JP6730883B2 - Design method of flexible support - Google Patents

Description

The present invention relates to a method for designing a contractible support structure that contributes to stabilization of the air inside a tunnel.

In mountain tunnel construction methods such as NATM, safety is ensured by spraying concrete sprayed on the ground surface exposed by excavation and tunnel support such as steel support construction assembled along the ground surface. ..
In a large overburden tunnel, a large amount of deformation of the ground around the tunnel may cause a large stress on the tunnel support work. The same applies to tunnels formed by excavating fault fracture zones and expansive rocks.
In a tunnel where large stress is expected to occur, the rigidity and strength of the tunnel support work may be increased. Increasing the rigidity and strength of the tunnel support by increasing the size of steel support, increasing the amount of shotcrete, and increasing the thickness of the spray increases the material cost and the labor required for construction, and also increases the cross-sectional dimension of the tunnel. Affects.

Therefore, in Patent Document 1, a shrinkable member made of a fiber-reinforced cement-based material containing steel fibers and hollow particles having a volume ratio of nearly 1.0% is provided in a gap formed in a part of a tunnel support work (support member). Disclosed is a method of stabilizing a tunnel which employs a contractible support provided with a member and absorbs the deformation of the ground by the contractible member. The shrinkable member has rigidity that does not give deformation to the supporting member such as shotcrete, and it deforms while maintaining a constant load strength, so the internal pressure of the tunnel is maintained even during shrinking. It is possible.

JP, 2005-232958, A

The design method of the contractible support work has not been established, and the number and arrangement of the contractible members are set by the experience and subjectivity of the designer. Therefore, there is a possibility that the support structure may differ depending on the skill level of the designer.
An object of the present invention is to propose a method of designing a retractable support that enables quantitative design of the retractable support according to the natural situation.

In order to solve the above-mentioned problems, a first invention is a contractible support for designing an optimum number and layout of the contractible members when the specifications (maximum deformation amount, yield strength, etc.) of the contractible members are given. This is the engineering design method. On the other hand, a second aspect of the present invention is a design method for shrinkable support work, which designs specifications, quantities, and layouts of shrinkable members according to natural conditions. The shrinkable support work is a tunnel support work provided with a support member having an arched or ring-shaped sprayed concrete and a shrinkable member arranged so as to divide the sprayed concrete . The collapsible member includes a columnar main body portion and a reinforcement body that is provided around the main body portion, and the main body is restrained from lateral deformation during compression of the main body portion by the reinforcement body. Suppress a sudden decrease in stress of the compressible member after yielding of the portion.
The first aspect of the present invention represents the relationship between the reaction force of the load acting on the compressible support (supporting internal pressure) and the amount of displacement of the tunnel wall surface (the amount of displacement of the natural rock in the radial direction of the tunnel), depending on the natural conditions. The work of obtaining the rock mass characteristic curve, the work of calculating the tunnel deformation amount which is the tunnel wall surface displacement amount according to the yield pressure of the compressible member by the rock mass characteristic curve, and the operation until the compressible member yields. The work of calculating the amount of shrinkable deformation by adding the amount of elastic deformation that is the amount of deformation of the shrunken support and the amount of plastic deformation that is the amount of deformation of the compressible support after the contractible member yields. , The work of setting the number and layout of the shrinkable members according to the shrinkable deformation amount.

According to the design method of the shrinkable support of the first aspect of the present invention, the layout of the shrinkable members can be set according to the ground condition, so that the shrinkable support can be designed quantitatively. That is, according to the present invention, since the contractible support is formed according to the stress acting on the tunnel by utilizing the natural characteristic curve, it is possible to economically design by making the most of the performance of the contractible member. I am trying.
Note that the "natural rock characteristic curve" is a curve that represents the relationship between the reaction force of the load acting on the contractible support (supporting internal pressure) and the amount of tunnel wall displacement (the amount of displacement of the natural rock in the radial direction of the tunnel). Therefore, it is calculated by, for example, a Fenner-Pacher type curve, a Salencon theoretical solution, or an Oka-type elastoplastic theoretical solution. The natural characteristic curve includes a straight line. Further, the natural characteristic curve does not necessarily have to be graphed (mapped).

