Strain measurement method related to early-age transverse cracking stress of top surface of semi-rigid base and cracking trend evaluation method

Abstract

The invention provides a semi-rigid base top surface early-age transverse cracking stress related strain measurement method and a cracking trend evaluation method. The method comprises the following steps: firstly, obtaining a dry shrinkage coefficient and a temperature shrinkage coefficient of a semi-rigid base material; obtaining the detection range of the construction site, and arranging a plurality of first strain sensors in the detection range along the longitudinal direction and the transverse direction; then manufacturing a semi-rigid base test piece, and arranging a second strain sensor on the top surface of the semi-rigid base test piece; and according to the difference value between the longitudinal strain of the top surface of the semi-rigid base and the longitudinal strain of the top surface of the semi-rigid base test piece, obtaining the early-age transverse cracking stress related strain of the top surface of the semi-rigid base at the construction site, and further obtaining the evaluation of the cracking trend. According to the method, the related strain of the cracking stress of the top surface of the semi-rigid base is accurately and continuously measured at the early age after the semi-rigid base is paved through simple operation, and the probability and trend of generation of transverse cracks at different positions of the top surface of the semi-rigid base are accurately evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of road engineering detection, and particularly relates to a method for measuring the stress-related strain of early-age transverse cracking on the top surface of a semi-rigid base and a method for evaluating the cracking trend. Background Art

[0002] The semi-rigid base has advantages such as high strength and large stiffness, and has been widely used in the construction of high-grade asphalt pavements in China. However, the semi-rigid base also has disadvantages such as poor resistance to volume deformation and sensitivity to temperature and humidity changes. During the early-age curing stage of the semi-rigid base, due to the differences in the external environment and curing conditions, transverse cracks caused by longitudinal shrinkage cracking are prone to appear first on the top surface, which will then cause reflection cracks and ultimately affect the road performance of the entire semi-rigid base asphalt pavement.

[0003] During the construction process, the shrinkage deformation of the semi-rigid base after paving will be restricted by the surrounding materials and the bottom base, resulting in the inability to achieve free expansion and contraction deformation when the temperature and humidity change, and thus internal stress is generated. Since the proportion of the volume change of the base material in the early age is significant, the internal tensile stress is often greater than its tensile strength during the curing stage, leading to early-age transverse cracking of the semi-rigid base. The patent with the application number CN202310177047.4 discloses a method for monitoring cracks in the semi-rigid base of an asphalt pavement based on intelligent perception. Intelligent particles integrated with resistive sensors are buried in the semi-rigid base of the asphalt pavement to collect the mechanical responses of the pavement structure, and the monitoring of the base cracks is realized. This method ignores the dry shrinkage and temperature shrinkage characteristics of the early-age semi-rigid base material and cannot quantitatively evaluate the influence of climate environment changes and on-site curing measures on the early-age transverse cracking trend of the semi-rigid base.

[0004] In view of this, it is necessary to design an improved method for measuring the stress-related strain of early-age transverse cracking on the top surface of a semi-rigid base and a method for evaluating the cracking trend to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for measuring the stress-related strain of early-age transverse cracking on the top surface of a semi-rigid base and a method for evaluating the cracking trend. Through simple operations, the stress-related strain of early-age transverse cracking on the top surface of the semi-rigid base can be accurately and continuously measured after the semi-rigid base is paved, the probability and trend of transverse cracks at different positions on the top surface of the semi-rigid base can be accurately evaluated, and the influence of climate environment changes and on-site curing measures on the early-age transverse cracking trend of the semi-rigid base can be quantitatively evaluated.

[0006] To achieve the above invention purpose, the present invention provides a method for measuring the stress-related strain of early-age transverse cracking on the top surface of a semi-rigid base, including the following steps:

[0007] S11. Obtain the dry shrinkage coefficient and temperature shrinkage coefficient of the semi-rigid base material;

[0008] S12. According to the dry shrinkage coefficient and temperature shrinkage coefficient obtained in step S11, obtain the detection range after paving the semi-rigid base at the construction site; and arrange a number of first strain sensors longitudinally and transversely within the detection range, and respectively read the readings ε of each first strain sensor at any time 基层i , which is recorded as the longitudinal strain of the semi-rigid base surface;

[0009] S13. Fabricate a number of semi-rigid base specimens using the same material as the semi-rigid base, and set second strain sensors on the top surface of each semi-rigid base specimen, and respectively read the readings ε of the second strain sensors at any time 试件i , and obtain the average value which is recorded as the longitudinal strain of the semi-rigid base specimen surface;

[0010] S14. According to the difference between the longitudinal strain of the semi-rigid base surface obtained in step S12 and the longitudinal strain of the semi-rigid base specimen surface obtained in step S13, obtain the transverse cracking stress-related strain at any early age of the semi-rigid base surface at the construction site.

