Completion time: June to July 1991, July to August 1998

Project Location: Beijing Liulihe Cement Plant, Changping Nankou Fertilizer Plant

Completion unit: Beijing Military Region Engineering Research and Design Institute

Project host and participants: Zuo Binghe, Zheng Jianzhong, Yin Huaitang, Gao Xinyuan, Su Yuqing, Liu Fuzhe, Wei Yanjun

Writers: Yin Huaitang, Zuo Binghe, Zheng Jianzhong

1 Project Overview

1.1 Beijing Liulihe Cement Plant Demolition Project

Beijing Liulihe Cement Plant needs to dismantle the original shaft kiln workshop and supporting buildings according to the needs of the technical renovation project. The total construction area of ​​the complex is 11,633m. The main building (length 81m, width 18.6m, height 27m) double-span four-layer unequal height reinforced concrete frame structure. There are 10 conical reinforced concrete shaft kiln (diameter 5.6m, wall thickness 0.8m) in the main building to form a whole with the main building. The hoisting machine has a length of 9.96m, a width of 8.5m and a height of 27.8m. The reinforced concrete frame structure consists of a flyover (four floors high 27.8m long and 19m long) connected to the main building and connected to the corridor, broken and clinker. Three circular auxiliary silos (diameter 7.4m, height 15m, thickness 0.3m) and a square silo (length 9m, width 8m, height 10m) are connected to each other and are located on the northwest side of the main building. Under the silo is a clinker crushing room (length 20m, width 7.5m). The north side of the main plant is a coal storage (length 42m, width 16m, height 10m). The whole building group is located in the factory production area, the surrounding environment is complex, the east 25m is the new production line kiln tail plant, the 5m is the main water supply pipe; the west 25m is the limestone joint storage; the northwest 18m is the 35kV substation, and the 1.5m is the cable trench South 15m is a cool pool; north 45m is Weinan Highway and high-voltage line (Figure 1).

1.2 Changping Fertilizer Plant Demolition Project

The demolition project of Beijing Changping Fertilizer Plant is a parallel two-seat composite structure shaft kiln, which is a high-temperature furnace for producing lime for chemical fertilizer plants. The kiln body is an upright cylindrical shape with a height of 22.5m and a diameter of 8.Om. A beam is placed every 2m high. The whole is made of steel lining (thickness 20mm), refractory brick (thickness O.37m), and masonry block stone ( Thickness 1.94m), block stone concrete (thickness 1.97m), reinforced concrete (thickness 0.24m), slag insulation layer (thickness 0.76m), vermiculite insulation layer (thickness 0.16m), brick casing (thickness 0.62m), etc. The composition of the kiln body is similar to the grenade shape, which makes the kiln wall into a concave arc shape and wall thickness. The kiln outlet is 2m high from the ground and 1.4m in diameter. The center of the bottom layer is filled with stone. The two kiln bodies are juxtaposed, 5m apart, and the reinforced concrete slabs and roofs are connected by stairwells and penthouses. The top floor is built with various types of rooms (see Figure 2).

Guizhou Runde blasting

　　1.2.1 Structural features

　　(1) The foundation of the kiln is stable, the center of gravity is low, the kiln body is tall and the two blocks are juxtaposed and integrated, and it is not easy to form directional collapse after blasting.

　　(2) The whole is a multi-layer composite type, and there is a space insulation layer with different strengths.

　　(3) The block stone filling structure layer has many pores and irregularities, low utilization rate of explosives and poor blasting effect.

　　1.2.2 ambient environment

　　The 5m east is the south gate chicken farm fence and simple bungalow, which needs protection. The south 9m is a 10kV high-voltage line, or power failure, must be safe. 50m in the west and south is Nanxin Highway, and 50m in the north is the workshop of the factory.

　　2 Blasting design and construction characteristics

　　2.1 Blasting Demolition of Structurally Connected Buildings

　　2.1.1 Segmentation by structure difference

　　Firstly, blasting coal storage, corridors, broken rooms, clinker rooms, flyovers and other peripheral buildings and handover buildings, can not be re-segmented to separate the main plant, the lifting machine room, the auxiliary silo and so on. The bridge was tilted to the north, and other structures were left in place.

　　2.1.2 auxiliary blasting

　　The 10 vertical kiln in the main building are not treated according to the blasting method of the general chimney and water tower. In order to make it burst with the main building, the amount of medicine is not too big. The blasting method is used on both sides of the vertical kiln. Open the hole, increase the empty surface of the inverted part, and reduce the total dose when the main body starts.

　　2.1.3 main body blasting

　　The main body of the building group takes the wrong start-up time and synchronous out-of-direction blasting.

