A method for preventing cracking of pipe gallery concrete
By deploying sensors on key sections of the utility tunnel structure to monitor temperature and deformation data, and obtaining the ultimate tensile strain value in real time for early warning, the problem of concrete cracking in the utility tunnel was solved, effective control of structural leakage was achieved, and the long-term durability of the structure was ensured.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEBEI XIONGAN RONGXI CONCRETE CO LTD
- Filing Date
- 2023-10-25
- Publication Date
- 2026-07-10
Smart Images
Figure CN117433581B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of safety protection technology for pipe gallery concrete, and in particular to a method for preventing cracking of pipe gallery concrete. Background Technology
[0002] Currently, the construction of integrated utility tunnels is booming. During the construction process, cracks of varying degrees have been found on the side walls of the tunnels. These cracks reduce the structure's load-bearing capacity and create channels for external corrosive media to enter the concrete, accelerating steel corrosion and concrete structural damage, thus reducing the structure's durability. Therefore, controlling cracks is crucial to achieving the 100-year design life of underground integrated utility tunnels.
[0003] Underground utility tunnels are typically two- or three-compartment structures. The compartments are divided according to function, such as power and communication compartments, gas compartments, heating compartments, and general utility compartments. Large-section pipes within the compartments, such as main water supply pipes, natural gas pipes, and steam pipes, are laid on the floor using supports. Small-section pipes, such as branch water supply pipes, greywater pipes, and various cables, such as power cables and communication cables, are fixed to the interior walls using brackets. Figure 1 As shown.
[0004] Based on feedback from the construction units of the utility tunnels and the results of a survey of currently under-construction open-cut and cast-in-place utility tunnel projects, various common quality defects have been found during the construction of utility tunnels, with concrete cracking being the most common. Cracks are frequently found in vertical walls and roof slabs, with longitudinal cracks being the most common in vertical walls, followed by roof slabs, while cracks are less common in floor slabs.
[0005] The presence and development of cracks reduce the load-bearing capacity of the structure and open up channels for external corrosive media to enter the concrete and corrode the steel bars, which is detrimental to long-term durability and safety.
[0006] Cracks in underground utility tunnels have always been a top priority in quality control during construction. Because underground waterproofing and seepage are involved, current engineering practices adhere to the principles of "prevention first, combining rigid and flexible methods, multiple layers of protection, adapting to local conditions, and comprehensive prevention and control." Among these, "prevention" is fundamental and a crucial area of research in the engineering field.
[0007] Therefore, there is an urgent need to provide a method to prevent cracking of the concrete in the utility tunnel, control structural leakage in advance, and solve the problem of cracks in the side walls and bottom slab of key parts of the cast-in-place buried tunnel. Summary of the Invention
[0008] The technical problem to be solved by the present invention is to provide a method for preventing cracking of concrete in pipe racks.
[0009] To solve the above problems, the technical solution adopted by the present invention is as follows:
[0010] A method for preventing cracking of concrete in utility tunnels, characterized in that the method comprises:
[0011] Step 1: Obtain the ultimate tensile strain value of the concrete in the pipe gallery at each age.
[0012] Step 2: Set up multiple monitoring points at the end, normal, and intermediate sections of the pipe gallery structure, and install one sensor at each monitoring point;
[0013] Step 3: Real-time acquisition of temperature and deformation data of the concrete in the pipe gallery at each of the aforementioned sensors at its corresponding monitoring points;
[0014] Step 4: When the cooling rate obtained by any sensor at any time reaches the preset cooling rate threshold, or when the actual deformation value obtained by any sensor at any time reaches the corresponding limit strain value for that day, a cracking warning is issued so that staff can take preventive measures to prevent the concrete of the pipe gallery from cracking.
[0015] In one embodiment of the invention, the end section is a section at 1 / 10L from the end, the ordinary position section is a section at 3 / 10L from the end, and the middle position section is a section at 1 / 2L from the end, where L is the length of a standard segment of the pipe gallery.
[0016] As one embodiment of the invention, monitoring points are set up on each cross section at the upper, middle, and lower parts of the vertical wall, the lower surface of the top plate at the mid-span, and at the junction with the vertical wall.
[0017] As one embodiment of the invention, in step two, a zero-stress bucket is set at the center of each cross section, and the detection point arranged in each zero-stress bucket is the reference monitoring point corresponding to its cross section, and the sensor installed is the reference sensor corresponding to its cross section.