[0011] As a further improvement of the present invention, in step S12, the first strain sensors are arranged at equal intervals longitudinally; and are arranged transversely according to the law of transverse stress distribution.

[0012] As a further improvement of the present invention, the first strain sensors are arranged transversely from the middle of the semi-rigid base to the side, and the spacing between adjacent first strain sensors increases sequentially from the middle of the semi-rigid base to the side.

[0013] As a further improvement of the present invention, in step S13, the semi-rigid base specimens are arranged on one side of the semi-rigid base, and the placement directions of the semi-rigid base specimens and the second strain sensors are the same as those of the first strain sensors; the curing methods of the semi-rigid base specimens and the semi-rigid base are the same.

[0014] As a further improvement of the present invention, the first strain sensors and the second strain sensors are respectively fixed to the semi-rigid base and the semi-rigid base specimens through anchor rods.

[0015] As a further improvement of the present invention, the embedding depth of the anchor rods does not exceed 1 / 6 of the thickness of the semi-rigid base specimens.

[0016] As a further improvement of the present invention, the same first strain sensor or the same second strain sensor is fixed by two of the anchor rods, and the distance between the two anchor rods for fixing the same first strain sensor or the second strain sensor is 1 / 3 to 1 / 2 of the length of the semi-rigid base specimen; the second strain sensor is installed longitudinally and centered on the top surface of the semi-rigid base specimen.

[0017] As a further improvement of the present invention, the curing method of the semi-rigid base specimen is: applying solid lubricating oil to the bottom of the semi-rigid base specimen, and wrapping the semi-rigid base specimen around and at the bottom with plastic film, and the curing conditions at the top of the semi-rigid base specimen are the same as those of the semi-rigid base at the site.

[0018] The present invention also provides a cracking trend evaluation method based on the above-mentioned strain measurement method related to the early-age transverse cracking stress on the top surface of the semi-rigid base, including the following steps:

[0019] S21. Establish the x-axis along the transverse direction within the detection range, with the positive direction of the x-axis extending from the center of the road surface to the side; establish the y-axis along the longitudinal direction, with the positive direction of the y-axis being the direction opposite to the on-site paving direction, and the zero point being the intersection of the x-axis and the y-axis to form a coordinate system; then set three rows of the first strain sensors parallel to the x-axis within the detection range, and set three columns of the first strain sensors parallel to the y-axis; the longitudinal length of the detection range along the y-axis is denoted as L, the width of the semi-rigid base is denoted as D, and the transverse length of the detection range along the x-axis is denoted as D / 2; the first to third rows of the first strain sensors are respectively located on the lines of y = 0, y = L / 2, and y = L, and the first to third columns of the first strain sensors are respectively located on the lines of x = 0, x = D / 6, and x = D / 2;

[0020] S22. According to the first strain sensor and the second strain sensor at the i-th location, obtain the transverse cracking stress-related strain value ε i (t) at any time t of the early age on the top surface of the semi-rigid base at the i-th location, and respectively obtain the variation functions L(x,t) of the transverse cracking stress-related strain with time in the directions of y = 0, y = L / 2, and y = L according to the following formula; the first strain sensors in the first row are sequentially denoted as the 1st, 2nd, and 3rd locations along the positive direction of the x-axis, the first strain sensors in the second row are sequentially denoted as the 4th, 5th, and 6th locations along the positive direction of the x-axis, and the first strain sensors in the third row are sequentially denoted as the 7th, 8th, and 9th locations along the positive direction of the x-axis;

[0021]

[0022]

[0023]

[0024] wherein, ε j (t) is the transverse cracking stress-related strain value at the top surface of the semi-rigid base at the early age at time t at the j-th location;

[0025] x is the coordinate value corresponding on the x-axis;

[0026] x i is the coordinate value corresponding on the x-axis at the i-th location; x j is the coordinate value corresponding on the x-axis at the j-th location; x1 = x4 = x7 = 0; x2 = x5 = x8 = D / 6; x3 = x6 = x9 = D / 2;

[0027] S23. Obtain the function D(y,t) of the stress-related strain varying with time at any position in the x-axis direction according to the following formula;

[0028]

[0029] wherein, L j (x,t) is the function of the transverse cracking stress-related strain varying with time in the j-th row obtained in step S22;

[0030] y is the coordinate value corresponding on the y-axis;

[0031] y j is the coordinate value corresponding on the y-axis at the j-th location; y1 = 0, y2 = L / 2, y3 = L;

[0032] S24. Obtain the function ε(x,y,t) of the stress-related strain varying with time at any position in the coordinate system according to the following formula;

[0033]

[0034] wherein, y j is the coordinate value corresponding on the y-axis at the j-th location;

[0035] S25. Obtain the cracking condition of the position to be measured (x,y) according to the function ε(x,y,t) obtained in step S24.