The second invention represents the relationship between the reaction force of the load acting on the compressible support (support internal pressure) and the displacement of the tunnel wall surface (displacement in the radial direction of the tunnel), depending on the natural conditions. A work for obtaining a rock mass characteristic curve, a work for assuming a maximum deformation amount of the compressible support, and a work for calculating a minimum yield pressure, which is an inner pressure of the support work according to the maximum deformation amount, by the rock mass characteristic curve. The work of calculating the maximum yield pressure of the compressible support work based on the relationship between the natural characteristic curve and the rigidity of the supporting member, and the contraction so that the maximum yield pressure falls within the range from the minimum yield pressure to the maximum yield pressure. The yield pressure of the supporting work is set, and the elastic deformation amount which is the deformation amount of the contractible supporting work until reaching the yield pressure and the plasticity which is the deformation amount of the contractible supporting work after reaching the yield pressure. It is characterized in that it comprises a work for calculating the shrinkable deformation amount by adding up the partial deformation amounts, and a work for setting the number and layout of the shrinkable members according to the shrinkable deformation amount.

According to the design method of the shrinkable support work of the second invention, the specifications, the quantity and the layout of the shrinkable members are set by utilizing the characteristic curve of the ground, so that the numerical calculation such as the FEM analysis is not required, which is economical. In addition, it is possible to easily design the contractible support work according to the natural condition. That is, according to the present invention, it is possible to set the specifications of the compressible member (yield strength and deformation performance) according to the natural condition (select the compressible member according to the natural condition), and It is possible to construct a contractible support work most suitable for the natural condition.

According to the method for designing the contractible support work of the present invention, it is possible to quantitatively design the contractible support work according to the natural condition.

(A) is sectional drawing which shows the tunnel which concerns on embodiment of this invention, (b) is a longitudinal section which shows the support structure of a tunnel. It is a perspective view showing a collapsible member concerning an embodiment of the present invention. It is a flowchart figure which shows the design method of the shrinkable support construction which concerns on 1st embodiment. It is a graph which shows the rock mass characteristic curve and the dynamic model of contractible support of the first embodiment. It is a flowchart figure which shows the design method of the contractible support work which concerns on 2nd embodiment. It is a graph which shows the rock mass characteristic curve and the dynamic model of contractible support of a second embodiment.

<First embodiment>
In the first embodiment, as shown in FIG. 1( a ), a method of designing a contractible support installed in a tunnel 1 constructed by NATM will be described.
The shrinkable support 2 of the present embodiment includes a support member 3 (see FIG. 1B) including a shotcrete 31, a steel support 32, a lock bolt 33, and the like, and a compressible member 4. .. The sprayed concrete 31 and the steel support 32 of the present embodiment are formed in an arch shape (horseshoe shape). The shapes of the shotcrete 31 and the steel supporters 32 are not limited, and may be ring-shaped.

The support member 3 is formed by spraying the sprayed concrete 31 on the ground exposed by the excavation of the ground, installing the steel support 32 and driving the lock bolt 33. The spraying thickness of the sprayed concrete 31 is not limited, and is appropriately determined depending on the ground condition and the like. The shotcrete 31 may be divided into a plurality of layers, for example, divided into a primary shot and a secondary shot. The steel support 32 is installed at a predetermined interval from the steel support 32 built in the previous construction cycle. The rock bolt 33 is placed by drilling a rock bolt hole in the ground around the tunnel 1, injecting mortar into the rock bolt hole, and inserting the lock bolt 33.

The collapsible member 4 is arranged so as to partition the arched sprayed concrete 31 as shown in FIG. The installation location of the collapsible member 4 in the collapsible support 2 is not limited. In the present embodiment, the shrinkable member 4 is arranged by spraying the spraying concrete 31 onto the natural ground G in a state where the shrinkable member 4 is arranged at a predetermined position in advance. The method of installing the shrinkable member 4 on the sprayed concrete 31 is not limited, and for example, a recess for installing the shrinkable member 4 may be formed after the sprayed concrete 31 is constructed. Alternatively, when the sprayed concrete 31 is constructed, a space along the tunnel axial direction may be formed in the sprayed concrete 31 in advance by box cutting or the like, and the collapsible member 4 may be disposed in this space. When the sprayed concrete 31 is divided into two layers, the collapsible member 4 is arranged so as to cross the secondary spray after the primary spraying, and then the secondary spraying is performed. You may go.