[0018] As one embodiment of the invention, each of the sensors is a vibrating wire strain sensor.
[0019] As one embodiment of the invention, step four includes:
[0020] Step S401: Obtain temperature data and deformation data sent by all sensors at the current moment;
[0021] Step S402: Based on the temperature data sent by each sensor, determine whether the corresponding cooling rate has reached the preset cooling rate threshold; and based on the deformation data sent by all sensors on each cross section, determine whether the actual deformation value at the current moment has reached the corresponding limit strain value for that day.
[0022] Step S403: When it is determined that the cooling rate obtained by any sensor at any time reaches the preset cooling rate threshold, or when it is determined that the actual deformation value obtained by any sensor at any time reaches the corresponding limit strain value for that day, a cracking warning is issued so that the staff can take preventive measures to prevent the concrete of the pipe gallery from cracking.
[0023] As one embodiment of the invention, in step S402, for any cross-section, determining whether the actual deformation value at the current moment has reached the corresponding limit strain value for that day based on the deformation data sent by all sensors on the cross-section includes:
[0024] Step S4021: Obtain the reference strain transmitted by the reference sensor on the cross section;
[0025] Step S4022: Subtract the reference strain from the deformation data of other sensors to obtain the actual deformation value corresponding to each sensor at the current moment;
[0026] Step S4023: Compare all actual deformation values with the corresponding ultimate hard strain value for that day, and determine whether the actual deformation value at the current moment has reached the corresponding ultimate hard strain value for that day.
[0027] As one embodiment of the invention, the preventive measures in step four include: covering the surface of the sensor location where the strain change value reaches the limit hard strain value and the sensor location where the temperature value reaches the temperature threshold for insulation.
[0028] As one embodiment of the invention, step one includes:
[0029] Step S101: Test the concrete of the test block cured in the previous standard segment of the current pipe gallery to obtain the actual splitting tensile strength and actual compressive strength of the concrete of the test block per day;
[0030] Step S102: Fit the actual splitting tensile strength of the concrete block every day to obtain the fitting curve of the splitting tensile strength of the concrete block over time.
[0031] Step S103: Obtain the fitted splitting tensile strength of the concrete specimen at each age based on the development fitting curve, so as to calculate the axial tensile strength of the concrete specimen at each age.
[0032] Step S104: Based on the actual compressive strength and elastic modulus of the concrete test block each day, calculate the elastic modulus of the concrete test block at each age.
[0033] The beneficial effects of adopting the above technical solution are as follows:
[0034] This invention provides a method for preventing cracking in the concrete of utility tunnels. After obtaining the ultimate tensile strain value of the concrete at each age, multiple monitoring points are set up at the end, intermediate, and middle sections of the tunnel structure. Sensors at each monitoring point dynamically monitor the temperature and deformation data of the concrete. Based on the on-site monitoring data, adjustments are made in real time. Especially when the measured temperature and strain data approach control targets, a cracking warning is issued, allowing staff to take preventative measures to prevent concrete cracking. By monitoring data in real time, cracking of the concrete can be predicted in advance, enabling proactive measures to avoid such situations. This effectively controls structural leakage and solves the problem of cracks in the sidewalls and floor slabs of key parts of cast-in-place buried tunnels. Attached Figure Description
[0035] Figure 1 This is a schematic diagram of a pipe gallery cross-section provided by existing technology.
[0036] Figure 2 This is an analytical block diagram of a cracking mechanism provided by the present invention.
[0037] Figure 3 This is a schematic diagram of a measuring point cross-section setting provided by the present invention.
[0038] Figure 4 This is a schematic diagram of the arrangement of measuring points on each cross section provided by the present invention.
[0039] Figure 5 This is a schematic diagram of the structure of a sensor provided by the present invention.
[0040] Figure 6 This is a temperature change curve at a certain measuring point provided by the present invention.
[0041] Figure 7 This invention provides a fitting curve for the development of splitting tensile strength of a test block.
[0042] Figure 8 This is a schematic diagram of a sensor position provided by the present invention.
[0043] Figure 9 yes Figure 8 The curve showing the strain change detected at point C5.
[0044] Figure 10 yes Figure 8 The actual deformation value curve at point C5.
[0045] Figure 11 This is a schematic diagram of the cracks actually observed.
[0046] In the diagram, 1-O-type sealing end block, 2-protective tube, 3-steel wire, 4-thermal coil and thermistor cover, 5-thermistor, 6-removable coil, 7-cable. Detailed Implementation
[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the invention will be described clearly and completely below in conjunction with specific embodiments.
