Recently, the seabed static cone penetration CPT equipment has been used in the sea. This equipment is mainly used to measure the cone tip resistance, side friction resistance and pore pressure of the soil layer at a certain depth below the seabed. Finally, the physics of the soil layer is calculated through these three measured parameters And mechanical properties. The in-situ test chapter of "Engineering Geology Handbook" elaborates on CPT.
1. Installation and connection
1) The CPT underwater unit has been installed by the manufacturer as a whole and can be used directly. The underwater unit has been installed as a whole by the manufacturer and can be used directly.
2) Install the equipped special pulley.
3) For armored cable installation, the CPT underwater unit needs to be connected with the armored cable pre-wrapped in the winch purchased. The connection between the external armor and the underwater unit requires special bearing head
4) to connect the winch slip ring.
5) When the above steps are connected, lift the CPT underwater unit to test. Underwater unit testing.
6) After the test is completed, install the probe.
7) Connect the deck unit and underwater.
The CPT deck unit has three interfaces. From left to right, the cables and power supply network are as shown in the figure below: A class cable connects to the CPT special winch, and then the winch optical cable connects to the CPT underwater unit.
The network port is connected to a laptop, and an English operating system is required.
The power supply is connected to a 220V power supply.
Note: The winch and communication optical cable can be replaced with other ones, but the specifications must be the same, and the length cannot exceed 5000m.
2. Instrument operation and software settings
1. Turn on the main power supply and high voltage control system, and the green light will light up as shown in the figure below:
2. Open the Neptune Control System software, the software will automatically connect to the communication.
3. After the software communication is completed, enter the main menu to select the probe model after the software communication is completed, as shown in the figure below:
4. Tuning within the software, click performance test, if the device runs well, it will prompt success, click OK and enter the next main interface. If the test fails, please carefully check whether all connections are connected and whether the underwater unit is powered.
5. System setting
1) After entering the management setting interface, fill in the relevant sampling information as required, as shown in the figure below:
2) After filling in the information, click Select Cone, the system will automatically calculate, and the system will automatically calculate the content of Cone Data.
3) Click Control Screen to enter the sampling control interface and enter the sampling control interface
6. Sampling control
1) Place the underwater unit on the deck, click Deck Baseline.
2) After the underwater unit enters the water, the height, inclination and other information will be displayed at the bottom of the screen in real time. After the instrument reaches the seabed, click Seabed Baseline.
3) After judging that the propulsion measurement is possible, click Thrust to push out the probe, and the cone tip resistance, sidewall friction and pore water pressure curve will be displayed in real time during sampling.
4) When the drilling is finished, the system will automatically pop up a dialog box, click to confirm and automatically retract the probe, and the measurement ends. Generally, according to the setting, after thrust, it should be automatically stopped and automatically recovered, but in the process, if the situation is encountered, or according to the needs, you can manually stop the thrust and retract.
5) If the cone tip resistance reaches the upper limit, it will stop drilling. At this time, retract the probe, put the CPT away from the water, and return to step 1. If both operations reach the upper limit of resistance and the preset depth is not reached, judge this The seabed is hard, and the next station operation is carried out.
6) After the job is completed, you need to fill in the "CPT Job Status Sheet".
7. Data saving
All measurement data will be saved in the previous setting folder, and organize and save as needed.
In this operation, due to the use of a large ship with dynamic positioning (DP), I was worried that the dynamic positioning could not be fixed. Later, the dynamic positioning could be fixed and it could move according to the direction and distance. Therefore, the GPS was tied near the lifting point of the CPT , Improve the accuracy of sampling and positioning, and ensure that the sampling and positioning error is less than 5m.
3. Routine maintenance methods and frequency
3.1 Routine maintenance methods
Maintenance steps that should be carried out after each launch:
1) Use fresh water to flush the underwater unit to reduce possible corrosion of the underwater unit.
2) Visually inspect the connecting cables and connectors to ensure that the cables are not damaged and all watertight connectors are in good condition.
3) Check that all bolts are free of external injuries and are tightened.
4) Check the load-bearing head, whether there is any connection problem, and confirm all bolts are tightened.
5) Inspect the armored cable to check for trauma.
6) In principle, you need to disassemble the base of the mud scraper and clean the probe after completing 1 station. In actual operation, it is generally cleaned after finishing 2-3 stations.
Daily maintenance method:
1) Keep all parts of the equipment clean.
2) Connect the CPT underwater unit, deck unit, winch and acquisition computer, open the Neptune Control System software, click performance test, if the equipment is running well, it will prompt success, then power on is complete.
3) After a project is used, maintenance should be carried out.
4) Gear maintenance does not require oiling, clean it with fresh water and keep it clean.
3.2 Frequency of maintenance
1) Perform power-on maintenance every 3 months. Power-on maintenance and inspection must be carried out before each entry and exit. The launch test will be conducted every 6 months after decommissioning.
2) The CPT must be energized and checked before each mission sails, and sea trials should be conducted if conditions permit.
After this operation is completed, after opening the protective cover (scraper) of the probe, it is found that the probe is not in the center, as shown in the figure below:
You need to adjust the upper two wheels to straighten the probe. We fiddled for 2-3 hours, and finally figure out how to do it, which is to loosen all the upper two wheels first, and observe where the probe is causing the probe to be absent. Center, then adjust the wheels, repeatedly retract and lower, straighten the probe.
Four, matters needing attention
1. When installing the probe, first reverse 3 turns, and then screw it along to prevent the internal wiring from tightening.
2. Make sure that the instrument is working normally before entering the water and check the watertight head. The watertight head must be kept clean and coated with silicone grease.
3. Measure the relationship between the CPT and the GPS antenna position, and you must ensure that the system receives the corrected GPS differential signal.
4. Before launching, pay attention to whether the dynamic positioning has been stabilized.
5. When the entire project is over, the CPT underwater unit must be rinsed with fresh water.
6. When working in the network area, the person in charge of the scene must come to command in person on the bridge.
7. Pay attention to the maximum withstand voltage of each part of the instrument. At present, the maximum depth of the 3000-type probe of Dongkan Institute
is 700m and 2500m; the maximum pressure-resistant depth of the CPT underwater unit is 3000m, and it is strictly forbidden to use it beyond normal.
8. If you need to replace the probe or adjust the angle between the probe and the CPT main body, you need to place it on a solid steel frame or tip the CPT over. It is very dangerous to replace the probe when the CPT is in the air.
9. The probe is returned to the factory for calibration once every six months, and calibration is performed before each major project.
When the difference between the factory value and the current value of the probe raw bits is greater than 1000, it needs to be returned to the factory for calibration (check in the software Engineering).
Five, thanks
Thanks to all the personnel in the field, especially the captain, for operating DP very well. Chenming's Yang Gong team operated the CPT winch so smoothly.
Some pictures cannot be uploaded. It is recommended to check xiaok marine surveying and mapping network or follow the public account of the same name.