Testing device and testing method for presuming compressive strength of sandstone core on site

Abstract

The invention belongs to the field of geotechnical engineering reconnaissance, and particularly relates to a testing device and method for presuming the compressive strength of a sandstone core on site, and the testing method comprises the following steps: establishing a data carrying out statistical analysis and data fitting on rebound test data and compressive strength data of a sandstone sample existing in a laboratory, obtaining a conversion curve database of the sandstone rebound value and the compressive strength under a certain impact kinetic energy condition; acquiring a rock core and performing a rebound test: acquiring a columnar sandstone rock core sample on site, judging the type of the sandstone rock core according to a region, and then performing the rebound test to obtain a rebound value; the conversion curve of the springback value and the compressive strength of the sandstone core of the corresponding region category in the database is searched, the compressive strength corresponding to the springback value is found out according to the springback value calculated on site, and the compressive strength is the compressive strength of the sandstone core which is presumed on site. According to the invention, rock compressive strength data can be rapidly provided on site, and a reconnaissance technician can be guided to accurately delimit a rock-soil layer.

Description

Technical Field

[0001] The invention belongs to the field of geotechnical engineering investigation, and in particular relates to a test device and a test method for inferring the compressive strength of sandstone cores on site. Background Art

[0002] Sandstone is a common rock in geotechnical engineering surveys, and its structure is very similar to that of concrete or mortar. The compressive strength of the rock is generally required in the survey results. The current common practice is to retrieve the rock core on site, make it into regular rock samples according to relevant standards, and then pressurize it with a professional rock strength testing machine to obtain the compressive strength of the rock sample; there are also a few that use point load tests and then convert it into rock compressive strength. Both of the above methods require professional large-scale equipment, and it is impossible to quickly obtain the compressive strength directly on site, which makes it difficult to meet the requirements for quickly determining the compressive strength of sandstone at the construction survey site.

[0003] Based on this, the present application provides a test device and a test method for on-site estimation of the compressive strength of sandstone cores to solve the above-mentioned problems. Summary of the invention

[0004] The present invention aims to solve the technical problems existing in the prior art. To this end, the present invention provides a test device and a test method for inferring the compressive strength of sandstone cores on site by using a rebound method.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] In a first aspect, a test method for estimating the compressive strength of a sandstone core on site is provided, comprising the following steps:

[0007] Step S1, establishing a database: statistically analyzing and fitting the rebound test data and compressive strength data of the existing sandstone samples in the laboratory, and obtaining a conversion curve database of the sandstone rebound value and compressive strength under certain impact kinetic energy conditions;

[0008] Step S2, obtaining a core and performing a rebound test: obtaining a columnar sandstone core sample on site, determining the type of the sandstone core according to the region, and then performing a rebound test to obtain a rebound value;

[0009] Step S3, estimated compressive strength: search the database for the conversion curve between the rebound value and the compressive strength of the sandstone core of the corresponding regional category, and find the corresponding compressive strength according to the rebound value calculated on site. The compressive strength is the estimated compressive strength of the sandstone core on site.

[0010] In some optional embodiments, in step S1, before data fitting, it is necessary to first group the existing sandstone samples by region and category, and then perform statistical analysis and data fitting on the rebound test data and compressive strength data of the sandstone samples of each category in each region.

[0011] In some optional embodiments, in step S2, the rebound test includes the following steps:

[0012] Step S21, grinding a plurality of fresh rock surfaces on the outer wall of the sandstone core;

[0013] Step S22, performing a rebound test on each rock surface, evenly arranging 3 to 4 rebound test points on each rock surface, and obtaining rebound value data;

[0014] Step S23, removing the maximum value and the minimum value of the rebound value of each sandstone core, calculating the average value of the remaining rebound values, and obtaining the rebound value of the sandstone core.

[0015] In some optional implementations, in step S21, four centrally symmetrical rock surfaces are polished, and the width of each rock surface is 2 to 6 cm, preferably 3 to 4 cm.

[0016] In some optional embodiments, in step S22, during the rebound test, each point is hit three times in succession, and the first two rebounds should not be read, and the third rebound is taken as the rebound value of the point.

[0017] In the second aspect, a test device for on-site estimation of the compressive strength of sandstone cores is provided, which is used to implement the test method. The test device includes an intelligent terminal, a core support, an angle grinder and a sandstone rebound hammer. The intelligent terminal is used to view data in a database, the core support is used to place the core horizontally, the angle grinder is used to grind the rock surface on the core surface for a rebound test, and the sandstone rebound hammer is used to perform a rebound test.

[0018] In some optional embodiments, the rebound hammer uses a pointer display rebound hammer or a digital display rebound hammer with an impact kinetic energy of 0.1J-0.2J, preferably a digital display rebound hammer with a statistical function and an impact kinetic energy of 0.15J-0.18J.

[0019] In some optional embodiments, a semicircular groove is provided in the middle of the core support, and the semicircular groove is lined with wear-resistant polypropylene hard plastic matching the diameter of the core, wherein the core support is preferably made of cast iron or aluminum or welded steel plates.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention can realize the rapid provision of rock compressive strength data on site, and guide survey technicians to accurately delineate rock and soil layers; at the same time, by taking rock compressive strength as a quantitative indicator, the cost can be saved as much as possible while ensuring the bearing capacity of the pile foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0023] Figure 1 It is a schematic diagram of placing the rock core provided by the present invention on the rock core support;

[0024] Figure 2 It is a schematic diagram of grinding the rock core provided by the present invention on the rock core support;

[0025] Figure 3 It is a schematic diagram of a rebound test of a rock core provided by the present invention on a rock core support.

