1 Necessity and importance of strengthening highway engineering test and detection work
1. 1 can make full use of local materials and facilitate local materials. Such as sand, gravel, fillers, etc. In the construction site, it can be tested by this effective means, such as sand density, gradation, silt content, crushing value, axial compressive strength, maximum dry bulk density, liquid-plastic index and so on. To determine whether the raw materials meet the requirements of the technical specifications for construction, so as to use local materials, select materials with good quality and large quantity, which are convenient for mining and transportation, and organize the construction plan, which can speed up the project progress and reduce the project cost.
1.2 is beneficial to the popularization and application of new technologies, new processes and new materials. Test a new material, new technology and new technology in time and effectively to identify its feasibility, applicability, effectiveness and advancement, so as to accumulate practical experience and collect relevant information and data for perfecting engineering design theory and construction technology. This will play a positive role in promoting the progress of construction technology and improving the progress and quality of the project.
1.3 Through necessary inspection, the quality of raw materials, finished products and semi-finished products can be scientifically evaluated. With this set of effective and scientific testing methods, any material can pass the relevant tests of its specified performance, so as to evaluate whether its products are qualified. This is very important for rational application of materials and improvement of engineering quality.
To sum up, it can be seen that the test will play a very important role in improving the quality of the project, speeding up the progress of the project, reducing the cost and promoting the progress of construction technology. Therefore, it is imperative to strengthen the test and detection work, which should be highly valued.
2 The main scope of the test work
(1) Before subgrade earthwork filling, soil moisture content, density, particle analysis, liquid-plastic limit, organic matter content, soil strength test (CBR) and standard compaction test must be carried out.
(2) Tests that must be conducted before the construction of bridge and culvert structures.
A. Sand and gravel test: apparent density, bulk density, screening, silt content test, stone needle content test, water content determination, crushing value, abrasion value and weak particle content test;
B cement material test: mechanical test, fineness, standard consistency, setting time and mortar strength test;
C. Cement mortar test: density, consistency and compressive strength test of cement mortar and standard test of mixture ratio design;
D. Cement concrete test: density, slump, compressive strength, frost resistance strength, splitting tensile strength and standard test of mix design of cement concrete;
E. Inspection and test of steel: inspection and test of standard code, surface shape, steel bar grade, nominal diameter, yield point, tensile strength, elongation, cold bending test, lap steel bar length and welding quality;
F. Water quality analysis: detection of chloride ion content, sulfate ion content and pH value.
(3) Tests that must be carried out before paving begins.
A. Test of inorganic binder stabilized materials: water content, standard compaction degree, compressive strength, tensile strength, indoor compressive resilience modulus, mixture ratio design of stabilized soil, determination of cement or lime dosage in stabilized soil, and chemical analysis of lime;
B. Mineral aggregate test
(1) Test the crushing value, abrasion value, apparent density, polishing value, slender flat particle content and particle composition of crushed stone. Test and detection of apparent density, compactness and sand equivalent of sand;
(2) Apparent density, water content and particle size range of mineral powder.
C. Asphalt mixture test
① Asphalt raw material test: relative density, softening point, penetration, viscosity, flash point, solubility, wax content and heat loss test;
② Asphalt mixture test: density, void ratio, Marshall stability and flow value, residual stability, asphalt content, screening test and mixture ratio design standard test.
3. Measures and ways to strengthen test and detection work and improve engineering quality
3. 1 The quality and technical level of testers need to be improved.
At present, the technical level of construction units in different parts of our province is different, the test and testing personnel are scarce, the quality is low, and they don't even need to learn. Lack of a team of quality inspectors with high professional quality. Therefore, in view of the current situation in our province, it is necessary to enrich the experimental team and improve its overall quality and professional level. In this regard, the competent department of transportation in our province has paid attention to it and started to implement it. The provincial quality supervision station has organized the technical personnel of highway system test and detection in the whole province to go to the relevant departments of the province for systematic training for several years, which is a good start.
3.2 Perfecting the legal system, improving quality inspection institutions and engineering quality management system is an important guarantee to improve the quality of highway engineering in our province.
In terms of laws and regulations, China has promulgated the Highway Law and related industry standards. Our province has also introduced some governance systems, methods and interim provisions. This will play a positive role in promoting the healthy development of highway construction in our province, but with the development of the situation, the existing laws and regulations can no longer meet the needs of the rapid development of highway construction. Therefore, it is necessary to further improve and develop the above laws and regulations, so that highway construction units have rules to follow and laws to follow. In addition, for experimental testing institutions, it is necessary to further improve, strengthen and strictly manage, and formulate a set of practical governance measures. Make quality inspection institutions gradually standardized and specialized.
