=200GPa=200 × 109Pa, the cross-sectional area A of the anchor pole 2s= 4.91cm2=4.91 × 10-4m2, the diameter (i.e. shank diameter) of the anchor pole 2 is 25mm, the section girth D of the anchor pole 2 =0.08m, tunnel surface surrounding rock supporting counter-force Pi=300kPa=300 × 103Pa (specifically refers to tunnel side wall surface country rock branch Protect counter-force), the distance r of the tunnel central point of inner end to current the constructed segment of the anchor pole 2b=8.3m, is currently constructed The broken swollen COEFFICIENT K of the tunnel surrounding rock mass of segmentp=1.05.
According to formula (10), the tunnel surrounding plastic zone equivalent redius of current segment of constructing during non-supporting is obtained
According to formula (9), obtain
According to formula (9-1), obtain
According to formula (8), obtain
According to formula (4), obtain
According to formula (3), obtain
According to formula (6), obtain
Meanwhile tunnel surrounding intensive parameter is calculated
According to formula (2), obtain
According to the equivalent redius after tunnel surface country rock bulking deformationCalculation formula, obtain
According to formula (5), obtain
According to formula (1), S=S is obtained1+S2=0.068+0.113=0.181m.
During carrying out constructing tunnel at present, tunnel to be caused to invade limit after avoiding soft-rock slope, generally prop up in the early stage The deflection for protecting and 80mm~120mm being reserved between secondary lining, i.e., (i.e. construction and excavation is set with the pre- allowance of excavation that originally designed Count pre- allowance) maximum value be 120mm.
And according to formula (1), the country rock inward displacement theoretical value S=of soft rock tunnel after the completion of supporting is calculated 0.181m, and show that country rock inward displacement theoretical value S coincide substantially with live country rock actual displacement amount according to on-the-spot test, but The country rock inward displacement theoretical value S being calculated is more than construction and excavation and designs pre- allowance, eventually leads to Tunnel structure There is serious cracking, and threaten the stabilization of later stage Tunnel Second Lining structure with circumferential in longitudinal direction, thus need to being constructed Reserved excavated volume when soft rock tunnel 1 excavates is redefined, and according to the country rock inward displacement theoretical value S being calculated It is determined.
And then according to the method described in step 4, used Tunnel structure is determined, then root It is synchronous that tunnel is carried out to the Tunnel from the front to the back during tunnel excavation according to identified Tunnel structure Preliminary bracing is constructed.
In the present embodiment, the Tunnel is additionally arranged at the bottom of anchor pole 2 and carries out supporting, and uses compressible tunneling boring steel branch Frame, while array pitch between anchor pole 2 is adjusted to 0.8m × 0.8m by 1.2m × 1.2m, the thickness of country rock built-up arch can be dramatically increased Degree;Meanwhile spray to form the concrete layer that thickness is 25cm in the Tunnel inner wall, the concrete sprayed is C30 Steel fiber reinforced concrete can further improve the preliminary bracing effect of soft rock tunnel 1.
In the present embodiment, the effective length of the anchor pole 2 is 3m.
The above is only presently preferred embodiments of the present invention, not the present invention is imposed any restrictions, every according to the present invention Any simple modification, change and the equivalent structure that technical spirit makees above example change, and still fall within skill of the present invention In the protection domain of art scheme.