[0048] This invention provides a method for preventing cracking of concrete in utility tunnels. To achieve the purpose of preventing cracking of concrete in utility tunnels, the cracking mechanism of concrete in utility tunnels is first explained as follows.
[0049] The reason why the utility tunnel structure cracks is that the deformation of the structure is constrained. The internal force generated by the constraint exceeds the structure's own resistance, thus causing cracking. The cracking principle is as follows: Figure 2 As shown.
[0050] Cracking of concrete in underground utility tunnel structures is the result of multiple factors acting together. From a mechanistic perspective, cracking occurs when the stress generated by the constraint of concrete deformation exceeds the tensile strength of the concrete. The factors causing deformation and those constraining the concrete can be categorized into two types: the first type is internal factors, such as deformation caused by temperature development during cement hydration and the gradual increase in the elastic modulus of concrete due to cement hydration. The second type is external factors, such as the influence of environmental temperature changes on the cement hydration process and volume deformation in concrete, and the constraining deformation effect of the foundation on the structure, and the constraint deformation effect of the substructure on the superstructure. This invention, based on the aforementioned internal and external factors leading to cracking, yields the method of this invention.
[0051] The method for preventing cracking of concrete in pipe gallery according to the present invention includes:
[0052] Step S1: Obtain the ultimate tensile strain value of the concrete in the pipe gallery at each age.
[0053] Step S101: Test the concrete of the test block cured in the previous standard segment of the current pipe gallery to obtain the actual splitting tensile strength and actual compressive strength of the concrete of the test block per day;
[0054] Step S102: Fit the actual splitting tensile strength of the concrete block every day to obtain the fitting curve of the splitting tensile strength of the concrete block over time.
[0055] Step S103: Obtain the fitted splitting tensile strength of the concrete specimen at each age based on the development fitting curve, so as to calculate the axial tensile strength of the concrete specimen at each age.
[0056] Step S104: Based on the actual compressive strength of the concrete test block each day, obtain the elastic modulus of the concrete test block at each age.
[0057] Step S105: Calculate the ultimate tensile strain value for each day of the concrete specimen based on the axial tensile strength and elastic modulus of the concrete at each age.
[0058] Specifically, the ultimate tensile strain value for each age period is obtained using the following formula:
[0059] in, This represents the ultimate tensile strain value (in με). This indicates the axial tensile strength of concrete in test blocks at the same age (in MPa). This indicates the elastic modulus of concrete in test blocks at the same age (in GPa).
[0060] Step S2: Set up multiple monitoring points at the end section, the ordinary section and the middle section of the pipe gallery structure, and install a sensor at each monitoring point.
[0061] The location and orientation of monitoring points play a crucial role in the overall effectiveness of the monitoring experiment. The monitoring point layout should consider both the representativeness and economy of the monitoring results. Too few monitoring points will not provide a sufficient understanding of the temperature and stress changes in the structure. Too many monitoring points will lead to data duplication and waste. Therefore, only a subset of key areas should be monitored. Thus, in order to comprehensively understand the temperature, strain trends, and stress patterns of the utility tunnel structure throughout the construction process, and to verify the rationality of the numerical simulation, the following principles for selecting the location of monitoring points are proposed:
[0062] (1) By making full use of the structural characteristic of being symmetrical about the middle section, points can be placed only on one side of the structural symmetry plane;
[0063] (2) When selecting the location of the measuring point, its economy, rationality and convenience of on-site testing should be taken into account.
[0064] (4) The location of the measuring points should be selected in areas with relatively little construction interference;
[0065] Since the overall structure of the utility tunnel is symmetrical about the middle section along its length, three representative sections were selected for the arrangement of sensor measuring points: the end position section (1 / 10L from the end), the ordinary position section (3 / 10L from the end), and the middle position section (1 / 2L from the end).
[0066] Where L represents the length of a standard segment of the utility tunnel, which can be 20m or 30m, for example... Figure 3As shown, this invention takes L as 30m as an example and illustrates the positions of section A at the end (3m from the end), section B at the normal position (9m from the end), and section C at the middle position (15m from the end).