[0036] As a further improvement of the present invention, according to the stress-related strain in the longitudinal direction, the semi-rigid base cracks near the position with a larger stress-related strain; according to the stress-related strain in the transverse direction, the cracks of the semi-rigid base develop from the position with a larger stress-related strain to the position with a smaller stress-related strain.

[0037] The beneficial effects of the present invention are:

[0038] (1) The method for measuring the stress-related strain of early-age transverse cracking on the top surface of the semi-rigid base of the present invention, after the semi-rigid base is paved, obtains the early-age dry shrinkage coefficient and temperature shrinkage coefficient of the semi-rigid base material; then, according to the dry shrinkage coefficient and temperature shrinkage coefficient, obtains the detection range at the construction site, and installs the first strain sensors longitudinally and transversely within this detection range according to specific principles, ensuring to the greatest extent that the first strain sensors can capture the time-history change of the stress-related strain during the generation of transverse cracks. At the same time, a semi-rigid base specimen and a second strain sensor are set up, and the change value of the stress-related strain of early-age transverse cracking on the top surface of the semi-rigid base over time is obtained through the difference between the continuous monitoring implemented by the first strain sensors and the second strain sensors. The present invention accurately and continuously measures the stress-related strain of transverse cracking on the top surface of the semi-rigid base at the early age after the semi-rigid base is paved through simple operations, accurately evaluates the probability and trend of transverse cracks occurring at different positions on the top surface of the semi-rigid base, and quantitatively evaluates the influence of climate environment changes and on-site curing measures on the early-age transverse cracking trend of the semi-rigid base.

[0039] (2) The longitudinal and transverse arrangement scheme of the first strain sensors on the top surface of the semi-rigid base of the present invention can achieve obtaining the key distribution law of the stress related to transverse cracks in the semi-rigid base during the curing process with the least number of sensors, and then obtaining the stress-related strain distribution on the top surface of the semi-rigid base, which can effectively evaluate the generation position and development trend of transverse cracks in the base.

[0040] (3) By optimizing the curing conditions and environment of the semi-rigid base specimen, the present invention can enable the semi-rigid base specimen to freely deform without restraint during the curing period, effectively reducing the error in measuring the stress-related strain of the semi-rigid base. Description of the Drawings

[0041] Figure 1 is the flow chart of the method for measuring the stress-related strain of early-age transverse cracking on the top surface of the semi-rigid base and the method for evaluating the cracking trend of the present invention.

[0042] Figure 2 is the layout relationship diagram of the first strain sensors and the second strain sensors in Embodiment 1.

[0043] Figure 3 is the curing structure diagram of the semi-rigid base specimen.

[0044] Figure 4 is the change relationship of the stress-related strain of transverse cracking at the i-th position over time.

[0045] Figure 5 is the stress-related strain diagram of early-age transverse cracking on the top surface of the semi-rigid base at each position in Embodiment 1.

[0046] Figure 6Schematic diagram of the stress-related strain distribution on the top surface of the semi-rigid base in Example 2.

[0047] Reference numerals

[0048] 1 - Semi-rigid base; 2 - First strain sensor; 3 - Semi-rigid base specimen; 4 - Second strain sensor; 5 - Anchor rod; 6 - Solid lubricating oil; 7 - Plastic film. Detailed implementation manners

[0049] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0051] In addition, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0052] As Figures 1 to 3 shown, the present invention provides a method for measuring stress-related strain of early-age transverse cracking on the top surface of a semi-rigid base, including the following steps:

[0053] S11. Obtain the relevant properties of the semi-rigid base material:

[0054] Obtain the dry shrinkage coefficient and temperature shrinkage coefficient of the semi-rigid base material. Specifically, according to the "Test Procedures for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG E51), use the same materials as the semi-rigid base 1 at the construction site to make medium beam specimens of preset sizes, and determine and calculate the dry shrinkage coefficient and temperature shrinkage coefficient of the materials according to T 0854-2009 and T 0855-2009.

[0055] S12. Arrange the first strain sensor:

[0056] According to the dry shrinkage coefficient and temperature shrinkage coefficient obtained in step S11, obtain the detection range after paving the semi-rigid base 1 at the construction site (i.e., obtain the arrangement range of the strain sensor). The longitudinal length of this detection range is denoted as L, and the width of the semi-rigid base 1 is denoted as D. The value of L is calculated and selected using bilinear interpolation according to Table 1.

