Deep-buried loess tunnel deformation control construction structure based on cover arch and method

Abstract

The invention discloses a deep-buried loess tunnel deformation control construction structure based on a cover arch and a method. The structure comprises a tunnel primary support structure body for primary support of a tunnel and the reinforcement cover arch arranged on the inner side of the tunnel primary support structure body, wherein the tunnel primary support structure body and the reinforcement cover arch form a reinforced primary support structure body. The method comprises the following steps of 1, carrying out tunnel excavation and primary support; and 2, carrying out reinforcement arc arch construction. The structure and the method have the advantages of being reasonable in design, simple and convenient in construction and good in use effect, the reinforcement cover arch is adopted to reinforce the tunnel primary support structure body and form the reinforced primary support structure body, an isolation layer is arranged between the reinforcement arc arch and the tunnel primary support structure body, in addition, the reinforcement cover arch adopts a plurality of cover arch units to reinforce the tunnel primary support structure body in a segmented mode, so that the construction is simple and convenient, moreover, the reinforced primary support structure body formed by construction has certain self-adaptive capacity and can effectively adapt to the deformation condition of soil mass on the peripheral side of the tunnel, and therefore the deformation resistance of the reinforced primary support structure body can be effectively enhanced.

Description

technical field [0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a construction structure and method for deformation control of a deeply buried loess tunnel based on an arch. Background technique [0002] Loess refers to wind-moved deposits of yellow silt during the Quaternary period in geological time. Loess collapsibility coefficient (also called collapsibility coefficient) is a mechanical parameter to evaluate the collapsibility of loess. Under a certain pressure, loess collapsibility coefficient refers to the ratio of the height difference before and after soaking of soil samples to the original height of soil samples. The collapsibility coefficient of loess is an important index to evaluate the collapsibility of loess, which can be directly measured by experiment. According to the different collapsibility coefficient of loess, loess can be divided into collapsible loess and non-collapsible loess. A large number o...

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Problems solved by technology

[0003] The loess itself is weak in soil quality and has well-developed vertical joints. In the case of rich water, the self-stabilization ability becomes poor, and the risk of tunnel construction is high. Engineering practice experience shows that the construction of deep loess tunnels often produces large surrounding rock deformation and lasts for a long time If the excavation method, support and construction parameters are unreasonable, it will lead to excessive deformation of the surrounding rock, cracking of the support structure, and even distortion and crushing of the steel frame.

Deep buried old loess generally does not have collapsibility, and the water content is generally 10% to 30%, but the water content has a relatively large impact on the tunnel deformation, and the mechanical properties of the surrounding rock when the loess encounters water deteriorates, which often leads to insufficient tunnel support strength. Large deformation, easy to cause tunnel collapse

When constructing a deep-buried loess tunnel with a burial depth greater than 50m, the construction difficulty is very high, the existing construction risks are higher, and the deformation of the tunnel is difficult to control, which is mainly reflected in the following three aspects: first, the low mechanical index of the surrounding rock, Large deformation: For deep loess tunnels, compared with the stress level of the location where the tunnel is located, the strength of the surrounding rock is low, the strength-stress ratio is small, and plastic deformation is prone to occur. During tunnel construction, the sinking of the vault and the convergence deformation of the arch foot Generally, the loess tunnel adopts flexible initial support. If the support strength is not enough, the tunnel is easy to deform too much and lead to collapse. Second, the moisture content has a great influence on deformation. : During the construction of the deep loess tunnel, the water content has a great influence on the deformation of the tunnel, and the property of the surrounding rock becomes worse when it encounters water, and the load increases, resulting in insufficient support strength of the tunnel and large deformation, which is easy to cause the tunnel to collapse; 3. The primary support structure is easily deformed and damaged: The monitoring results of the surrounding rock pressure of the deep-buried old loess tunnel show that the pressure of the surrounding rock at the tunnel vault and the arch waist is generally high, and the primary support structure at the vault and the arch waist is prone to damage. Rack prone to distortion

Especially for cross sections greater than 100m 2 When constructing a large-section deep-buried loess tunnel, the construction is more difficult and the tunnel deformation is more difficult to control

If the cross section is greater than 100m 2 When constructing a large-section deep-buried loess tunnel with a burial depth of more than 90m, the loess is sandy old loess or clayey old loess with well-developed vertical joints. The change rate of roof sinking value is 10mm / d~20mm / d, the change rate of horizontal convergence value is 15mm / d~35mm / d), the cumulative deformation is large (specifically the cumulative value of vault sinking value and horizontal convergence value The deformation of the deep loess tunnel is quite large, and the deformation lasts for a long time, and the unreasonable design of the support structure often leads to structural cracking and buckling of the steel frame.

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