[0067] In terms of cross-sectional location, areas with higher stress concentration are selected. Therefore, in this invention, monitoring points are arranged at typical locations: the upper, middle, and lower parts of the vertical wall, the lower surface of the top slab at mid-span, and the area at the junction of the vertical wall and the top slab. Here, "upper part" refers to the portion 0-1m from the bottom of the vertical wall, "middle part" refers to the portion 1.5-1.8m from the bottom of the vertical wall, and "upper part" refers to the portion 2-3m from the bottom of the vertical wall. Figure 4 For example, in the figure, A1-A13 represent 13 monitoring points. In this figure, A1 is located at the bottom of the vertical wall, A5 and A6 are located in the middle of the vertical wall, A13 is located at the top of the vertical wall, A10 is located on the lower surface of the top slab in the middle of the span, and A12 and A9 are located at the junction of the vertical wall and the top slab.
[0068] In addition, in step two, a zero-stress bucket is set at the center of each cross section, and the detection point arranged in each zero-stress bucket is the reference monitoring point corresponding to its cross section, and the sensor installed is the reference sensor corresponding to its cross section.
[0069] Step S3: Real-time acquisition of temperature and deformation data of the concrete in the pipe gallery at each of the aforementioned sensors at its corresponding monitoring points.
[0070] To achieve full-process data collection on temperature deformation and shrinkage deformation of the pipe gallery during construction, the sensor in this application is a vibrating wire strain sensor.
[0071] Vibrating wire strain sensors can simultaneously monitor strain and temperature. They can utilize existing structures, and this invention does not impose specific limitations on their application. (See also...) Figure 5 Its main components include steel wire, coil, thermistor, and protective tube.
[0072] The basic principle of the vibrating wire strain gauge method is to calculate the strain at a given location by utilizing the relationship between the frequency of the steel wire and the magnitude of its tension. Before measurement, a steel wire of a certain length is fixed between two end blocks, which are firmly attached to the surface of the component being measured. If the component deforms, the two end blocks will inevitably move relative to each other, causing a change in the tension of the steel wire and a change in its resonant frequency. The frequency is then measured to monitor the strain change in the component.
[0073] Step S4: When the cooling rate obtained by any sensor at any time reaches the preset cooling rate threshold, or when the strain change value obtained by any sensor at any time reaches the corresponding limit strain value for that day, a cracking warning is issued so that staff can take preventive measures to prevent the concrete of the pipe gallery from cracking.
[0074] Step S401: Obtain temperature data and deformation data sent by all sensors at the current moment;
[0075] Step S402: Based on the temperature data sent by each sensor, determine whether the corresponding cooling rate has reached the preset cooling rate threshold; and based on the deformation data sent by all sensors on each cross section, determine whether the actual deformation value at the current moment has reached the corresponding limit strain value for that day.
[0076] The following sections will further explain the methods for making judgments based on temperature and strain changes.
[0077] (1) Regarding the strain change value:
[0078] In this step, for any cross section, the following steps are used to determine whether the strain change value at the current moment has reached the corresponding limit strain value for that day, based on the deformation data sent by all sensors on the cross section:
[0079] Step S4021: Obtain the reference deformation data sent by the reference sensor on the cross section.
[0080] Since the strain output by sensors other than the reference sensor is a combination of two types of strain: the constrained strain of the concrete structure and the free expansion and contraction temperature strain of the concrete structure, the free expansion and contraction temperature strain of the concrete structure does not generate internal stress. Therefore, the constrained strain of the concrete structure, that is, the strain generated by the concrete structure under constraint, plays a major role in determining the stress of the concrete structure.
[0081] For example, if the shrinkage of a concrete structure is uniform, then the shrinkage will only generate strain, not stress. However, during the integral casting process of a pipe gallery concrete structure, the shrinkage of the concrete structure is unlikely to be uniform. Therefore, the shrinkage strain of the concrete structure must be subtracted from the calculated strain of the concrete structure (the reference deformation data sent by the reference sensor) in order to accurately calculate the constraint strain of the concrete structure and better analyze and explain the stress distribution and cracking problems of the concrete structure.
[0082] Step S4022: Compare all actual deformation values with the corresponding ultimate hard strain value for that day, and determine whether the actual deformation value at the current moment has reached the corresponding ultimate hard strain value for that day.
[0083] It should be noted that for any single sensor, deformation data detected at multiple moments can form a strain change curve. Similarly, subtracting the baseline deformation data (zero-stress barrel strain) from the strain change value at each moment will also generate an actual deformation curve.
[0084] Step S4023: Compare all actual deformation values with the corresponding ultimate hard strain value for that day, and determine whether the actual deformation value at the current moment has reached the corresponding ultimate hard strain value for that day.
