A method for detecting the weathering degree of red sandstone for building under wet-dry cycles

Abstract

This invention belongs to the field of testing technology and relates to a method for detecting the degree of weathering of red sandstone used in construction under wet-dry cycles. The method includes: taking freshly prepared thin red sandstone sheets and blocks as specific reference samples 1 and 2, recording the thickness, and measuring the initial ultrasonic velocity; subjecting the freshly prepared thin red sandstone sheets and blocks to unidirectional wet-dry cycle erosion under a simulated wet-dry cycle environment, repeating this process multiple times until the thin red sandstone sheets are completely weathered, and measuring the ultrasonic velocity value each time; constructing a relationship equation between the weathering depth and the thickness of the freshly prepared thin red sandstone sheets and blocks, the initial ultrasonic velocity, and the ultrasonic velocity during the cycle; and performing data fitting to obtain the relationship between ultrasonic velocity and weathering depth, as well as the relationship between ultrasonic velocity and the propagation time of ultrasonic waves in the red sandstone. This method can intuitively obtain the relationship between the degree of weathering of the tested red sandstone from the surface and its depth, and can achieve non-destructive testing.

Description

Technical Field

[0001] This invention belongs to the field of detection technology and relates to a method for detecting the degree of weathering of red sandstone used in construction under dry and wet cycles. Background Technology

[0002] Red sandstone is a soft rock that is easily softened and disintegrated when exposed to water. Therefore, the alternating wet and dry erosion has a significant impact on the weathering of red sandstone. The weathering process of red sandstone is accompanied by changes in physical properties such as the rock's bulk density, specific gravity, porosity, and wave velocity ratio, as well as mechanical properties such as compressive strength.

[0003] Currently, the main methods for determining the weathering degree and classifying the weathering grade of red sandstone primarily refer to the "Code for Geotechnical Engineering Investigation." This mainly utilizes parameters such as wave velocity ratio and compressive strength to determine the degree of rock weathering. Obtaining these parameters requires sampling from rock strata at different depths before analysis of the various parameters can proceed. Wave velocity ratio is a crucial parameter for determining the degree of rock weathering. Ultrasonic waves of the same frequency propagate at different speeds in different media. For the same medium (such as red sandstone), different degrees of weathering alter its physical properties, causing changes in the propagation speed of ultrasonic waves of the same frequency. This change can be used to determine the weathering degree of a particular red sandstone.

[0004] Conventional wave velocity ratio calculation methods generally use drilling, which requires multiple boreholes for sampling and then analyzing the wave velocity of the rock at different depths. The analysis involves slicing the obtained samples, without taking into account that weathering is a continuous process, which can damage the object under test. In addition, the detection is complex and labor-intensive. Summary of the Invention

[0005] Based on this, and addressing the aforementioned technical problems, this invention takes two samples, assumes a unidirectional wet-dry cycle, and uses the number of cycles and time as experimental variables to record and fit the functional relationships V(x) between ultrasonic velocity and sample depth, and V(t) between ultrasonic velocity and ultrasonic propagation time. Based on the method of determining the degree of weathering based on wave velocity ratio, the wave velocity ratio H(x) corresponding to different depths is obtained.

[0006] This invention provides a method for detecting the weathering degree of red sandstone used in construction under wet-dry cycles, the method specifically comprising:

[0007] Newly prepared thin red sandstone slices and red sandstone blocks were used as specific reference sample 1 and reference sample 2, and the thicknesses were recorded and the initial ultrasonic velocity was measured.

[0008] The specific reference sample 1 and reference sample 2 were subjected to unidirectional dry-wet cycle erosion in a simulated dry-wet cycle environment. This process was repeated multiple times until the specific reference sample 1 was completely decomposed, and the ultrasonic velocity value was measured each time.

[0009] Equations relating weathering depth to the thickness of the specific reference specimen 1 and reference specimen 2, the initial ultrasonic velocity, and the ultrasonic velocity during the cyclic process were constructed, and data fitting was performed to obtain the relationships between ultrasonic velocity and weathering depth, and between ultrasonic velocity and the propagation time of ultrasonic waves in the weathered rock medium.

