CN116203584A - Non-contact sprayed concrete rebound rate testing method and device - Google Patents

Abstract

The invention discloses a non-contact sprayed concrete rebound rate testing method, which specifically comprises the following steps: s1, scanning a tunnel wall of a section to be constructed before concrete spraying by using a laser radar to obtain laser point cloud 1; s2, performing sprayed concrete construction, preparing a density measurement test piece at the same time, and measuring a density value rho of sprayed concrete based on the density measurement test piece; s3, scanning the tunnel wall of the section to be constructed after concrete injection through a laser radar to obtain laser point cloud 2; s4, performing point cloud downsampling on the laser point cloud 1 and the laser point cloud 2 to form a laser point cloud 3 and a laser point cloud 4; and S5, modeling the laser point cloud 3 and the laser point cloud 4 respectively, wherein the difference value of the two model volumes is the sprayed concrete volume v attached to the tunnel wall, and then the rebound rate of the sprayed concrete is calculated. According to the invention, a three-dimensional laser scanning technology is adopted for non-contact measurement, and canvas is not required to be laid for weighing; the rebound rate of the sprayed concrete is calculated based on the mass ratio of the concrete instead of the volume ratio of the concrete, so that the influence of the volume change of the mass concrete before and after spraying is avoided.

Description

Non-contact test method and device for shotcrete rebound rate

technical field

The invention belongs to the technical field of concrete spraying, and more specifically, the invention relates to a non-contact method and device for testing the rebound rate of shotcrete.

Background technique

Shotcrete is concrete that uses compressed air to spray cement, sand and gravel and other mixed materials to the sprayed surface and quickly solidifies and hardens. It has many advantages such as high construction efficiency, simple process, good support and reinforcement effect, strong adaptability, and significant economic and technical benefits. It is an important tunnel support measure in the construction of tunnel engineering. However, the rebound rate of sprayed concrete is generally large during construction, which not only leads to a large waste of raw materials, affects the construction progress, but also increases the cost of waste concrete treatment and increases the environmental load.

The paper "Tunnel Shotcrete Rebound Measurement Based on 3D Laser Scanning" uses a ground-type 3D laser scanning instrument to measure the volume V _j of concrete sprayed onto the tunnel, and uses the ratio of V _j to the _total volume V of shotcrete during construction as rebound rate. This method has the following problems: (1) The volume of concrete of the same quality changes before and after construction, so the volume is difficult to represent the amount of concrete; and the mixing station usually weighs the raw materials to prepare concrete according to the weight, so it is difficult to obtain the _exact value of V; ( 2) This method assumes that the volume of sprayed concrete on the excavation surface in a certain mileage is equal to the sum of the sprayed concrete areas of N sections, so when the section spacing is small, there are more point cloud sections to be processed, and the workload in the office is large; when the section spacing is large Can not represent the real situation of shotcrete in this section of mileage.

Contents of the invention

The invention provides a non-contact method for testing the rebound rate of shotcrete, aiming to improve the above problems.

The present invention is achieved like this, a kind of non-contact sprayed concrete rebound rate testing method, described method specifically comprises the following steps:

S1. Scan the tunnel wall of the section to be constructed before concrete spraying by laser radar to obtain laser point cloud 1;

S2 conducts sprayed concrete construction, prepares density measurement specimens at the same time, and measures the density value ρ of the concrete after spraying based on the density measurement specimens;

S3. Scan the tunnel wall of the section to be constructed after concrete spraying by laser radar to obtain laser point cloud 2;

S4. After down-sampling the laser point cloud 1 and the laser point cloud 2, the laser point cloud 3 and the laser point cloud 4 are formed;

S5. Modeling the laser point cloud 3 and the laser point cloud 4 respectively, the volume difference between the two models is the volume v of the shotcrete attached to the tunnel wall, and then calculates the rebound rate of the shotcrete.

Further, the downsampling method of laser point cloud 1 is as follows:

1) Project the coordinates in the laser point cloud 1 to the world coordinate system, and import the tunnel design outline into the world coordinates;

2) Read the coordinates of all points in the laser point cloud 1 in the world coordinate system, traverse all the points in the laser point cloud 1, project each point P _i onto the tunnel design outline, and obtain the point P _i on the tunnel design outline The curve length x _i of the projection point P _i ′ to the left arch foot of the tunnel, the tunnel mileage y _i of point P _i , and the minimum distance z _i from point P _i to the tunnel design contour surface;

3) Establish a space Cartesian coordinate system, generate a mapping point Q _i (xi _, y _i , z _i ) of point P _i , traverse all points P _i , and finally form a point cloud Q;

4) Traversing all points Q _i (xi _, y _i , _zi ) of point cloud Q, removing points with |z _i |≥z ₀ in point cloud Q, where z ₀ is the set threshold;

5) Thinning the point cloud Q, and storing the remaining valid points into the array {Q _i }.

