Non-destructive testing method for compactness of backfill soil foundation based on intelligent sensor

Abstract

The invention discloses a backfill soil foundation compactness nondestructive testing method based on an intelligent sensor. The backfill soil foundation compactness nondestructive testing method comprises the following steps of S1, the intelligent sensor, S2, a GPS positioning system, S3, a wireless transmission network and S4, an information monitoring and collecting system. An on-site road roller is modified, an RTK-GPS receiver, a wireless communication antenna and an acceleration sensor are installed, accurate measurement of the position and the running speed of the rolling machine can be achieved through an automatic rolling system based on RTK-GPS and closed-loop feedback control, the acceleration sensor is fixed to a vibrating wheel, vertical acceleration signals of the vibrating wheel are collected in real time, and the vibration speed of the vibrating wheel is measured. A CMV value and a field compaction degree evaluation result are analyzed in real time through a background development system, then a correlation relation is established between a compaction degree value and the CMV value which are measured by using a standard compaction degree inspection method in a test section, and real-time compaction degree monitoring control can be carried out.

Description

Technical Field

[0001] The invention belongs to the technical field of roadbed compaction calculation, and in particular relates to a non-destructive detection method for backfill soil foundation compaction based on an intelligent sensor. Background Art

[0002] In the current construction mode, the control of compaction quality still relies mainly on traditional methods. There are two main methods: one is point control from the perspective of physical indicators, and the other is process control from the perspective of construction technology. Both can be used as a basis for evaluating the compaction of the roadbed. At the construction site, the roller rolling operation is mainly controlled by the subjective judgment of the supervisor and on-site construction personnel. The compaction times are estimated based on experience. There are usually management negligence, which can easily cause under-pressure, over-pressure and other phenomena, making it difficult to ensure the construction quality of replacement compaction. In addition, traditional detection methods such as sand filling method, ring knife method, and core sampling method are generally used to detect and evaluate the compaction of roads. The compaction is judged based on the sampling of pits during acceptance. However, since this method only characterizes the compaction of the entire construction working surface based on a limited number of test points, there are usually large errors in the evaluation results and it is impossible to truly reflect the compaction of the entire working surface. At the same time, this method will interfere with other construction operations and may even affect the construction progress, and it is impossible to achieve real-time monitoring and feedback of the compaction process. Therefore, according to the construction characteristics of the roller, the changes in the soil during the compaction process of the roller are re-studied. Under normal circumstances, when the roller is performing compaction operations, the density increases significantly with the increase of the number of rolling passes within a reasonable number of passes, but it should not be too much. Excessive compaction will reduce the compaction degree. It can be seen that the correct driving of the rolling trajectory of the roller during the compaction process and the number of rolling passes have an important influence on the compaction degree. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a non-destructive detection method for the compaction degree of backfill foundation based on intelligent sensors, which has the advantages of helping to improve engineering construction efficiency, reducing human resources and time costs, etc., and solves the problem that the current method for detecting the compaction performance of backfill foundations is often to take samples at limited random locations after the entire backfill project is completed, and transport the samples to the laboratory for relevant tests, and this method cannot provide comprehensive and real-time information.

[0004] Technical solution: A nondestructive detection method for backfill foundation compaction based on an intelligent sensor of the present invention comprises the following steps:

[0005] S1. Install an intelligent sensor on the vibrating wheel of the roller to monitor the rebound force during the compaction process, and collect the vibration data of the roller within a set time and the actual compaction value of the road surface according to the set sampling frequency;

[0006] S2. Install GPS positioning systems on control points and rollers to record the trajectory of compaction machinery, ensure that compaction covers the entire construction area evenly, and collect continuous vibration compaction values ​​(CMV);

[0007] S3, the wireless transmission network established transmits the measured compaction value from the intelligent sensor to the monitoring terminal in the cab of the roller in real time;

[0008] S4. Build an information monitoring and collection system, which is used to record the key indicators of compaction times and vibration wheel rebound force, providing a basis for construction management and quality control;

[0009] S5. According to step S1, the intelligent sensor is installed on the vibrating wheel of the roller, and the instantaneous acceleration of the vibrating wheel under the action of the exciting force, the vibrating wheel's own gravity and the resistance F(x) is measured. In the information monitoring and acquisition system, the vibrating wheel's own gravity and the exciting force are the roller's own parameters, and the strength of the acceleration is regarded as a direct reflection of the resistance. The continuous vibration compaction value CMV value defines the ratio of the resistance to the exciting force, and a relationship model between the continuous vibration compaction value CMV value and the density of backfill soil is established.