[0010] Furthermore, the step of constructing the equations relating the weathering depth to the thickness of the specific reference sample 1 and reference sample 2, the initial ultrasonic velocity, the ultrasonic velocity during the cyclic process, and the ultrasonic propagation time specifically includes:

[0011] After the first unidirectional wet-dry cycle erosion, the weathering degree of specific reference sample 1 is H1, and the ultrasonic velocity is V1. Assuming that reference sample 2 has a portion with a thickness of d1 and a weathering degree of H1, the ultrasonic velocity is measured as V. s1 The propagation time of ultrasound in part d1 is t. 1,1 At the same time, there is the relation t 1,1 =d1 / V1, the relational equation is:

[0012] D = V s1 T1 = V1·t 1,1 +V0·(T1-t 1,1 )

[0013] Where D is the thickness of reference sample 2; T1 is the propagation time of the ultrasonic wave in reference sample 2 after the first unidirectional wet-dry cycle erosion, t 1,1 V0 is the time for ultrasonic waves to propagate in d1, and V0 is the initial ultrasonic velocity before the simulated unidirectional wet-dry cycle erosion of specific reference specimens 1 and 2.

[0014] After a second unidirectional wet-dry cycle erosion, the weathering degree of reference sample 1 is H2, and the ultrasonic velocity is V2. The weathering degree of part d1 in reference sample 2 is H2. Assuming further erosion inside, the weathering degree of part d2 is H1. The ultrasonic propagation velocity in reference sample 2 is measured to be V. s2 Then the relational equation is:

[0015] D = V s2 ·T2=V1·t 2,2 +V2·t 2,1 +V0·(T2-t 2,1 -t 2,2 )

[0016] Where T2 is the propagation time of the ultrasonic wave in reference sample 2 during the second measurement, t 2,1 =d1 / V2,t 2,2 =d2 / V1

[0017] Continuing with unidirectional wet-dry cycle erosion, after n cycles, the resulting relational equation is:

[0018]

[0019] Where T n For the nth measurement, the propagation time of the ultrasonic wave in reference specimen 2 is t. n,i =d i / V n+1-i , where t n,i For reference sample 2 in n unidirectional wet-dry cycle erosion. i The time it takes for some ultrasound waves to travel;

[0020] Assuming that the maximum thickness of the wet-dry cycle erosion is reached after n repetitions, then The time taken for the ultrasound to propagate in the weathered portion, i.e., along (0, d), is [equation missing]. From the data obtained above, we can fit a function V(x) relating the ultrasonic wave propagation speed to the weathering depth x, and a function V(t) relating the ultrasonic wave propagation speed to the propagation time of the ultrasonic wave in the sandstone. The updated equations are as follows:

[0021]

[0022] In particular, the ultrasonic measurement velocity in reference sample 1 is represented by V. i It means, V i The ultrasonic propagation velocity of a specific reference sample 1 after the i-th wet-dry cycle is given by H, which represents the degree of weathering. i H represents the degree of weathering of a specific reference sample 1 after the i-th wet-dry cycle. i The corresponding ultrasonic velocity is V. i The ultrasonic speed measured in reference sample 2 is V. si express.

[0023] Furthermore, the weathering degree of the red sandstone is H(x) = V(x) / V0.

[0024] Furthermore, the detection method also includes:

[0025] When the weathering degree of red sandstone of thickness L is tested:

[0026] When L≥d, or L≤d but a portion of the interior is clearly unweathered, then we have

[0027]

[0028] Assume the ultrasonic velocity on the eroded surface of the test object is V. p In the function V(t), V p=Vt(a), where Vt(a) is a point on V(t), and a∈(0,t). According to the above formula, a is the ultrasonic propagation time point corresponding to the ultrasonic velocity Vt(a) in V(t). Since V(t) and V(x) are both monotonic functions, and according to the data acquisition process, there is a one-to-one correspondence between V(t) and V(x), we can take Vt(a) = Vx(b), where b is the sample depth corresponding to the ultrasonic velocity Vx(b) in V(x), and its weathering degree with depth can be recorded as:

[0029]

[0030] When L≤d, and weathering occurs from the outside in, and the interior has also been weathered;

[0031]

[0032] Similarly, taking Vt(a) = Vx(b), the degree of weathering with depth can be denoted as:

[0033]

[0034] Furthermore, the unidirectional wet-dry cycle erosion process in the simulated wet-dry cycle environment specifically includes:

[0035] The collected rainwater was used as the soaking solution. The sample was soaked at room temperature for 0.5 hours and then air-dried in a natural environment for 23.5 hours.

[0036] Beneficial effects:

[0037] This invention utilizes the difference in the propagation speed of ultrasound in different media. Based on the change in ultrasound speed and its depth under different dry and wet cycles of the test sample, from the perspective of continuous analysis, it fits the relationship between ultrasound speed and depth x, V(x), and the relationship between ultrasound propagation speed and propagation time t, V(t). Furthermore, it obtains the relationship between wave velocity ratio and depth x according to different situations. This method can intuitively obtain the relationship between the weathering degree of the tested red sandstone from the surface and the depth, and can achieve non-destructive testing.