[0026] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0027] 1—Sandstone rebound tester, 2—Core support, 3—Rock core, 4—Angle grinder. DETAILED DESCRIPTION

[0028] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] A test method for estimating the compressive strength of sandstone core on site comprises the following steps:

[0032] Step S1, establishing a database: grouping the existing sandstone samples in the laboratory by region and category (such as argillaceous sandstone, calcareous sandstone, gravelly sandstone, etc.), statistically analyzing and fitting the rebound test data and compressive strength data of the sandstone samples of each category in each region, and obtaining a conversion curve database of the sandstone rebound value and compressive strength under certain impact kinetic energy conditions. The survey site can access the data in the database using an intelligent terminal, which can be a mobile phone, a computer, etc.;

[0033] Step S2, obtaining a core and performing a rebound test: obtaining a columnar sandstone core sample on site, determining the type of the sandstone core according to the region, and then performing a rebound test to obtain a rebound value;

[0034] The rebound test comprises the following steps:

[0035] Step S21, grinding a plurality of fresh rock faces on the outer wall of the sandstone core, specifically grinding out four centrally symmetrical rock faces, and each rock face has a width of 2 to 6 cm, preferably 3 to 4 cm;

[0036] Step S22, performing a rebound test on each rock surface, arranging 3 to 4 rebound test points evenly on each rock surface, and obtaining rebound value data; specifically, each point is continuously struck 3 times, and the first two rebounds should not be read, and the third rebound is taken as the rebound value of the point;

[0037] Step S23, remove the maximum and minimum values ​​of the rebound value of each sandstone core (the measured value with a deviation from the average value exceeding three times the standard deviation is regarded as an abnormal value), calculate the average value of the remaining rebound values ​​(accurate to 0.1), and obtain the rebound value of the sandstone core.

[0038] In the rebound test, due to the problem that the cylindrical core is easy to roll or the rebound value is too small due to surface cracks or mud, a core support is customized for the cylindrical core, as shown in the attached Figure 1 As shown, the middle of the core support is provided with a semicircular groove, and the semicircular groove is lined with wear-resistant polypropylene hard plastic matching the diameter of the core, and the core support is preferably made of cast iron or aluminum or welded steel plates. The rock surface on the core is ground using an angle grinder, such as the attached Figure 2 As shown in the figure, the core is placed on the core support during grinding, and four rock faces are grinded out in sequence. The ground core can be limited in the semicircular groove of the core support using the four rock faces, which can effectively solve the problem of the core rolling easily during the rebound test. Figure 3 As shown, the rebound hammer should be vertical to the fresh rock surface during the test.

[0039] Step S3, estimated compressive strength: search the database for the conversion curve between the rebound value and the compressive strength of the sandstone core of the corresponding regional category, and find the corresponding compressive strength according to the rebound value calculated on site. The compressive strength is the estimated compressive strength of the sandstone core on site.

[0040] It is worth noting that the database can also be replaced by carrying the data in the form of paper documents.

[0041] The above experimental method is also applicable to other rocks with structures similar to concrete or mortar, such as mudstone, limestone, etc. For such rocks, the impact kinetic energy of the rebound tester should be appropriately increased.

[0042] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A test method for estimating the compressive strength of sandstone core on site, characterized in that: The following steps are involved: Step S1, establishing a database: statistically analyzing and fitting the rebound test data and compressive strength data of the existing sandstone samples in the laboratory, and obtaining a conversion curve database of the sandstone rebound value and compressive strength under certain impact kinetic energy conditions; Step S2, obtaining a core and performing a rebound test: obtaining a columnar sandstone core sample on site, determining the type of the sandstone core according to the region, and then performing a rebound test to obtain a rebound value; Step S3, estimated compressive strength: search the database for the conversion curve between the rebound value and the compressive strength of the sandstone core of the corresponding regional category, and find the corresponding compressive strength according to the rebound value calculated on site. The compressive strength is the estimated compressive strength of the sandstone core on site.

2. The test method according to claim 1, characterized in that: In step S1, before data fitting, the existing sandstone samples need to be grouped by region and category, and then the rebound test data and compressive strength data of the sandstone samples of each category in each region need to be statistically analyzed and data fitted.

3. The test method according to claim 1, characterized in that: In step S2, the rebound test includes the following steps: Step S21, grinding a plurality of fresh rock surfaces on the outer wall of the sandstone core; Step S22, performing a rebound test on each rock surface, evenly arranging 3 to 4 rebound test points on each rock surface, and obtaining rebound value data; Step S23, removing the maximum value and the minimum value of the rebound value of each sandstone core, calculating the average value of the remaining rebound values, and obtaining the rebound value of the sandstone core.

4. The test method according to claim 3, characterized in that: In step S21, four centrally symmetrical rock surfaces are polished, and the width of each rock surface is 2 to 6 cm.

5. The test method according to claim 3, characterized in that: In step S22, during the rebound test, each point is hit three times in succession, and the first two rebounds should not be read, and the third rebound is taken as the rebound value of the point.

6. A test device for estimating the compressive strength of sandstone core on site, characterized in that: Used to implement the test method described in any one of claims 1 to 5, the test device includes an intelligent terminal, a core support, an angle grinder and a sandstone rebound hammer, the intelligent terminal is used to view data in a database, the core support is used to place the core horizontally, the angle grinder is used to grind the rock surface on the surface of the core for a rebound test, and the sandstone rebound hammer is used to perform a rebound test.

7. The test device according to claim 6, characterized in that: The rebound hammer adopts a pointer display rebound hammer or a digital display rebound hammer with an impact kinetic energy of 0.1J to 0.2J.

8. The test device according to claim 6, characterized in that: A semicircular groove is arranged in the middle of the core support, and the semicircular groove is lined with wear-resistant polypropylene hard plastic matching the diameter of the core.

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