Beijing urban construction north company overcomes the hidden problem of the project and builds a resettlement house on the top of the karst cave

Beside the stone flower cave in Fangshan in winter, the branches trembled with the cold wind. In the cold environment, a group of builders from urban construction north company are working enthusiastically here.

They are responsible for the construction of the shed reconstruction and resettlement housing project in Hebei town, Fangshan District. It is the first shantytown reconstruction project in Beijing to adopt PPP mode. As one of the key points in the transformation of shantytowns in Beijing, the project is a new attempt for the joint operation of government and private capital.

1896 resettlement houses to solve the housing problems of 4 villages

The project of replacing shed with resettlement house in Hebei town, Fangshan District is located on the highland of the former No. 1 cement plant of Shuangshan cement group in Banbidian village, Hebei town, Fangshan District, covering an area of about 100 mu, with a total construction area of about 198000 square meters. It is divided into two bid sections. The first bid section consists of 12 single buildings such as 1#-7# residential buildings and 26# underground garages, with a construction area of about 93000 square meters; Bid section II consists of 17 single buildings, including 8#- 16# residential buildings and 27# underground garages, with a construction area of about 105000 square meters.

"The project mainly faces the villagers of the four natural villages of Banbidian, Wanfo hall, cijiawu and Huangtupo nearby. There are 1869 houses in total, with an area ranging from 30 square meters to 125 square meters." Project executive manager Liang Fei said.

The karst cave is filled with concrete to support the building

For the residential construction itself, the project is not too difficult. The difficulty of this project lies in the invisible place.

The project is less than 1km away from Fangshan Shihua Cave Scenic Spot, and all houses are built on the hillside. "This shows that our engineering foundation construction is likely to face the problem of karst cave." Liang Fei said.

People who have been to Shihua Cave know that the karst cave is a cave hidden in the mountains, in which the huge stalactites and stalagmites have magnificent scenery, but for construction, one karst cave is a fatal problem.

The initial geological survey report of the project shows that there are only karst caves in building 6 underground. However, after the excavation of the project, the project team found that there are a number of karst caves scattered here.

"The caves are as small as tens of cubic meters and as large as thousands of cubic meters. There are such caves under four or five buildings." Liang Fei said.

In the face of such a dense karst cave, the project technical team began to study countermeasures and transfer the location of the building number. Obviously, the geological conditions in the mountainous area and the construction area of the site are not allowed, that is, the building number can only be built on the karst cave. How to solve the problem of stress safety?

Liang Fei said that at that time, the team finally decided to use the pouring method, which is to fill the cave with the same amount of concrete according to the size of the cave. "This method is the most economical and can also improve the construction efficiency. Finally, we filled about 10000 cubic meters of concrete." Liang Fei said.

10000 cubic meters! What is this concept? The project has a total of 16 residential buildings, each of which is more than ten stories high, and the concrete consumption of one house is less than 5000 cubic meters. The concrete filled in the karst cave is enough to cover two houses, which can be seen from the large amount of earth and rock filled.

Blasting hard stone by freezing expansion method

In addition to the caves in the mountains, another problem is a special kind of stone. Due to the mountain breaking operation of the project, from the perspective of environmental protection and safety, the project does not use explosives, but uses a gun hammer to smash the mountain bit by bit. Ordinary limestone mountains are easy to break, but just in the middle of the construction, Liang Fei found that there are special snow-white and fat like rock layers exposed in the green gray limestone mountains. The broken materials of this rock layer are powdery, and the overall stone seems relatively loose, but it can be easily broken. The gun hammer of the limestone mountains can't attack it for a long time.

"At that time, when the gun hammer hit a position more than ten times, it hit some white powder without even cracks." Liang Fei said. If such high-strength rock mass is not broken, the project cannot be promoted.

After the research of the project technical team, it is decided to adopt a freezing crushing method, and several half meter long cylindrical steel pipes are the implementation equipment of this method. Liang Fei said: "this process uses liquid nitrogen to rapidly freeze in the steel pipe, then insert one steel pipe into the mountain with holes drilled in advance, drive the steel pipe to bear force through the expansion of liquid nitrogen, split the mountain, and then peel it off at one time with crushing equipment. This method has a good effect, and the challenge of rock formation has been solved at present."

Realizing intelligent management by informatization

In the face of many construction difficulties, the management of the project department makes full use of informatization to realize the constant monitoring of project management. There is a two-dimensional code on the business cards of the employees of the project department. After scanning the code and paying attention, you can not only see the company profile, project profile, team building, civilized construction and other contents, but also the leaders' care, image progress, leaders' visits and other news are updated in real time. The safety and civilized construction, quality, progress and other information are updated weekly, with pictures and texts. You only need a business card to know all the developments of the project without going to the site in person. "Our construction site is the focus of attention, and there are at least two or three inspections every week. This card not only publicizes the company, but also allows the superior and company leaders to know the project situation at any time". The relevant person in charge said.

"Ding Dong", just as he was saying, Liang Fei's mobile phone gave a prompt sound, "the project department has issued a new notice again". Liang Fei took out his mobile phone and said that this is our own office platform, called "pocket assistant". It is reported that the project department has adopted a third-party free app to improve communication and work efficiency. On this app, the project department has realized various functions such as attendance, approval, notification and communication. More importantly, through this software, it has realized a clear division of labor of various work. The responsible person, auxiliary person and completion time are clear at a glance. You can also discuss technical problems in real time. Through the work report function, each employee can write down the daily work report, work content, experience, harvest, difficulties and suggestions of the day, which can be uploaded and submitted in the form of text and pictures, so as to facilitate the project leadership team to find problems and deficiencies in work in time and adjust work thinking.