Three thousand drill holes were drilled to reinforce the Yangtze River levees

Five pile drivers erected in the playground, the roar, pile drivers in the playground left a small pile hole. This is no ordinary drill hole, but to open a series of "nutrient conduits" through which mud will be pumped more than 10 meters deep into the Yangtze embankment to "replenish" it and make it more stable.

During the flood season last year, the Yangtze River in our city had a high water level of 9.96 meters, and the Shuren School section of the Yangtze River was in danger. The playground of the Shuren International School of the Affiliated Middle School of Southern Normal School was flooded. After emergency rescue, the Yangtze River levee was safe and in danger. This year, the Shuren school section of the Yangtze River started the reinforcement and elimination project, because of the difficulty of construction, high technical requirements, the project became the city's flood control and elimination of the first project this year. Just after the Spring Festival, the construction site has been in full swing.

The site of the reinforcement and elimination project of the Shuren School section of the Yangtze River is on the west side of the school, and half of the school's playground has now become part of the construction site. Looking down from the levee, there was a lot of mud on the playground, which had been drilled, and around each pile driver several workers were working nervously. On the levee, a high-pressure rotary jet machine, about six stories high, is in operation.

Reporters noted that each hole drilled was not large, only more than 10 centimeters in diameter, but deep. Project manager Ye Xuangui explained that this section of the Yangtze River dike used a different technology, the use of high-pressure jet grouting pile technology, through a dense hole, a certain proportion of mixed mud into the ground for reinforcement, only half of the playground and the embankment, 3,000 holes drilled. "Each hole has to be filled three times to make sure all the loose Spaces in the ground are filled." Ye Xuangui said.

This section of the Yangtze River is only 500 meters long, but its reinforcement project is the city's most difficult project this year, because the construction site underground is the Yangtze River tunnel. "The distance between the Yangtze River tunnel and the ground is about 15 to 18 meters. To strengthen the dike, we need to drill holes. If the depth of the holes is too shallow, they cannot strengthen the dike. Qian Haifeng, chief of the Yangtze River Management Department, said that this is No. 1 project is not too much, the past Yangtze River local reinforcement projects are located in non-built-up areas, the site construction conditions are better, and this section of the ground there are schools, underground Yangtze River tunnel, coupled with very complex geological conditions, the construction difficulty beyond imagination.

In order to determine the construction plan, the city invited experts in the field of water conservancy and transportation to discuss, and finally determined the construction plan is: the bottom of the levee through high pressure rotary spraying, pouring two pile walls, forming two anti-seepage walls, play a double reinforcement role; Under the playground of Shuren School, due to its proximity to the Yangtze River tunnel, the depth of the borehole is 12 meters, the hole spacing is encrypted, and mud is injected to fill and reinforce the underground.

On January 17, the project officially started. Before the full start of construction, the construction unit carried out repeated tests. "In addition to the depth test, the most important test is the pressure test." Ye Xuangui said that if the grouting pressure is too large, it will cause the levee and surrounding buildings to shift and deformation, affecting safety, which is absolutely not allowed to happen. To this end, the construction side invited a third party testing institution. The levee and surrounding buildings are monitored continuously every day during construction, except during the trial phase.

"Levees and buildings can't be deformed, to what extent?" The reporter asked.

"Never more than 4mm!" Ye Xuangui said.

Water conservancy elimination project must be completed before the flood season, the construction period is very tight, during the Chinese New Year, the site is not completely shut down. On February 2, while most units were still on holiday, the site was fully reopened. "The temperature was low a few days ago, and thick ice formed in the borehole every day. Workers used light bulbs to bake the ice and melt it before construction." "Said a worker at the site. In addition to the construction difficulty, high technical requirements, environmental conditions also put forward higher requirements for the project, noise, dust must be reduced to a minimum.

City Yangtze River management Office, the significance of this project is also for the city in the complex geological conditions and construction conditions to strengthen the Yangtze River embankments to provide experience.

Source: A1, Nanjing Daily, February 16, 2017