Application of Plastic Drainage Board in Soft Soil Roadbed

Abstract: The plastic drainage board treatment soft soil roadbed technology not only has high strength, good extension, convenient transportation, simple construction, fast progress, good drainage effect, high economic and social benefits. In combination with a highway soft soil roadbed construction project, for the plastic drainage board technology, the construction characteristics, construction process and precautions of the plastic drainage board are introduced in detail, and it is hoped that it will be useful for similar projects in the future.

Keywords: highway; plastic drainage board; soft soil roadbed; soft foundation treatment

Introduction

With the rapid development of China’s economy, people have increased their investment in the transportation industry. The scale of highway construction is becoming larger and larger. It has gradually changed from the original low starting point to the current high starting point and high standard. Therefore, the construction requirements for highways are also Higher and higher. Soft soil roadbed is relatively common. If it is not handled properly, the pavement is prone to settlement problems and various road surface diseases, which has a serious impact on road safety. Plastic drainage board can strengthen the soft soil roadbed and avoid road construction. After the roadbed settlement is too large or uneven, the purpose of the engineering accident.

1. Project Overview

This project is a road construction project. The road is located at the traffic fortress. The traffic volume is large and the vehicle overload is serious. The flood season is abundant and the roadbed of this section is in the soft soil area. How to handle the road soft soil roadbed? It is directly related to the construction quality and service life of highway engineering. Table 2 shows the design parameters of the plastic drainage board.

Table 1 Basic physical and mechanical parameters of clay

Table 2 Design parameters of the plastic drainage board

After research and discussion by the relevant staff, it was decided to use plastic drainage board construction technology in this project construction project, and hope to have a reference for similar projects in the future.

2. Overview of plastic drainage boards

As a commonly used construction technology for soft soil roadbed in road construction, the plastic drainage board is mainly used in soft soil. The plastic board is placed on the soft soil, and then the water in the soft soil roadbed is pre-loaded. The method of pressing is excluded to achieve the purpose of consolidating the roadbed. The plastic drainage board is obtained by combining the sand drainage method and the cardboard drainage method. The operation is simple and flexible, the utility is high, and the construction input cost is low, and it is widely applied to the highway soft soil roadbed treatment.

The construction process of the plastic drainage board is as follows: leveling the construction site and cleaning → measuring the lofting → digging through the side ditch → laying the sand layer → compacting → positioning of the drainage plate hole → sinking the pipe into the plate → compacting → filling the roadbed.

3. Construction points

3.1 Precautions
In the construction of highway drainage roadbed using plastic drainage board construction technology, the following matters need to be noted:

(1) Do a good job in plugging construction. In order to prevent problems such as kinking and breakage, the construction personnel should carry out the plastic drainage board insertion work according to the insertion process and re-insert the problematic drainage boards. After the construction of the pile position is completed in accordance with the sequence, the construction personnel need to inspect the quality of the plastic plate inserting, and the next pile position can be carried out after passing the test.

(2) The insertion work of the plastic plate needs to be carried out according to the set elevation. If the construction personnel encounter underground obstacles during the insertion process and there is no way to carry out the work, they must give up the work of the pole position and transfer the pile position. The piles also need to be inserted around, and the moving distance of the new pile position It is necessary to control it at around 45cm and insert it into it. In the hard soil layer, the depth of the plastic drainage board should be controlled at about 50cm, and the construction work should be carried out in strict accordance with the set elevation to prevent deviation problems.

(3) Control of the insertion time. It is necessary to control the insertion time of the plastic drainage board and the operation time of the up-and-down operation within a reasonable range. It is about one minute or so. If there is a problem of returning the belt, the speed of the upper dialing must be reduced immediately or the reverse insertion mode can be directly selected. After the construction of the plugging, the outer leakage part is ensured, and the soil around the drainage board is removed to prevent pollution problems.

(4) Control of the length of the tape return. During the construction process, the length of the plastic drainage board should be controlled to about 50cm. If it exceeds, it needs to be repaired. The whole version can be used in the construction to ensure the construction quality of the drainage board. In addition, plastic drainage boards are not allowed to be used for the extension.