[0085] Through the aforementioned steps, the strain changes of the pipe gallery concrete can be monitored in real time and from all angles.
[0086] (2) Regarding temperature:
[0087] Cracking of early-age concrete in utility tunnels is closely related to temperature development. Specifically, during the early stages of hydration and heat release, heat accumulates rapidly, causing the concrete temperature to rise quickly and resulting in volume expansion. After reaching the peak temperature, workers typically remove the formwork from the utility tunnel concrete, leading to a rapid cooling of the concrete structure during the cooling period and subsequent volume shrinkage.
[0088] Therefore, in this invention, the temperature of each monitoring point is also monitored, and it is determined in real time whether the cooling rate of each monitoring point reaches the preset cooling rate threshold, which is 2.0℃ / d.
[0089] For example: the temperature monitored at a certain measuring point, such as... Figure 9 As shown in the monitoring results, the concrete reached its highest temperature of approximately 57.3℃ about 13 hours after pouring, after which it began to cool down. Figure 6 By knowing the temperature value after cooling at each time point, the corresponding cooling rate at each time point can be obtained. Therefore, it is possible to determine in real time whether the cooling rate at each monitoring point has reached the preset cooling rate threshold.
[0090] Step S403: When it is determined whether the cooling rate obtained by any sensor at any time reaches the preset cooling rate threshold, or when it is determined that the actual deformation value obtained by any sensor at any time reaches the corresponding limit strain value for that day, a cracking warning is issued so that the staff can take preventive measures to prevent the concrete of the pipe gallery from cracking.
[0091] Preventive measures include covering the surfaces of sensors where strain changes reach the ultimate rigid strain value and where temperature values reach the temperature threshold with geotextile or cotton blankets for insulation. Inside the cabin, insulation can be achieved by sealing the cabin door and adding heat sources inside.
[0092] Of course, in order to help staff know what conditions caused the cracking, the warning prompts in step four include: temperature warning prompts and strain warning prompts;
[0093] Wherein, the temperature warning is audible, and the strain warning is visual; or,
[0094] The temperature warning is indicated by light, and the strain warning is indicated by sound; or...
[0095] Both the temperature warning and the strain warning are audible, but they have different audible sounds.
[0096] This invention provides a method for preventing cracking in the concrete of utility tunnels. After obtaining the ultimate tensile strain value of the concrete at each age, multiple monitoring points are set up at the end, intermediate, and middle sections of the tunnel structure. Sensors at each monitoring point dynamically monitor the temperature and deformation data of the concrete. Based on the on-site monitoring data, adjustments are made in real time. Especially when the measured temperature and strain data approach control targets, a cracking warning is issued, allowing staff to take preventative measures to prevent concrete cracking. By monitoring data in real time, cracking of the concrete can be predicted in advance, enabling proactive measures to avoid such situations. This effectively controls structural leakage and solves the problem of cracks in the sidewalls and floor slabs of key parts of cast-in-place buried tunnels.
[0097] To verify the accuracy of this application, the method of this application will be applied to an engineering project for further explanation.
[0098] (1) Obtain the ultimate tensile strain of the pipe gallery concrete at 2 days:
[0099] Depend on Figure 7 The splitting tensile strength development curve of the specimen can be used to estimate that the splitting tensile strength at 2 days is approximately 2.92 MPa. The axial tensile strength of concrete at the same age is taken as 2.92 / 0.8 = 3.65 MPa.
[0100] In addition, the test results showed that the elastic modulus of the 2-day cured test block was 28.8 GPa.
[0101] Therefore, the ultimate tensile strain of the pipe gallery concrete at 2 days should be:
[0102] (2) The strain value obtained from engineering data monitoring data during actual biological mutation.
[0103] Taking data from a specific point (point C5) monitored at a certain construction site as an example. Point C5 is located in the middle of a pipe gallery segment (15m from the end), and its position in the cross-section of the pipe gallery is as follows: Figure 8 As shown. Point C15 is the location of the zero-stress bucket.
[0104] The strain change curve detected at point C5 is shown below. Figure 9 As shown, the actual deformation curve at point C5 (minus the strain of the zero-stress barrel at point C15) is as follows: Figure 10 As shown.