[0010] Furthermore, in step S1, the measured value of the compaction degree of the road surface is specifically calculated as follows:

[0011] The dry relative density Dr represents the ratio of the actual density of the soil to the theoretical density at the maximum compacted state and is calculated using the following formula:

[0012] Dr=(Dd-Dsat) / (Dmax-Dsat)*100%

[0013] Where Dd is the dry bulk density of soil, in g / cm 3 , Dsat is the saturated bulk density of soil, unit: g / cm 3 , Dmax is the maximum dry bulk density of soil, unit is g / cm 3；

[0014] The micro-compaction degree Ed refers to the proportion of particles with a diameter smaller than a certain limit value during the compaction process, and is calculated using the following formula:

[0015] Ed=(Ms-Ma) / (Mb-Ma)*100%

[0016] Among them, Ms is the total mass of particles less than the limit value before compaction, in g, Ma is the total mass of particles less than the limit value after compaction, in g, and Mb is the total mass of particles initially less than the limit value, in g.

[0017] Furthermore, in step S1, the vibration data calculation of the road roller specifically includes the calculation of vibration frequency, amplitude and vibration power:

[0018] Calculation of vibration frequency: The vibration frequency refers to the number of times the steel wheel of the roller rolls the road during construction, usually in Hertz (Hz). The calculation of vibration frequency involves the rotation speed of the steel wheel. The specific calculation formula is:

[0019]

[0020] Where f is the vibration frequency, ω is the angular frequency, and the angular frequency ω is calculated by the angular velocity of the steel wheel, and the angular velocity is obtained by the design parameters of the roller;

[0021] Calculation of amplitude: The amplitude refers to the maximum distance that the roller's steel wheel presses down on the road surface, usually in millimeters. The calculation of the amplitude involves the design parameters of the roller. The calculation formula for the amplitude is:

[0022] A=2×π×f×e

[0023] Where A is the amplitude, f is the vibration frequency, and e is the eccentricity of the eccentric vibrator;

[0024] Calculation of vibration power: Vibration power reflects the energy consumption of the roller during operation. The calculation of vibration power involves the exciting force F0 and angular frequency ω. The calculation formula is:

[0025] P=F0×ω

[0026] The exciting force F0 is formed by the centrifugal force when the eccentric vibrator exciter rotates at high speed, and is related to the static eccentric moment Me and angular frequency ω of the eccentric vibrator. The specific calculation formula is:

[0027] F0=Μe×ω 2

[0028] Among them, ω=2πf, so the calculation formula of the final vibration power is expressed as:

[0029] Ρ=F0×2πf.

[0030] Further, step S2 is specifically as follows: the GPS positioning system receives radio signals from multiple satellites, measures the signal propagation time, calculates the distance between the receiver and the satellite, and then uses geometric relationships to determine the three-dimensional coordinates of the receiver on the earth's surface. Through error correction means, the GPS system provides high-precision, all-weather, global positioning, navigation and timing services, locates the roller, and cooperates with the pressure sensor set in the roller wheel of the roller to sense the slight tilt change of the measuring unit caused by the foundation settlement. The wireless data acquisition terminal adopts CAN field bus communication technology to collect the inclination measurement signals of each settlement measurement unit connected to the bus, calculate each measured settlement, and transmit the wireless remote transmission to the cloud through the GPRS / 4G wireless communication module at regular intervals. The CMV value is obtained by analyzing the relationship between the vibration wheel of the roller and the resistance response of the roadbed fill body. The vibration acceleration signal of the vibration wheel during the compaction process is collected by means of the field test section, and a fast Fourier transform is performed to obtain the continuous vibration compaction value CMV. The calculation formula of the calculated CMV value is as follows:

[0031]

[0032] Where CMV represents the vibration compaction value, β CMV It represents the calibration coefficient of the vibration compaction value, f represents the frequency domain amplitude of the fundamental wave, and f2 represents the frequency domain amplitude of the second harmonic.

[0033] Furthermore, the continuous vibration compaction value CMV is characterized by the CMV value obtained by instrument measurement and the CMV value obtained by calculation. Taking compaction degree as an indicator, each CMV sample is input into the information monitoring and acquisition system to predict the compaction degree prediction value of each CMV sample, and the error between the compaction degree prediction value of each CMV sample and the compaction degree measured value in each CMV sample is calculated. The error is recorded as the CMV error. The CMV error satisfies the Gaussian distribution. Then, the CMV error is screened by the 3σ criterion, and the CMV samples whose CMV errors are within the corresponding standard deviation are retained, and the original samples corresponding to the retained CMV samples are stored in the CMV sample set.

[0034] Furthermore, in step S3, the wireless transmission network responsible for data processing includes a microcontroller, an embedded operating system, a wireless communication protocol and a communication line. The microcontroller is responsible for processing and controlling data in the wireless transmission process, including receiving, parsing and sending data. The embedded operating system provides a network TCP / IP stack to realize remote control functions and manage computer hardware and software resources. The wireless communication protocol includes a physical layer communication protocol and a link layer communication protocol, which are used to establish, maintain and disconnect physical connections between entities in the data link and provide electrical, mechanical and functional characteristics. The communication line is the physical medium for data transmission, including twisted pair copper wires, coaxial cables and optical fibers. Each module works together to ensure the operation of the wireless transmission network and the transmission of data.

