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Large diameter pile bridge combination

Categories:Shaft Construction
Time of issue:2022-06-15

(Summary description)Since reform and opening , with the national economy continues to climb, China's highway bridge construction has also been rapid development. Span is getting bigger, the upper structure type mix, and its related infrastructure projects has been little change , the lack of original technology . Bridge engineers generally " under the light back on ."

Large diameter pile bridge combination

Categories:Shaft Construction
Time of issue:2022-06-15 16:16
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( A ) the development of bridge pile combination

1 . Basic objectives

Since reform and opening , with the national economy continues to climb, China's highway bridge construction has also been rapid development. Span is getting bigger, the upper structure type mix, and its related infrastructure projects has been little change , the lack of original technology . Bridge engineers generally " under the light back on ." In order to finish the work often apply design drawings , and even small span rivers are covered with caps . As we all know , pile underwater construction difficulties , not only long duration , high cost, most builders " headache " is often affected by the floods and threats. Therefore, in less than one hundred meters span bridge to achieve "no cap " is the foundation engineer's dream.

2 . Pile diameter new record

Graduate students in my school rock found in the work of teaching and research : the famous "national outstanding contributions to science and technology experts" - Professor Shang Xing early nineties in the last century had made a complete set of " variable cross-section , no caps, combination of large diameter pile technology ", [ Reference 1 ] . He presided over the project, worked in "90m continuous beam ", "2 × 50m cable-stayed bridge ", "2 × 100m Steel Tube Concrete supporting arch ", "120m pushing tied arch " and "4 × 52m stone arch bridge "of a different type of bridge pile foundation design, are to achieve a " no cap . " Have created a Ф6m Shen hollowed heart piles , Ф4m bored piles and Ф5.6m hollow tapered large pile diameter bored piles and other records , the technology level has been ranked the international forefront .

3 . "Combination piles" name

In the " bridge " construction manual defines a diameter greater than 2.5m pile called the large diameter piles . But to achieve one hundred meters span bridge pile foundation without cap, pile diameter to achieve Ф4m, Ф5m, Ф6m, so this article is defined as " large diameter piles ."

Universal Foundation Engineering Handbook often will " sinking ", " digging holes ", " drill " and " precast driven piles " and define the basis for the different types . In order to solve different geological layers encountered difficulties in the construction and implementation of the "no cap " in the bridge foundation projects often are several basic types of the above used in combination , known as the " bridge mix pile ."

Based on the above two aspects , we made these piles is defined as " large diameter pile bridge combination ." In Table 1 lists the combination of domestic than Ф3m piles ( pile diameter to the diameter of the surface of the riverbed prevail ) . In Figure 1, is given on the picture.

This graduate thesis, it Introduction "large diameter pile bridge mix " practical situations , for the younger generation bridge engineers reference, hope in their own further development of engineering practice and innovation.

( Two ) variable cross-section large diameter bored piles

1 . Guangdong Jiujiang Bridge raised

In 1985, the first time the implementation of the Guangdong Jiujiang Bridge " bridge projects ( design and construction ) contractor " tender . Cantonese Hunan Company 2 × 160m single tower cable-stayed bridge and the 21 × 50m bid pushing continuous beam program . In order to reduce construction costs, the cable-stayed main pier foundations abandoned within the double wall steel cofferdam plus bored piles conventional methods , at a depth of 16m boldly launched a new high- pile foundation structure . In order to 2000t boating collision force under the control of the main pier is designed to 24Φ2.5m bored piles, pile length 55 ~ 72m. 50m beam push piers designed to 6Φ1.5m bored piles, pile on the set .

1 ) . Uniform piles produce : 160t vibration hammer with steel casing injections Φ3m buried 14m, 8m considering After scouring the sand still covering layer . If we consider the combined effect of steel casing , then 18 (Φ3/Φ2.5m) piles and piles resist horizontal forces 24Φ2.5m effect equal ; Since rock-socketed pile tip segment because there is no moment only the vertical supporting force , making full use of the pile sharp granite high strength (140MPa) case, but also will Φ2.5m rock-socketed pile diameter is reduced to Φ2m. Thus forming a diameter (Φ3/Φ2.5/Φ2m) of variable cross-section of large diameter bored piles . This new concept based pier foundation engineering decreased six long pile , cost savings of up to 1.2 million yuan ( 85 years price ) .