6) Select the point P _i corresponding to each point Q _i of the array {Q _i } from the laser point cloud 1, delete the remaining points, and obtain the down-sampled laser point cloud 1.

Further, before step S1, it also includes:

S1. Shotcrete pre-construction: Prepare a small amount of concrete for trial transportation and trial spraying before formal construction.

Further, the preparation process of the density measurement specimen is as follows:

Place the concrete slab test mold obliquely along the side wall of the tunnel to be constructed. When the wet spraying machine is in a stable working state, spray it on the concrete slab test mold to form a concrete specimen.

Further, there are multiple concrete slab test molds, which are placed at different positions along the side wall of the tunnel to be constructed.

Further, the method for determining the concrete density value ρ after spraying is as follows:

Test the density of each concrete specimen, and the average density of all concrete specimens is the density value of the concrete after spraying.

Further, the formula for calculating the rebound rate k of shotcrete is as follows:

Among them, m is the total mass of concrete before spraying, ρ is the density value of concrete after spraying, and v is the volume of shotcrete.

Further, before step S0, after step S1, the following steps are also included:

Concrete is prepared and weighed, and the total mass of concrete before leaving the station is recorded as m.

The present invention is achieved in that a non-contact shotcrete rebound rate testing device, said device comprises:

A processor installed in a UAV equipped with a laser radar and connected to the laser radar;

Before the concrete spraying, control the UAV to scan the tunnel wall of the construction section along the set route, and obtain the laser point cloud 1. After the concrete spraying, control the UAV to scan the tunnel wall of the construction section along the set route, The laser point cloud 2 is obtained, and the laser point cloud 1 and the laser point cloud 2 are sent to the processor, and the processor obtains the rebound rate of the shotcrete based on the non-contact test method for the rebound rate of shotcrete.

The non-contact method for testing the rebound rate of shotcrete provided by the invention has the following beneficial technical effects:

(1) The present invention adopts three-dimensional laser scanning technology to carry out non-contact measurement, without laying canvas to weigh;

(2) The present invention calculates the rebound rate of sprayed concrete based on the proportion of concrete mass instead of the proportion of concrete volume, which avoids the influence of the volume change of the same quality concrete before and after spraying;

(3) The new method for down-sampling of tunnel point cloud proposed by the present invention first converts the measured point cloud P of the cylindrical tunnel into a new point cloud Q that is easy to handle according to the principle that the minimum distance from each point to the tunnel design contour surface remains unchanged, Secondly, the new point cloud Q is down-sampled by the method of irregular triangulation encryption, and finally the redundant points and noise points are removed from the measured point cloud P according to the one-to-one mapping relationship, so as to improve the measurement accuracy of the shotcrete volume, and then improve the shotcrete volume. Calculation accuracy of concrete rebound rate.

Description of drawings

Fig. 1 is the flow chart of non-contact sprayed concrete rebound rate testing method that the embodiment of the present invention provides;

Fig. 2 is a schematic plan view of the projection process of each point in the laser point cloud on the tunnel design outline provided by an embodiment of the present invention;

Fig. 3 is a three-dimensional schematic diagram of the projection process of each point in the laser point cloud on the tunnel design outline provided by the embodiment of the present invention.

Detailed ways

The specific implementation of the present invention will be described in further detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concepts and technical solutions of the present invention.

Fig. 1 is the non-contact shotcrete rebound rate testing method flowchart that the embodiment of the present invention provides, and this method specifically comprises the following steps:

S1. Pre-construction of sprayed concrete: In order to reduce the quality error caused by the adhesion of concrete in the transport tanker and wet spraying machine, a small amount of concrete is prepared for trial transportation and trial spraying before the official construction to ensure that the concrete is fully infiltrated on the inner wall of the construction machine. In this way, the loss of concrete adhering to the inner wall of the construction machine is minimized.

