Characteristics Analysis of Load Caused by Punching Pile Construction of Highway Bridge Pile Foundation

Transcription

1 American Journal of Civil ngineering 6; 4(4): 9-97 hp:// doi:.648/j.ajce ISSN: (Prin); ISSN: (Online) Characerisics Analysis of Load Caused by Punching Pile Consrucion of Highway Bridge Pile Foundaion She Yanhua School of Urban Consrucion, Yangze Universiy, Jing Zhou, China mail address: To cie his aricle: She Yanhua. Characerisics Analysis of Load Caused by Punching Pile Consrucion of Highway Bridge Pile Foundaion. American Journal of Civil ngineering. Vol. 4, No. 4, 6, pp doi:.648/j.ajce Received: June 9, 6; Acceped: June, 6; Published: July, 6 Absrac: The characerisics of impac loads caused by punching pile consrucion of highway bridge pile foundaion and he propagaion law of vibraion wave in he soil were researched. Combined wih sie monioring vibraion signal which is generaed by he bridge pile foundaion consrucion of Zhang Shi xpressway across he Shaanxi Beijing pipeline, signal waveforms of he punching pile consrucion and blasing consrucion were analyzed conrasively. I expounded he characerisics of impac loads, and deduced he mahemaical expressions of impac loads. On he basis of he analysis model, hrough he numerical simulaion, he propagaion law of vibraion wave in he soil caused by he impacing poin source exciaion was revealed. Thus, i indicaes ha because of he buried pipeline, he local gradien of vibraion wave velociy field increased in he area beween he vibraion source and he pipeline, bu decreased in he far direcion. Keywords: Punching Pile Consrucion, Impac Loads, Vibraion Wave, Propagaion Law. Inroducion Wih he acceleraion of he naional infrasrucure, dynamic load acing on he buried pipeline is becoming more and more complex, such as rockfall impac loads, raffic loads, consrucion vibraion loads and so on. The consrucion vibraion loads are mainly produced by blasing, dynamic compacion, impac drilling piles and oher consrucion. The scholars have carried ou various researches on he influence of he exernal dynamic loads on he buried pipeline, such as seismic loads [, ], rockfall impac loads [3], piling vibraion loads [4, 5], raffic loads [6] and blas loads [7, 8], and achieved a lo of research resuls. Bu here have fewer sudies on characerisics of impacing load caused by punching pile consrucion of bridge pile foundaion and his mechanical shock load effecing on he adjacen buried pipeline. And i s very imporan o clarify his kind of impac loads aced on he buried pipeline in pracical engineering. Therefore, he characerisics of punching pile consrucion load and vibraion wave propagaion generaed by i have been researched in he paper.. Impac Load Characerisic Analysis.. Impac Load Characerisic In he punching pile consrucion, he hammer drops down from a cerain heigh colliding wih he soil as a greaer impac which is very difference from he vibraion caused by general earhquake or blasing. Selecing a fragmen of he ypical vibraion signal of consrucion of Zhang Jiakou o Shi Jiazhuang (Zhang-Shi) expressway across Shan xi-beijing gas pipeline bridge pile foundaion, he vibraion waveform of punching pile consrucion is shown in Figure, while he Figure shows he curve of maximum vibraion velociy of corresponding punching deph a differen measuring poins. The vibraion waveform of each measuring poin is shown in Figure 3, while Figure 4 and Figure 5 are he ypical signal specrum analysis of he consrucion vibraion and blasing vibraion of he pile foundaion separaely.