[0035] Furthermore, in step S5, the relationship model is a physical model of a rigid disk subjected to a simple harmonic excitation force. According to the force balance relationship, it can be known that:

[0036]

[0037] Among them, N is the force exerted by the ground on the disk. According to elastic mechanics, N = k0fx, where k0 is the static stiffness of the soil, and f is a complex function that depends on the size and mass of the disk and the soil parameters:

[0038]

[0039] Among them, 2Er is the mass of the disk, 1-v 2 is the size of the disk;

[0040] The vibration equation of the equivalent vibration system is:

[0041]

[0042] Since the force is a simple harmonic excitation force, the displacement is also a simple harmonic displacement. The above two equations can be transformed into:

[0043] -w 2 m r x+k0fx=F0 sinωt

[0044] -w 2 m2x+iwc2x+k2x=F0 sinωt

[0045] When calculating, let k2=k0, m2=m3+m r =λm r , where λ represents the additional mass coefficient of the soil, m3 represents the mass of the vibrating soil, w is the mass ratio in the combination, and m ris the mass corresponding to the current compaction degree, c2 is the damping of the roadbed, and through calculation, we can get:

[0046] k0f=k2+(1-λ)w 2 m r +iwc2

[0047] Among them, i represents the degree of freedom. According to the principle of equation equivalence, let the real part and the imaginary part in the above formula be equal, and we can get a function about b, which is expressed as follows:

[0048]

[0049] Where b is the dimensionless mass ratio, ρr 3 is the mass, and the additional mass coefficient λ and damping ratio ξ can be obtained from this value.

[0050] Furthermore, in the calculation process of the relationship model, it is necessary to first solve the radius of the equivalent circle of the vibration system model. According to the principle of equal area, the contact between the steel wheel and the soil during rolling is regarded as the mutual contact between the cylindrical surface and the soil surface. In terms of its cross section, it is the mutual contact of a section of circular arc. The contact length is the width of the steel wheel. The contact area between the cylindrical surface and the soil surface is equal to the contact area of ​​the rigid disc. Thus, the radius of the equivalent circle can be calculated. Assuming that the wheel width of the roller is L and the arc length of the contact between the roller and the soil is B, the contact area of ​​the roller is A=BL. If the contact area of ​​the rigid disc is equal to it, then πr 2 =BL, so we can get After correction, we know:

[0051]

[0052] And because B = Rsinβ, we can get:

[0053]

[0054] Among them, β is the angle between the tangent line of the contact point between the rolling wheel and the soil and the horizontal line, R is the radius of the rolling wheel, and the angle should not be greater than the internal friction angle;

[0055] Substituting the equivalent circle radius into the stiffness calculation formula yields:

[0056]

[0057] According to the obtained value of b and the soil additional mass coefficient λ, the mass of the vibrating soil is obtained as follows:

[0058] m3=(λ-1)m r

[0059] The damping ratio ξ of the soil can be obtained, so the damping of the soil is:

[0060] c2=2ξw n m3

[0061] In the formula, w n is the natural frequency of the soil foundation, and its value is The mechanical parameters of soil are not only related to the physical properties, chemical structure and water content of the soil, but also to the soil environment, conditions and measurements. Due to the existence of randomness and accidental influences, it is necessary to design a large number of tests and experiments on the mechanical parameters of soil to find out the relevant laws and obtain the soil parameter values.

[0062] The present invention also discloses a computer device, comprising a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the method of the present invention.

[0063] The present invention also discloses a computer-readable storage medium on which a computer program / instruction is stored. When the computer program / instruction is executed by a processor, the steps of the method of the present invention are implemented.

[0064] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0065] (1) The present invention provides a nondestructive detection method for the compaction of backfill soil foundation based on intelligent sensors. By modifying the on-site roller to install an RTK-GPS receiver, a wireless communication antenna, and an acceleration sensor, an automatic rolling system based on RTK-GPS and closed-loop feedback control can be used to accurately measure the roller position and driving speed. The acceleration sensor is fixed on the vibrating wheel to collect the vertical acceleration signal of the vibrating wheel in real time. The CMV value and the on-site compaction evaluation result are analyzed in real time by the background development system. The intelligent compaction CMV corresponding to the intelligent compaction system can be expressed by the following formula: CMV=100*A1 / A0. Then, a correlation is established between the compaction value measured by the standard compaction test method in the test section and the CMV value, so that real-time compaction monitoring and control can be performed.

[0066] (2) The CMV-RTK intelligent sensor non-destructive testing technology solution is used to quickly detect and evaluate the compaction quality of backfill foundation on site. This project is used as a typical project to study the basic parameters of the backfill soil used and the relevant conversion coefficients of density. Combined with the previous research on the rapid on-site detection technology of backfill foundation compaction quality using an intelligent sensor system, it was found that the relevant conversion coefficients used in the backfill foundation compaction technology also need to be adjusted and converted according to the geological conditions of different regions to meet the different construction needs of each region.

