I. Status quo of the project
The middle road along the Yangtze River is an important east-west secondary trunk road in Anqing, and it is also an important flood control channel in flood season (the sidewalk on the south side of it is adjacent to the flood control wall). The smoke-burning pavilion designed and reconstructed this time starts from the middle and west of the Yangtze River and reaches Hu Xin Road in the east, with a total length of 2175m, which is connected with the primary and secondary roads in cities such as Longshan Road, Nanmen Street Road, Jianshe Road, Yicheng Road and Huxin South Road, respectively, and is an important link of traffic engineering in Anqing. The current situation of the reconstructed road section is 13m wide concrete pavement, and the old pavement was built in the late 1980s. Due to the large traffic volume, a new concrete flood control wall was built in 2004, and the pavement was seriously damaged, with cracks and staggered platforms in most plates and potholes in some plates. At the beginning of 2005, the Municipal Party Committee and the Municipal Government decided to rebuild this road, and combined with the flood control wall and decoration project built by the water conservancy department on the south side of the road, this road was built into a landscape avenue in Anqing City. After many scheme demonstrations, it is considered that the original road 13m can no longer meet the needs of existing traffic and landscape. Combined with the current terrain, it is decided to widen the road to 16m. In order to save the project investment and shorten the construction period, after comparing the road structure forms for many times and considering the actual situation in Anqing, it is decided to still use cement concrete pavement, that is, put a concrete surface layer on the original concrete pavement, and the widening part on the north side shall be implemented according to the standard of new concrete pavement.
Second, the choice of transformation technology scheme
The difficulty of this project lies in how to make better use of the existing 13m concrete pavement, reduce the number of cutting boards as much as possible, shorten the construction period and not increase too much cost under the condition of ensuring the engineering quality. After repeated argumentation, it is decided to adopt technologies such as "asphalt felt laying, drilling grouting, seam clearance grouting", and grouting plate is the main technical measure for reconstruction. At the same time, the anti-reflection crack measures of overlay are considered from two aspects, namely, paving asphalt felt isolation layer and adding structural reinforcement layer to improve the deformation ability of surface layer, enhance the anti-reflection ability of overlay and improve the stress distribution of overlay. The technical scheme of concrete overlay is as follows: on the basis of the original concrete pavement, after treatment,16cm30 concrete surface layer is added, Ф 8 @ 200 steel mesh is added at the center line (ridge) of the original pavement, and two layers of Ф 8 @ 200 steel mesh are also added at the joint between the 3.0m concrete slab and the old pavement.
III. Disposal of Old Cement Concrete Slabs
1, handling principle
The treatment principle is mainly based on deflection value control, and it is necessary to measure the deflection value of the original pavement by carpet and repair it by plate control, as follows:
A. The measured deflection value of the original pavement is between 0 ~ 14, so it will not be treated.
B. The measured deflection value of the original pavement is between 14~40, and drilling and grouting are carried out.
C. if the measured deflection value of the original pavement is greater than 40, it shall be treated as a hollow slab, the whole slab shall be broken, the base course shall be treated, and then the concrete slab shall be poured again.
D. Deflection difference control of the plates on both sides of the joint: namely, load the plate on one side of the joint area and measure the deflection difference on both sides of the joint. For the joint where the deflection of two adjacent plates is greater than or equal to 0.06 mm, cut 50 cm at the full depth on both sides of the joint and treat it as a hollow plate.
2. Processing method
A. For slabs with voids and slabs with longitudinal, transverse and oblique cracks, the old slabs should be broken and transported away, the base should be cleaned, repaired with C 15 concrete, and then C30 concrete should be poured again (if there are loose silt blocks, trenches should be dug until the base is solid).
B. For corner fracture, the joint fracture treatment is as follows: according to a certain length and width (including fracture and fracture range), cut it into a rectangle with a cutting machine, break and remove the debris, and visually inspect the base. If the overall performance of the substrate is poor, dig it down to a level with good integrity, and then treat it according to the method of hollowing out the plate.
C. Treatment of staggered platform between plates: if the staggered platform is less than or equal to 1cm, it may not be treated. When the staggered platform is greater than 1cm, the staggered platform should be cut from 30cm~50cm above one side until it is flush with the edge of the sinker.
3, the old and new pavement isolation layer Settings:
A. clean up the surface impurities on the old pavement;
B. Remove impurities and caulking materials from old pavement joints, and refill the joints with polyurethane.
C, laying a two-felt three-oil isolation layer.
4, drilling grouting treatment
Plates with measured deflection values between 16~40 need to be drilled and grouted, and the specific treatment measures are as follows: each plate should be drilled 40cm away from the plate end. High-pressure jet grouting is adopted, the main grouting material is 425# ordinary portland cement, the water cement ratio is 1:3, the grouting pressure is 0.4MPa, and the grouting is completed when the cement slurry overflows from the borehole.
Fourth, the construction technology
This project is a brand-new attempt. At that time, there was no similar project in this area. Therefore, the determination of this scheme is through repeated argumentation and access to a large number of materials. During the construction, our designers went to the site for treatment and research many times, and strictly required the construction unit to organize the construction according to the design requirements, especially the grouting treatment. Our designers visited the site for many times to supervise grouting and observe the state of the slab after grouting. The supervision unit shall supervise each grouting treatment board on site and make records. After treatment, the deflection value of the plate is obviously improved, and the measured deflection value of more than 80% of the plate is within 20. Slabs whose deflection value does not meet the design standard are grouted twice, and the construction technology is the same. After treatment, the measured deflection values of all plates meet the design requirements. It can be seen that this treatment method has achieved great results.
Five, the construction matters needing attention
A. In this project, before adding concrete surface, the original slab should be cleaned, and the joints of the old pavement should also be cleaned, and polyurethane should be refilled.
B. The setting of two-felt and three-oil isolation layers shall be strictly guaranteed, and the reinforcement with steel mesh shall be carried out in strict accordance with the drawings. In order to effectively prevent reflection cracks, the construction quality must be strictly guaranteed.
C drilling and grouting shall be carried out in strict accordance with the design requirements, and must be handled plate by plate. After processing, the deflection value of the plate should be measured. For plates that do not meet the design requirements, secondary grouting should be carried out until they meet the design requirements.
Conclusion of intransitive verbs
Since the reconstruction project of the middle Yangtze River Road started in May 2005, although the construction period is very urgent (the effective construction period is 6 months), the project content is complex (involving the flood control wall project of the water conservancy department) and there are many construction disturbances (many commercial outlets and many comprehensive pipelines), after the implementation of the concrete pavement scheme, the construction period is effectively shortened, the project cost is reduced and the construction difficulty is reduced. After inspection and evaluation, the project was completed as scheduled (the main project of concrete pavement was completed in that year 10). After two years of engineering use, there are no abnormal conditions such as reflection cracks and uneven settlement on the pavement. Today, the project has been put into use for nearly 6 years. According to the pavement conditions, it is basically used normally, without uneven settlement, broken slab and staggered platform. It can be seen that the transformation method is feasible and successful, and good economic and social benefits have been achieved.
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