S2. Concrete preparation and weighing: the mixing station mixes the required concrete, and records the total mass of the concrete before leaving the station as m;

S3. Scanning the tunnel wall of the section to be constructed before concrete spraying by laser radar to obtain laser point cloud 1;

Before spraying, use a drone equipped with a lidar module to scan the tunnel wall in the section to be constructed.

S4, carry out shotcrete construction, prepare the density measurement specimen at the same time, measure the density value ρ of the concrete after spraying based on the density measurement specimen;

In the embodiment of the present invention, the preparation process of the density measurement specimen is as follows:

Place several concrete slab test molds at different positions along the side wall of the tunnel to be constructed. When the wet spraying machine is in a stable working state, spray on the concrete slab test molds to form several concrete specimens.

In the embodiment of the present invention, the density of each concrete specimen is tested, and the average density of all concrete specimens is the density value ρ of the concrete after spraying.

S5. Scan the tunnel wall of the section to be constructed after concrete spraying by laser radar to obtain laser point cloud 2;

S6. After down-sampling the laser point cloud 1 and the laser point cloud 2, the laser point cloud 3 and the laser point cloud 4 are formed;

S7. Based on the 3D reshaper, the laser point cloud 3 and the laser point cloud 4 are modeled respectively. The difference between the volumes of the two models is the volume v of the shotcrete attached to the tunnel wall, and then the rebound rate of the shotcrete is calculated.

In the embodiment of the invention, the formula for calculating the rebound rate of shotcrete is as follows:

In the embodiment of the present invention, point cloud down-sampling is performed for laser point cloud 1 and laser point cloud 2, and the same point cloud down-sampling method is used, and the point cloud down-sampling method is described in detail by taking laser point cloud 1 as an example , the method is as follows:

1) Project the coordinates in the laser point cloud 1 to the world coordinate system, and import the tunnel design outline into the world coordinates;

The world coordinate system is a coordinate system constructed at a certain point of the tunnel, and can also be understood as a construction coordinate system.

2) Read the coordinates of all points in the laser point cloud 1 in the world coordinate system, traverse all the points in the laser point cloud 1, and project each point onto the tunnel design outline. The projection method of the i-th point P _i is as follows :

Determine the projection point P _i ′ of point P _i on the tunnel design outline, and obtain the curve length x _i from the projection point P _i ′ to the left arch foot of the tunnel; determine the tunnel mileage y _i of point P _i ; point P _i to the tunnel design The minimum distance z _i of the contour surface is shown in Figure 2 for the plane view and Figure 3 for the three-dimensional view;

3) Establish a space Cartesian coordinate system, generate the mapping point Q _i of point P _i , set Q _i (xi _, y _i , z _i ); traverse all points P _i , and finally form a point cloud Q;

4) Traverse all points Q _i (xi _, y _i , zi ₎ of point cloud Q, determine the threshold z ₀ according to the statistical law of _zi , and remove the points of | _zi |≥ z ₀ in point cloud Q.

5) Thinning the point cloud Q, thereby removing the noise points and redundant points in the point cloud Q, retaining the valid points related to the tunnel outline features, and storing the valid points into the array {Q _i }.

The thinning method uses the LIDAR point cloud data thinning algorithm in the paper "LIDAR Point Cloud Data Thinning Algorithm Considering Terrain Features".

6) Select the point P _i corresponding to each point Q _i of the array {Q _i } from the laser point cloud 1, delete the remaining points, and obtain the down-sampled laser point cloud, that is, the laser point cloud 3.

The present invention also provides a non-contact sprayed concrete rebound rate testing device, which device includes:

It is installed in the UAV equipped with lidar, and the processor connected to the lidar communication,

Before the concrete spraying, control the UAV to scan the tunnel wall of the construction section along the set route, and obtain the laser point cloud 1. After the concrete spraying, control the UAV to scan the tunnel wall of the construction section along the set route, The laser point cloud 2 is obtained, and the laser point cloud 1 and the laser point cloud 2 are sent to the processor, and the processor obtains the rebound rate of the shotcrete based on the non-contact test method for the rebound rate of shotcrete.

The present invention has been exemplarily described, and obviously the specific implementation of the present invention is not limited by the above-mentioned manner, as long as various non-substantial improvements are carried out by adopting the method concept and technical scheme of the present invention, or unimproving the present invention Ideas and technical solutions that are directly applied to other occasions are within the protection scope of the present invention.