[0067] (3) The compaction quality of the backfill foundation is crucial to the structural service performance of the newly built substation. A good compaction condition can effectively avoid uneven settlement of the foundation, thereby ensuring the service safety of the upper substation and the underground pipeline corridor. However, the current method for testing the compaction performance of the backfill foundation is often to take samples at limited random locations after the entire backfill project is completed, and then transport the samples to the laboratory for relevant tests. This method cannot provide comprehensive and real-time information. Therefore, it is necessary to develop new non-destructive testing technology solutions to evaluate the compaction quality of the backfill foundation of the newly built substation.

[0068] (4) The use of intelligent sensors will help improve the detection technology level of compaction quality in newly built substations. At the same time, this non-destructive testing technology solution will also help improve engineering construction efficiency and reduce human resources and time costs. This will further promote scientific and technological innovation and modernization in my country's substation construction and contribute to sustainable development and social progress. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is a schematic diagram of the compaction detection process;

[0070] Figure 2 It is a schematic diagram of the mechanical model and the vibration system model;

[0071] Figure 3 It is a schematic diagram of the contact section between the pressure wheel and the soil;

[0072] Figure 4 It is a schematic diagram of the working process of the vibratory roller in compaction state;

[0073] Figure 5 This is a schematic diagram of the working process of a vibratory roller. DETAILED DESCRIPTION

[0074] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0075] Embodiment 1: A nondestructive detection method for backfill soil compaction based on intelligent sensors, such as Figure 1 As shown, the following steps are included:

[0076] S1. Smart sensor: The sensor installed on the vibrating wheel monitors the rebound force during compaction in real time. According to the set sampling frequency, it collects the vibration data of the roller within the set time and the measured value of the compaction degree of the road surface, which is the key parameter for evaluating the compaction effect.

[0077] S2. GPS positioning system: GPS base stations are installed at control points and rollers to accurately record the trajectory of compaction machinery and ensure that compaction evenly covers the entire construction area;

[0078] S3, wireless transmission network: the wireless local area network is established to transmit compaction data from the sensor to the display controller or other monitoring terminals in the cab in real time;

[0079] S4. Information monitoring and acquisition system: The integrated data acquisition system is responsible for recording key indicators such as the number of compaction passes and the rebound force of the vibrating wheel, providing a basis for construction management and quality control.

[0080] According to S1, the sensor is installed on the vibratory roller to measure the instantaneous acceleration of the vibrating wheel under the action of the exciting force, the vibrating wheel's own gravity and the resistance F(x). In this system, the vibrating wheel's own gravity and the exciting force are the roller's own parameters (known quantities), so the strength of the acceleration can be considered as a direct reflection of the resistance. The purpose of the CMV value is to define the ratio of the resistance to the exciting force, and then establish a relationship model between the CMV value and the density of the backfill soil.

[0081] The corresponding indicators of the roller machinery are obtained through the CMV sensor: vibration strength, amplitude information, and frequency information; the main parameters are as follows: axial sensitivity 100mV / g±5%, measurement range (peak) ±50g, maximum lateral sensitivity ≤5%, installation resonance frequency 15000Hz, working temperature range -40~+120℃, impact limit 2000g, working voltage (constant current source) +12~+24VDC, working current +2~+10mA, maximum output signal (peak) ≤6V, the sensor is equipped with a D48 lifting ring magnet. When choosing the installation position, it is necessary to choose the vibration motor on the inner side of the steel wheel of the vibrating roller to ensure that the vibration sensor and the vibration motor are hard connected. The installation direction of the D48 lifting ring magnet is vertical to the ground. In order to ensure firmness, the surface loose soil can be wiped clean and the equipment can be sucked on it. At the same time, a circle of AB glue is applied on the outside to reinforce it to ensure that the equipment is not It will fall off due to vibration. When routing the CS200 vibration sensor, pay attention to walking it into the cab in an orderly manner along the original vehicle cable and connecting it to the RollBox piezoelectric interface to ensure that the cable is not worn or torn during construction. The acceleration sensor is installed on the vibratory roller to measure the instantaneous acceleration of the vibrating wheel under the action of the exciting force, the vibration wheel's own gravity and the resistance F(x). In this system, the vibration wheel's own gravity and the exciting force are the roller's own parameters (known quantities), so the strength of the acceleration can be considered as a direct reflection of the resistance. The purpose of the CMV value is to define the ratio of the resistance to the exciting force, and then establish a relationship model between the CMV value and the compaction degree of the backfill soil. According to the principle of dynamic interaction between the soil and the vibratory roller, the key point to solve the resistance is to study how the vertical acceleration response signal of the vibrating wheel works under the action of mechanics. This is the core step to establish a detection and evaluation of the compaction state of the entire rolling road surface.

