Pile body stress testing method for miniature steel pipe pile

Abstract

The invention belongs to the technical field of geotechnical engineering in situ tests, and in particular relates to a pile body stress testing method for a miniature steel pipe pile. According to thepile body stress testing method, when a self-compensating miniature optical fiber grating strain sensor is subjected to tension or pressure, the elongation or compression of the sensor changes an optical fiber grating period, further an effective refractive index of the optical fiber grating strain sensor is changed, thus bending stress distribution of the miniature steel pipe pile under the action of water-earth pressure is obtained. The pile body stress testing method has the advantages of simple process, high measurement precision, high sensitivity, small error, high anti-electromagnetic field interference and high survival rate, and is easy to realize quasi-distributed and automated monitoring.

Description

Technical field: [0001] The invention belongs to the field of geotechnical engineering in-situ test technology, and particularly relates to a method for testing the stress of micro-steel pipe piles in foundation pit or slope support, which makes up for and improves the deficiencies of the current testing device and testing method. The self-compensating miniature optical fiber grating strain sensor string embedded in the pile body can more accurately obtain the bending stress distribution law of the micro-steel pipe pile under the action of water and soil pressure, which provides a certain reference for more in-depth research and actual engineering in the future value. Background technique: [0002] Micro-pile is a small-diameter pile developed on the basis of tree root piles, and the pile diameter is generally 90-300mm. The micro-steel pipe pile refers to a type of micro-pile that uses steel pipes as reinforcements. Due to the advantages of micro-steel pipe piles such as s...

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Problems solved by technology

Chinese patent 201320628409.9 discloses a static pressure high-strength prestressed concrete pipe pile body stress test device. The high-strength prestressed concrete pipe pile is cut with shallow grooves, and the optical fiber Bragg grating sensor and armored optical cable are connected in series according to quasi-distributed welding. The optical fiber Bragg grating sensor and armored optical cable are implanted in the shallow groove of the high-strength prestressed concrete pipe pile and encapsulated with epoxy resin mixture for protection. Lay out according to the elevation; the inside of the top of the high-strength prestressed concrete pipe pile is drilled with a pile body drill hole, and the armored optical cable is connected with the data acquisition system through the pile body drill hole; the device is simple in structure, easy to operate, high in measurement accuracy and high in sensitivity , strong anti-electromagnetic field interference ability, high survival rate, and easy to realize quasi-distributed and automatic monitoring compared with traditional force-measuring elements, but this test device is mainly aimed at prestressed high-strength concrete pipe piles in weak strata, embedded optical fiber Bragg Once one of the grating sensor strings fails, it will have a great impact on the test process, and even cause the entire sensor string to fail; in addition, the slotting of the pile body will have a certain impact on the strength of the pile, and the temperature caused by the temperature cannot be eliminated during the test. The change of the pile strain caused by it will affect the accuracy of the test results

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