[0038] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. 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 effort.

[0040] Figure 1 This is a flowchart of a method for detecting the weathering degree of red sandstone for building under wet-dry cycles, provided in an embodiment of the present invention.

[0041] Figure 2 This is a diagram showing the direction of dry-wet cycle erosion and the arrangement of specific product samples during the dry-wet cycle erosion process, as provided in an embodiment of the present invention.

[0042] Figure 3 A diagram illustrating the relationship between the ultrasonic velocity in one cycle and the depth x of the sample 2, and the ultrasonic velocity and propagation time, provided for embodiments of the present invention.

[0043] Figure 4 A diagram illustrating the relationship between the ultrasonic velocity in two cycles and the sample depth x, and the ultrasonic velocity and propagation time, provided in an embodiment of the present invention.

[0044] Figure 5 The present invention provides a description of the relationship between ultrasonic velocity V and weathering depth x, and between ultrasonic velocity V and propagation time t. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] like Figure 1 As shown in the embodiments of the present invention, a method for detecting the weathering degree of red sandstone used in construction under wet-dry cycles is proposed, specifically including:

[0047] Step S101: Take freshly prepared thin red sandstone slices and red sandstone blocks as samples, record the thickness and measure the initial ultrasonic velocity.

[0048] In this embodiment of the invention, a thin red sandstone sheet of thickness d0 used in newly constructed buildings is taken as a specific reference sample 1. A new red sandstone sheet of thickness D used in newly constructed buildings is taken as a reference sample 2, such as... Figure 2As shown. The first-wave method was used to measure the ultrasonic velocity and propagation time of specific reference sample 1 and reference sample 2. Multiple measurements were taken and averaged, which were recorded as the initial ultrasonic velocity values ​​V0 and T of the newly prepared red sandstone for building. In order to make the detection more accurate, d0 should be as small as possible, while D ≥ maximum weathering depth d, where d is calculated as follows.

[0049] Step S102: The newly prepared thin red sandstone sheet and red sandstone block are subjected to unidirectional wet-dry cycle erosion under a simulated wet-dry cycle environment. In order to simulate the wet-dry cycle of rainfall-evaporation, locally collected rainwater is used as the erosion solution. The erosion experiment is carried out in a natural environment. Since red sandstone has strong water absorption, the soaking time of the solution should be as short as possible in order to obtain more accurate data. In this invention, the two samples are soaked in collected rainwater for 30 minutes (rainwater at room temperature 20℃), and then placed in a natural environment to air dry for 23.5 hours, which is regarded as one wet-dry cycle. This is repeated multiple times until the thin red sandstone sheet is completely weathered, and the ultrasonic velocity value is measured each time. This is repeated multiple times until the thin red sandstone sheet is completely weathered, and the propagation time of ultrasonic waves in sample 2 is measured. The ultrasonic transmission velocity is obtained by converting the ultrasonic propagation time.

[0050] Step S103: Construct equations relating weathering depth to the thickness of the newly prepared thin red sandstone sheet and block, initial ultrasonic velocity, ultrasonic velocity during the cycle, and ultrasonic propagation speed, and perform data fitting to obtain the relationships between ultrasonic velocity and weathering depth, and between ultrasonic velocity and propagation time.

[0051] In this embodiment of the invention, reference sample 1 and reference sample 2 were placed in a simulated wet-dry cycle environment. Unidirectional wet-dry cycle erosion was performed. It is known that naturally occurring red sandstone will decrease by approximately 90% after 20 wet-dry cycles, indicating a rapid rate of change. In this experiment, a wet-dry cycle was performed once a day as the recording period. After each wet-dry cycle, the method described in step one was used to repeatedly measure the ultrasonic velocity values ​​of reference sample 1 and reference sample 2, as well as the ultrasonic wave propagation velocity in sample 2. The average value was recorded as V. i V si and T i .

[0052] After the first unidirectional wet-dry cycle erosion, the weathering degree of specific reference sample 1 is considered to be H1, and the ultrasonic velocity is V1. Assuming that reference sample 2 has a portion with a thickness of d1 weathered to the degree of H1, while the remaining portion D-d1 is in an unweathered state, the ultrasonic velocity is measured to be V. s1 The propagation time of ultrasound in part d1 is t. 1,1 At the same time, there is the relation V s1 =D / T1,t 1,1 =d1 / V1, which gives D, T1, t1, and V1, V s1The relationship is shown in equation (1), and its expression is as follows: Figure 3 As shown.

