Detection and analysis of early diseases of highway subgrade and pavement?

1, subgrade and pavement disease detection technology

General detection technology of 1. 1

1. 1. 1 asphalt pavement damage detection

The investigation index of asphalt concrete pavement damage is mainly the comprehensive damage rate of pavement. Because the research field of automatic detection of pavement damage can be said to be just started, and the types of asphalt concrete pavement diseases are very complicated, even advanced detection equipment can hardly achieve the effect of investigation. Therefore, at present, the investigation of pavement diseases mainly adopts manual field investigation and auxiliary instruments and equipment for detection.

1. 1.2 asphalt pavement flatness detection

Pavement smoothness index is an important index to evaluate pavement quality, construction quality and damage degree of existing pavement. Smoothness is not only an index of pavement appearance, but also an important index to measure pavement quality and damage degree of existing pavement.

The detection equipment for pavement smoothness can be divided into two categories: cross-section detection equipment and reaction detection equipment. Cross-section detection equipment is an instrument for measuring the convexity and concavity of pavement, such as the most commonly used 3m straightedge and continuous flatness instrument. The commonly used reaction detection equipment is vehicle-mounted buffer accumulator.

1. 1.3 asphalt pavement strength detection

Deflection value is the most important mechanical index reflecting pavement strength, and the research on asphalt concrete pavement strength index is mainly about the deflection value of asphalt pavement. Automatic deflectometer or falling weight deflectometer is often used to investigate expressways and first-class highways. Beckmann beam survey can be used for other highways at all levels.

I. 1.4 GPR detection

Ground penetrating radar (GPR) technology is a high-tech geological radar survey and detection technology, which gradually replaces the cumbersome, slow and expensive core sampling method with its unique advantages of fast, economical, accurate and continuous reflection of space objects.

1. 1.5 seismic image detection

Shallow seismic method is a widely used shallow geophysical method developed in recent years. The basic principle is the shallow seismic reflection method, which records the amplitude and travel time of near-normal or normal reflection signals at the reflection interface by using equal offset or zero offset excitation and reception.

In areas where the working conditions of electrical and electromagnetic methods are limited, their advantages can be fully exerted. Seismic images are used to detect the problems or hidden dangers existing in the sub-surface base and embankment fill, and analyze the possible causes of pavement cracking. Seismic image detection mainly adapts to longitudinal cracks, but also takes into account transverse cracks. The detection depth of this instrument is generally 30m, and the key section f (such as bridge site) is not less than 50m.

1.2 special detection technology

1.2. 1 geological borehole detection

Geological borehole detection of asphalt concrete pavement belongs to pavement nondestructive testing technology. The main feature is that the results can directly and accurately reflect the diseases of concealed works, and its quality can be quantitatively described through test detection, but it has certain damage to the pavement, followed by slow progress and low efficiency. Scope of application: detection of small-scale diseases and serious road sections of subgrade and pavement. The impact on road traffic safety should be considered during the test.

1.2.2 digital borehole imaging detection

Digital borehole imaging system is a brand-new intelligent exploration equipment recently developed. It integrates electronic technology, video technology, digital technology and computer application technology, solves the problem of completeness and accuracy of engineering geological information collection in borehole, gets rid of the borehole TV mode in which borehole camera technology stays in analog mode for a long time, and makes it reach the highest level of borehole camera technology, that is, panoramic technology in digital mode. The system not only has the ability of panoramic observation, but also has the functions of measurement, calculation and analysis. It can be widely used in geological exploration, engineering safety monitoring and engineering quality inspection in water conservancy, civil engineering, energy, transportation, mining and other fields.

1.2.3 full-face excavation detection

For the section with serious diseases of asphalt concrete pavement, if the section has no direct impact on the driving safety of the whole road or the excavation of the diseased section has no direct economic loss and progress impact on the whole line, the whole section of the diseased section can be excavated and inspected to accurately understand the occurrence and development of subgrade and pavement diseases. Main features: the damage degree is relatively large, but the damage situation of subgrade and pavement can be accurately understood, and the degree of disease can be quantitatively expressed through field test. Scope of application: Full-face excavation detection means is only applicable to specific conditions.