Tapered design difficulty lies in the "bridge rules" and general " Manual" are no different layers of different pile diameter horizontal force of the force calculation method , which is designed to restrict long steel casing does not truthfully consider the role of reason lies.

Guangdong Jiujiang Bridge Navigable main pier foundation 18 variable cross-section of large diameter piles, through traffic and Design Institute of Hunan , Hunan Road and Bridge a well-designed and well construction company , successfully completed in just five months . Creating a domestic deepwater high pile Pile use steel casings forming uniform piles precedent.

2 ) . No cap plan proposed : Jiujiang Bridge North Shore 6 × 50 +40 = 340m pushing continuous beam in the water there are six piers . Tight schedules in early 1997 , at the initiative of Chief Engineer Shangguan Xing , Guangdong Highway Engineering Institute Guo range will have bearing platform 6Φ1.5m cobalt pile modified to 2 (Φ3/Φ2.5/Φ2m) variable cross-section , no order units, single-row double -post pile pier . With the removal of the cap , bringing great convenience to the construction of Hunan Road and Bridge asked a company just three months , ahead of the completion of 12 pre-flood task tapered piles , which fully demonstrates the superiority of non- bearing platform . This is the first pier 50m single row without pile pile .

2 . Xiangtan Xiangjiang River Bridge Development

The power of new technology is unstoppable. Guangdong Jiujiang Bridge spans 50m without caps uniform piles produce the new structure ,

Pile foundation design to conservative tremendous impact. 88-92 years, more than a dozen bridges in Hunan Province , the construction units are strongly urged to modify the small-diameter pile group without cap uniform piles . Bridge Engineering Without innovation , there is no progress , there is no vitality. Traffic Engineering and Design Institute of Hunan Province Zhao Guoqiang timely Xiangtan Xiangjiang River Bridge piers comprehensive revision of the water 12 is no cap variable cross-section of large diameter piles, bored piles in the development history of China to write a glorious chapter .

Xiangtan Xiangjiang River Bridge spans at 90m , 20m wide bridge in the successful implementation of the single-row tapered bearing platform without large diameter piles (Φ5m/Φ3.5m), Wuhan, China in 1992, the tenth meeting of the bridge by experts reputation as " a milestone in the development of Chinese bored ." In its promotion, Anhui Tongling Yangtze River Bridge in a timely manner to modify the design , but also a record bored pile diameter (Φ4.6/Φ4/Φ2.8m) new record. Due to various reasons , in addition to promotion of Hunan rarely considered outside the domestic steel casing participatory role in the formation of uniform piles . Until 2003 in the " Su- Tong Yangtze River Bridge " 1088m cable-stayed main pier design was officially adopted uniform piles (Φ2.8/Φ2.5m). Why promote innovative technologies belated 18 years worth pondering .

3 . Caisson - Drilling Composite Pile

1 ) Combination : For deep water and rock formations deep long-span bridges can be caisson , digging holes and drilling of several processes such as local conditions combined with each other to create new combinations of engineering bridge pile . For example caisson bigger diameter bored piles casing to achieve no cap, so that not only solve the large-diameter steel casing injections sinking difficulties , but also make heavy use of caisson drilling machine construction platform . When digging holes inside the caisson difficulties could be replaced by drilling and punching , forming caisson - bored composite pile . 2002 , in the cross four aircraft engineers will institute Huang Jianhong 120m in Shaoguan wuliting supporting arch bridge designed tapered main pier pile diameter is (Φ5.6/Φ3.5/Φ3m), the most famous Chinese bored piles ( Figure 2 ) , in turn Xiangtan Bridge 90m record single-row piles pushed 30m.

2 ) Construction : Concrete and steel caisson upper Φ5.6m Department of Law and the island built using the platform sinking . Construction Xeon weathered rock surface ( depth 11m) after the caisson top mounting Φ3.5m impact drilling rigs. Bored piles of rock face to the breeze ( depth 15m), and back to drill (Φ3m), embedded in rock deep 5m, the formation of composite pile .