　　(1) The main workshop and 10 vertical kiln simultaneous blasting, in order to prevent the 10 vertical kiln from sitting in the original place to support the main building, affecting the main plant's dumping disintegration, the vertical kiln non-reverse surface does not explode. The vertical kiln's inverted surface adopts a low blasting gap, which simultaneously detonates with the main plant's inverted surface, and uses the main building to form a large overturning moment to drive the vertical kiln to dump.

　　(2) In order to ensure the safety of the workshop substation, and not to stand with the auxiliary silo, the design of the upgraded machine room is tilted to the northeast direction in the diagonal direction.

　　(3) The round and square four-piece conjoined silos containing large and semi-storage raw materials, because of the low center of gravity, are not easy to deviate, it is difficult to dump and disintegrate. In order to prevent the collapse, the 2/3 part is used as the fulcrum to finally blast, forcing it Dumped south.

　　2.1.4 Blasting method

　　(1) The combination of the explosion height difference and the time difference. In order to disintegrate the complex structure building, it must have a certain slump height and slump difference, so that it can generate large overturning moment and landing speed in the expected direction. When dumping, each component will naturally bend and compress and break and break the ground to destroy the disintegration. According to the experience of the actual explosion of a single structure, only the blasting height difference is used to control the dumping, and the recoil distance is large, which directly threatens the safety of the protected object, and it is difficult to control the amount of the blasting dose. If only the detonation time difference is used to control the dumping, the material of the building is unclear, and the time is not accurate. If it is not good, it will fall into a whole. Only by combining the blast height difference and the detonation time difference can the complex fabric be dumped and disintegrated.

　　(2) Combination of large and small doses. In order to make the building directional instability, a large amount of the bottom of the wall column in the collapse direction is required to make the wall column blast, while the upper part is only required to be loose, and a small dose is used.

　　2.2 Composite structure

　　2.2.1 Blasting method

　　A blasting notch is opened in the bottom layer of the composite structure kiln, and the opening is segmented in the cross section, the kiln body is longitudinally sectioned, and the blasting part of the bottom layer is divided, and the thick-walled cylindrical kiln body is divided into three curved supporting blocks to make the whole A gap is formed, causing instability and directed dumping and disintegration.

　　The local longitudinal section is carried out by the north kiln door, and the composite layer of the longitudinal section of the notch support block is drilled, and the base part of the northern half of the outdoor floor is blasted once, which is fully broken and loses the role of supporting the kiln body, resulting in the overall The center of gravity is offset. Under the action of the center of gravity offset torque of the upper part of the kiln body, the inner side of the retained shaft support block is pressed and the outer side is pulled. When the eccentric moment is greater than the bending rigidity of the edge of the kiln support section, all of them lose support. The kiln body collapsed to the north and collapsed.

　　2.2.2 auxiliary construction

　　The kiln can be viewed as a homogeneous cylindrical body that is approximately axisymmetric, as can be seen from the following simple geometric relationships (Figure 3):

Guizhou Runde blasting

　　(1) Divide the circumference of the outer edge of the kiln into three equal parts, so that point C is within the range of the shaft support block, and points A and B are supported by the gap.

　　Within the block range, the three parts A, M, and C have a certain strength, which can support the balance and stability of the cylindrical kiln. The front opening and the symmetrical opening chord length are determined by the chord length of the notch support block. The chord length of the notch support block is determined according to the mechanical construction ability. Considering the 7555 rock drill in the horizontal layer of the kiln composite layer, the depth can be in the range of 2.5 to 3.Om. The minimum resistance line of the drug hole parameter is about 0.7m, and the chord length of the notch support block is 3.2m.

　　(2) Open a front opening of 5m high and 6.1m long to expose the structure of the composite kiln. The symmetry mouth is opened centered on point C, and the shaft support block of 1/3 circumference is reserved. The two symmetrical mouths are 5 m high and the chord length is 6.1 m, so that the single kiln forms a three-legged support structure.

　　3 blasting effect

　　(1) On August 11, 1991, the blasting of buildings connected by structures was carried out. According to the original design plan, the buildings from east to west and from north to south are disintegrated and disintegrated. The whole project uses 3,674 detonators and 247.65 kg of explosives. The factory has not stopped working during the blasting. The cables in the cable trenches at 1m, the 35kV substation and the overhead high-voltage lines are always powered, and everything around them is safe and sound.

　　(2) In August 1998, after the blasting demolition of the composite structure kiln was detonated, the center of gravity of the double kiln shifted to the north, and the whole body naturally fell. Under the action of the overturning moment, the two-seat vertical kiln was tilted downwards, and the gap was along the ground. The blasting dynamic load causes axial and lateral vibration of the kiln body, and the stress in the axial direction changes, causing cracks. As the pouring progresses, the crack expands, the kiln body breaks from bottom to top, and the composite structure collapses and disintegrates. The whole pouring slab and top cover are torn, oriented to the north, and placed at the front of the main slag.