Plastic drainage boards are alias plastic drainage belts, which have a variety of shapes such as wavy and harmonica. In the middle is an extruded plastic core board, which is the skeleton and channel of the drainage belt. Its cross-section is parallel cross, and the two sides are wrapped with non-woven geotextile as filter layer. The core belt plays a supporting role and the water infiltrated by the filter layer is discharged upwards. , It is a good vertical channel for the treatment of soft foundation by using the drainage consolidation method such as silt, silt soil, flushing fill and other saturated viscous and miscellaneous fill, greatly shortening the consolidation time of soft soil.
First, the principle of plastic drainage board
The plastic drain board is inserted into the soft ground with the inserter and the void water in the soft ground is discharged from the plastic drain board into the sand layer or the horizontal plastic drain pipe under the upper part and discharged from other places under the action of the upper preloading. Consolidation of soft ground. In the soft ground treatment, the function of the plastic drainage board is designed, and the construction equipment is basically the same as the sand and sand well.
Second, the advantages of plastic drainage board to strengthen the soft ground
1. Good water drainage, smooth drainage, and guaranteed drainage.
2. The material has good strength and ductility and can adapt to the deformation ability of the foundation without affecting the drainage performance.
3. The drainage plate has a small cross-section, and the disturbance to the foundation during the application of the drainage plate is small.
4. The plugboard construction can be performed on the super soft foundation.
5. The construction is fast and the construction period is short. Each sheeting machine can be inserted more than 5000m per day, and the cost is lower than the bag sand well.
For the consolidation of deep soft ground using drainage consolidation, it is technically and economically considered that the use of drainage panels is almost the only economical, effective and feasible method.
Third, the plastic drainage board construction
1. Main materials and equipment
(1) Plastic drainage board (Product specifications according to the design requirements combined with construction technology conditions to choose its type and model).
(2) Main construction equipment (including guide frame, casing, vibratory hammer with driven casing sinking, reel and windproof device for loading the drainage board, etc.) to be used for drain board, and IJB-16 type can also be used. The flapper can also be used to change the working device with a crane pile driver and a simple flapper.
2, operating conditions
(1) In the technical preparation before construction, according to the design requirements of the foundation and the topographic and geological conditions, the layout of the drainage holes and the order of the drainage boards shall be determined.
(2) Construction sites and roads shall comply with the requirements for plugging drainage boards, such as the entry and exit of construction personnel and equipment, and arrangements for temporary facilities (including hydropower, communications, etc.).
(3) After the site drainage hole position is determined according to the construction organization design, the jack position shall be marked with a bamboo stick.
(4) The working conditions for the dredger fill.
Fourth, plastic drainage board operation process
1. When the board is inserted, after the board insertion machine is in position, the vibratory hammer drives the bushing to align with the jack position to sink. The drainage board is connected from the bushing through the anchoring shoe of the head, and the bushing presses the anchor board to push the drainage board. Insert the design into the soil depth, pull up the casing, anchor the anchor with the drain board left together in the soil, and then cut off the continuous drain board, that is, complete a drain hole insert plate operation. The card inserter can be moved to the next drain hole to continue playing.
2. When cutting the drainage board, leave a 15-30cm 'platen' on the original ground; then dig up the 20cm deep bowl-shaped concave position next to the 'plate', and then expose the board head. Cut it out, fill it in, and complete construction of the flapper.
Fifth, plastic drainage board quality standards
1, plastic drainage board material requirements
The plastic drain board is the factory's styling product, and the combined indexes for checking the performance and effect of the product when making the selection are as follows:
(1) The choice of tensile strength shall not be less than 1KN (the actually used SPB-1 plastic drain plate tensile index ---- Core: 1.7N/mm2; Filter: 0.44N/mm2).
(2) The elongation rate is 2%-10%.
(3) The tear resistance should exceed 300N (actual SPB-1 filter tear is 1340N).
(4) Water permeability ≥10-3mL/s.
(5) The membrane permeability coefficient is not less than 4.2×10-4cm/s (we must also consider the deformation resistance, soil-preservation, and long-term drainage effects of the drainage plate).
2. Drainage hole requirements
(1) The spraying process maintains the verticality of the drainage hole, and the vertical deviation is controlled according to the depth of entry ≤1.5-2cm/m (1.5%-2%).
(2) The position of the drain hole shall be applied at the spacing required by the design, and the general position deviation shall not exceed 5cm.
3, Drainage board plug request
(1) Maintain the continuity of the drainage board into the soil and find that the fracture is reapplied.
(2) The length of the upper and lower lap joints connecting the drainage board shall not be less than 10CM, and the connection shall be firm.
(3) Remove the pipe after inserting the drain board to the design depth.
(4) After the drain plate is inserted and cut, the length of the 'plate' exposed on the ground cannot be less than 15cm.
4. The relevant parameters of soft soil or super-soft soil foundation through pre-pressure drainage consolidation are as follows:
Site preloading -15-120KN/M2.
After one month of classification and loading, the settlement amount reached more than 20% of the total thickness of the soil layer; the water content of the soil was reduced to about 50%.
Sixth, plastic drainage board construction precautions
1, pay attention to the technical performance of the drainage board, according to the design requirements of each batch of products approaching the site inspection and inspection before construction.
2. Before the construction, check the geological data and make necessary penetrating (exploration) inspections in the area where the drainage holes are located, so as to avoid hitting underground obstacles when the drainage holes are applied. (Detector hole depth should not exceed 60cm depth of design hole).
3, when the collision with the underground obstacles can not continue to enter or tilt the hole (above the allowable deviation), you should discard the hole and extubate the shift (about 45CM or so), re-play drainage holes.
4, the drainage hole of the casting process to use fixed-load vibration injection method, has been hit to the depth of the design requirements, does not allow hammer slamming.
5, Drainage board during the shipment and storage, it is necessary to pack a thick protective layer, storage at the construction site should pay attention to sunscreen and mud, dust pollution or other objects collision damage.
6. When the drainage board is inserted and inserted, it should be noted whether it is actually sent into the soil during the insertion, or when the pipe (mandrel) is extubated, the drainage board is brought back up. Always pay attention to the consumption of plastic plates in the roll (or use an automatic recording device).
7. Set an appropriate pre-pressure settlement observation point, pay attention to the amount of compression and uniformity of the classification of the load.
8. It is necessary to implement technical specifications for the temporary use of electricity on the construction site to avoid accidents.