[0053] D = V s1 T1 = V1·t 1,1 +V0·(T1-t 1,1 (1)

[0054] Where D is the thickness of reference sample 2; T1 is the propagation time of the ultrasonic wave in reference sample 2 after the first unidirectional wet-dry cycle erosion, t 1,1 V0 represents the propagation time of the ultrasonic wave in d1, V0 represents the initial ultrasonic velocity of specific reference specimens 1 and 2 before unidirectional wet-dry cycle erosion, and H represents the wave velocity ratio, used to determine the degree of weathering. i H represents the degree of weathering of a specific reference sample 1 after the i-th wet-dry cycle. i The corresponding ultrasonic velocity is V. i According to this method, d1 and t can be obtained. 1,1 ,as well as Figure 3 The relationship between the expressions.

[0055] After a second unidirectional wet-dry cycle erosion, the weathering degree of reference sample 1 is H2, and the ultrasonic velocity is V2. The weathering degree of part d1 in reference sample 2 is H2. Assuming further erosion inside, the weathering degree of part d2 is H1. The ultrasonic propagation velocity in reference sample 2 is measured to be V. s2 Then the relational equation is:

[0056] D = V s2 ·T2=V1·t 2,2 +V2·t 2,1 +V0·(T2-t 2,1 -t 2,2 )

[0057] Where T2 is the propagation time of the ultrasonic wave in reference sample 2 during the second measurement, t 2,1 =d1 / V2,t 2,2 =d2 / V1, from which t2 and Figure 4 Relationship diagram.

[0058] By repeating the above steps, the thickness d of different weathering stages can be obtained sequentially based on the above pattern. i and the speed of ultrasonic wave propagation t i This continues until the specific reference sample 1 is completely weathered, i.e., the ultrasonic velocity V ≤ 0.1V0. Assuming this is performed n times, the resulting relational equation is:

[0059]

[0060] Where Tn For the nth measurement, the propagation time of the ultrasonic wave in reference specimen 2 is t. n,i =d i / V n+1-i Where ti is the reference sample 2 after the nth unidirectional wet-dry cycle erosion, d i The time it takes for some ultrasound waves to travel;

[0061] Assuming that the maximum thickness of the wet-dry cycle erosion is reached after n repetitions, then That is, when the surface is in a completely weathered state, the depth of alternating wet and dry weathering is considered to be d. Completely weathered sandstone can no longer be formed. Therefore, the depth from completely weathered to unweathered is considered to be a constant value, d. The time required for ultrasound to propagate in the weathered portion, i.e., along the (0, d) plane, is... Since d is a constant and the function V(x) remains constant on (0, d), the propagation time t of ultrasound on d is also considered a constant. Based on this, we can obtain a graph showing the relationship between depth and ultrasound velocity, and ultrasound velocity and propagation time, from completely weathered to unweathered areas, as shown below. Figure 5 As shown.

[0062] The more experimental cycles and the more detailed the records, the more likely a general functional relationship can be obtained by fitting this data, which can be used to represent the relationship between V and x, V(x), and the relationship between V and t, V(t).

[0063] The new relational expression can then be changed to:

[0064]

[0065] After obtaining V(x) and V(t), the weathering degree and weathering depth of any red sandstone to be tested can be calculated. The calculation method is as follows:

[0066] For a building that is considered to be subject to unidirectional wet-dry cycle erosion, assuming its thickness is L, and the relationship between its weathering degree and water depth x is H(x), then:

[0067] (1) L≥d, or L≤d but there is a clear part inside that has not been weathered (weathering from the outside to the inside).

[0068]

[0069] Where Vs, L, and T are measurable, V0 is known, and t represents the time it takes for the ultrasonic wave to propagate at the maximum weathering depth d, which has already been calculated in the above process, and t and d are assumed to be fixed values. Assume the ultrasonic velocity on the eroded surface of the test object is V. p In the function V(t), V p=Vt(a), where Vt(a) is a point on V(t), and a∈(0,t). Since V(t) and V(x) are both monotonic functions, and according to the data acquisition process, there is a one-to-one correspondence between V(t) and V(x), we can take Vt(a) = Vx(b), where b is the sample depth in V(x) corresponding to the ultrasonic velocity Vx(b), and its weathering degree with depth can be denoted as:

[0070]

[0071] H represents the wave velocity ratio, which is used to measure the degree of weathering of red sandstone.

[0072] (2) L≤d, weathering occurs from the outside in, and the interior has also been weathered.

[0073]

[0074] Similarly, taking Vt = (a) = Vx(b), the relationship between the weathering degree of the object under test and depth can be denoted as:

[0075]

[0076] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

[0077] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0078] It should be understood that although the steps in the flowcharts of the various embodiments of the present invention are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the various embodiments may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least a portion of the sub-steps or stages of other steps.