As shown in FIG. 2, in the present embodiment, as the collapsible member 4, a member provided with a main body portion 41 formed in a quadrangular prism shape and a reinforcing body 42 provided around the main body portion 41 is used. The structure of the collapsible member 4 is not limited, and may be, for example, a hardened body of fiber-reinforced concrete having innumerable bubbles or a member in which a steel pipe having a multi-layer structure is deformed while buckling. ..
The main body portion 41 is formed of a hardened body of mortar containing cement, a porous material, and water. The composition of the mortar is such that the compressive strength of the main body 41 is lower than the compressive strength of the shotcrete 21. The main body 41 is not limited to mortar, but may be concrete, for example. Further, the shape of the main body portion 41 is not limited to the rectangular column shape, and may be, for example, a column shape.

In this embodiment, a fiber sheet (so-called civil engineering sheet) is wound around the main body 41 as the reinforcing body 42. The reinforcing body 42 restrains the outer periphery of the main body portion 41 and suppresses lateral deformation that occurs when the main body portion 41 is compressed. That is, the compressible member 4 is in the triaxial state because the reinforcing body 42 is provided around the main body 41, and the stress of the compressible member 4 does not suddenly decrease even after the yield of the main body 41. It is possible to absorb the displacement of the tunnel wall surface. The reinforcing body 42 is not limited to the fiber sheet as long as it can suppress the lateral deformation of the main body 41 during compression.

Next, a method of designing the quantity and layout of the contractible members 4 will be described. As shown in FIG. 3, the design method of the contractible support work of the present embodiment is, as shown in FIG. 3, a tunnel shape setting work S10, a ground condition setting work S11, a ground characteristic curve setting work S12, a preceding displacement amount setting work S13, and a tunnel deformation. An amount calculation work S14, a compressible deformation amount calculation work S15, and a layout setting work S16 are provided. In the present embodiment, the compressible member 4 whose deformation amount and yield pressure P _y are known is used. Here, the yield pressure P _y of the compressible member 4 is a stress in the tunnel radial direction corresponding to the yield strength σ _y of the compressible member 4, and can be expressed by P _y =σ _y ×t/R. .. The yield strength σ _y is the uniaxial compressive strength of the collapsible member 4, and when the collapsible member 4 is installed on the tunnel wall surface, if the stress in the tunnel circumferential direction exceeds the yield strength σ _y , Surrender. Further, t is the thickness of the supporting member (shot concrete), and R is the excavation radius of the tunnel.

In the tunnel shape setting operation S10, the tunnel excavation radius is set. The tunnel excavation radius is the value obtained by adding the lining concrete thickness, supporting member thickness, and deformation allowance to the design inner radius. The amount of deformation allowance is set as appropriate according to the natural characteristics, the sectional shape of the tunnel, and the like. The method for setting the tunnel excavation radius is not limited.
The ground condition setting work S11 is a work for setting the ground physical property value according to the soil cover, the ground classification, and the like. Ground physical property values are unit volume weight of ground, deformation coefficient, adhesive force, internal friction angle, Poisson's ratio, etc., and are set based on existing data, geological survey results, ground survey results, physical survey results, etc. ..

In the ground characteristic curve setting operation S12, the ground characteristics representing the relationship between the reaction force of the load acting on the compressible support 2 (support internal pressure) and the amount of tunnel wall displacement (the amount of displacement of the ground in the radial direction of the tunnel). Find the curve. The rock mass characteristic curve is set according to rock mass conditions such as soil cover and rock physical property values. In the present embodiment, as shown in FIG. 4, a ground characteristic curve (Fenner-Pacher type curve) L ₁ is created. The natural characteristic curve is not limited to the Fenner-Pacher type curve, and for example, the Salencon theoretical solution or the Oka-type elasto-plastic theoretical solution may be adopted.