Claims (10)

1. a kind of Soft Rock Tunnel Excavation and preliminary bracing method, it is characterised in that:Direction is longitudinally extended along tunnel from the front to the back to divide Constructed soft rock tunnel (1) is excavated for multiple segments and preliminary bracing construction, the excavation of multiple segments and initial stage branch Protect construction method all same;Any segment of soft rock tunnel (1) is excavated and preliminary bracing construct when, including following step Suddenly:
Step 1: country rock basic mechanical parameter determines:Laboratory test is carried out by boring sample to scene, to current section of constructing The country rock basic mechanical parameter of section is tested, and record is synchronized to test result;
It is determined Step 2: excavated volume is reserved in tunnel:According to country rock basic mechanical parameter identified in step 1, to currently being applied The reserved excavated volume of work segment is determined;
When being determined to the reserved excavated volume of current segment of constructing, according to the inside position of the country rock of soft rock tunnel after the completion of supporting Theoretical value S is moved to be determined;Wherein, S=S1+S2(1);
In formula (1), S1For the plastic displacement amount of soft rock tunnel surface country rock,In formula (2), P0By currently the tunnel of construction segment encloses before excavation The stress of primary rock of rock rock mass;ξ by current construction segment tunnel surrounding intensive parameter and Currently to be applied The internal friction angle of the tunnel surrounding rock mass of work segment;σcThe uniaxial compressive of tunnel surrounding rock mass by current construction segment is strong Degree;r0By the equivalent excavation radius in tunnel of current institute construction segment, E by currently construction segment tunnel surrounding rock mass synthesis Elasticity modulus, Poisson's ratios of the μ by the tunnel surrounding rock mass of current construction segment,By construction segment current after the completion of supporting Tunnel surrounding plastic zone equivalent redius, P0、σcUnit with E is Pa, r0WithUnit be m;In formula (3), PiIt is used during to carry out preliminary bracing to soft rock tunnel (1) The Support Resistance of anchor pole (2) and its unit are Pa;Cohesive strengths and its unit of the c by the tunnel surrounding rock mass of current construction segment It is coefficient for Pa, A and t,In formula (4), G is Pa by the rock mass modulus of shearing of the tunnel surrounding rock mass of current construction segment and its unit,Ea is anchor The elasticity modulus of bar (2) and its unit are Pa, AsIt is m for the cross-sectional area of anchor pole (2) and its unit2, rbFor the interior of anchor pole (2) It holding to the distance of the tunnel central point of current construct segment and its unit m, k is supporting coefficient and k=0.8,Before supporting The shift value of the tunnel surface country rock of current segment of constructing and its unit are m;PmaxFor the axial tension on anchor pole (2) body of rod Maximum value and its unit are N;
In formula (1), S2For the displacement after the country rock bulking deformation of soft rock tunnel surface,In formula (5), tunnel surrounding rock mass of the Kp by current construction segment Broken swollen coefficient,By the tunnel surrounding relaxation zone equivalent redius for segment of currently constructing after the completion of supporting,
Step 3: tunnel excavation:It is right from the front to the back according to the reserved excavated volume of current constructed segment identified in step 2 Current segment of constructing is excavated, and obtains the Tunnel for excavating and completing;
Step 4: Tunnel structure determination:Used Tunnel structure is laid from the front to the back including multiple And the tunneling boring steel bracket of tunneling boring supporting is carried out to Tunnel and the Bolt net and jet initial stage branch of tunneling boring supporting is carried out to Tunnel Protection structure, the structure snd size all same of multiple tunneling boring steel brackets and its be in uniformly distributed, the tunneling boring steel bracket Shape it is identical with the transverse shape of Tunnel;The Bolt net and jet preliminary bracing structure is to be constructed using bolt-mesh-spurting supporting method Molding preliminary bracing structure, the Bolt net and jet preliminary bracing structure include multiple suspension roof support units laid from the front to the back, Multiple suspension roof support units are in uniformly distributed and its installation position laying position with multiple tunneling boring steel brackets respectively One-to-one correspondence is put, a suspension roof support unit is laid on the outside of each tunneling boring steel bracket, each anchor pole Supporting unit includes the anchor pole (2) that multiple excavation contour lines along Tunnel are laid, each suspension roof support unit with The tunneling boring steel bracket on its inside is laid on the same cross section of Tunnel;It is more in the suspension roof support unit The length all same of a anchor pole (2), the length l'=l of the anchor pole (2)1'+l+l2', wherein l1'=10cm~20cm, l2'=30cm~50cm, l are the effective length of anchor pole (2) and its unit is m,And l >= 1.5m;
Step 5: Tunnel is constructed:According to Tunnel structure identified in step 4, from the front to the back to working as Preceding constructed segment carries out Tunnel construction;
Step 6: next segment is excavated and preliminary bracing construction:Step 1 is repeated to step 5, next segment is excavated and Preliminary bracing is constructed;
Step 7: step 6 is repeated several times, until completing whole excavations of soft rock tunnel (1) and preliminary bracing work progress.
2. a kind of Soft Rock Tunnel Excavation described in accordance with the claim 1 and preliminary bracing method, it is characterised in that:Multiple sections The longitudinal length of section is 10m~50m.
3. according to a kind of Soft Rock Tunnel Excavation and preliminary bracing method described in claims 1 or 2, it is characterised in that:Step 2 The middle country rock inward displacement theoretical value S according to segment of constructing current after the completion of excavation opens current the reserved of segment of constructing When digging amount is determined, it is determined according to formula Δ d=S+ Δs d1 (7);In formula (7), Δ d is current construction segment Reserved excavated volume, Δ d1=0~0.2m.