3 ) Features : Due to the gravel overburden caisson huge anti- push rigidity constrains the horizontal displacement of the pile , so the design boldly between the two horizontal linkages are all canceled , the formation of the new structure of Single Pile single column . In 2004 , it has withstood the test of 100-year flood , unharmed. Such considerations steel casing ( caisson ) combined effect of the large diameter of the pile for the bridge arch and boating collision with piers for the control has a very important meaning, which is worthy of special attention bridge foundation engineers .

( Three ) prestressed hollow bored piles ( pier )

1 . Achievement promotion

A ) reason: Hunan Provincial Communications Department at the Ministry of Communications bear "eight five" industry joint scientific and technological projects - " Bridge Construction in Dongting Lake area of new technology research and development " in the research , because of the Dongting Lake area lake river fork staggered, weak foundation , the lack of gravel materials, difficult road bridge harder . For this feature , the research group in the study Henan Research Institute of Highway Ministry of Roads and " hollow bored piles" of new technologies based on the combination of Hunan No Slab diameter piles characteristics, by optimizing the structure , process improvements proposed more perfect "no cap, prestressed hollow large diameter bored piles " technology. Hunan highway design company has been actively promoting the development identified by the Ministry of bored hollow pile results in just three years to complete the 84 , total length 2293m hollow large diameter bored piles, made to reduce the volume of water 30% significant effect. Which Changde Stone Turtle Bridge 3 × 80m continuous beam alone single column pier foundations implemented diameter bored hollow pile up (Φ5/Φ4m) record for the highest in the world .

2 ) Feature: " No Slab diameter bored piles prestressed hollow " has a novel structure , reasonable force , saving materials and construction to achieve assembly of characteristics . In the one hundred meters across the bridge used to cancel difficult concrete pile cap construction . If further improvements in the East China Sea Bridge and Hangzhou Bay Bridge in the promotion and application of geological conditions , will produce enormous economic benefits.

2 . Construction Technology

" No Slab diameter bored piles prestressed hollow " is a new pile foundation construction technology , which combines the current international and domestic advanced technology and the culmination of the pile . Its characteristics are as follows:

1 ) are buried drilling construction method . Set bored piles and one of the advantages of precast piles , bored piles can effectively prevent the process of hole collapse into a pile of pile mass incidents caused , but also solve the sinking piles or pile Shen did not go deviation is too large mass incidents ;

2 ) the use of prefabricated pile . Vertical section segmented hollow pile fight, segmentation settings prestressed and segmented into the hole into the pile lifting . Because precast piles and drilling operations in parallel , it can achieve factory construction, and is made of high strength concrete pile opened the way ;

3 ) Section pile splicing . Epoxy adhesive seam method , fast , good quality, excellent simplifies joint structure ;

4 ) With the end of the hollow pile . Take full advantage of the buoyancy of water to ease the crane lifting capacity on demand , good applicability in developing countries ;

5 ) Fill stone pile grouting . The slurry under pressure and infiltration of soil compaction , greatly improving the friction piles , pile pile secondary grouting can handle precipitation , but also make the pile of subsoil compaction and reinforcement to get the role of preload , give full play to pile of subsoil reaction force effect.

3 . Push discuss relevant issues

1 ) allow settlement: Large diameter bored hollow pile encountered in the development process heavy resistance. The first is theoretical research can not keep up , quality inspection stations by Chinese standard small -diameter pile ultimate settlement amount δ = 4m, as Φ4 hollow pile settlement allowed to issue a signal to destroy the pile , so that senior leaders fear. Today, the introduction of Germany and the United States Bridge regulations , we finally know the pile and the pile settlement allowed diameter D is proportional ( to 1% D), that Φ4 hollow pile settlement during construction 4m, with Φ1 bored pile settlement with 1cm within the allowable range , an elastic range , not destroyed.