[0082] According to the first embodiment, the calculation formula of the compaction degree is as follows:

[0083] S1. Dry relative density (Dr). Dry relative density (Dr) indicates the ratio of the actual density of soil to the theoretical density under the maximum compacted state, which can be calculated using the following formula:

[0084] Dr=(Dd-Dsat) / (Dmax-Dsat)*100%

[0085] Where Dd is the dry bulk density of soil (g / cm 3 ), Dsat is the saturated bulk density of soil (g / cm 3 ), Dmax is the maximum dry bulk density of soil (g / cm 3 ).

[0086] S2. Micro-compactness (Ed). Micro-compactness (Ed) refers to the proportion of particles whose diameter is smaller than a certain limit value during the compaction process. It can be calculated using the following formula:

[0087] Ed=(Ms-Ma) / (Mb-Ma)*100%

[0088] Among them, Ms is the total mass of particles less than the limit value before compaction (g), Ma is the total mass of particles less than the limit value after compaction (g), and Mb is the total mass of particles initially less than the limit value (g).

[0089] According to the first embodiment, the vibration data calculation formula of the road roller mainly includes the calculation of vibration frequency, amplitude, and vibration power:

[0090] S1. Calculation of vibration frequency: The vibration frequency refers to the number of times the steel wheel of the roller rolls the road during construction, usually in Hertz (Hz). The calculation of the vibration frequency involves the rotation speed of the steel wheel. The specific calculation formula is:

[0091]

[0092] Where f is the vibration frequency, ω is the angular frequency, and the angular frequency ω can be calculated from the angular velocity of the steel wheel, and the angular velocity can be obtained from the design parameters of the roller;

[0093] S2. Calculation of amplitude: The amplitude refers to the maximum distance that the roller's steel wheel presses down on the road surface, usually in millimeters (mm). The calculation of the amplitude involves the roller's design parameters, such as the mass of the steel wheel, the static eccentricity of the eccentric vibrator, etc. The calculation formula for the amplitude is:

[0094] A=2×π×f×e

[0095] Where A is the amplitude, f is the vibration frequency, and e is the eccentricity of the eccentric vibrator;

[0096] S3. Calculation of vibration power: Vibration power is an important performance indicator of a roller, which reflects the energy consumption of the roller during operation. The calculation of vibration power involves the exciting force F0 and the angular frequency ω. The calculation formula is:

[0097] P=F0×ω

[0098] The exciting force F0 is formed by the centrifugal force when the eccentric vibrator exciter rotates at high speed. It is related to the static eccentric moment Me and angular frequency ω of the eccentric vibrator. The specific calculation formula is:

[0099] F0=Μe×ω 2

[0100] Among them, ω=2πf, so the calculation formula of the final vibration power can be expressed as:

[0101] Ρ=F0×2πf

[0102] According to the first embodiment, the GPS positioning system receives radio signals from multiple satellites, accurately measures the signal propagation time, calculates the distance between the receiver and the satellite, and then uses geometric relationships to determine the three-dimensional coordinates of the receiver on the earth's surface. Through various error correction methods, the GPS system can provide high-precision, all-weather, global positioning, navigation and timing services, and can accurately locate the roller. In conjunction with the pressure sensor set in the roller wheel of the roller, it can sense the slight tilt change of the measuring unit caused by the foundation settlement. The wireless data acquisition terminal adopts CAN field bus communication technology to automatically collect the inclination measurement signals of each settlement measurement unit connected to the bus in real time, automatically calculate each measured settlement, and regularly transmit the wireless remote transmission to the cloud through the GPRS / 4G wireless communication module. The CMV value is obtained by analyzing the relationship between the vibration wheel of the roller and the resistance response of the roadbed fill body. The vibration acceleration signal of the vibration wheel during the compaction process is collected by means of the field test section, and a fast Fourier transform is performed to obtain a continuous vibration compaction value (CMV). The calculation formula of the calculated CMV value is as follows:

[0103]

[0104] Where CMV represents the vibration compaction value, β CMV It represents the calibration coefficient of the vibration compaction value, f represents the frequency domain amplitude of the fundamental wave, and f2 represents the frequency domain amplitude of the second harmonic.

[0105] According to Example 1, the CMV value measured by the instrument and the CMV value calculated are used as features, and compaction degree is used as an indicator. Each CMV sample is input into the information monitoring and acquisition system to predict the compaction degree prediction value of each CMV sample, and the error between the compaction degree prediction value of each CMV sample and the compaction degree measured value in each CMV sample is calculated. The error is recorded as the CMV error. The CMV error satisfies the Gaussian distribution. Then, the CMV error is screened by the 3σ criterion, and the CMV samples whose CMV errors are within the corresponding standard deviation are retained, and the original samples corresponding to the retained CMV samples are stored in the CMV sample set.