[0057] Table 1 L values corresponding to the dry shrinkage coefficient and temperature shrinkage coefficient

[0058]

[0059] A number of first strain sensors 2 are arranged longitudinally and transversely respectively within the determined detection range. Each first strain sensor 2 is connected to a data acquisition instrument, and the data acquisition instrument reads the indication ε of each first strain sensor 2 at any moment at each position 基层i , which is recorded as the longitudinal strain at the corresponding position on the top surface of the semi-rigid base 1. The first strain sensors 2 are arranged at equal intervals longitudinally; they are arranged according to the law of transverse stress distribution transversely (in practical applications, through a large number of tests, it is found that arranging according to the law of transverse stress distribution transversely results in more accurate and representative measurement results compared to equal-spacing arrangement); the spacing between adjacent first strain sensors 2 increases sequentially from the middle of the semi-rigid base 1 to the side. The number of first strain sensors 2 arranged longitudinally and transversely can be freely set. Considering the accuracy of the detection results and cost, three first strain sensors 2 can be selected and arranged longitudinally and transversely respectively. As Figure 2 shown, at this time, the distance between two adjacent first strain sensors 2 distributed longitudinally is L / 2; the distances between two adjacent first strain sensors 2 arranged transversely from the middle of the semi-rigid base 1 to the side are D / 6 and D / 3 respectively.

[0060] S13. Arranging second strain sensors:

[0061] According to the "Test Regulations for Inorganic Binder Stabilized Materials in Highway Engineering" (JTG E51), a number of semi-rigid base specimens 3 are made of the same material as the semi-rigid base 1, and second strain sensors 4 are set on the top surface of each semi-rigid base specimen 3. Each second strain sensor 4 is connected to a data acquisition instrument, and the data acquisition instrument reads the indication ε of each second strain sensor 4 at any moment 试件i , and the average value of the indications of a number of second strain sensors 4 is taken and recorded as the longitudinal strain on the top surface of the semi-rigid base specimen 3. The first strain sensors 2 and the second strain sensors 4 use the same sensors, and the naming is only to distinguish the different set positions.

[0062] As Figure 2 shown, the semi-rigid base specimen 3 is set on one side of the semi-rigid base 1, and the placement directions of the semi-rigid base specimen 3 and the second strain sensors 4 are the same as those of the first strain sensors 2 to reduce the detection error.

[0063] The semi-rigid base specimen 3 and the semi-rigid base 1 are cured in the same way to further reduce the detection error. Specifically, as Figure 3As shown in the figure, the curing method of the semi-rigid base specimen 3 is as follows: Apply solid lubricating oil 6 to the bottom of the semi-rigid base specimen 3 to minimize the friction generated during its shrinkage, so as to achieve unconstrained free deformation. Wrap the plastic film 7 around the perimeter and bottom of the semi-rigid base specimen 3 to prevent moisture loss. The top and other curing conditions are the same as those of the semi-rigid base 1 at the construction site.

[0064] The first strain sensor 2 and the second strain sensor 4 are respectively fixed to the semi-rigid base 1 and the semi-rigid base specimen 3 through the anchor rods 5. The embedding depth of the anchor rods 5 on the semi-rigid base 1 and the semi-rigid base specimen 3 does not exceed 1 / 6 of the thickness of the semi-rigid base specimen 3 to ensure that the anchor rods 5 are firm and cannot move freely after installation.

[0065] Two anchor rods 5 are required to fix the same first strain sensor 2 or the same second strain sensor 4. The distance between the two anchor rods 5 used to fix the same first strain sensor 2 or the same second strain sensor 4 is 1 / 3 - 1 / 2 of the length of the semi-rigid base specimen 3. In addition, the second strain sensor 4 is installed longitudinally in the center of the top surface of the semi-rigid base specimen 3.

[0066] S14. Calculate the strain related to the early-age transverse cracking stress on the top surface of the semi-rigid base:

[0067] Based on the difference between the longitudinal strain on the top surface of the semi-rigid base 1 obtained in step S12 and the longitudinal strain on the top surface of the semi-rigid base specimen 3 obtained in step S13, the strain related to the early-age transverse cracking stress at any moment on the top surface of the semi-rigid base 1 at the construction site is obtained.

[0068] As Figure 4 shown, it is the relationship between the strain related to the transverse cracking stress at the i-th position (i.e., a certain position) obtained by this method and time.

[0069] The present invention also provides a cracking trend evaluation method based on the measurement method of the strain related to the early-age transverse cracking stress on the top surface of the semi-rigid base, including the following steps:

[0070] S21. Establish a coordinate system:

[0071] Establish the x-axis horizontally within the detection range, with the positive direction of the x-axis extending from the center of the road surface towards the side. Establish the y-axis vertically, with the positive direction of the y-axis being the direction opposite to the on-site paving direction. The zero point is the intersection of the set x-axis and y-axis, forming a coordinate system. Then, set three rows of first strain sensors 2 parallel to the x-axis within the detection range, and set three columns of first strain sensors 2 parallel to the y-axis. The longitudinal length of the detection range along the y-axis is denoted as L, the width of the semi-rigid base course 1 is denoted as D, and the transverse length of the detection range along the x-axis is denoted as D / 2. The first to third rows of first strain sensors 2 are respectively located on the lines of y = 0, y = L / 2, and y = L, and the first to third columns of first strain sensors 2 are respectively located on the lines of x = 0, x = D / 6, and x = D / 2.