2 9 She Yanhua: Characerisics Analysis of Load Caused by Punching Pile Consrucion of Highway Bridge Pile Foundaion (a) Disance of 5m from he source (b) Disance of 7m from he source (b) Disance of 7m from he source (c) Disance of m from he source Figure 3. Wave of blasing vibraion signal. (c) Disance of m from he source Figure. Vibraion vaveform in punching pile consrucion. Figure 4. Specrum analysis of ypical vibraion signal in punching pile consrucion. Figure. The variaion of he maximum vibraion velociy of differen punching deph. (a) Disance of 5m from he source Figure 5. Specrum analysis of ypical vibraion signal of blasing consrucion. Compared wih he analysis and research of he naural and blasing vibraion, he characerisics of he consrucion vibraion of he punching pile are mainly as follows: () I belongs o he insananeous shock ype poin source vibraion, and is acion ime is very shor. As shown in Figure, despie he high ampliude of he vibraion velociy, bu he failure zone is limied due o rapid decay and under he acion of earhquake induced he compared srucure forced vibraion are essenially differen, and he blasing vibraion effec is also of very big difference (shown in

3 American Journal of Civil ngineering 6; 4(4): Figure 3); () Under normal siuaion, he vibraion srengh will decrease wih pile hole deph increase. Bu a large number of experimenal resuls show ha he vibraions are magnified and low frequency vibraion even in he presence of muliple rebound phenomenon, which may relaed o geological facors (shown in Figure ); (3) Field ess illusrae ha he punching pile consrucion vibraion are generally in low-frequency region of 5-5Hz (shown in Figure 4), and he principal frequency is closer o inheren frequency of adjacen srucures compared wih he blasing (shown in Figure 5); (4) The serious harm on adjacen srucures of he cumulaive effec should no be overlooked in he follows as muliple punching, shor inerval, and inensive vibraion period, belonging o he relaively long-erm cyclic loading... Analyical Model of Impac Load Hammer, wih a cerain speed impacing on he soil layer (gravel soil or rock), due o he small relaive siffness of he soil, will rush o a cerain deph of he soil afer a rapid decrease o zero, and ge a smaller rebound generally. This process will have a greaer impac because of he very shor acion ime. The simplified impac physical model is shown in Figure 6, and he hammer wih a cerain mass dropping down from he S sroke acs wih he soil mass. conac par by paraboloid, i can obain he following formula []: M 6 ( ) ρ F =.5 η () ν In he formula (), ρ he densiy of he hammer, he elasic modulus of he soil medium, and ν he poisson's raio of he soil medium. Subsiuing formula () ino he formula (), i ges he following differenial equaion: dη d ( ρ ) η = M ν Among hem, he iniial condiions are: = dη η =, = gs d = The above wo equaions are all nonlinear differenial equaions, and he relaed solving mehods provided by reference [] can be obained he maximum η and he conac ime ν [ ( M ρ ) gs] (3) (4) η = (5) (6).5 =.94(gs) η Subsiuing he formula (5) ino he formula (), he peak impac load F can be calculaed as F =.76( ) M ρ ( gs) ν (7) Figure 6. Physical model of he hammer impac soil layer. The hammer is regarded as a rigid body, which is assumed o be no deformed in he collision wih he soil medium, no considering he graviy effec and he fricion beween he punch and he soil medium. The equaion of moion of he hammer can be lised as [9] dη M d = F In he formula (), M he qualiy of he hammer, η he displacemen of he soil mass which is conaced wih he hammer, he ime of he hammer conacing wih he soil mass, and F he impac force generaed by he hammer conacing wih he soil mass. The relaionship beween he effecive impac force F and he displacemen η is obained by he exising resuls abou he conac problem of elasic heory. Approximaing he () As shown in Figure 7, he riangle load can be used o describe he impac load F approximaely, and is expression is as follow: F ( ) = F ( ) F (8) The dimensionless ime funcion ϕ ( ) is used o express he load characers and he impac load can be expressed for uniy as F( ) Fϕ ( ) = (9)