[0079] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for detecting the weathering degree of red sandstone used in construction under wet-dry cycles, characterized in that, The detection method specifically includes: Newly prepared thin red sandstone slices and red sandstone blocks were used as specific reference sample 1 and reference sample 2, and the thickness was recorded and the initial ultrasonic velocity was measured. The specific reference sample 1 and reference sample 2 were subjected to unidirectional dry-wet cycle erosion in a simulated dry-wet cycle environment. This process was repeated multiple times until the specific reference sample 1 was completely decomposed, and the ultrasonic velocity value was measured each time. Equations were constructed to establish the relationship between weathering depth and the thicknesses of the specific reference specimens 1 and 2, the initial ultrasonic velocity, and the ultrasonic velocity during the cyclic process. Data fitting was then performed to obtain the relationships between ultrasonic velocity and weathering depth, and between ultrasonic velocity and the propagation time of ultrasonic waves in the weathered rock medium. Specifically, this included: After the first unidirectional wet-dry cycle erosion, the weathering degree of specific reference sample 1 is H1, and the ultrasonic velocity is V1. Assuming that reference sample 2 has a portion with a thickness of d1 and a weathering degree of H1, the ultrasonic velocity is measured as V. s1 The propagation time of ultrasound in part d1 is t. 1,1 At the same time, there is the relation t 1,1 =d1 / V1, the relational equation is: D=V s1 T1=V1·t 1,1 +V0·(T1-t 1,1 ) Where D is the thickness of reference sample 2; T1 is the propagation time of the ultrasonic wave in reference sample 2 after the first unidirectional wet-dry cycle erosion, t 1,1 V0 is the time for ultrasonic waves to propagate in d1, and V0 is the initial ultrasonic velocity before the simulated unidirectional wet-dry cycle erosion of specific reference specimens 1 and 2. After a second unidirectional wet-dry cycle erosion, the weathering degree of reference sample 1 is H2, and the ultrasonic velocity is V2. The weathering degree of part d1 in reference sample 2 is H2. Assuming further erosion inside, the weathering degree of part d2 is H1. The ultrasonic propagation velocity in reference sample 2 is measured to be V. s2 Then the relational equation is: D=V s2 ·T2=V1·t 2,2 +V2·t 2,1 +V0·(T2-t 2,1 -t 2,2 ) Where T2 is the propagation time of the ultrasonic wave in reference sample 2 during the second measurement, t 2,1 =d1 / V2,t 2,2 =d2 / V1 Continuing with unidirectional wet-dry cycle erosion, after n cycles, the resulting relational equation is: Where T n For the nth measurement, the propagation time of the ultrasonic wave in reference specimen 2 is t. n,i =d i / V n+1-i , where t n,i For reference sample 2 in n unidirectional wet-dry cycle erosion. i The time it takes for some ultrasound waves to travel; Assuming that the maximum thickness of the wet-dry cycle erosion is reached after n repetitions, then The time taken for the ultrasound to propagate in the weathered portion, i.e., along (0, d), is [equation missing]. From the data obtained above, we can fit a function V(x) relating the ultrasonic wave propagation speed to the weathering depth x, and a function V(t) relating the ultrasonic wave propagation speed to the propagation time of the ultrasonic wave in the sandstone. The updated equations are as follows: The weathering degree of the red sandstone is H(x) = V(x) / V0; The detection method further includes: When the weathering degree of red sandstone of thickness L is tested: When L≥d, or L≤d but some parts inside are clearly unweathered, then we have Assume the ultrasonic velocity on the eroded surface of the test object is V. p In the function V(t), V p =Vt(a), where Vt(a) is a point on V(t), and a∈(0,t). According to the above formula, a is the ultrasonic propagation time point corresponding to the ultrasonic velocity Vt(a) in V(t). Since V(t) and V(x) are both monotonic functions, and according to the data acquisition process, there is a one-to-one correspondence between V(t) and V(x), we can take Vt(a) = Vx(b), where b is the sample depth corresponding to the ultrasonic velocity Vx(b) in V(x), and its weathering degree with depth can be recorded as: When L≤d, and weathering occurs from the outside in, and the interior has also been weathered; then we have Similarly, taking Vt(a) = Vx(b), the degree of weathering with depth can be denoted as:

2. The method for detecting the degree of weathering of red sandstone for construction under wet-dry cycles according to claim 1, characterized in that, The unidirectional wet-dry cycle erosion process under simulated wet-dry cycle environment is specifically as follows: The collected rainwater was used as the soaking solution. The sample was soaked at room temperature for 0.5 hours and then air-dried in a natural environment for 23.5 hours.

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