3.3 Further establish and improve the highway engineering quality assurance system and enhance the engineering quality awareness.
At present, our province implements a three-level quality assurance system of "government supervision, social supervision and enterprise self-inspection". Quality management departments at all levels should perform their respective duties and take effective measures to continuously improve the quality management level in accordance with the principle of quality first and the requirements of total quality management. In practical work, we should strictly implement quality self-inspection, strengthen quality management and supervision, and gradually establish and improve a three-level quality assurance system. Secondly, it is necessary to strengthen the quality awareness of all aspects of construction, take responsibility for the division of labor, and truly implement the quality post responsibility system.
4 highway engineering tunnel construction detection points
Highway tunnel construction detection mainly includes two aspects: one is to detect the quality of highway tunnel construction, and the other is to monitor and measure highway tunnel construction.
4. 1 Highway Tunnel Construction Quality Inspection
First, from the various quality problems that often appear in highway tunnel engineering, many quality hidden dangers are mostly buried because of improper management in the construction process, so it is necessary to strengthen the quality inspection in the construction process. Second, the strength of advanced support is not enough, and the pre-reinforcement does not meet the construction requirements, which may cause major accidents such as tunnel collapse or roof fall, seriously affect the construction quality, seriously affect the construction progress, and cause great waste of engineering materials. Thirdly, necessary auxiliary measures must be taken to ensure the stability of surrounding rock before and during tunnel excavation. For example, tunnel face excavation can complete reinforcement and arch modification at the same time.
Second, first, the subsequent processes are mainly directly affected by the blasting results. We should conscientiously implement the special requirements of extra-long tunnel construction, fully understand the engineering risks, especially the unforeseen risks in complex tunnel hydrogeology, make full use of tunnel profiler to detect the blasting quality in time, especially check the tunnel section after blasting, compare it with the designed section, grasp the over-excavation and under-excavation of the tunnel, check the surrounding rock deformation of the tunnel, and resolutely put an end to blind construction and random construction.
Third, first, pay attention to the quality of support, especially the quality of anchor installation, strictly control the quality of sprayed concrete and pay attention to the quality of steel members. Second, the engineering quality inspection department must detect the spacing and direction of anchor bolts, and pay attention to the pull-out resistance of grouting anchor bolts. Thirdly, the thickness and smoothness of sprayed concrete are carefully detected to meet the construction requirements. The fourth is to check whether the specifications and dimensions of steel members meet the requirements, whether the bolt connection and the inter-node connection are stable, whether the spacing length of steel frames is appropriate, and the contact between each member and surrounding rock. Fifth, at the same time, strengthen the detection of the construction behind the support, especially the backfill density. Strictly check the quality of all kinds of support, ensure the operation process of tunnel construction, and do a good job of corresponding testing.
Fourthly, the quality inspection of lining concrete includes the inspection of lining geometry size, lining concrete strength, concrete integrity, concrete cracks, backfill density behind lining, and the distribution of steel frames and steel bars in lining. Measure the external dimensions with a ruler, detect the strength and integrity of concrete with nondestructive technology, detect the cracks of concrete with a feeler gauge or a crack observer, and detect the backfill density behind the lining with drilling method or geological radar method. The quality control of lining concrete is carried out in strict accordance with the Code for Construction of Highway Tunnels, and it is tested according to the tunnel engineering test and detection technology.
4.2 Highway Tunnel Construction Monitoring and Measurement
Construction monitoring and measurement is an important content of NATM construction, which is not only a safeguard measure for construction safety, but also an important means to optimize structural stress and reduce material consumption. The basic contents of measurement include the deformation of tunnel surrounding rock, supporting stress and lining stress. The displacement around the tunnel is measured by convergence meter and total station. The settlement of tunnel vault is measured by precision level and total station. The internal displacement of surrounding rock is measured by mechanical multipoint displacement. The axial force of anchor rod is measured by force measuring anchor rod.
4.3 Highway Tunnel Environmental Monitoring
Environmental monitoring is mainly divided into construction environment monitoring and operation environment testing. The main task of construction environment detection is to detect dust and harmful gases during construction. The harmful gas here is mainly CH4. If CH4 reaches a certain concentration, improper preventive measures during construction may lead to explosion, resulting in casualties or economic losses.
With the rapid development of high-grade highway construction, rural highway construction is in full swing, and quality is the life of the project, which has become common sense. In my opinion, as the only effective means to test the quality of the project-test detection can not be ignored. Therefore, how to strengthen the test and improve the quality of highway engineering is worth discussing.
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