1.2.4 section deformation monitoring

Deformation monitoring of highway subgrade and pavement is mainly to observe the settlement and horizontal displacement of subgrade and pavement. The horizontal displacement of subgrade and pavement is mainly monitored by inclinometer. Its basic device is mainly composed of measuring system, pipe socket, inclinometer and its connecting pipe, protective pipe sleeve, etc. Its main function is to reflect the inclination of a part of soil or structure.

The vertical displacement of subgrade and pavement is mainly monitored by layered settlement instrument. At present, electromagnetic settlement meters are mostly used for deep settlement observation. The working principle of electromagnetic sedimentation meter is to install an electromagnetic oscillation coil in the probe or controller. When the oscillating coil approaches the iron ring buried in the soil, eddy current loss occurs in the iron ring, which absorbs a large amount of magnetic field energy of the oscillating circuit, thus weakening the oscillator until it stops oscillating. At this time, the crystal sound will make a sound, and the position will be read on the ruler according to the moment when the sound just comes out.

2, the principle of subgrade and pavement disease detection technology selection

Damage detection technology of asphalt concrete pavement plays a very important role in correctly evaluating pavement performance, so it is particularly important to correctly select one or more pavement disease detection methods. The selection of detection methods for asphalt pavement diseases should follow the following principles.

2. 1 accuracy principle

When selecting the detection methods of various diseases of asphalt concrete pavement, one or several detection technologies and methods can be selected for detection, which requires that all detection methods complement and restrict each other. According to the damage degree of different pavement diseases, three-dimensional detection means combining destructive detection and non-destructive detection can be selected. When selecting detection methods and instruments, we should ensure that they are reliable, easy to operate and analyze, and can accurately reflect the damage and degree of pavement.

2.2 the principle of efficiency

Because the detection is generally carried out when the expressway is fully open to traffic, it is impossible to completely close the expressway when detecting diseases, which requires the selection of detection means to be fast and accurate.

2.3 the principle of economy

When choosing the detection method of diseases, we should also follow the principle of economy, and strive to achieve the purpose and effect of detection with the least cost.

3. Reasonable selection of early disease detection technology for subgrade and pavement.

Under the guidance of the selection principle of subgrade and pavement disease detection technology, combined with the characteristics and application scope of various detection technologies, through the classification of different pavement diseases, a reasonable detection technology is selected.

(1) When the disease of asphalt concrete pavement shows local damage and the pavement performance is excellent, nondestructive testing can be selected when selecting testing technology.

(2) When the early diseases of asphalt concrete pavement are damaged in a large area under the action of traffic load and natural factors, and the pavement performance is poor, but it will not affect the traffic of the whole road, when choosing the detection technology, we should first consider using nondestructive detection technology to detect the pavement performance, and if necessary, we can choose a small number of destructive detection methods to detect the diseases of subgrade and pavement.

(3) When the diseases of asphalt concrete pavement show very serious damage in some areas, and the cause of damage cannot be determined, we should consider using nondestructive testing technology and destructive testing technology to detect them.

(4) When the subgrade and pavement diseases are obviously damaged, which has seriously affected the road traffic on the pavement, all the subgrade and pavement can be selected for nondestructive testing.

The nondestructive testing technology of subgrade and pavement is mainly suitable for high-grade highways, and the pavement diseases are not serious. Will not seriously affect the pavement performance. Among them, ground penetrating radar image detection technology can detect pavement and subgrade diseases, and seismic wave image detection technology can detect tiny deformation of subgrade pavement and its development trend. Non-destructive testing technology of subgrade and pavement is mainly suitable for subgrade and pavement diseases of high-grade highways. In particular, the diseases caused by it are difficult to be detected by nondestructive testing technology, and the diseases hidden under the subgrade are clear at a glance.

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