Stride high ductility tunnel supporting construction of activity fracture
Technical Field
The invention relates to a tunnel supporting structure, in particular to a cross-activity fracture high-ductility tunnel supporting structure.
Background
With the rapid development of western large-scale development and traffic industry, the number of tunnels is increased increasingly, the construction scale is increased increasingly, the encountered geological conditions are more and more complex, and the tunnel construction and operation process faces a severe challenge of adverse disaster environment. The situation that tunnels in western mountainous areas of China penetrate through special geological structure sections such as movable fracture zones is common. Active fractures, also known as active faults, are faults that have been active since the fourth (or late) age, are still active to date, and may still be active for some period of time in the future. The influence of the active fault on the tunnel structure is mainly reflected in two aspects: firstly, the influence of fault activity, such as fracture of a small river in the south of the cloud, is fracture of new-world activity, the recorded average annual slip rate is 9.4 +/-1.2 mm/year, and for a tunnel structure with service life of hundreds of years, the slip dislocation of a fault has great influence on the safety of a tunnel supporting structure. Secondly, the earthquake action is influenced by the earthquake-induced fault, the tunnel passing through the fault or the fault fracture zone can be seriously damaged in the earthquake, and the lining close to the fault can generate larger transverse and vertical dislocation in the plane vertical to the tunnel axis. The existing research shows that the tunnel structure has larger shearing stress at the fault fracture zone transition position, obvious stress concentration exists at the fault fracture zone position, and the tunnel structure is easy to damage.
At present, for crossing a movable fracture tunnel, scholars at home and abroad have carried out some research works and conclude 3 measures for preventing the tunnel from being damaged by fault shearing: avoidance, reinforcement and fracture resistance design; the foam concrete with the damping function and the cross-fault tunnel anti-damping technology are developed. For example, the patent number is ZL200910058875.6 and the invention name is: the invention relates to an invention patent of a shock-proof structure of a cross-active fault tunnel; the patent number is ZL201320646366.7, and the invention name is: patent for the invention of a tunnel supporting structure spanning an active fault. The invention patents all adopt the foam concrete as the shock absorption layer, absorb the earthquake capability and provide a certain displacement space through the shock absorption layer, and respectively perform the anti-shear design of the tunnel structure under the earthquake condition and the earthquake-free condition. However, the above patent also has the following problems:
firstly, the shock absorption is realized only by the foam concrete, and the shock absorption is realized without considering the change of the performances of rigidity, strength, damping and the like of the tunnel, so that the tunnel is easy to follow the deformation of the stratum, and the reaction of the tunnel is reduced. Patent No. ZL201320646366.7, which uses a multi-layer lining structure, increases the structural rigidity, but increases the amount of material used and the mass of the tunnel, resulting in the tunnel bearing higher seismic loads, is not economical and has a high possibility of damage during earthquakes. Moreover, the foam concrete layer designed by the method is only arranged on the arch part, and the inverted arch part is not provided, so that the damping effect of the bottom structure is not facilitated.
Secondly, the tunnel supporting structure designed by the invention patent adopts the traditional concrete structure for the primary support and the secondary lining, and has poor tensile, shearing and bending resistance. In the earlier stage of tunnel operation, the action of shear resistance and slippage dislocation of active fracture can be eliminated by means of a foam concrete damping layer, along with the increase of service life, the resistance is also realized by primary support and secondary lining, if the primary support and the secondary lining are in high-ductility structures, the deformation and stress generated by structure dislocation are suitable, the structure can still consume seismic energy and cannot be damaged after reaching the non-elastic state, and the method can be an effective support structure and an anti-vibration technology.
Therefore, aiming at the defects of the existing anti-shock technology for crossing the active fault, a high-ductility tunnel supporting structure for crossing the active fault is needed to be provided.
Disclosure of Invention
The invention aims to provide a high-ductility tunnel supporting structure which is formed by PVA-ECC (Polyvinyl alcohol Fiber-reinforced cement-based composite materials, PVA-ECC for short) and has strong deformability, good crack resistance and good earthquake resistance, and simultaneously has the capabilities of resisting movable fracture, slippage, dislocation damage and shock resistance.
The specific technical scheme of the invention is as follows: the high-ductility tunnel supporting structure capable of crossing the active fracture comprises a crossing active fracture supporting section 8 and a common supporting section 9 which are arranged at intervals along the longitudinal direction of the tunnel, wherein the common supporting section 9 is sequentially provided with a reinforced concrete secondary lining 7, a waterproof plate 2 and a concrete spraying primary support 6 from inside to outside, the crossing active fracture section 8 is sequentially provided with a reinforced PVA-ECC secondary lining 1, a waterproof plate 2, a foam concrete layer 3 and a sprayed PVA-ECC primary support 4 from inside to outside, the foam concrete layer 3 is filled between the sprayed PVA-ECC primary support 4 and the reinforced PVA-ECC secondary lining 1, and the waterproof plate 2 is arranged between the foam concrete layer 3 and the reinforced PVA-ECC secondary lining 1.