In the preceding displacement amount setting operation S13, a displacement amount (preceding displacement amount δ ₁ ) that occurs on the tunnel wall surface before the contractible support 2 is installed is assumed. The preceding displacement amount δ ₁ is assumed by a past case, numerical analysis, or the like, based on rock mass physical property values, rock cover conditions, and other rock mass conditions.
In the tunnel deformation amount calculation work S14, the deformation amount of the tunnel wall surface is assumed to be δ _y . Assuming that the amount of deformation of the tunnel δ _y is the amount of displacement (strain) of the tunnel wall surface corresponding to the yield pressure P _y of the compressible member 4, the yield pressure P _y of the compressible member 4 is defined as the support work internal pressure in the natural characteristic curve. In this case, the tunnel wall displacement amount (tunnel wall displacement amount at point A) is equal to the tunnel deformation amount δ _y .

In the contractible deformation amount calculation work S15, the deformation amount of the contractible support work 2 (compressible deformation amount) is calculated.
First, the elastic component of the deformation amount of the retractable support 2 (hereinafter referred to as “elastic component deformation amount δ ₂ ”) is calculated. The elastic component deformation amount δ ₂ is the deformation amount of the compressible support 2 when the yield pressure P _y of the compressible member 4 acts. That is, the elastic deformation amount δ ₂ is the deformation amount in the tunnel radial direction that occurs in the contractible support 2 until the contractible member 4 yields.
Next, the plastic component of the deformation amount (hereinafter referred to as “plastic component deformation amount δ ₃ ”) which is the tunnel wall surface displacement amount absorbed by the contractible member 4 after yielding is calculated. The plastic deformation amount δ ₃ is a value obtained by subtracting the preceding displacement amount δ ₁ and the elastic deformation amount δ ₂ from the tunnel deformation amount δ _y .
Then, the elastic deformation amount δ ₂ and the plastic deformation amount δ ₃ are added together to calculate the contractible deformation amount δ ₂ +δ ₃ .

In the layout setting work S16, the number and layout of the contractible members 4 are set.
First, the number of the shrinkable members 4 per cross section is set according to the shrinkable deformation amount δ ₂ +δ ₃ . That is, the quantity of the compressible members 4 (quantity in the circumferential direction of the tunnel) is set by dividing the amount of deformation δ ₀ per shrinkable member 4 from the amount of shrinkable deformation δ ₂ +δ ₃ . At this time, the deformable amount according to the number of the contractible members 4 (the deformation amount per unit δ ₀ ×the number of the contractible members 4) exceeds the contractible deformation amount δ ₂ +δ ₃ , Determine the quantity. For example, when the amount of deformation δ ₀ per shrinkable member 4 is 0.3 and the amount of shrinkable deformation δ ₂ +δ ₃ =1, the number of shrinkable members 4 is 4 (>1/0. It should be set to 3). However, the deformation amount δ ₀ is the deformation amount in the tunnel radial direction, and the deformation amount δ′ _{0 in} the circumferential direction of the compressible member 4 (corresponding to the deformation amount in the axial direction during the uniaxial compression test) is δ′ _0. =2π×δ ₀ .
When the number of the shrinkable members 4 is determined, the layout of the shrinkable members 4 is set. For example, when the number of the contractible members 4 is eight, four may be arranged on the left and right sides of the tunnel cross section (see FIG. 1A). When the number of the shrinkable members 4 is four, two shrinkable members 4 may be arranged on each side of the tunnel cross section. The layout of the collapsible member 4 is not limited, and for example, a plurality of the collapsible members 4 may be continuously arranged in the tunnel circumferential direction.

According to the design method of the contractible support of the present embodiment, the contractible member 4 to which the amount of deformation and the yield pressure is applied can be arranged according to the ground condition, so that the compressible support is quantitatively performed. The work 2 can be designed. Since the retractable support 2 corresponding to the stress acting on the tunnel 1 is formed by utilizing the natural characteristic curve, it is possible to maximize the performance of the retractable member 4, which leads to economical design. It will be possible.
Since the shrinkable member 4 having lower strength than the sprayed concrete 31 is used, the deformation of the tunnel support work due to the external force can be concentrated on the shrinkable member 4. Therefore, the excessive stress that causes the deformation of the support member 3 does not occur, and the safety as the support (or lining) of the tunnel 1 can be maintained.