[0106] According to the first embodiment, the components responsible for data processing in the wireless transmission network include a microcontroller, an embedded operating system, a wireless communication protocol and a communication line. The microcontroller is responsible for processing and controlling data in the wireless transmission process, including receiving, parsing and sending data. The embedded operating system provides a network TCP / IP stack to implement remote control functions and manage computer hardware and software resources. The wireless communication protocol includes a physical layer communication protocol and a link layer communication protocol, which are used to establish, maintain and disconnect physical connections between entities in the data link and provide electrical, mechanical and functional characteristics. The communication line is the physical medium for data transmission, which can be a twisted copper pair, a coaxial cable, an optical fiber, etc. These parts work together to ensure the normal operation of the wireless transmission network and the effective transmission of data.

[0107] According to the first embodiment, the relationship model is a physical model of a rigid disk under the action of a simple harmonic excitation force. According to the force balance relationship, it can be known that:

[0108]

[0109] Among them, N is the force exerted by the ground on the disk. According to elastic mechanics, N = k0fx, where k0 is the static stiffness of the soil, and f is a complex function that depends on the size and mass of the disk and the soil parameters:

[0110]

[0111] The vibration equation of the equivalent vibration system is:

[0112]

[0113] Since the force is a simple harmonic excitation force, the displacement is also a simple harmonic displacement. The above two equations can be transformed into:

[0114] -w 2 m r x+k0fx=F0 sinωt

[0115] -w 2 m2x+iwc2x+k2x=F0 sinωt

[0116] When calculating, let k2=k0, m2=m3+m r =λm r , where λ represents the additional mass coefficient of the soil, and m3 represents the mass of the vibrating soil. By calculation, we can get:

[0117] k0f=k2+(1-λ)w 2 m r +iwc2

[0118] According to the principle of equation equivalence, let the real part and the imaginary part in the above formula be equal, and we can get a function about b, the expression is:

[0119]

[0120] Where b is the dimensionless mass ratio, from which the added mass coefficient λ and the damping ratio ξ can be obtained.

[0121] According to the first embodiment, in the calculation process, it is necessary to first solve the radius of the equivalent circle of the vibration system model. According to the principle of equal area, the project team regards the contact between the steel wheel and the soil during rolling as the mutual contact between the cylindrical surface and the soil surface. In terms of its cross section, it is the mutual contact of a section of circular arc. The contact length is the width of the steel wheel. The contact area between the cylindrical surface and the soil surface is equal to the contact area of ​​the rigid disc. Thus, the radius of the equivalent circle can be calculated. Assuming that the wheel width of the roller is L and the arc length of the contact between the roller and the soil is B, the contact area of ​​the roller is A=BL. If the contact area of ​​the rigid disc is equal to it, then πr 2 =BL, so we can get After correction, we know:

[0122]

[0123] And because B = Rsinβ, we can get

[0124]

[0125] Among them, β is the angle between the tangent line and the horizontal line at the contact point between the rolling wheel and the soil, and R is the radius of the rolling wheel. As shown in the figure below, it can be seen from relevant literature that the angle should not be greater than the internal friction angle;

[0126] Substituting the equivalent circle radius into the stiffness calculation formula yields:

[0127]

[0128] According to the obtained value of b, the additional mass coefficient λ of the soil is obtained by consulting the literature, so the mass of the vibrating soil can be calculated as:

[0129] m3=(λ-1)m r

[0130] The damping ratio ξ of the soil can be obtained, so the damping of the soil is:

[0131] c2=2ξw n m3

[0132] In the formula, w n is the natural frequency of the soil foundation, and its value is The mechanical parameters of soil are not only related to the physical properties, chemical structure and water content of the soil, but also to the soil environment, the conditions and measurements. Due to the randomness and accidental influences, it is necessary to design a large number of tests and experiments on the mechanical parameters of soil to find out the relevant laws and obtain the soil parameter values.

[0133] The beneficial effects of the present invention are as follows: by modifying the on-site roller to install an RTK-GPS receiver, a wireless communication antenna, and an acceleration sensor, the automatic rolling system based on RTK-GPS and closed-loop feedback control can achieve accurate measurement of the roller position and driving speed. The acceleration sensor is fixed on the vibrating wheel to collect the vertical acceleration signal of the vibrating wheel in real time. The CMV value and the on-site compaction evaluation result are analyzed in real time through the background development system. The intelligent compaction CMV corresponding to the intelligent compaction system can be expressed by the following formula: CMV=100*A1 / A0. Then, a correlation is established between the compaction value measured by the standard compaction test method in the test section and the CMV value, so that real-time compaction monitoring and control can be performed.