[0072] S22. Respectively obtain the variation functions L(x, t) of the transverse cracking stress-related strain with time in the directions of y = 0, y = L / 2, and y = L:

[0073] According to the first strain sensor 2 and the second strain sensor 4 located at the i-th position, obtain the transverse cracking stress-related strain value ε i (t) of the top surface of the semi-rigid base course 1 at the early age at any time t at the i-th position. Respectively obtain the variation functions L(x, t) of the transverse cracking stress-related strain with time in the directions of y = 0, y = L / 2, and y = L according to the following formula; the first strain sensors 2 in the first row are successively denoted as the 1st, 2nd, and 3rd positions along the positive direction of the x-axis, the first strain sensors 2 in the second row are successively denoted as the 4th, 5th, and 6th positions along the positive direction of the x-axis, and the first strain sensors 2 in the third row are successively denoted as the 7th, 8th, and 9th positions along the positive direction of the x-axis.

[0074]

[0075]

[0076]

[0077] Among them, ε j (t) is the transverse cracking stress-related strain value of the top surface of the semi-rigid base course 1 at the early age at the j-th position at the time t;

[0078] x is the coordinate value corresponding on the x-axis;

[0079] x i is the coordinate value corresponding on the x-axis at the i-th position; x j is the coordinate value corresponding on the x-axis at the j-th position; x1 = x4 = x7 = 0; x2 = x5 = x8 = D / 6; x3 = x6 = x9 = D / 2.

[0080] S23. Obtain the function D(y, t) of stress-related strain at any position in the x-axis direction changing with time:

[0081] Obtain the function D(y, t) of stress-related strain at any position in the x-axis direction changing with time according to the following formula;

[0082]

[0083] where, L j (x, t) is the function of the stress-related strain of transverse cracking in the j-th row obtained in step S22 changing with time;

[0084] y is the coordinate value corresponding on the y-axis;

[0085] y j is the coordinate value corresponding on the y-axis at the j-th place; y1 = 0, y2 = L / 2, y3 = L.

[0086] S24. Obtain the function ε(x, y, t) of stress-related strain at any position in the coordinate system changing with time:

[0087] Obtain the function ε(x, y, t) of stress-related strain at any position in the coordinate system changing with time according to the following formula;

[0088]

[0089] where, y j is the coordinate value corresponding on the y-axis at the j-th place; x j , y j etc. have the same meanings as those represented above and will not be elaborated here.

[0090] In this formula, x is the independent variable, and x in D(y, t) is a given value.

[0091] S25. Obtain the cracking condition of the position to be measured (x, y)

[0092] According to the function ε(x, y, t) obtained in step S24, obtain the cracking condition of the position to be measured (x, y).

[0093] Specifically, according to the obtained function graph, compare the stress-related strains in the longitudinal direction. The semi-rigid base layer 1 cracks near the position with a larger stress-related strain; compare the stress-related strains in the transverse direction, and the cracks of the semi-rigid base layer 1 will develop from the position with a larger stress-related strain to the position with a smaller stress-related strain.

[0094] The present invention will be described in detail below through specific embodiments.

[0095] Embodiment 1

[0096] A method for measuring the strain related to the early-age transverse cracking stress on the top surface of a semi-rigid base course, comprising the following steps:

[0097] S11. Obtain the relevant properties of the semi-rigid base course material:

[0098] According to the "Test Regulations for Inorganic Binding Material Stabilized Materials for Highway Engineering" (JTG E51), use the same material as the semi-rigid base course 1 at the construction site to fabricate a middle beam specimen with dimensions of 100 mm × 100 mm × 400 mm, and determine and calculate the dry shrinkage coefficient and temperature shrinkage coefficient of the material as 86×10 -6 and 10.6×10 -6 .

[0099] S12. Arrange the first strain sensors:

[0100] According to the dry shrinkage coefficient and temperature shrinkage coefficient obtained in step S11, obtain the detection range after paving the semi-rigid base course 1 at the construction site (that is, obtain the arrangement range of the strain sensors). The longitudinal length of this detection range is denoted as L = 17.46 m (the value of L is calculated and selected using the bilinear interpolation method according to Table 1, which will not be elaborated here), and the width of the semi-rigid base course 1 is denoted as D = 9 m.

[0101] Table 1 L values corresponding to the dry shrinkage coefficient and temperature shrinkage coefficient

[0102]

[0103] Arrange a number of first strain sensors 2 along the longitudinal and transverse directions respectively within the determined detection range. As Figure 2 shown, set three first strain sensors 2 in the longitudinal and transverse directions respectively. The distance between two adjacent first strain sensors 2 distributed longitudinally is L / 2; the distances between two adjacent first strain sensors 2 distributed transversely from the middle of the semi-rigid base course 1 to the sides are D / 6 and D / 3 respectively.