2 ) quality of the accident : Stone Turtle Bridge Design bored hollow pile Total 20 , except 35 # pier continuous mismanagement due to construction

Quality accident occurred three times , the remaining 19 are of good quality . Buried hollow pile drilling accident rate η = 1/20 = 5%, the same as with the bored pile is normal . Ten years on , continuous observation of hollow pile settlement already liquidated . But very few executives to the department, bureau leaders falsely accused Stone Turtle Bridge is just a hollow Φ4m bored piles, the results calculated accident rate is 100%. Regrettably this common-sense errors are not promptly corrected , and finally to " hollow bored piles" flower colorful flower burial technology for a decade.

3 ) 2005 Xi'an Highway University, Dr. Feng Zhongju thesis " of large diameter bored piles prestressed concrete hollow " won the State Ministry of Transportation funding , in the People's Communications Press bridge pile of new technologies monograph published [ Reference 2 ] . Comprehensively and systematically expounded bored hollow pile stress mechanism and pushed the pile strength and bearing capacity calculation methods , in order to promote the development of its theoretical foundation . Technological development course description , a lot of good things is the first innovation after practice theory .

4 ) with Chinese characteristics "no Slab diameter bored piles prestressed hollow " the most prominent advantage is difficult to cancel the construction of the large volume of concrete pile cap size, it has a novel structure, reasonable force to achieve material savings and assembly the characteristics of the construction , very significant economic benefits . Bored hollow pile appeared finally overcome Bored tip cushion layer, and is difficult to control the quality of concrete pillar two major problems . Its emergence and development of bridge foundation engineering major breakthrough.

( Four ) large diameter pile Shen hollowed heart

1 . Generation: In the soft ground of the " Order of the bench without burying large diameter hollow pile " of success, in order to solve the difficulties of Hunan mountain arch foundation , the research group will dig holes two processes caisson and combinations , that " Shen dig hollow pile "a new style . 1995 in Zhangjiajie City Guanyin Bridge (4 × 52m stone plate rib arch ) works in practice to be successful. Specific approach : ① to do with the island built caisson method ( foot blade height 1m, diameter Φ4.5m), then take to do high caisson pier , OD Φ3.5m ( thickness 0.5m); ② Shen underwater excavation downhole 6-8m falls weathered rock surface ; ③ with underwater jet grouting concrete or concrete foot blade closed two processes to achieve sealing purposes ; ④ drained to artificial weathering of rocks in the excavation dug pile Φ2.5m ( depth of 4-6m); ⑤ water will dig holes in concrete piles and caisson foot blade consolidation ; ⑥ not fill within the caisson concrete pier as part of the hollow , so the formation of a " hollowed heart sink piles ( pier ) ." the new structure .

2 . Features: The caisson and dug pile process of combining two traditional method is particularly applicable to the mountains with impermeable clay under sand and gravel formations . It construction speed, but also save a lot of concrete hollow structure volume ; dominated by artificial excavation , no large-scale equipment, so at the local highway projects has important practical significance.

3 . Taoyuan Bridge Development : 1995 Hunan Highway Bridge Design Company promptly created by Shen Yin hollowed heart piles ( pier ) promotion of new technologies in Taoyuan Yuan River Bridge. In the 16 × 54m box arch rib adopted two separate (Φ4.5/Φ2.5m) No caps Shen hollowed heart tapered piles ( pier ) ; in 2 × l00m CFST arch used in two separate (Φ6 / Φ4m) no caps Shen hollowed heart tapered piles ( pier ) . Taoyuan Bridge in the 1000m long bridge across even in 19 Pier 38 separate Shen also started digging pile , just one year ahead of the completion of the entire lower part of the structure, pile drilling program compared with more than 10 million savings million, fully demonstrated with Chinese characteristics, " Shen hollowed heart piles" enormous vitality . Taoyuan Bridge arch to create a one hundred meters without cap a new record.

4 . Promotion: " Shen hollowed heart piles" born to solve the local roads and bridges in the absence of large-scale infrastructure projects underwater drilling equipment difficulties , fill sand and gravel foundation piles of large diameter hollow blank , so spread rapidly . Only in Hunan Province to promote six bridges , totaling 73 length 1051m.

