This project belongs to the field of civil construction engineering, mainly to improve the penetration test instruments using photoelectric technology in geotechnical tests for geotechnical engineering surveys. The purpose of penetration testing is to measure the permeability coefficient of soil. Permeability coefficient is an important physical and mechanical indicator to measure the permeability properties of soil. It is also a basic parameter required to analyze the consolidation and settlement rate of foundation, estimate the permeability and seepage stability of natural foundations, earth dams and high-fill embankments, as well as water supply and drainage design, construction selection, artificial water level reduction and foundation reinforcement design.
Nowadays, the usual method to measure the permeability coefficient is to use indoor permeability test. It is divided into constant head permeability test and variable head permeability test based on the difference in the test equipment. The constant head test is suitable for the measurement of the permeability coefficient of coarse grained soil, while the variable head permeability test is suitable for the measurement of the permeability coefficient of fine-grained soil.
Both the constant head penetration test and the variable head penetration test obtain data by observing the liquid level in the glass tube with the naked eye and reading the scale of the reference ruler next to it. The shortcomings of this manual reading are as follows: first, for coarse grained soil, the test speed is too fast (less than 20 seconds), and it is too late to read the scale; second, for fine-grained soil, the test speed is too slow (more than 3 days). In order to prevent missing the scale reading at night, the test is generally closed and the test continues the next day, which is inefficient; 3. When manually reading the scale, there are visual errors; 4. Manual operation is prone to mistakes; 5. Personnel are required to squat and the cost is high. Compared with the constant head penetration test, the water head changes faster during the variable head penetration test, the number of readings is large, and there are more factors affecting the accuracy of test data collection. Therefore, this project applies photoelectric technology to the variable head penetration test to obtain More accurate and effective data. Key innovations include:

1. This project involves optoelectronic technology. It is a light-controlled device installed on a variable head penetration test instrument to measure the penetration level of soil samples.
2. This project uses photoelectric technology to realize real-time dynamic measurement of the seepage level of soil samples, and can measure the seepage head at precise nodes.
3. This project is automated and reading. For fine-grained soil with slow testing speed, testing can be carried out continuously at night to improve efficiency.
4. The photoelectric sensor of this project uses point light source technology to overcome visual errors and improve test accuracy.
5. This project installs optoelectronic devices and compiles corresponding programs to automatically collect data and automate process control. There is no need for personnel to sit down, and the results are directly printed and output in the form of tables, saving labor costs.
   The project has obtained 9 authorized patents and published 3 papers. The research results have reached the domestic leading level (attached inspection results acceptance report). The research results have been successfully applied to key municipal projects of the hospital and other units:"Phase II Project of Rail Transit Line 13 (Changqing Road StationZhangjiang Station) Detailed Survey Project "," Geotechnical Engineering Survey of Shanghai Rail Transit Line 14 Project "," New Construction Project of Beizhai Road (CentralOuter Ring) Channel "," New Construction Project of Riverside Channel "," Phase III Project of Rail Transit Line 9 "," Huangpu River Marriott Hotel Project "," Shanghai Aviation Service Center Plot ", etc. are all ultra-deep large foundation pits. The penetration test indicators are crucial for the design of foundation pit enclosures. After adopting this topic test device, It not only ensures the observation accuracy, but also saves human resources, etc., so it has been widely praised by the user units.
   This project has improved the labor intensity of test operators and reduced human resource costs. It has also played a leading role in improving soil testing technology in this industry, especially in the context of labor-oriented survey industry, and has contributed to promoting the engineering survey industry in this city and even the country. Geotechnical testing and corresponding technical improvements have made contributions. In the future, technology will be commercialized and entered the mass production stage, striving to be widely promoted and applied in the industry.