Preferably, a damping gap 5 is arranged between the movable fracture spanning supporting section 8 and the common supporting section 9, and a steel bar mesh or a steel arch is hung in the concrete spraying primary support 6 and the PVA-ECC spraying primary support 4.
Preferably, the PVA-ECC comprises the components of cement, fly ash, sand, water, a water reducing agent and PVA fiber, wherein the mass percentage of the cement is as follows: fly ash: sand: water: water reducing agent =1: 1.0-1.2: 0.6-0.8: 0.42-0.57: 0.001 to 0.003; the total volume of the cement, the fly ash, the sand and the water reducing agent after being uniformly mixed is taken as a base number, and the doping amount of the PVA fiber is 13-20 kg/m3。
Preferably, the cement is P.O.42.5 portland cement, the fly ash is first-grade fly ash, the particle size of the sand is 0.2 mm-0.4 mm, the length of the PVA fiber is 12mm, the diameter is greater than 30 μm, the tensile strength is greater than 1200MPa, the elastic modulus is greater than 30GPa, and the elongation at break is greater than 6%.
Preferably, the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent with the water reducing rate of more than 40%.
The red reinforcement reinforced PVA-ECC secondary lining 1 is provided with longitudinal reinforcements and circumferential reinforcements, the high-toughness and high-strength PVA-ECC and the good bonding performance of the reinforcements can be utilized, the rigidity and the deformability of the secondary lining are enhanced, and the ductility and the seismic performance of the secondary lining are obviously improved.
The invention has the beneficial effects that:
(1) the high-toughness PVA-ECC material has the compression strength of over 35MPa and ultimate tensile strain of over 3%, which is over 300 times that of common concrete, has the characteristics of strain hardening and multi-crack cracking under the load of stretching, bending and shearing, has good bonding property with reinforcing steel bars, and has the characteristics of high toughness, high durability, high energy consumption, good shock resistance and deformation resistance, and the like.
(2) The invention adopts the primary support and the secondary lining of the high-toughness PVA-ECC material, obviously improves the overall performance of the composite lining consisting of the primary support and the secondary lining, greatly improves the ductility and the deformability of the support structure, and enhances the bearing of the stress and the displacement caused by the slippage and dislocation of the fault. And the foam concrete layer filled in the middle can effectively reduce the vibration and consume energy, so that the tunnel supporting structure has excellent capability of resisting movable fracture, slippage, dislocation damage and vibration reduction.
(3) After the primary support and the secondary lining of the high-toughness PVA-ECC material are adopted, the lining thickness and the foam concrete layer thickness can be reduced according to the requirement, the tunnel excavation space and the number of support structure materials are saved, and the support structure is more simple, convenient and flexible to set.
Drawings
Fig. 1 is a schematic longitudinal section view of a cross-active fracture high-ductility tunnel supporting structure of the present invention;
fig. 2 is a schematic cross-sectional view of the high-ductility tunnel supporting structure across a fracture of the present invention;
the reference numerals in the figures denote:
1-reinforcing a PVA-ECC secondary lining with steel bars; 2-waterproof board; 3-foam concrete layer; 4-PVA-ECC preliminary bracing; 5, damping seams; 6-spraying concrete primary support; 7-reinforced concrete secondary lining; 8, spanning a movable fracture support section; 9-common support section.
Detailed Description
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings.
Example 1: as shown in FIGS. 1-2: the high-ductility tunnel supporting structure capable of crossing the active fracture comprises a crossing active fracture supporting section 8 and a common supporting section 9 which are arranged at intervals along the longitudinal direction of the tunnel, wherein the common supporting section 9 is sequentially provided with a reinforced concrete secondary lining 7, a waterproof plate 2 and a concrete spraying primary support 6 from inside to outside, the crossing active fracture section 8 is sequentially provided with a reinforced PVA-ECC secondary lining 1, a waterproof plate 2, a foam concrete layer 3 and a sprayed PVA-ECC primary support 4 from inside to outside, the foam concrete layer 3 is filled between the sprayed PVA-ECC primary support 4 and the reinforced PVA-ECC secondary lining 1, and the waterproof plate 2 is arranged between the foam concrete layer 3 and the reinforced PVA-ECC secondary lining 1.
And a damping gap 5 is arranged between the movable fracture spanning support section 8 and the common support section 9, and a reinforcing mesh or a steel arch frame and the like can be hung in the concrete spraying primary support 6 and the PVA-ECC spraying primary support 4 according to requirements.
Example 2: wherein the common supporting section 9 is a composite lining structure, and the construction process is the same as that of the conventional composite lining structure; the components of the PVA-ECC material in the cross-active fracture supporting section 8 are cement, fly ash, sand, water, a water reducing agent and PVA fibers, wherein the cement comprises the following components in percentage by mass: fly ash: sand: water: water reducing agent =1: 1.0-1.2: 0.6-0.8: 0.42-0.57: 0.001 to 0.003; the total volume of the cement, the fly ash, the sand and the water reducing agent after being uniformly mixed is taken as a base number, and the doping amount of the PVA fiber is 13-20 kg/m3。
The cement is P.O.42.5 Portland cement, the fly ash is first-grade fly ash, the particle size of the sand is 0.2-0.4 mm, the length of the PVA fiber is 12mm, the diameter is greater than 30 micrometers, the tensile strength is greater than 1200MPa, the elastic modulus is greater than 30GPa, the elongation at break is greater than 6%, and the PVA-ECC is also added with a polycarboxylic acid high-efficiency water reducing agent with the water reducing rate of more than 40%.
