CN211783355U - An effective grouting length testing system for bolts - Google Patents

Abstract

The utility model belongs to the technical field of geotechnical engineering, in particular to an effective grouting length testing system for bolts. The bolt effective grouting length test system includes a bolt effective grouting length test structure, and also includes a digital oscilloscope, a post-amplifier, a pre-amplifier and a sound wave sensor provided outside the core, and the sound wave sensor is set when the bolt is in the drilling position. At one end outside the hole, the acoustic wave sensor is connected to a preamplifier via a transmission cable, the preamplifier is connected to a post-amplifier via a transmission cable, and the post-amplifier is connected to a digital oscilloscope via a transmission cable. The utility model provides a test system for the effective grouting length of an anchor rod, which can effectively, conveniently, non-destructively and quantitatively realize the test of the effective grouting length of the anchor rod, without the need for destructive tests and expensive coring tests on the anchor rods, which is a good test for rock and soil. The support quality evaluation of the project provides an effective means.

Description

An effective grouting length testing system for bolts

technical field

The utility model belongs to the technical field of geotechnical engineering, in particular to an effective grouting length testing system for bolts, which is suitable for geotechnical engineering such as caverns, slopes, etc. that need to be excavated in the fields of hydropower, mines, and transportation.

Background technique

Anchor rods are widely used in tunnels, mines, slopes and other civil engineering, using anchor rods to prevent the movement and deformation of rock and soil, thereby improving or maintaining the stability of the project. The common practice of bolt installation is to insert the bolt into the pre-drilled hole, and then grouting to bond the bolt to the surrounding rock mass, thereby playing a reinforcing role. During this process, however, due to gravity, the grouting material will flow outwards, creating a non-grouting bond zone at the front end of the bolt. Since grouting transfers the load by generating shear strength between the bolt and the rock, the grouting length is an important part of the stability of the bolt system, and the ultimate load of the bolt increases with the increase of the grouting length. decrease and increase. Therefore, in order to ensure the stability of the project, it is necessary to evaluate the grouting quality of the bolt.

The inspection of bolt grouting quality generally adopts pull-out test or core inspection, but these two methods are destructive, time-consuming and expensive, and the inspection quality is difficult to be completely determined. These two methods are used in engineering practice. It has also been gradually replaced by non-destructive testing methods. The acoustic wave method is a non-destructive testing method commonly used in the engineering geophysical exploration field for the anchoring quality of bolts. Although some theoretical research work has been done on the use of electromagnetic wave method to detect the quality of bolt anchoring, but it has not been put into practice. The theoretical basis of the sound wave method to detect the quality of the bolt is the kinematic characteristics of the wave propagating in the rod. The received reflected signal is analyzed in time domain and frequency domain to obtain parameters such as effective anchoring length, mortar saturation, working load and ultimate bearing capacity of the bolt, and the anchoring quality of the bolt is evaluated accordingly. Because its detection conclusion is greatly affected by human factors, its accuracy is low, and it is often difficult to meet the requirements of actual engineering. Therefore, the acoustic detection method needs to be further developed and improved.

Utility model content

The purpose of the utility model is to provide an effective grouting length testing system for bolts in view of the deficiencies in the prior art.

For this reason, the above-mentioned purpose of the present utility model is achieved through the following technical solutions:

A bolt effective grouting length test system, characterized in that: the bolt effective grouting length test system includes a bolt effective grouting length test structure, and also includes a digital oscilloscope, a post-amplifier, and a pre-amplifier provided outside the core. and a sound wave sensor, the sound wave sensor is arranged at the end of the bolt outside the borehole, the sound wave sensor is connected with the preamplifier through a transmission cable, the preamplifier is connected with the post amplifier through a transmission cable, the The post-amplifier is connected with the digital oscilloscope through the transmission cable; the effective grouting length test structure of the bolt includes a rock core, a hole is drilled in the core, and a bolt is arranged in the drill hole, and the bolt is connected with the drill. Fill the holes with grout.

While adopting the above technical solutions, the present invention can also adopt or combine the following technical solutions:

As a preferred technical solution of the present invention, the length of the grouting body is 40% or 60%, 80% or 100% of the total length of the bolt.

As a preferred technical solution of the present invention, the length of the bolt is 2-4m, the diameter is 20-30mm; the inner diameter of the borehole on the rock core is 30-40mm.