4. a kind of Soft Rock Tunnel Excavation described in accordance with the claim 3 and preliminary bracing method, it is characterised in that:In step 3 into Before row tunnel excavation, first according to the reserved excavated volume of current constructed segment identified in step 2, and current institute is combined The design excavation contour line of construction segment is determined the practical excavation contour line of current segment of constructing;
The practical excavation contour line of current segment of constructing is located at the design excavation contour line outside and two of current segment of constructing Spacing between person is Δ d;
When being excavated from the front to the back to current segment of constructing in step 3, according to the reality of identified current constructed segment Border excavation contour line is excavated.
5. according to a kind of Soft Rock Tunnel Excavation and preliminary bracing method described in claims 1 or 2, it is characterised in that:Step 3 In when being excavated from the front to the back to current segment of constructing, excavated using full face tunneling method or benching tunnelling method.
6. according to a kind of Soft Rock Tunnel Excavation and preliminary bracing method described in claims 1 or 2, it is characterised in that:Step 4 Described in tunneling boring steel bracket be shape steel bracket, the tunneling boring steel bracket includes carrying out the arch wall of Tunnel the steel arch of supporting Frame and the arc steelframe that supporting is carried out to Tunnel bottom, the arc steelframe are located at the underface of the steel arch-shelf, the arc The both ends of shaped steel frame are fixedly connected respectively with two side bottoms of the steel arch-shelf;
The Bolt net and jet preliminary bracing structure further includes one layer of bar-mat reinforcement and one mated formation on multiple tunneling boring steel brackets Layer is injected in concrete layer on Tunnel inner wall, the inner end of all anchor poles (2), Duo Gesuo in multiple suspension roof support units It states tunneling boring steel bracket and the bar-mat reinforcement is both secured in the concrete layer;The concrete layer is steel fiber concrete layer And its thickness is 20cm~30cm;
When Tunnel construction is carried out in step 5, first using multiple tunneling boring steel brackets from the front to the back to Tunnel Supporting is carried out, then preliminary bracing is carried out using bolt-mesh-spurting supporting method, obtains the Tunnel structure of construction molding.
7. according to a kind of Soft Rock Tunnel Excavation and preliminary bracing method described in claims 1 or 2, it is characterised in that:Step 2 Described inIn formula (8), K is cutting in anchor pole (2) body of rod unit length It is Pa/m to cut stiffness coefficient and its unit, and D is the section girth of anchor pole (2) and its unit is m,The unit of B is m2;rmNeutral point for anchor pole (2) is to current institute The distance between tunnel central point of construction segment and its unit are m, For not The tunnel surrounding plastic zone equivalent redius of current segment of constructing and its unit are m during supporting,
8. according to a kind of Soft Rock Tunnel Excavation and preliminary bracing method described in claim 7, it is characterised in that:Institute in step 2 Anchor pole (2) is stated as grouting rock bolt, shear stiffness coefficient K=2MPa/m=2 × 106Pa/m;
P described in step 2maxFor the axial tension at anchor pole after the completion of supporting (2) neutral point position.
9. according to a kind of Soft Rock Tunnel Excavation and preliminary bracing method described in claims 1 or 2, it is characterised in that:Step 2 Described inlsThe outer edge line length of current by what is be pre-designed the tunnel cross section of construction segment;
Described in step 2
The tunnel central point of current segment of constructing by currently construction segment tunnel cross section equivalent circular the center of circle, rb=l+ r0
10. according to a kind of Soft Rock Tunnel Excavation and preliminary bracing method described in claims 1 or 2, it is characterised in that:Step 4 In anchor pole (2) in the front and rear two neighboring suspension roof support unit in being laid staggeredly, phase in each suspension roof support unit Spacing between adjacent two anchor poles (2) is a, between the front and rear two neighboring suspension roof support unit and front and rear adjacent two Spacing between a tunneling boring steel bracket is a;The Tunnel structure is that the group of supporting is carried out to Tunnel Close arch;
It when Tunnel structure determination is carried out in step 4, also needs according to formula b=l-acot θ (11), a is carried out true It is fixed;In formula (11), b be the built-up arch thickness andθ is anchor pole (2) to tunnel surrounding rupture zone rock The angle of action of body compression and θ=45 °.
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