4 94 She Yanhua: Characerisics Analysis of Load Caused by Punching Pile Consrucion of Highway Bridge Pile Foundaion 3. Numerical Simulaion of he Shock Wave Propagaion Figure 7. Impac Load Curve. For he impac physical model shown in Figure 5, he ANSYS / DYNA LS- finie elemen analysis sofware is used o analyze he propagaion of vibraion waves generaed by shock source exciaion in soil mass. The 5 hammer dropping from he 3m heigh impacs foundaion soil (sand and gravel soil). Soil model akes m long, m wide, and 5m heigh wih homogeneous soil. In he disance m from he soil model cener, here has a seel pipeline wih buried deph of 3m. The calculaion model is shown in Figure 8. The maerial calculaion parameers are shown in Table. Figure 8. Mechanical Calculaion Model (Uni: m). Table. Maerial Parameers and Relaed Calculaion Condiions. Maerial ype Maerial Parameer Boundary Condiion impac hammer soil seel pipe ρ (kg/m 3 ) (GPa) µ 78.3 ρ µ ϕ c (kg/m 3 ) (MPa) (kpa) ρ an µ σ s (kg/m 3 ) (GPa) (GPa) _ exer no reflecion boundary on he lef and righ sides and he boom surface According o he previous analysis, he impac of he hammer on he soil is loaded wih riangular pulse load, wih.8s duraion ime and he maximum load a.4s. The load- ime curve is shown in Figure 9, and he load ime value is shown in Table. _

5 American Journal of Civil ngineering 6; 4(4): Figure 9. Time Hisory Curve of Impac Load. (c).8s Table. Values of Impac Load and Time Array. No. Time (s) Force ( 7 N) The change of vibraion wave propagaion a differen ime can be expressed by animaion, he numerical simulaions of ypical vibraion wave propagaion under differen condiions are shown as in Figure and Figure. (d).s (a).s (e).4s (f).7s (b).5s Figure. The Propagaion of he Shock Wave in he Soil Mass.

6 96 She Yanhua: Characerisics Analysis of Load Caused by Punching Pile Consrucion of Highway Bridge Pile Foundaion (a).s (b).6s As shown in Figure, when =.s, he hammer jus conacing wih he soil, he soil vibraes severely by shock waves. And hen soil paricle vibraion velociy increases gradually; when =.8s, i reaches maximum value, and hen he shock wave aenuaes for he sress wave, wih oval surrounding diffusion in he soil. While he peak velociy begins o decline. I can be seen from Figure, when =.6s, he responden sress wave is a verical incidence o he buried pipeline aack of he laeral vibraion, due o he wave fron in he free surface reflecing he formaion of ensile sress wave, and he oward laeral vibraion velociy relaive o wave fron is grea more han he oher wave array faces; when =.3s, he ouermos layer of wave fron reaches he dorsal laeral vibraion of buried pipeline, hen he sress wave under pipeline diffracs where he speed is relaively slow. A he side of he pipeline, he velociy is sill larger han he behind. When =.34s, he radius of he wave fron is expanding, he back side of he pipeline is coninued o spread, and is velociy is gradually fading. The above analysis shows ha he impac of vibraion wave in soil mass is almos uniform when here is no buried pipeline. The exisence of buried pipeline hinders he wave propagaion which makes he local gradien larger in he vibraing wave velociy field and smaller in far from pipeline direcion. 4. Conclusion (c).3s I has obained he relaionship beween force and displacemen of conac problem, and induced ou he mahemaical expression of he impac load, which can express by riangular load approximaely; he vibraion wave developmen process from shock source cener ouward propagaing reveals he rules of velociy in he soil wih ime. The analysis shows ha exisence of buried pipeline makes he vibraion wave velociy field of he local gradien larger beween he near field source and he pipeline, and smaller in far from pipeline field. Acknowledgemens This work is financially suppored by Naional Naural Science Foundaion of China (NSFC, 54857) & Youh Talen Projec of Yangze Universiy (5cqr6). References [] Zhao Xinwei, Zeng Xiangguo, Yao Anlin. e al., China Peroleum Machinery, vol. 4, 4, pp (d).34s Figure. Influence of he Transmission of Shock Wave o he Buried Pipeline. [] Peng Xingyu, Liang Guangchuan, Zhang Peng. e al., Naural Gas Indusry, vol. 3,, pp [3] Xiong Jian, Deng Qing-lu, Zhang Hong-liang e al., Safey and nvironmenal ngineering, vol., 3, pp. 8-4.

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