New construction techniques of ground and foundation engineering
With uninterrupted development of building ground treatment techniques in China, our county assumes multiple key scientific and technological projects for building ground treatment, and successfully applied multiple new construction techniques for ground treatment during port engineering, road and bridge engineering, housing construction engineering, airport engineering as well as ground and foundation engineering.
In the mid 1980s, foundation reinforcement technique with vacuum preloading method developed with direct participation of our company was successfully applied during project implementation of Tianjin Port for the first time. It is at the international leading position, and wins the national patent, the first prize in major scientific and technological achievements of the Ministry of Transport and the award of national "sixth five-year plan" key scientific and technological project. The company also applies two patents of floating box type pile driver and spile machine hanging pile shoe device. The ground treatment reinforcement method has been widely applied at present. The cumulative area of ground treatment construction with the vacuum preloading method applied by our company has been over 28,000,000m2.
In the composite ground treatment techniques, our company has been engaged in scientific and technological innovation activities, and successfully applied multiple new techniques for composite ground treatment, such as: vibroflotation method, sand-gravel pile method, CFG pile method, cement deep mixing method, soil-lime compaction pile method, high pressure jet grouting method and so on. The cumulative total area of composite ground treatment exceeds 3,000,000m2.
In addition, our company also has uncommon performance in the fields of pile foundation, deep foundation pit support and so on. Especially, the construction technology of deep foundation pit support of the wagon tippler shed and corridor engineering is at the national leading position.
The following is detailed introduction of scientific and technological achievements of our company in the field of foundation construction.
1After technology accumulation and improvement for many years, the gas-water separation fourth-generation split-type vacuum jet device is widely used at present. Compared with the third generation, the fourth generation has large improvement in the pump efficiency and pump box structure. However, 7.5kw two-stage pump is still used for pump selection, and there is no large improvement at the jet gun, nozzle and other key positions.
For this reason, we assume to adopt the jet pump with low power in Lot I of Phase III ground treatment of Tianjin north harbor basin, and conduct technical transformation in the ejector, nozzle, connecting pipe caliber size, gate valve, butterfly valve and other components, finally reaching the purpose of saving power consumption by over 40%.
。As per the achievement, we apply the patent of "energy-saving split-type vacuum preloading jet device" with patent number: 200920220845.6. It was authorized in July 2010.
2 Sand ditch is the new construction technique applicable for soft ground reinforcement of the hydraulic fill sand soil. After the drainage board is driven, excavate the sand ditch, arrange the filter tube, and pave the sand cushion for soft ground reinforcement at the position of the drainage board. Plenty of water will be discharged during driving of the drainage board, and drainage shall be conducted firstly. Excavate the main drainage ditch surrounding the construction area, excavate the small drainage ditch about 30cm in the area, and connect it with the main drainage ditch. Guarantee that the water level in the area is below the ground, so as to guarantee normal construction of the sand ditch.
The sand ditch shall be excavated at the position of the drainage board after the drainage board is driven, the spacing shall be the same with the drainage board, and each drainage board shall be arranged in the sand ditch, so as to facilitate subsequent embedding of the filter tube.
Laying of the sand cushion with the sand ditch method is only applicable for hydraulic fill sand soil and other geologies.
According to soft ground reinforcement engineering of construction project Phase I of Bluestar Tianjin Chemical Industry Base constructed by our company, the sand ditch method is adopted for construction to reduce the construction cost and save the medium coarse sand cushion by about 61% and expense by about 51%.
As per the achievement, we declare the invention patent: "construction method with net drainage cushion substituting the full-spread sand cushion" with patent number: 200910070562.2. It was authorized in January 2011.
3.Soft ground reinforcement technique with high vacuum dewatering
Soft ground reinforcement technique with high vacuum dewatering is to install the longitudinal and horizontal drainage channels in the soft soil body, utilize the negative pressure effects of the high vacuum pump to remove partial water content in the soil and re-arrange the soil particles, and accelerate soil consolidation through the externally applied load, such as vibroflotation, dynamic compaction and other methods. The process is applicable for large-area reinforcement treatment of the silty soil, sandy soil and other soil with large permeability coefficients.
It is widely applied in ground treatment engineering of the east-west taxiway link of expansion project of Shanghai Pudong International Airport, ground treatment engineering of third runway of expansion project of Shanghai Pudong International Airport, ground treatment and drainage engineering of west runway system and airside apron of expansion project of Shanghai Hongqiao Airport.