[0104] Each first strain sensor 2 is respectively connected to a data acquisition instrument, and the readings ε 基层i (i = 1, 2,..., 9) of each first strain sensor 2 at any time at each position are read through the data acquisition instrument, which is denoted as the longitudinal strain at the corresponding position on the top surface of the semi-rigid base course 1; at the same time, draw the change curve of ε 基层i (i = 1, 2,..., 9) with the age.

[0105] S13. Arrange the second strain sensors:

[0106] According to the "Test Regulations for Inorganic Binding Material Stabilized Materials in Highway Engineering" (JTG E51), three semi-rigid base specimens 3 are made of the same materials as the semi-rigid base 1, and a second strain sensor 4 is set on the top surface of each semi-rigid base specimen 3. Each second strain sensor 4 is respectively connected to a data acquisition instrument, and the readings ε of the second strain sensor 4 at any moment are respectively read through the data acquisition instrument 试件i (i = 1, 2, 3), and the average value of the readings of the three second strain sensors 4 is taken and recorded as the longitudinal strain on the top surface of the semi-rigid base specimen 3. At the same time, a curve of ε 试件 changing with age is plotted.

[0107] As Figure 2 shown, the semi-rigid base specimen 3 is set on one side of the semi-rigid base 1. The placement directions of the semi-rigid base specimen 3 and the second strain sensor 4 are the same as those of the first strain sensor 2 to reduce the detection error.

[0108] The curing methods of the semi-rigid base specimen 3 and the semi-rigid base 1 are the same to eliminate the strain difference between the semi-rigid base 1 at the construction site and the semi-rigid base specimen 3 during the curing process due to different environments. Specifically, as Figure 3 shown, the curing method of the semi-rigid base specimen 3 is: applying solid lubricating oil 6 to the bottom of the semi-rigid base specimen 3 to achieve free deformation without restraint, and wrapping plastic film 7 around the semi-rigid base specimen 3 and at the bottom to prevent moisture loss. The top and other curing conditions are the same as those of the semi-rigid base 1 at the construction site.

[0109] Preferably, as Figure 2 shown, the size of the semi-rigid base specimen 3 is 100 mm × 100 mm × 400 mm. The first strain sensor 2 and the second strain sensor 4 are respectively fixed to the semi-rigid base 1 and the semi-rigid base specimen 3 through anchor rods 5. The embedding depth of the anchor rods 5 in the semi-rigid base 1 and the semi-rigid base specimen 3 is 15 mm.

[0110] Two anchor rods 5 are required to fix the same first strain sensor 2 or the same second strain sensor 4. The distance between the two anchor rods 5 used to fix the same first strain sensor 2 or the same second strain sensor 4 is 150 mm. In addition, the second strain sensor 4 is installed in the center along the longitudinal direction on the top surface of the semi-rigid base specimen 3.

[0111] S14. Calculate the strain related to the early-age transverse cracking stress on the top surface of the semi-rigid base:

[0112] Based on the difference between the longitudinal strain at the top surface of the semi-rigid base course 1 obtained in step S12 and the longitudinal strain at the top surface of the semi-rigid base course specimen 3 obtained in step S13, the variation relationship of the early-age transverse cracking stress-related strain with time at the top surface of the semi-rigid base course 1 at the construction site is obtained, and the result is as Figure 5 shown.

[0113] Example 2

[0114] A cracking trend evaluation method based on the method for measuring the early-age transverse cracking stress-related strain at the top surface of a semi-rigid base course in Example 1, comprising the following steps:

[0115] S21. Establish a coordinate system:

[0116] Establish an x-axis along the transverse direction and a y-axis along the longitudinal direction within the detection range to obtain a coordinate system. Specifically, the magnitude of the stress-related strain at the i-th first strain sensor 2 at any time t is denoted as ε i (t), as Figure 2 shown. The zero point is at the first position. An x-axis is established along the transverse direction, and the positive direction is towards the third position; a y-axis is established along the longitudinal direction, and the positive direction is towards the seventh position, forming a coordinate system. The longitudinal length of the detection range along the y-axis is denoted as L, the width of the semi-rigid base course 1 is denoted as D, and the transverse length of the detection range along the x-axis is denoted as D / 2; the first to third rows of the first strain sensors 2 are respectively located on the straight lines of y = 0, y = L / 2, and y = L, and the first to third columns of the first strain sensors 2 are respectively located on the straight lines of x = 0, x = D / 6, and x = D / 2.

[0117] S22. Respectively obtain the variation functions L(x,t) of the transverse cracking stress-related strain in the directions of y = 0, y = L / 2, and y = L at specific times:

[0118] According to the stress-related strain values at the top surface of the semi-rigid base course 1 at the moment of t = 7d (i.e., 168h) obtained in Example 1, predict the variation functions L1(x,t), L2(x,t), and L3(x,t) of the transverse cracking stress-related strain with time in the directions of y1 = 0, y2 = L / 2, and y3 = L.

