| The physical properties of seabed sediments are known by acoustic detection,and the types of sediments are identified and retrieved.In situ acoustic detection is one of the most important research methods in the study of submarine sedimentary acoustics.The research and development of domestic submarine in situ acoustic detection system is relatively rapid.Compared with foreign equipment research,there is still a lack of in situ shear wave detection function.Based on this,this paper presents the key technologies of the acoustic in situ measurement system of ballast submarine sediments with the dual functions of compression wave and shear wave detection.The main contents are as follows:1.Design system acoustic measurement module.By analyzing the principle of submarine in situ acoustic measurement array and combining the design criteria of transducer transceiver spacing,the acoustic attenuation array of shear wave measurement system is designed.The distance between two shear wave receiving transducers and transmitting transducers is 200mm?400mm,respectively.The structure of shear wave transducer is designed.2.Carry out penetration resistance analysis and strength check of acoustic measuring rod.Using static pressure pile penetration analysis method,the penetration mechanism of acoustic probe rod is studied by using compression wave measurement as an example.Based on finite element ABAQUS,the penetration resistance of probe rod is analyzed.The design of compression wave head is optimized to reduce penetration resistance of probe rod,and the end of compression wave measurement probe rod with 60 mm diameter is expanded to 65 mm?70mm?75mm respectively.The simulation results show that the maximum penetration resistance of extended end rod is better than that of ordinary rod(compression wave measuring rod without expansion treatment),and the resistance of end rod with 70 mm diameter is the most optimized,The maximum resistance in the penetration process is 30.83% lower than that of the ordinary rod.Based on the stabilization of compressive bar theory,the strength and stiffness conditions of the probe rod are analyzed,and the strength of the weak link of the shear wave measuring rod is checked to verify its reliability.3.Testing of acoustic emission acquisition systems for shear waves.The performance evaluation and testing methods of acoustic emission acquisition system are studied.The results show that the bottom noise intensity of the system is 1.75% of the waveform signal,the signal acquisition channel is consistent,the voltage response is linear,the error between the actual response gain value and the design value is less than 2.5%,and the actual gain value between the two signal acquisition channels is less than 0.1%.4.Carry out calibration of shear wave transducer.The consistency of the receiving transducer is the premise of the gap measurement method.The consistency of the shear wave receiving transducer is tested and calibrated by the principle of single factor experiment method.The test results show that the system delayed time of SR2(2 shear wave transducer)is 1.98 us larger than SR1,and the amplitude is about 6% larger than SR1,and the shear wave measurement system is corrected accord this.5.carry out shear wave measurement module beach experiment.The test frame of shear wave beach is designed and the beach experiment of shear wave measurement module is completed on Qingdao Sculpture Park Beach.The experiment shows that the insitu system shear wave transducer can perform good acoustic test at 400?3000Hz,and the optimum test frequency range is between 600?1500Hz.The measured attenuation coefficient is between 50?200d B,and the overall trend increases with the frequency. |
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