<Second embodiment>
In the second embodiment, as in the first embodiment, a method of designing a retractable support installed in the tunnel 1 constructed by NATM will be described.
As shown in FIGS. 1(a) and 1(b), the shrinkable support 2 of the present embodiment includes a support member 3 made up of shotcrete 31, steel support 32 and lock bolts 33, and a compressible member. 4 and.
The details of the support member 3 and the collapsible member 4 are the same as those shown in the first embodiment, and thus detailed description thereof will be omitted.

Next, a method of designing the quantity and layout of the contractible members 4 will be described. As shown in FIG. 5, the design method of the contractible support work of this embodiment is as follows: tunnel shape setting work S20, natural condition setting work S21, natural characteristic curve setting work S22, preceding displacement amount setting work S23, maximum deformation. An amount calculation work S24, a minimum yield pressure calculation work S25, a maximum yield pressure calculation work S26, a yield pressure setting work S27, a compressible deformation amount calculation work S28, and a layout setting work S29 are provided. In the present embodiment, a case will be described in which a compressible member 4 having an optimum yield strength (yield pressure) is selected from a plurality of types of compressible members 4 having different yield strengths (yield pressures) and arranged. To do. The shrinkable member 4 may be manufactured to have a yield strength (yield pressure) according to the natural condition. Here, the yield pressure P _y of the compressible member 4 is a stress in the tunnel radial direction corresponding to the yield strength σ _y of the compressible member 4, and can be expressed by P _y =σ _y ×t/R. .. The yield strength σ _y is the uniaxial compressive strength of the collapsible member 4, and when the collapsible member 4 is installed on the tunnel wall surface, if the stress in the tunnel circumferential direction exceeds the yield strength σ _y , Surrender. Further, t is the thickness of the supporting member (shot concrete), and R is the radius of the tunnel.
The details of the tunnel shape setting work S20, the rock condition setting work S21, the rock characteristic curve setting work S22, and the preceding displacement amount setting work S23 are described in detail in the tunnel shape setting work S10 and the rock condition setting work described in the first embodiment. Since it is the same as S11, the natural characteristic curve setting work S12, and the preceding displacement amount setting work S13, detailed description thereof will be omitted.

In the maximum deformation amount calculation operation S24, the maximum deformation amount δ _max (allowable value of tunnel wall displacement amount) of the retractable support 2 is assumed (see FIG. 6 ). The maximum deformation amount δ _max is estimated according to the natural characteristics, the tunnel cross-sectional shape, and the like.
In the minimum yield pressure calculation work S25, the minimum yield pressure P _min of the collapsible member 4 is calculated. The minimum yield pressure P _min is a support work internal pressure according to the maximum deformation amount δ _max . That is, as shown in FIG. 6, the supporting internal pressure corresponding to the maximum deformation amount δ _max (point A) is obtained from the natural characteristic curve (natural characteristic curve), and this is calculated as the minimum yield pressure P _min of the compressible member 4. And

In the maximum yield pressure calculation work S26, the maximum yield pressure P _max of the contractible support work 2 is calculated. The maximum yield pressure P _max is the straight line L ₂ indicating the elastic behavior of the compressible member and the natural characteristic curve L ₁ so that the yield pressure of the contractible support 2 does not become excessive with respect to the natural characteristics. The internal pressure of the supporting work at the intersection B with In this embodiment, it is assumed that the support member 3 is installed when the tunnel wall surface displacement amount reaches the preceding displacement amount δ ₁ . That is, the intersection point B of the straight line L ₂ extending from (δ ₁ , 0) as the base point and the natural characteristic curve L ₁ is obtained, and the supporting work internal pressure corresponding to this intersection point B is set as the maximum yield pressure P _max .