The utility model provides a test system for the effective grouting length of an anchor rod, which can effectively, conveniently, non-destructively and quantitatively realize the test of the effective grouting length of the anchor rod, without the need for destructive tests and expensive coring tests on the anchor rods, which is a rock-soil test system. The support quality evaluation of the project provides an effective means.

Description of drawings

FIG. 1 is a schematic diagram of the bolt effective grouting length testing system provided by the utility model.

Detailed ways

The present utility model will be described in further detail with reference to the accompanying drawings and specific embodiments.

A bolt effective grouting length testing system includes a bolt effective grouting length test structure, and also includes a digital oscilloscope 101, a post-amplifier 102, a pre-amplifier 103 and a sound wave sensor 104 provided outside the rock core 201. The sound wave sensor 104 is provided with At the end of the bolt 203 outside the borehole 202, the acoustic wave sensor 104 is connected to the preamplifier 103 via a transmission cable, the preamplifier 103 is connected to the post-amplifier 102 via a transmission cable, and the post-amplifier 102 is connected to the digital amplifier via a transmission cable. The oscilloscope 101 is connected.

The effective grouting length test structure of the bolt includes a core 201, a hole 202 is drilled in the core 201, a bolt 203 is arranged in the hole 202, and a grouting body 204 is filled between the bolt 203 and the hole 202, and the length of the grouting body 204 is 40% or 60% or 80% or 100% of the total length of the bolt 203 .

The length of the bolt 203 is 2-4 m, and the diameter is 20-30 mm; the inner diameter of the drilled hole 202 on the core 201 is 30-40 mm.

The above anchor bolt effective grouting length test system is tested in the following ways:

(1) Excitation signal

The hammering is used as the seismic source to generate sound waves with high energy. These sound waves propagate along the bolt and are reflected back from the end of the bolt, and can be detected by the acoustic wave sensor, pre-amplifier and post-amplifier, where the pre-amplifier The sonic sensor's microvolt signal is converted to a higher volt signal and filtered to amplify the original signal, providing a high signal-to-noise ratio. The preamplifier can also match the high impedance of the acoustic transducer to the low impedance of the signal cable. The post-amplifier, also known as the power amplifier, can provide voltage gain for the acoustic signal.

(2) Grouting saturation test

The cores retrieved from the site were used for drilling. The hole diameter of the drilling holes was the same as the outer diameter of the grouting, which was 35mm, the core diameter was 50mm, and the diameter and length of the bolts were 25mm and 3.0m.

The grouting ratios are 40%, 60%, 80% and 100%, and the grouting length at this time is the effective grouting length. The grouting ratio is the ratio of the length of the grouting body to the total length of the bolt.

High-energy sound waves are generated by hammering. Although both the grouting body and the core may affect the leakage of acoustic wave propagation, the measured signal has higher amplitude and lower attenuation compared with the non-buried bolt signal, so the test effect can be guaranteed.

(4) Result analysis

Record the sound wave velocity under the conditions of 40%, 60%, 80% and 100% grouting ratio, conduct the same sound wave test in field practice, and compare the wave velocity with the wave velocity under the above conditions of different grouting ratios, and then the actual field response can be obtained. effective grouting length.

The above-mentioned specific embodiments are used to explain the present utility model, and are only preferred embodiments of the present utility model, rather than limiting the present utility model. Any modification, equivalent replacement, improvement, etc., all fall into the protection scope of the present invention.

Claims (3)

1. The utility model provides an effective grout length test system of stock which characterized in that: the anchor rod effective grouting length testing system comprises an anchor rod effective grouting length testing structure, a digital oscilloscope, a post amplifier, a pre-amplifier and an acoustic wave sensor, wherein the digital oscilloscope, the post amplifier, the pre-amplifier and the acoustic wave sensor are arranged outside a rock core; the effective grouting length testing structure of the anchor rod comprises a core, a drill hole is drilled in the core, the anchor rod is arranged in the drill hole, and grouting bodies are filled between the anchor rod and the drill hole.

2. The anchor rod effective grouting length testing system of claim 1, wherein: the length of the grouting body is 40% or 60% or 80% or 100% of the total length of the anchor rod.

3. The anchor rod effective grouting length testing system of claim 1, wherein: the length of the anchor rod is 2-4 m, and the diameter of the anchor rod is 20-30 mm; the inner diameter of the drill hole in the rock core is 30-40 mm.

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