[0134] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A nondestructive detection method for backfill foundation compaction based on intelligent sensors, characterized in that: The following steps are involved: S1. Install an intelligent sensor on the vibrating wheel of the roller to monitor the rebound force during the compaction process, and collect the vibration data of the roller within a set time and the actual compaction value of the road surface according to the set sampling frequency; S2. Install GPS positioning systems on control points and rollers to record the trajectory of compaction machinery, ensure that compaction covers the entire construction area evenly, and collect continuous vibration compaction values ​​(CMV); S3, the wireless transmission network established transmits the measured compaction value from the intelligent sensor to the monitoring terminal in the cab of the roller in real time; S4. Build an information monitoring and collection system, which is used to record the key indicators of compaction times and vibration wheel rebound force, providing a basis for construction management and quality control; S5. According to step S1, the intelligent sensor is installed on the vibrating wheel of the roller, and the instantaneous acceleration of the vibrating wheel under the action of the exciting force, the vibrating wheel's own gravity and the resistance F(x) is measured. In the information monitoring and acquisition system, the vibrating wheel's own gravity and the exciting force are the roller's own parameters, and the strength of the acceleration is regarded as a direct reflection of the resistance. The continuous vibration compaction value CMV value defines the ratio of the resistance to the exciting force, and a relationship model between the continuous vibration compaction value CMV value and the density of backfill soil is established.

2. The method for nondestructive detection of compaction of backfill soil based on intelligent sensors according to claim 1, characterized in that: In step S1, the measured value of the compaction degree of the road surface is specifically calculated as follows: The dry relative density Dr represents the ratio of the actual density of the soil to the theoretical density at the maximum compacted state and is calculated using the following formula: Dr=(Dd-Dsat) / (Dmax-Dsat)*100% Where Dd is the dry bulk density of soil, in g / cm 3 , Dsat is the saturated bulk density of soil, unit: g / cm 3 , Dmax is the maximum dry bulk density of soil, unit is g / cm 3； The micro-compaction degree Ed refers to the proportion of particles with a diameter smaller than a certain limit value during the compaction process, and is calculated using the following formula: Ed=(Ms-Ma) / (Mb-Ma)*100% Among them, Ms is the total mass of particles less than the limit value before compaction, in g, Ma is the total mass of particles less than the limit value after compaction, in g, and Mb is the total mass of particles initially less than the limit value, in g.

3. The method for nondestructive detection of compaction of backfill soil based on intelligent sensors according to claim 1, characterized in that: In step S1, the vibration data calculation of the road roller specifically includes the calculation of vibration frequency, amplitude and vibration power: Calculation of vibration frequency: The vibration frequency refers to the number of times the steel wheel of the roller rolls the road during construction, usually in Hertz (Hz). The calculation of vibration frequency involves the rotation speed of the steel wheel. The specific calculation formula is: Where f is the vibration frequency, ω is the angular frequency, and the angular frequency ω is calculated by the angular velocity of the steel wheel, and the angular velocity is obtained by the design parameters of the roller; Calculation of amplitude: The amplitude refers to the maximum distance that the roller's steel wheel presses down on the road surface, usually in millimeters. The calculation of the amplitude involves the design parameters of the roller. The calculation formula for the amplitude is: A=2×π×f×e Where A is the amplitude, f is the vibration frequency, and e is the eccentricity of the eccentric vibrator; Calculation of vibration power: Vibration power reflects the energy consumption of the roller during operation. The calculation of vibration power involves the exciting force F0 and angular frequency ω. The calculation formula is: P=F0×ω The exciting force F0 is formed by the centrifugal force when the eccentric vibrator exciter rotates at high speed, and is related to the static eccentric moment Me and angular frequency ω of the eccentric vibrator. The specific calculation formula is: F0=Μe×ω 2 Among them, ω=2πf, so the calculation formula of the final vibration power is expressed as: Ρ=F0×2πf.

4. The method for nondestructive detection of compaction of backfill soil based on intelligent sensors according to claim 1, characterized in that: Step S2 is specifically as follows: the GPS positioning system receives radio signals from multiple satellites, measures the signal propagation time, calculates the distance between the receiver and the satellite, and then uses geometric relationships to determine the three-dimensional coordinates of the receiver on the earth's surface. Through error correction means, the GPS system provides high-precision, all-weather, global positioning, navigation and timing services, locates the roller, and cooperates with the pressure sensor set in the roller wheel of the roller to sense the slight tilt change of the measuring unit caused by the foundation settlement. The wireless data acquisition terminal adopts CAN field bus communication technology to collect the inclination measurement signals of each settlement measurement unit connected to the bus, calculate each measured settlement, and transmit the wireless remote transmission to the cloud through the GPRS / 4G wireless communication module at regular intervals. The CMV value is obtained by analyzing the relationship between the vibration wheel of the roller and the resistance response of the roadbed fill body. The vibration acceleration signal of the vibration wheel during the compaction process is collected by means of the field test section, and a fast Fourier transform is performed to obtain the continuous vibration compaction value CMV. The calculation formula of the calculated CMV value is as follows: Where CMV represents the vibration compaction value, β CMV It represents the calibration coefficient of the vibration compaction value, f represents the frequency domain amplitude of the fundamental wave, and f2 represents the frequency domain amplitude of the second harmonic.

