Double-speed low strain method for detecting integrity of existing pile foundation through carrying out excitation inside pile body

Abstract

The invention discloses a double-speed low strain method for detecting integrity of an existing pile foundation through carrying out excitation inside a pile body. The double-speed low strain method comprises the steps of location of a pile top position: finding the central position of a to-be-detected pile according to a construction drawing, and marking the central position; drilling of a foundation and a foundation pile: drilling a hole in the central marked position of the to-be-detected pile, and sampling; sensor mounting: mounting two sensors on the hole wall of the obtained drilled hole, wherein the two sensors are in different depths; vibration excitation seat mounting: mounting a vibration excitation seat below the pile top and at the upper end of the upper senor, wherein the vibration excitation seat is in close contact with the hole wall of the drilled hole and does not slide on the hole wall under the action of a vibration excitation hammer; vibration excitation of the vibration excitation hammer: selecting the vibration excitation hammer according to the pile diameter, the pile length and the defect position to perform vibration excitation for a plurality of times; and sampling and data analysis: carrying out synchronous sampling on the two sensors, and analyzing sampled signals. The double-speed low strain method has the beneficial effects that the principle is simple and clear, an acquisition device is simple, the result is more accurate and reliable, and relatively good engineering application and popularization prospect is achieved.

Description

technical field [0001] The invention relates to a dual-velocity low-strain method for detecting the integrity of existing pile foundations by using excitation inside the pile body. Background technique [0002] Existing pile foundation integrity detection is of great significance for the safety and quality appraisal of existing buildings. When there is doubt about the quality of building pile foundations, pile foundation integrity (pile length, defect) detection is required. Due to the existing The building pile foundation is deeply buried under the building structure and foundation, which is a concealed project. Its detection is affected by the upper foundation and structure, and the integrity detection of the pile foundation is relatively difficult. [0003] The most common method currently used is the low-strain method, which uses a small hammer or a force rod to excite the pile top, uses a velocity or acceleration sensor to measure the velocity or admittance curve of the...

AI Technical Summary

Problems solved by technology

The number of sensors installed by the two methods is large, the equipment is more complicated, the requirements for the data acquisition system are higher, and the on-site operation is cumbersome and time-consuming

[0008] In addition, when the conventional low-strain method and the above two methods determine the pile length and defect location, they are determined according to the defect or the first peak time difference Δt of the reflected wave arrival velocity at the bottom of the pile multiplied by the wave velocity Wc, because the wave velocity is based on the concrete strength The empirical relationship with the wave velocity is determined, the randomness is large, and the error of the result is large, especially for end-bearing piles, when it is necessary to accurately determine the pile length, it is often powerless, and other methods such as core drilling are required to determine

[0009] The effect of using the low-strain method to detect the existing pile foundation of the building is not ideal, the defect signal is difficult to distinguish, the wave velocity and pile length cannot be accurately measured, the equipment is relatively complicated, and no effective solution has been proposed

Images