4 New construction techniques of pile foundation engineering
1）Application of the post grouting bored pile
In order to eliminate influence of mud during drilling, improve boundary conditions of the pile, substantially improve the bearing capacity of the single pile, and reduce pile foundation settlement, "post grouting technique" of the bored pile is a better method. The bearing capacity of the single pile can be substantially improved through post grouting of bored pile. Therefore, the investment can be saved by reducing pile layout and shortening pile length or pile diameter in design.
The construction technology of post grouting bored pile is successfully applied in the engineering of business building of 24 Company of Tianjin Port and First Harbor buildings. Without increasing the pile length or pile diameter, it improves the bearing capacity of the single pile by 30 to 60%, reduces the engineering settlement, and reduces the pile foundation construction cost.
2）Application of casing oscillator in pore forming of of riprap mound cast-in-place pile at the dock
Dumping fill of prism stone, two-piece stone backfill and construction of the mixture inverted filter shall be conducted behind Bayuquan Ansteel dock project, and cast-in-place pile construction shall be conducted after certain onshore construction conditions are formed. Considering influence on pore forming quality of thickness and porosity of two-piece stone backfill layer, backfill, head difference and so on, the buried depth of the bushing must exceed the two-piece stone backfill layer. The previous punching drill rig is adopted for construction at the initial stage of commencement. However, it is found through pile testing that the friction force between the mixed slag of two-piece stone is small nd compaction degree is small. Hole collapse is easily caused with the process, and the construction speed is slow, which cannot satisfy demands for construction period.
We decide to introduce the domestic advanced casing oscillator for construction through research and discussion. The casing with diameter of 1.2m and casing bit shall be repeatedly rubbed section by section in small angle and pressed into the stratum with the casing oscillator. The percussion bit, punching grab and other rock drilling apparatus shall be utilized to punch and grab soil in the casing out of the ground. Casing driving and grabbing shall be conducted alternatively, the internal bushing with diameter of 1.1m shall be buried after the two-piece stone layer is penetrated, and the bushing is 15m long. The previous construction process is adopted for subsequent construction afterwards. The process greatly improves the construction speed of the cast-in-place pile, lowers the cost, and guarantees construction quality of the cast-in-place pile.
3）Application of connective cast-in-place pile in foundation pit support
The connective cast-in-place pile is a kind of new support structure between the diaphragm wall and the cast-in-place pile. The principle is to adopt the inter-pile broaching device between piles to make the inter-pile section with thickness of 400mm based on construction of the tangent cast-in-place pile, which can satisfy the foundation pit support and waterproof use requirements. The slot section is taken as the construction unit during connective pile construction, and 5 to 8 piles are taken as a slot section generally. The common drilling machine is adopted for pore forming and synchronous broaching. After pore forming, adopt the pneumatic lift method for hole cleaning, and then conduct concrete pouring construction with the slot section as the unit.
Our company adopts the new technology of connective cast-in-place pile support in the foundation pit support of Binhai New Town Development Engineering of citizen square. The anti-bending and waterproof effects are verified after excavation of the deep foundation pit. The design requirements are satisfied, and there is no collapse or big hole water seepage. The effects are affirmed by the owner and the main construction unit.
5 Deep foundation pit support technique
1）Application of deep foundation pit support technique of underground diaphragm wall
The underground diaphragm wall foundation pit support technique and underground diaphragm wall combined with in-concrete foundation pit support technique are mostly adopted in the wagon tippler shed and other engineering undertaken by the company. The maximum depth of the foundation pit is 18m.
2）Application of soil nailing wall and soil nailing anchor bolt technique in water intake of Capital Steel at Caofeidian and foundation pit support of China Resources power plant project
In the water intake engineering of Caofeidian Capital Steel and intake engineering of China Resources power plant, we successfully applied the construction technique of soil nailing wall and soil nailing anchor bolt foundation pit support in combination with actual geological conditions of Caofeidian. The support depth reaches the record of deepest 18m.
Construction of building diaphragm wall of Shenhua Southern Headquarter
Construction of building diaphragm wall of Shenhua Southern Headquarter
7 Complete construction technique of the wagon tippler shed
Our company has undertaken 9 wagon tippler shed engineering up to now, and a set of perfect construction technique is formed during construction, mainly including:
1）Deep well dewatering of the wagon tippler shed and corridor
2）Deep foundation pit support and excavation of the wagon tippler shed
3）Concrete pouring construction technique of the wagon tippler shed
4）Mass concrete anti-seepage and anti-crack construction technique of the wagon tippler shed and corridor
5）Water stop and anti-seepage of engineering node of the wagon tippler shed and corridor
6）Template construction technique of the wagon tippler shed
Huanghua Port Phase III wagon
tippler shed engineering
Contact
Address：Airport Construction Engineering Co.,Ltd
Tel：022-66708712
Fax：022-66708713
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