In the yield pressure setting operation S27, the yield pressure P _y corresponding to the yield strength σ _y of the compressible member 4 is set.
The yield pressure P _y is set to be equal to or lower than the yield pressure P _sy of the support member and equal to or higher than the minimum yield pressure P _min . The yield pressure _Psy of the support member is set so as to fall within the range of the maximum yield pressure _Pmax to the minimum yield pressure _Pmin . In the present embodiment, a yield pressure P _y that falls within the range of the yield pressure P _sy of the support member to the minimum yield pressure P _min among the plurality of contractible members 4, 4,... With different yield pressures P _y may be used. The contracting member 4 is selected.

In the shrinkable deformation amount calculation work S28, the shrinkable deformation amount of the shrinkable support work 2 is calculated.
First, the elastic component deformation amount δ ₂ which is the elastic component deformation amount of the contractible support corresponding to the yield pressure P _y is calculated. The elastic deformation amount δ ₂ is the deformation amount of the contractible support 2 until the contractible member 4 yields. Subsequently, the tunnel deformation amount δ ₄ , which is the tunnel wall surface displacement amount corresponding to the yield pressure P _y , is calculated from the rock mass characteristic curve (ground rock characteristic curve L ₁ ) (point C). Then, the plastic component deformation amount δ ₃ of the shrinkable support, which is the amount of displacement of the tunnel wall surface absorbed by the compressible support 2, is calculated. The plastic deformation amount δ ₃ is a value obtained by subtracting the preceding displacement amount δ ₁ and the elastic deformation amount δ ₂ from the tunnel deformation amount δ ₄ . When the plastic component deformation amount δ ₃ is determined, the elastic component deformation amount δ ₂ and the plastic component deformation amount δ ₃ are added to calculate the contractible deformation amount.

In the layout setting work S29, the quantity and the layout are set.
First, it is considered that the material has an optimum yield strength (yield pressure) satisfying P _min ≤P _y <P _sy from among the plurality of types of compressible members 4 having different yield strength σ _y (yield pressure P _y ). The shrinkable member 4 is selected. Next, the quantity of the shrinkable member 4 is calculated by dividing the amount of deformation δ ₀ per shrinkable member 4 from the amount of shrinkable deformation (elastic deformation amount δ ₂ +plastic deformation amount δ ₃ ). .. At this time, the number of the shrinkable members 4 is determined such that the amount of deformation according to the number of the shrinkable members 4 (deformation amount per piece δ ₀ ×quantity) exceeds the shrinkable deformation amount δ ₂ +δ _3. .. For example, when the amount of deformation δ ₀ per shrinkable member 4 is 0.3 and the amount of shrinkable deformation δ ₂ +δ ₃ =1, the number of shrinkable members 4 is 4 (>1/0. It should be set to 3). However, the deformation amount δ ₀ is the deformation amount in the tunnel radial direction, and the deformation amount δ′ _{0 in} the circumferential direction of the compressible member 4 (corresponding to the deformation amount in the axial direction during the uniaxial compression test) is δ′ _0. =2π×δ ₀ .
When the number of the shrinkable members 4 is determined, the layout of the shrinkable members 4 is set. For example, when the number of the contractible members 4 is eight, four may be arranged on the left and right sides of the tunnel cross section (see FIG. 1A). When the number of the shrinkable members 4 is four, two shrinkable members 4 may be arranged on each side of the tunnel cross section.

The yield strength σ _y of the compressible member 4 is set to a value lower than the design reference strength (σ′ _ck ) of the support member 3 (shot concrete 31) (F _s ×σ _y ≦σ′ _ck : F _s). = Safety factor).
Here, the number of the contractible members 4 is set in consideration of economical efficiency and workability. That is, when the number of the compressible members 4 is large, it is uneconomical and time-consuming to construct, etc., the number and layout are examined again by using another compressible member having a different yield pressure P _y . When the compressive member 4 having a large yield pressure P _y (yield strength σ _y ) is used, the number of the compressible members 4 can be reduced. When the number of the shrinkable members 4 is small, the labor at the time of construction can be omitted, but increasing the strength of the shrinkable members 4 may increase the cost of the shrinkable members 4. On the other hand, when the compressible member 4 having a small yield pressure P _y (yield strength σ _y ) is used, it is necessary to increase the number of the compressible members 4. By reducing the strength of the collapsible member 4, the manufacturing cost of the collapsible member 4 can be reduced, but by disposing a large number of the collapsible members 4, it takes time and effort for construction. Therefore, it is necessary to determine the optimum combination of the specifications, quantity, and layout of the shrinkable members 4 in consideration of workability and economy.