[0105] According to the monitoring data, 2.4 days after pouring (i.e., 57.6 hours after pouring), the strain at point C5 underwent a sudden change, with the actual strain value increasing from 157 με to 867 με, a change of 710 με. Therefore, the strain (157 με) reached the ultimate tensile strain (127 με) when the sudden change occurred. This demonstrates the high accuracy of the method in this application.
[0106] Furthermore, to verify its accuracy:
[0107] Alternatively, the predicted crack width can be obtained using the following formula:
[0108]
[0109] Where ΔL is the crack width, L is the length of the sensor (measured to be 200 mm), and ε is the actual strain change. Substituting these values, the crack width should be... The calculated results are largely consistent with the observed results. For example... Figure 11 As shown.
[0110] By obtaining the crack width, the accuracy of the method in this application can be evaluated by comparing the theoretically calculated crack width based on monitoring data with the actually measured crack width.
Claims
1. A method for preventing cracking of concrete in pipe racks, characterized in that, The method includes: Step 1: Obtain the ultimate tensile strain value of the concrete in the pipe gallery at each age. Step 2: Set up multiple monitoring points at the end, normal, and intermediate sections of the pipe gallery structure, and install one sensor at each monitoring point; Step 3: Real-time acquisition of temperature and deformation data of the concrete in the pipe gallery at each of the aforementioned sensors at its corresponding monitoring points; Step 4: When the cooling rate obtained by any sensor at any time reaches the preset cooling rate threshold, or when the actual deformation value obtained by any sensor at any time reaches the corresponding limit strain value for that day, a cracking warning is issued so that staff can take preventive measures to prevent the concrete of the pipe gallery from cracking. The section at the end position is the section at 1 / 10L from the end, the section at the normal position is the section at 3 / 10L from the end, and the section at the middle position is the section at 1 / 2L from the end, where L is the length of the standard segment of the pipe gallery; On each cross section, monitoring points are set up at the upper, middle, and lower parts of the vertical wall, the lower surface of the top slab at the middle span, and at the junction of the vertical wall and the top slab. In step two, a zero-stress bucket is set at the center of each cross section, and the detection point arranged in each zero-stress bucket is the reference monitoring point corresponding to its cross section, and the sensor installed is the reference sensor corresponding to its cross section. Step four includes: Step S401: Obtain temperature data and deformation data sent by all sensors at the current moment; Step S402: Based on the temperature data sent by each sensor, determine whether the corresponding cooling rate has reached the preset cooling rate threshold; and based on the deformation data sent by all sensors on each cross section, determine whether the actual deformation value at the current moment has reached the corresponding limit strain value for that day. Step S403: When it is determined that the cooling rate obtained by any sensor at any time reaches the preset cooling rate threshold, or when it is determined that the actual deformation value obtained by any sensor at any time reaches the corresponding limit strain value of the day, a cracking warning is issued so that the staff can take preventive measures to prevent the concrete of the pipe gallery from cracking. In step S402, for any cross section, based on the deformation data sent by all sensors on the cross section, it is determined whether the actual deformation value at the current moment has reached the corresponding limit strain value for that day, including: Step S4021: Obtain the reference strain transmitted by the reference sensor on the cross section; Step S4022: Subtract the reference strain from the deformation data of other sensors to obtain the actual deformation value corresponding to each sensor at the current moment; Step S4023: Compare all actual deformation values with the corresponding ultimate hard strain value for the day, and determine whether the actual deformation value at the current moment has reached the corresponding ultimate hard strain value for the day. Step one includes: Step S101: Test the concrete of the test block cured in the previous standard segment of the current pipe gallery to obtain the actual splitting tensile strength and actual compressive strength of the concrete of the test block per day; Step S102: Fit the actual splitting tensile strength of the concrete block every day to obtain the fitting curve of the splitting tensile strength of the concrete block over time. Step S103: Obtain the fitted splitting tensile strength of the concrete specimen at each age based on the development fitting curve, so as to calculate the axial tensile strength of the concrete specimen at each age. Step S104: Based on the actual compressive strength and elastic modulus of the concrete test block each day, calculate the elastic modulus of the concrete test block at each age.
2. The method for preventing cracking of concrete in pipe gallery according to claim 1, characterized in that, Each of the aforementioned sensors is a vibrating wire strain sensor.
3. The method for preventing cracking of concrete in pipe racks according to claim 1, characterized in that, The preventive measures in step four include: covering the surface of the sensor location where the strain change value reaches the limit hard strain value, and the sensor location where the temperature value reaches the temperature threshold, with geotextile or cotton quilt for insulation.