Theoretical And Applied Research On Evaluation Of Quality Status Of Hydraulic Concrete Based On Surface Wave Method Of Impact Elastic Wave

Many hydraulic structures have only one measurable surface,such as channels,tunnels,and culverts.This paper mainly introduces the theory and application of surface waves in the quality inspection of hydraulic concrete.The SASW method is used to verify the internal quality of the lining structure and the lining and surrounding rock voiding.The technical essentials for improving the detection accuracy are found.A SASW-MASW-FK surface wave analysis software was developed,which greatly improved the processing efficiency of surface wave detection data.Taking the hydraulic water conveyance tunnel as an example,the surface wave method was used to evaluate the internal quality of the lining and the combination of the lining and the surrounding rock.Combined with the Shisanling Pumped Storage Power Station,the surface wave method was used to diagnose the cracking condition of concrete facing.For the operational dam,the surface wave was studied to detect the internal quality of the dam concrete.In combination with the environmentally friendly damming technology of cemented sand and gravel dams that have emerged in recent years,the surface wave is used to test the quality of cemented gravel to judge the construction quality.The main research contents are as follows:(1)Software development of Surface wave method numerical simulation:The calculation of different media models shows that the SASW method can accurately identify the contact gap between the lining and the surrounding rock.When the sensor track pitch is 1.0～1.5 times of the thickness of the lining,the data quality collected by the SASW method is the best,which is beneficial to improve the defect recognition accuracy.On-site inspection by SASW method is to use a hammer to quicken the stroke.The obtained oscillation curve has less interference,and the signal collected by the sensor is more accurate.The F-K method makes full use of multi-surface wave data recording information,and can obtain information of a larger range of medium to be tested.Usually,the basic mode is used to extract the R wave dispersion curve,which is very suitable for the slab in the hydraulic structure.(2)Deterioration of concrete impervious lining of pumped storage power station:A total of 12 panels were tested in the upper reservoir of the Shisanling Pumped Storage Power Station,and the concrete R wave velocity Vr of the 48 surveyed areas was basically above 2200 m/s.Nearly 60%of the concrete R wave velocity VR exceeds 2400 m/s.The lining and the cushion layer are in good contact,the slab joint water-stop is in good condition,and no leaking destroys the cushion layer.The SASW method gives a quantitative evaluation of the deterioration degree of the lining of the pumped storage power station,which is not affected by the intensive steel bar inside the slab and the moisture content of the slab.This is a function that the ground penetrating radar does not have.(3)The internal quality assessment method of concrete dams:The relationship between the compressive strength of the RCC core sample and its P wave velocity is established.When the velocity of the P wave exceeds 3600 m/s,the strength of the RCC can reach 20 MPa.When the wave velocity of the three-dimensional P wave exceeds 4000 m/s,the strength of the RCC can reach 30 MPa.The quality of the concrete is uniform within a certain depth range below the measuring surface.The surface wave method is used to detect the internal quality of the dam.The distance between the sensor channels is about 3-5m,and the distance between the sensor channels is generally about 5～10m.All test results are comprehensively judged,and the concrete strength exceeds 30 MPa and meets the design requirements,especially the concrete near the grout corridor.Compared with the rebound method and the core method to detect the internal strength of concrete,the surface wave method is simple to operate,and the effective detection depth of the internal quality of the dam can reach 3～10m.The dam surface concrete is the most susceptible to the deterioration.The surface wave method provides a new method for evaluating the internal quality of concrete dams and other large-volume concrete,which is worthy of promotion.(4)Construction quality evaluation of cemented gravel dam construction:A quality inspection system for cemented sand and gravel dams is built to achieve the purpose of front detection and rear processing data,and the test results can be promptly fed back to the site to guide construction.When the surface wave velocity is 186 m/s,the design density can reach 2.45 g/cm3.After 6-pass of vibration,the average wave velocity is 228.7 m/s.At this time,the design requirements have been met.After the first day of pouring,the average wave velocity is 360.3 m/s.after the final setting.The density increases and the construction quality is more guaranteed.With the help of the cement sand gravel quality inspection system and the density calibration of the pit impounding,the CSG construction compaction can be quickly and extensively measured.