Long-term monitoring apparatus and method for soil pressure outside duct piece of shield tunnel

Abstract

The invention discloses a long-term monitoring apparatus for a soil pressure outside a duct piece of a shield tunnel. The long-term monitoring apparatus is composed of a fiber grating strain brick, a fiber grating temperature compensation block, a cable box, and an armored cable. The fiber grating strain brick consists of a measuring stone and a mortar layer coating the outside of the measuring stone; and four fiber gratings are arranged at each of three surfaces, being perpendicular to each other, of the measuring stone. The fiber grating temperature compensation block includes a hollow metallic cylinder and a temperature compensation stone arranged inside the metallic cylinder; the space between the temperature compensation stone and the metallic cylinder is filled with EVA foam; and four fiber gratings are arranged at each of three surfaces, being perpendicular to each other, of the temperature compensation stone. In addition, the invention also discloses a long-term monitoring method for a soil pressure outside a duct piece of a shield tunnel. Using the apparatus and method disclosed by the invention, the soil pressure monitoring error can be reduced; and the installation survival rate can be improved. Moreover, the apparatus and method have characteristics of good anti-electromagnetic-interference and corrosion-resistant performances and low signal attenuation; and the soil pressure outside a duct piece of a shield tunnel can be monitored accurately for long time.

Description

Technical field [0001] The invention relates to geotechnical engineering testing technology, in particular to a long-term monitoring device for the external earth pressure of a shield tunnel segment, and also relates to a long-term monitoring method of the external earth pressure of a shield tunnel segment. Background technique [0002] With the rapid development of urban infrastructure in my country, a large number of subways and highway tunnels have been planned and constructed in large and medium cities in my country. Because shield construction has the advantages of fast construction speed, high efficiency, good working environment, and high degree of safety protection, most subway tunnels and cross-river highway tunnels adopt shield construction. During the construction and operation of the shield tunnel, the magnitude of the earth pressure outside the segment directly affects the internal force of the segment structure and the changes in the joints, which in turn affects th...

AI Technical Summary

Problems solved by technology

[0005] Due to the large difference in stiffness among soil, segmental concrete, earth pressure box body, earth pressure box film, and grouting body behind the wall, stress concentration will occur in the local area where the earth pressure box is located under the action of outer earth pressure , causing the error between the measured result of earth pressure and the true value

[0006] 2. Uneven stress on the bearing surface

[0007] The segment is a prefabricated structure, and the earth pressure box needs to be pre-embedded in the segment during the production process of the segment, and then contact the outer soil with the segment during the on-site installation process. The soil contact is good; at the same time, due to the difference in compression modulus between the soil pressure cell film and the segmental concrete, the pressure on the pressure cell film is not uniform, causing measurement errors

[0008] 3. Not suitable for long-term monitoring

[0009] Traditional earth pressure cells are greatly affected by the environment, such as moisture, chemical corrosion, etc., especially the zero point of traditional resistive or vibrating wire sensors will drift for a long time, and the results of long-term strain tests will be seriously distorted, which is not suitable for long-term monitoring

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