[0119]

[0120]

[0121]

[0122] Among them, ε j (t) is the value of the early-age transverse cracking stress-related strain at the top surface of the semi-rigid base course 1 at the j-th position at time t;

[0123] x is the coordinate value corresponding on the x-axis;

[0124] x i is the coordinate value corresponding to the i-th position on the x-axis; x j is the coordinate value corresponding to the j-th position on the x-axis; x1 = x4 = x7 = 0; x2 = x5 = x8 = D / 6; x3 = x6 = x9 = D / 2.

[0125] S23. Obtain the variation function D(y, t) of the stress-related strain at any position in the x-axis direction at a specific moment:

[0126] Obtain the variation function D(y, t) of the stress-related strain at any position in the x-axis direction with respect to time according to the following formula;

[0127]

[0128] where, L j (x, t) is the variation function of the transverse cracking stress-related strain of the j-th row obtained in step S22 with respect to time;

[0129] y is the coordinate value corresponding to the position on the y-axis;

[0130] y j is the coordinate value corresponding to the j-th position on the y-axis; y1 = 0, y2 = L / 2, y3 = L.

[0131] S24. Obtain the variation function ε(x, y, t) of the stress-related strain at any position in the coordinate system at a specific moment: Obtain the variation function ε(x, y, t) of the stress-related strain at any position in the coordinate system with respect to time according to the following formula; Obtain the image as shown Figure 6 by this function.

[0132]

[0133] where, y j is the coordinate value corresponding to the j-th position on the y-axis; x j , y j etc. have the same meanings as those described above and will not be elaborated here.

[0134] In this formula, x is the independent variable, and x in D(y, t) is a given value.

[0135] S25. Obtain the cracking condition of the position to be measured (x, y)

[0136] According to the curve of the ε(x, y, t) function obtained in step S24 (i.e., Figure 6 as shown), obtain the stress-related strain distribution of the top surface of the semi-rigid base at the 7-day age. From Figure 6It can be seen that the stress-related strain is the largest at the top surface of the semi-rigid base at x = 0 and y = 7.9. Cracks are more likely to occur at this location on the semi-rigid base 1 and develop along the edge of the semi-rigid base 1 in the transverse direction.

[0137] In summary, a method for measuring the stress-related strain of early-age transverse cracking on the top surface of a semi-rigid base and a method for evaluating the cracking trend provided by the present invention can accurately and continuously measure the stress-related strain of early-age transverse cracking on the top surface of a semi-rigid base through simple operations in the early age after the semi-rigid base is paved, accurately evaluate the probability and trend of transverse cracks occurring at different positions on the top surface of the semi-rigid base, and quantitatively evaluate the influence of climate environment changes and on-site curing measures on the early-age transverse cracking trend of the semi-rigid base.

[0138] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for measuring the strain related to the early - age transverse cracking stress on the top surface of a semi - rigid base course, characterized in that, It includes the following steps: S11. Obtain the dry shrinkage coefficient and temperature shrinkage coefficient of the semi-rigid base course material; S12. Based on the dry shrinkage coefficient and temperature shrinkage coefficient obtained in step S11, obtain the detection range after paving the semi-rigid base at the construction site; and arrange a number of first strain sensors longitudinally and transversely within the detection range, and respectively read the readings ε of each first strain sensor at any time 基层i , which is recorded as the longitudinal strain on the top surface of the semi-rigid base; S13. Fabricate a number of semi-rigid base specimens using the same material as the semi-rigid base, and install second strain sensors on the top surface of each semi-rigid base specimen. Read the readings ε of the second strain sensors at any time, respectively, and obtain the average value. 试件i , and obtain the average value which is recorded as the longitudinal strain on the top surface of the semi-rigid base specimen. S14. Obtain the transverse cracking stress-related strain at any early age of the top surface of the semi-rigid base course at the construction site according to the difference between the longitudinal strain of the top surface of the semi-rigid base course obtained in step S12 and the longitudinal strain of the top surface of the semi-rigid base course specimen obtained in step S13.

2. The method for measuring the early-age transverse cracking stress-related strain on the top surface of the semi-rigid base according to claim 1, characterized in that In step S12, the first strain sensors are arranged at equal intervals longitudinally; and are arranged transversely according to the transverse stress distribution law.

3. The method for measuring the early-age transverse cracking stress-related strain on the top surface of the semi-rigid base according to claim 2, wherein The first strain sensors are arranged transversely from the middle of the semi-rigid base course to the side, and the distance between adjacent first strain sensors increases successively from the middle of the semi-rigid base course to the side.

4. The method for measuring the stress-related strain of early-age transverse cracking on the top surface of a semi-rigid base according to claim 1, wherein In step S13, the semi-rigid base course specimen is arranged on one side of the semi-rigid base course, and the placement directions of the semi-rigid base course specimen and the second strain sensors are the same as those of the first strain sensors; the curing methods of the semi-rigid base course specimen and the semi-rigid base course are the same.