( Five ) combined bridge pile bearing capacity

As we all know , in deep water for pile construction , first applied in the construction of the platform to play steel casing . Before the bridge foundation design are generally not considered construction steel casing the joint action , often by other cross section calculation is actually a waste. Despite the uniform piles already started using some bridge engineering , but in general the relative lack of research on the general theory . Therefore, the level of variable cross-section up pile bearing capacity and settlement determined by allowing theoretical capacity is not only a pile of their own development needs , it is the urgent requirement of engineering .

1 . Vertical bearing capacity

1 ) vertical bearing capacity of the soil pile bearing capacity of the pile , the pile material strength and the upper structure allowed pile Shen

Lowering the amount of three aspects of control . Theoretical study of pile capacity generally have a number of ways , for example: load transfer method , elastic theory method , shear displacement method , finite element method. However, due to many factors bored pile construction that is still not recognized capacity (N) - settlement (S) correlation curve theory calculations . Currently solely on ultimate bearing capacity of pile foundation design in addition to the safety factor to determine the bearing capacity (N) and settlement (S) relationship is still loading test to obtain .

2 ) in 2005 , through more than a decade , Professor Shang Xing bored pile settlement curve for the research work , combined with the Su- Tong Bridge 17 test pile data proposed a " bored pile load settlement curve (σ-y) calculation" [ Document 3,4 ] . Idea is to firmly grasp the characteristics of the three stages of settlement to 30 test piles rich data as the basis , from engineers familiar way to start , summed up a series of concise formula , then the introduction of different experiences sedimentation coefficient of the theoretical calculations very close to the measured value curves , the accuracy can be achieved engineering. The method of characteristics is the first reflection of the horizontal to vertical drilling mud craft bearing capacity.

2 . Horizontal bearing capacity

1 ) When using the bridge program , since the horizontal thrust, must use large diameter bored pile foundation . But after the pile diameter greater than 2.5m , it is difficult through the sand egg cover, so should first consider the use of large diameter caisson to make casings , forming uniform piles . When the caisson through the cover layer after a certain depth , due to the reduction of soil resistance moment but also can reduce the pile diameter , into digging ( drilling, buried ) pile until stratum to bear vertical force . The different processes formed by a combination of tapered bridge pile foundation is safe and economical , but also ease of construction , is worth promoting. However, a variety of different types of non- tapered composite pile caps have encountered a common problem : how to calculate the horizontal force of internal forces . Under the current "bridge rules" and the general pile books are no answers , only existing domestic Codex Manual horizontal bearing capacity of single pile peer -sectional design method .

2 ) Ministry of Industry Joint technology research group ( Hunan ) After detailed investigation that: Transportation Research Institute , Liaoning Province, the original chief engineer Wang Bohui proposed " uniform piles horizontal force computing" approach [ Reference 1 ] , conceptual clarity , formula concise , easy to calculate the microcomputer also experts considered solved . In order to verify the reliability of the method , the research team decided to conduct eight Taoyuan Bridge pile horizontal load test . According to the inverse of m ( ground scale factor ) calculated pile displacements and rotations at the ground and measured values are very close. In addition to pile soil resistance , but also included a variable cross-section at the foundation pile vertical reaction force generated by the bending moment on the pile on the ground against the horizontal displacement at the impact of this more in line with the actual situation . Can be used in combination of large diameter pile bridge set meter .

( Six ) Main references

[ 1 ] Wang Bohui , Shangguan Xing . " Bored Chinese New Development ." People's Communications Press, 1999.8 .

[ 2 ] Feng Zhong home, Shangguan Xing . " Large diameter bored piles prestressed concrete hollow ." People's Communications Press, 2005 .

[ 3 ] Shangguan Xing . " Using Load (N) - sedimentation (S) curve to determine the vertical pile bearing capacity ." National large-caliber works well Nanjing will

Talk anthology , 1999 .

[ 4 ] Xiongguo Hui , Jiang Wei . Bored Pile Curve ( Su Tong Act ) . " 2006 National Bridge Conference Papers

Set . " People's Communications Press, 2006 .

Author : Jiang Wei , East China Jiaotong University Graduate School of Architecture, Civil Engineering

Zip: 330013 Tel: 13755642660.

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