Claims (9)

1. A non-contact sprayed concrete rebound rate testing method is characterized by comprising the following steps:

s1, scanning a tunnel wall of a section to be constructed before concrete spraying by using a laser radar to obtain laser point cloud 1;

s2, performing sprayed concrete construction, preparing a density measurement test piece at the same time, and measuring a density value rho of sprayed concrete based on the density measurement test piece;

s3, scanning the tunnel wall of the section to be constructed after concrete injection through a laser radar to obtain laser point cloud 2;

s4, performing point cloud downsampling on the laser point cloud 1 and the laser point cloud 2 to form a laser point cloud 3 and a laser point cloud 4;

and S5, modeling the laser point cloud 3 and the laser point cloud 4 respectively, wherein the difference value of the two model volumes is the sprayed concrete volume v attached to the tunnel wall, and then the rebound rate of the sprayed concrete is calculated.

2. The non-contact sprayed concrete rebound rate testing method as claimed in claim 1, wherein the downsampling method of the laser point cloud 1 is specifically as follows:

1) Projecting coordinates in the laser point cloud 1 to a world coordinate system, and importing tunnel design contours into the world coordinate;

2) Reading coordinates of all points in the laser point cloud 1 under a world coordinate system, traversing and taking all points in the laser point cloud 1, and enabling all points P to be _i Projected onto the tunnel design contour to obtain point P _i Projection point P on tunnel design contour _i Curve length x of' to left arch leg of tunnel _i Point P _i Tunnel mileage y of (2) _i Point P _i Minimum distance z to tunnel design profile _i ；

3) Establishing a space rectangular coordinate system to generate a point P _i Mapping point Q of (2) _i (x _i ,y _i ,z _i ) Traversing all points P _i Finally forming a point cloud Q;

4) Traversing all points Q of point cloud Q _i (x _i ,y _i ,z _i ) Removing z in point cloud Q _i ≥z ₀ Point z of (1) ₀ Is a set threshold value;

5) Thinning the point cloud Q, and storing the rest effective points into an array { Q ] _i }。

6) Screening and selecting an array { Q } from the laser point cloud 1 _i Each point Q _i Corresponding point P _i And deleting the rest points, and acquiring the down-sampled laser point cloud 1.

3. The method for testing rebound resilience of sprayed concrete without contact according to claim 1, further comprising, before step S1:

s1, pre-construction of sprayed concrete: and preparing a small amount of concrete for test transportation and test spraying before formal construction.

4. The method for testing rebound rate of sprayed concrete in a non-contact manner according to claim 1, wherein the density measurement test piece is prepared by the following steps:

and (3) obliquely placing the concrete large plate test mould along the side wall of the tunnel in the section to be constructed, and spraying the concrete large plate test mould when the operation state of the wet spraying machine is stable, so as to form a concrete test piece.

5. The method for testing the rebound resilience of sprayed concrete according to claim 4, wherein the plurality of concrete large plate test molds are arranged at different positions along the side wall of the tunnel in the section to be constructed in an inclined manner.

6. The non-contact sprayed concrete rebound rate test method as claimed in claim 5, wherein the method for determining the sprayed concrete density value ρ is specifically as follows:

and testing the density of each concrete test piece, wherein the average density of all the concrete test pieces is the density value of the sprayed concrete.

7. The non-contact sprayed concrete rebound rate test method as claimed in claim 1, wherein the rebound rate k of the sprayed concrete is calculated by the following formula:

where m is the total mass of the concrete before the spraying, ρ is the density value of the concrete after the spraying, and v is the volume of the sprayed concrete.

8. The method for testing rebound resilience of sprayed concrete without contact according to claim 1, wherein before step S0, after step S1, further comprising the steps of:

and (3) preparing and weighing the concrete, and recording the total mass of the concrete before the concrete is discharged to the station as m.

9. A non-contact sprayed concrete resilience testing device, the device comprising:

the processor is arranged on the unmanned aerial vehicle carrying the laser radar and is in communication connection with the laser radar;

before the concrete is sprayed, the unmanned aerial vehicle is controlled to scan the tunnel wall of the section to be constructed along a set route, the obtained laser point cloud 1 is controlled to scan the tunnel wall of the section to be constructed along the set route after the concrete is sprayed, the laser point cloud 2 is obtained, the laser point cloud 1 and the laser point cloud 2 are sent to a processor, and the processor obtains the rebound rate of sprayed concrete based on the non-contact sprayed concrete rebound rate testing method according to any one of claims 1 to 8.

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