According to the design method of the contractible support work of the present embodiment, the specifications, the quantity and the layout of the contractible member 4 are set by using the natural characteristic curve, so that the numerical calculation such as the FEM is not required, and more. Economically, the flexible support 2 can be easily and quickly designed according to the natural conditions. That is, it is possible to set the yield strength and the deformation performance of the shrinkable member 4 according to the natural ground condition (select the shrinkable member 4 according to the natural ground condition), which in turn is excellent in workability and It is possible to construct a contractible support work 2 that is most suitable for the natural situation.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the respective constituent elements described above can be appropriately modified without departing from the spirit of the present invention.
The structure of the collapsible member is not limited to the one including the main body and the reinforcing body shown in each of the embodiments. For example, it may be made of a fiber-reinforced cementitious material containing steel fibers and hollow particles.
The contractible member may be manufactured in advance in a factory or the like, or may be manufactured on site.
The support structure of the tunnel may be appropriately determined according to the ground condition (ground classification).
Furthermore, the tunnel construction method that can be adopted by the design method of the flexible support of the present invention is not limited to NATM, and may be applied to, for example, a conventional construction method, a TBM or a shield construction method.

1 tunnel 2 shrinkable support 3 support member 4 shrinkable member

Claims (2)

A supporting member comprising a sprayed concrete formed in an arch shape or a ring shape, and a collapsible member arranged so as to divide the sprayed concrete, and a method of designing a shrinkable support work, comprising:
The collapsible member includes a columnar main body portion and a reinforcement body that is provided around the main body portion, and the main body is restrained from lateral deformation during compression of the main body portion by the reinforcement body. Suppresses a sudden decrease in the stress of the compressible member after yielding of the part,
Depending on the ground conditions, work to obtain a rock characteristic curve that represents the relationship between the reaction force of the load acting on the compressible support and the tunnel wall displacement,
A work of calculating a tunnel deformation amount which is a tunnel wall surface displacement amount according to the yield pressure of the compressible member by the natural characteristic curve,
The elastic component deformation amount, which is the deformation amount of the contractible support until the contractible member yields, and the plastic component deformation amount, which is the deformation amount of the contractible support after the contractible member yields, are added. Work to calculate the amount of contractible deformation by
A method of designing a shrinkable support, comprising: setting the number and layout of the shrinkable members according to the shrinkable deformation amount. A supporting member comprising a sprayed concrete formed in an arch shape or a ring shape, and a collapsible member arranged so as to divide the sprayed concrete, and a method of designing a shrinkable support work, comprising:
The collapsible member includes a columnar main body portion and a reinforcement body that is provided around the main body portion, and the main body is restrained from lateral deformation during compression of the main body portion by the reinforcement body. Suppresses a sudden decrease in the stress of the compressible member after yielding of the part,
Depending on the ground conditions, work to obtain a rock characteristic curve that represents the relationship between the reaction force of the load acting on the compressible support and the tunnel wall displacement,
Work assuming a maximum amount of deformation of the retractable support,
Work to calculate the minimum yield pressure, which is the internal pressure of the supporting work according to the maximum deformation amount, based on the natural characteristic curve,
A work for calculating the maximum yield pressure of the contractible support work based on the relationship between the natural characteristic curve and the rigidity of the support member;
Work to set the yield pressure of the contractible support work so that it falls within the range from the minimum yield pressure to the maximum yield pressure,
It is possible by adding the elastic deformation amount which is the deformation amount of the contractible support until reaching the yield pressure and the plastic component deformation amount which is the deformation amount of the contractible support after reaching the yield pressure. Work to calculate the amount of shrinkage deformation,
A method of designing a shrinkable support, comprising: setting the number and layout of the shrinkable members according to the shrinkable deformation amount.

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