5. The method for nondestructive detection of compaction of backfill soil based on intelligent sensors according to claim 4 is characterized in that: The continuous vibration compaction value CMV is characterized by the CMV value obtained by instrument measurement and the CMV value obtained by calculation. With compaction degree as an indicator, each CMV sample is input into the information monitoring and acquisition system to predict the compaction degree prediction value of each CMV sample, and the error between the compaction degree prediction value of each CMV sample and the compaction degree measured value in each CMV sample is calculated. The error is recorded as the CMV error. The CMV error satisfies the Gaussian distribution. Then, the CMV error is screened by the 3σ criterion, and the CMV samples whose CMV errors are within the corresponding standard deviation are retained, and the original samples corresponding to the retained CMV samples are stored in the CMV sample set.

6. The method for nondestructive detection of compaction of backfill soil based on intelligent sensors according to claim 1, characterized in that: In step S3, the wireless transmission network responsible for data processing includes a microcontroller, an embedded operating system, a wireless communication protocol and a communication line. The microcontroller is responsible for processing and controlling data in the wireless transmission process, including receiving, parsing and sending data. The embedded operating system provides a network TCP / IP stack to realize remote control functions and manage computer hardware and software resources. The wireless communication protocol includes a physical layer communication protocol and a link layer communication protocol, which are used to establish, maintain and disconnect physical connections between entities in the data link and provide electrical, mechanical and functional characteristics. The communication line is the physical medium for data transmission, including twisted copper pair, coaxial cable and optical fiber. Each module works together to ensure the operation of the wireless transmission network and the transmission of data.

7. The method for nondestructive testing of backfill foundation compaction based on intelligent sensors according to claim 1, characterized in that: In step S5, the relationship model is a physical model of a rigid disk subjected to a simple harmonic excitation force. According to the force balance relationship, it can be known that: Among them, N is the force exerted by the ground on the disk. According to elastic mechanics, N = k0fx, where k0 is the static stiffness of the soil, and f is a complex function that depends on the size and mass of the disk and the soil parameters: Among them, 2Er is the mass of the disk, 1-v 2 is the size of the disk; The vibration equation of the equivalent vibration system is: Since the force is a simple harmonic excitation force, the displacement is also a simple harmonic displacement. The above two equations can be transformed into: -w 2 m r x+k0fx=F0sinωt -w 2 m2x+iwc2x+k2x=F0sinωt When calculating, let k2=k0, m2=m3+m r =λm r , where λ represents the additional mass coefficient of the soil, m3 represents the mass of the vibrating soil, w is the mass ratio in the combination, and m r is the mass corresponding to the current compaction degree, c2 is the damping of the roadbed, and the following can be obtained by calculation: k0f=k2+(1-λ)w 2 m r +iwc2 Among them, i represents the degree of freedom. According to the principle of equation equivalence, let the real part and the imaginary part in the above formula be equal, and we can get a function about b, which is expressed as follows: Where b is the dimensionless mass ratio, ρr 3 is the mass, and the additional mass coefficient λ and damping ratio ξ can be obtained from this value.

8. The method for nondestructive testing of compaction of backfill soil based on intelligent sensors according to claim 7, characterized in that: In the calculation process of the relationship model, it is necessary to first solve the radius of the equivalent circle of the vibration system model. According to the principle of equal area, the contact between the steel wheel and the soil during rolling is regarded as the mutual contact between the cylindrical surface and the soil surface. In terms of its cross section, it is the mutual contact of a section of circular arc. The contact length is the width of the steel wheel. The contact area between the cylindrical surface and the soil surface is equal to the contact area of ​​the rigid disc. Therefore, the radius of the equivalent circle can be calculated. Assuming that the wheel width of the roller is L and the arc length of the contact between the roller and the soil is B, the contact area of ​​the roller is A=BL. If the contact area of ​​the rigid disc is equal to it, then πr 2 =BL, so we can get After correction, we know: And because B = Rsinβ, we can get: Among them, β is the angle between the tangent line of the contact point between the rolling wheel and the soil and the horizontal line, R is the radius of the rolling wheel, and the angle should not be greater than the internal friction angle; Substituting the equivalent circle radius into the stiffness calculation formula yields: According to the obtained value of b and the soil additional mass coefficient λ, the mass of the vibrating soil is obtained as follows: m3=(λ-1)m r The damping ratio ξ of the soil can be obtained, so the damping of the soil is: c2=2ξw n m3 In the formula, w n is the natural frequency of the soil foundation, and its value is The mechanical parameters of soil are not only related to the physical properties, chemical structure and water content of the soil, but also to the soil environment, conditions and measurements. Due to the existence of randomness and accidental influences, it is necessary to design a large number of tests and experiments on the mechanical parameters of soil to find out the relevant laws and obtain the soil parameter values.

9. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method of claim 1.

10. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the method according to claim 1 are implemented.

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