Example 3: in the embodiment, the reinforcement reinforced PVA-ECC secondary lining 1 is formed by pouring a PVA-ECC material, the PVA-ECC primary support is formed by spraying a PVA-ECC material, the PVA-ECC material comprises the following components in percentage by mass: fly ash: sand: water: water reducing agent =1:1.2:0.72:0.57:0.003, based on the total volume of the cement, the fly ash, the sand and the water reducing agent after being uniformly mixed, the mass mixing amount of the PVA fiber is 20kg/m3. The cement is P.O.42.5 Portland cement, the fly ash is first-grade fly ash, the particle size of the sand is 0.2 mm-0.4 mm, the PVA fiber is a fiber produced in Japan, the length is 12mm, the diameter is 39 mu m, the tensile strength is 1620MPa, the elastic modulus is 42.8GPa, and a Sika polycarboxylic acid high-efficiency water reducing agent is added. The performance of the above PVA-ECC material was tested as follows:
(1) and (3) curing the test block by using a prism test block of 100mm multiplied by 300mm for 28d according to a standard curing method, and performing an axial compressive strength test. The test result shows that: the average value of the compressive strength of the PVA-ECC material is 40MPa, and the test block has obvious compressive toughness in the process of breaking.
(2) A beam type test piece with the thickness of 100mm multiplied by 400mm is adopted, and a four-point bending test is carried out after the test piece is maintained for 28 days according to a standard maintenance method. The test result shows that: the ultimate tensile strain of the PVA-ECC material reaches 3.2 percent, is more than 300 times of the ultimate tensile strain of common concrete, and shows the characteristics similar to the strain hardening and multi-slit cracking of steel under bending load.
The test results show that the ultimate tensile strain of the PVA-ECC material is far higher than that of the ordinary plain concrete, and the test piece is in ductile failure when being subjected to compression and bending failure and shows high toughness characteristics.
The stirring method of the PVA-ECC material comprises the following steps: and adding the cement, the fly ash and the sand into a stirrer according to the mass ratio, uniformly stirring, adding the PVA fiber according to the mass ratio, uniformly stirring, then adding the water and the water reducing agent according to the mass ratio, and uniformly wet-stirring to obtain the high-toughness PVA-ECC material.
The casting method of the reinforcement reinforced PVA-ECC secondary lining 1 by adopting the PVA-ECC material comprises the following steps: and (3) pouring the PVA-ECC mixture by using a lining template trolley by adopting a conventional pumping process, and removing the template trolley after finishing pouring and curing for 3 days to obtain the PVA-ECC secondary lining.
The PVA-ECC primary support 4 is sprayed by adopting a PVA-ECC material spraying method, which comprises the following steps: and (3) placing the PVA-ECC mixture in a sprayer for spraying, and spraying in layers by adopting a wet spraying process, wherein the spraying thickness of each layer is 3-5 cm.
The thicknesses of the reinforcement reinforced PVA-ECC secondary lining 1, the foam concrete layer 3 and the sprayed PVA-ECC primary support 4 are comprehensively determined according to the requirements of fault activity, slip rate and structural strength of the service life of the tunnel, in the embodiment shown in the figure, the thickness of the reinforcement reinforced PVA-ECC secondary lining 1 is 30 cm-50 cm, the thickness of the foam concrete layer 3 is 20 cm-30 cm, and the thickness of the sprayed PVA-ECC primary support 4 is 15 cm-30 cm.
The calculation parameters of the foam concrete layer 3 can be set according to the existing standards such as "foam concrete" (JG/T266-2011) and "foam concrete application technical rules" (JGJ/T341-2014), and in the embodiment, the calculation parameters are as follows: the compressive strength is 3.0-5.0 MPa, the elastic modulus is 0.6-1.2 GPa, and the porosity is more than 50%.
The cross-active fracture section 8 and the common supporting section 9 are flexibly connected, and specifically, as shown in fig. 1, damping seams 5 are arranged between two ends of the cross-active fracture section 9 and the common supporting section 9.
Waterproof board 2 is sealed at tunnel hoop all ring, adopts the high molecular polymer coiled material, like polyvinyl chloride waterproofing membrane, EVA waterproofing membrane, HDPE high density ethylene waterproofing membrane etc.. In the embodiment shown in the figure, a softer EVA waterproof roll is adopted.
While the present invention has been described in detail with reference to the embodiments, the present invention is not limited to the embodiments and various changes can be made without departing from the spirit and scope of the present invention by those skilled in the art.