3.2 Laying of drainage mats
After the construction workers lay the gravel drainage cushion, the construction work of the plastic drainage board can be carried out. After the roadbed and the stakeout work are completed, the trench can be excavated. Before the construction, the surface water of the roadbed is cleaned, and then the manual operation method is used to lay the drainage cushion. In the process of laying gravel, the thickness of the gravel should be strictly controlled, as shown in Table 3 below.

Table 3 Relationship between grit size and content

3.3 Positioning of the pole position
Before the positioning of the pole position, the construction personnel should do the design work of the plastic drainage board, and make reasonable calculations on the number of rows and columns of the drainage board. The length and width of the design are the main considerations in the design process. Use a triangle. After the calculation of the pile placement is completed, the layout diagram can be drawn and numbered. In the event of a skewed structure, in order to prevent leakage and over-type problems, the constructor needs to set two triangles on both sides. The work of laying the pile position must be carried out in strict accordance with the pile position drawing. The laying work should be carried out on the top surface of the sand cushion layer, and then marked with 1.5 cm long steel bar material.

3.4 Plug-in construction
In this project, the construction of the plastic drainage board can be carried out using a self-made rail type tape machine. During the operation of the tape feeder, the direction is mainly along the road track. The components of the plastic drainage belt have a core and a filter membrane. From a physical point of view, the moisture in the soft soil layer enters the core through the filter membrane under pressure and then is discharged from the groove through the drainage cushion. When the insertion work is in progress, the plastic drainage belt should be installed on the already stable frame, and then the drainage belt should be folded back and folded from the pipe boots and fixed on the pile tip so that the drainage performance is greatly improved. Can be improved. In order to prevent the inclination of the sleeve and the control of the insertion speed during the insertion operation, the construction personnel needs to strictly control the speed of the insertion. When the depth of the drainage plate inserted into the soil is within 2 m of the set height, the speed needs to be slowed down. After the casing has reached the design depth, it needs to be pulled out slowly, and then the drainage belt is cut. If the casing is taken out of the soil after it is pulled out, it needs to be cleaned up, and finally, the gravel is filled.

3.5 laying of geotextile
The laying of geotextiles can ensure the construction effect of the plastic drainage board, so that the drainage and reinforcement performance can be improved, thereby improving the bearing capacity and stability of the soft soil roadbed. After the laying work, approximately 300 mm of soil was laid on its surface. In order to prevent distortion and wrinkles, the longitudinal overlap needs to be handled well and the fold length is controlled. The construction personnel should check the time during the laying process. If there is a tearing problem or a broken problem, it must be repaired or reconstructed in time. After the geotextile is laid, the preloading load needs to be filled. In order to avoid the shearing problem caused by the excessive loading speed, the construction personnel should control the loading speed. Filling preloading operations can only be carried out after the foundation stability analysis work is performed and the monitoring technology is used to monitor the loading rate during the loading process. In order to avoid the occurrence of the instability of the foundation, it is necessary to observe the horizontal displacement of the side pile and set the position of the settlement plate and the side pile reasonably, and do the settlement detection.

4. Construction quality inspection points

The construction of plastic drainage board should be carried out in strict accordance with the requirements of the construction drawings. During the construction process, a special person should be arranged to check the construction quality from time to time. The depth and spacing of the plastic drainage board insertion are the key inspection tasks and the quality inspection records are done. The precision error of the insertion position should be controlled within a certain range. The board spacing is controlled within 15cm and the spot check is done. In order to ensure that the length of the construction can meet the construction design requirements, the error of the length of the board must be greater than the design value and the spot check and inspection work should be done. The verticality error of the plastic drainage board must be controlled within 1.5% while the recording and inspection work is required.

5. Conclusion

In the process of highway construction, soft soil roadbed is a common roadbed condition. For different soft soil characteristics, appropriate treatment methods should be adopted, otherwise, it will lead to various disease problems such as settlement on the road surface. By combining the example of a highway project, the road has a soft soil condition and the vehicle is overloaded seriously, which causes the road surface to sink. Finally, the plastic drainage board treatment plan is selected. During the implementation of the project, the purpose of consolidating the roadbed is achieved by inserting a plastic plate into the soft soil and then pre-pressing the water to remove the water in the soft foundation. The implementation effect of this project shows that the construction of plastic drainage board is simple and flexible, and the engineering cost is low. At the same time, it can strengthen the soft soil roadbed and can be popularized and applied in similar projects.