Beijing Urban Construction North Company Overcame the Invisible Problem of the Project to Build a Housing on Top of the Karst Cave

Source: Capital Construction News Author: Yan Qiangshi Furui Time: December 04, 2017

Next to the stone flower cave in Fangshan in winter, the branches trembled with the cold wind. In the chilly environment, a group of builders from Urban Construction North Company are working here in full swing.

They are responsible for the construction of the shantytown resettlement housing project in Hebei Town, Fangshan District, which is the first shantytown renovation project in Beijing that uses the PPP model. As one of the key points of the transformation of shanty towns in Beijing, the project is a new attempt by the government and private capital.

1896 sets of resettlement houses to solve the living problems of 4 villages

The Penggai resettlement housing project in Hebei Town, Fangshan District is located on the highland of the former site of the first cement plant of Shuangshan cement Group in Banbidian Village, Hebei Town, Fangshan District, covering an area of about 100 mu and a total construction area of about 198000 square meters. it is divided into two sections, the first section is 12 units such as 1-7 residential building and 26 underground garage, with a construction area of about 93000 square meters; the second bid section is 17 units such as 8#-16# residential building and 27# underground garage, with a construction area of about 105000 square meters.

"The project is mainly aimed at villagers in the four natural villages of Banbidian, Wanfotang, Cijia and Huangtupo. There are 1869 houses with an area ranging from 30 square meters to 125 square meters." Project execution manager Liang Fei said.

Cave filled with concrete to support the building

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

The project is located less than 1km away from Fangshan Shihua Cave Scenic Area, and all residential buildings are built halfway up the mountain. "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 karst caves are caves hidden in the mountains. The huge stalactites and stalagmites in them are magnificent, but for construction, each karst cave is a fatal problem.

The initial geological survey report of the project showed that only building 6 had karst caves in the underground part, but after the excavation of the project, the project team found that there were several karst caves scattered here.

"Karst caves are as small as dozens of cubic meters and as large as thousands of cubic meters. There are such caves under four or five building numbers." Liang Fei said.

Faced with 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 on site are not allowed, that is to say, the building number can only be built on the karst cave. How can the problem of stress safety be solved?

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. In the end, 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 with more than a dozen stories high, and the amount of concrete used in a residential building is less than 5000 cubic meters, and the concrete filled in the cave is enough to build two residential buildings, and the amount of earth and stone filled in can be seen.

Crushing Hard Rock by Freezing Expansion

In addition to the cave in the mountains, another problem is a special kind of stone. Because the project is to break the mountain, but from the perspective of environmental protection and safety, the project did not use explosives, but smashed the mountain with a gun hammer. Ordinary limestone mountain is easy to break, but in the middle of the construction, Liang Fei found that the green gray limestone mountain exposed a special rock layer as white as coagulated grease, the debris of this rock layer is in powder form, the overall stone seems to be relatively loose, but can easily chop up limestone mountain hammer competition for a long time to attack it.

"At that time, when the cannon hammer hit a position more than ten times, it hit a little white powder and there was no crack." Liang Fei said. Such a high-strength rock mass is not broken, the project can not be promoted.

After the project technical team research, decided to adopt a frozen crushing method, a few half meters long cylindrical steel pipe is the implementation of this method equipment. Liang Fei said: "This process uses liquid nitrogen to rapidly freeze the steel pipe, then inserts the steel pipe into the mountain with holes punted in advance, drives the steel pipe to be forced to crack the mountain through the expansion of liquid nitrogen, and then peels off the mountain with crushing equipment at one time. This method has a good effect. At present, the challenge of rock formation has been solved."

Information to achieve intelligent management

In the face of many construction difficulties, the management of the project department makes full use of information technology to achieve constant monitoring of project management. There is a two-dimensional code on the business card of the staff of the project department. after scanning the code, you can not only see the company profile, project profile, team building, civilized construction and other contents, but also the leadership care, image progress and other news. the news such as the leadership visit is updated in real time. the safe and civilized construction, quality and progress are updated weekly with pictures and texts, which are very rich. All you need is a business card and you don't have to be there to know all the dynamics of the project. "Our construction site is the focus of attention. There are at least two or three inspections a week. This card not only promotes the company, but also allows superiors and company leaders to keep abreast of the project". The relevant person in charge said.

"Ding Dong", just then, Liang Fei's mobile phone issued a prompt tone, "the project department has issued a new notice", Liang Fei took out his mobile phone and said, this is our own office platform, the name is "pocket assistant". According to reports, in order to improve communication and work efficiency, the project department has adopted a third-party free APP. On this APP, the project department has realized various functions such as attendance, approval, notification, communication, etc. More importantly, through the software, a clear division of labor has been realized for various tasks. The responsible person, auxiliary person and completion time are clear at a glance. You can also discuss technical issues in real time on it. Through the work report function, each employee can write down the daily work report, work content, experience, difficulties and suggestions of the day, etc., which can be uploaded and submitted in the form of words and pictures, so as to facilitate the project leadership to find problems and deficiencies in the work in time and adjust the working ideas.