5. The method for measuring the early-age transverse cracking stress-related strain on the top surface of the semi-rigid base according to claim 1, characterized in that The first strain sensors and the second strain sensors are respectively fixed to the semi-rigid base course and the semi-rigid base course specimen through anchor rods.

6. The method for measuring the early-age transverse cracking stress-related strain on the top surface of the semi-rigid base according to claim 5, characterized in that The embedding depth of the anchor rods does not exceed 1 / 6 of the thickness of the semi-rigid base course specimen.

7. The method for measuring the stress-related strain of early-age transverse cracking on the top surface of the semi-rigid base according to claim 5, characterized in that The same first strain sensor or the same second strain sensor is fixed by two anchor rods, and the distance between the two anchor rods used to fix the same first strain sensor or the second strain sensor is 1 / 3 to 1 / 2 of the length of the semi-rigid base course specimen; the second strain sensors are installed longitudinally in the middle of the top surface of the semi-rigid base course specimen.

8. The method for measuring the early-age transverse cracking stress-related strain on the top surface of the semi-rigid base according to claim 4, characterized in that The curing method of the semi-rigid base course specimen is: apply solid lubricating oil to the bottom of the semi-rigid base course specimen, wrap the semi-rigid base course specimen around the perimeter and at the bottom with plastic film, and keep the curing conditions at the top of the semi-rigid base course specimen consistent with those of the semi-rigid base course at the site.

9. A method for evaluating the cracking trend of a semi-rigid base surface at early age related to the transverse cracking stress strain measurement method according to any one of claims 1 to 8, characterized in that, It includes the following steps: S21. Establish the x-axis transversely within the detection range, with the positive direction of the x-axis extending from the center of the road surface to the side, establish the y-axis longitudinally, with the positive direction of the y-axis being the direction opposite to the on-site paving direction, and the origin being the intersection of the x-axis and the y-axis to form a coordinate system; then set three rows of the first strain sensors parallel to the x-axis within the detection range, and set three columns of the first strain sensors parallel to the y-axis; the longitudinal length of the detection range along the y-axis is denoted as L, the width of the semi-rigid base course is denoted as D, and the transverse length of the detection range along the x-axis is denoted as D / 2; the first to third rows of the first strain sensors are respectively located on the lines of y = 0, y = L / 2, and y = L, and the first to third columns of the first strain sensors are respectively located on the lines of x = 0, x = D / 6, and x = D / 2; S22. Obtain the strain value ε related to transverse cracking stress at any early age time t on the top surface of the semi-rigid base layer at the i-th location according to the first strain sensor and the second strain sensor located at the i-th location i (t), and respectively obtain the time-varying functions L(x,t) of the strain related to transverse cracking stress in the directions of y = 0, y = L / 2, and y = L according to the following formula; The first strain sensors located in the first row are sequentially denoted as the 1st position, the 2nd position, and the 3rd position in the positive x-axis direction, the first strain sensors located in the second row are sequentially denoted as the 4th position, the 5th position, and the 6th position in the positive x-axis direction, and the first strain sensors located in the third row are sequentially denoted as the 7th position, the 8th position, and the 9th position in the positive x-axis direction; Among them, ε j (t) is the transverse cracking stress-related strain value of the top surface of the semi-rigid base at the early age at the j-th position at time t; x is the coordinate value corresponding on the x-axis; x i is the coordinate value corresponding to the $i$-th position on the $x$-axis; $x$ j is the coordinate value corresponding to the $j$-th position on the $x$-axis; $x_1 = x_4 = x_7 = 0$; $x_2 = x_5 = x_8 = D / 6$; $x_3 = x_6 = x_9 = D / 2$; S23. Obtain the variation function D(y, t) of stress-related strain with time at any position in the x-axis direction according to the following formula; Among them, L j (x, t) is the function of the change of the strain related to the transverse cracking stress of the j-th row obtained in step S22 with respect to time; y is the coordinate value corresponding on the y-axis; y j is the coordinate value corresponding to the j-th position on the y-axis; y1 = 0, y2 = L / 2, y3 = L; S24. Obtain the variation function ε(x, y, t) of stress-related strain with time at any position in the coordinate system according to the following formula; where y j is the coordinate value corresponding to the j-th position on the y-axis; S25. Obtain the cracking condition of the position (x, y) to be measured according to the ε(x, y, t) function obtained in step S24.

10. The method for evaluating the early-age transverse cracking tendency of the semi-rigid base course top surface according to claim 9, characterized in that, According to the stress-related strain in the longitudinal direction, the semi-rigid base course cracks near the position with a larger stress-related strain; according to the stress-related strain in the transverse direction, the cracks in the semi-rigid base course develop from the position with a larger stress-related strain to the position with a smaller stress-related strain.

Images