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［ 10］ CHIEW Y M . Mechanics of riprap failure at bridge piers［J］. J . Hydraul . Eng . ，1995，121（9）：635-643 .
［ 11］ CHIEW Y M，LIM F H . Failure behavior of riprap layer at bridge piers under live-bed conditions［J］. J . Hy⁃
draul . Eng . ，2000，126（1）：43-55 .
［ 12］ BREUSERS H N C，NICOLLET G，SHEN H W . Local scour around cylindrical piers［J］. J . Hydraul . Res . ，
1977，15（3）：211-252 .
［ 13］ LAUCHLAN C S，MELVILLE B W . Riprap protection at bridge piers［J］. J . Hydraul . Eng . ，2001，127（5）：
412-418 .
［ 14］ SIMARRO G，CHRETIES C，TEIXEIRA L . Riprap sizing for pile groups［J］. J . Hydraul . Eng . ，2011，137
（12）：1676-1679 .
［ 15］ POSEY C J . Tests of scour protection for bridge piers［J］. J . Hydraul . Eng . ，1974，100（12）：1773-1783 .
［ 16］ UNGER J，HAGER W H . Riprap failure at circular bridge piers［J］. J . Hydraul . Eng . ，2006，132（4）：
354-362 .
［ 17］ CHIEW Y M . Local scour and riprap stability at bridge piers in a degrading channel［J］. J . Hydraul . Eng . ，
2004，130（3）：218-226 .
［ 18］ ASHTIANI B A，BEHESHTI A A . Experimental investigation of clear-water local scour at pile groups［J］. J . Hy⁃
draul . Eng . ，2006，132（10）：1100-1104 .
［ 19］ MELVILLE B W，CHIEW Y M . Time scale for local scour at bridge piers［J］. J . Hydraul . Eng . ，1999，125
（1）：59-65 .
［ 20］ AMINI A，MELVILLE，B W，ALI T M，et al . Clear water local scour around pile groups in shallow-water flow
［J］. J . Hydraul . Eng . ，2012，138（3）：177-185 .
［ 21］ LANCA R，FAEL C，MAIA R，et al . Clear-water scour at pile groups［J］. J . Hydraul . Eng . ，2013，139（10）：
1089-1098 .

Scour at pile groups and effects of riprap gradation
and thickness on the scour reduction

1 2 1
QI Meilan ，ZHOU Masheng ，TANG Gaichun
（1. Scholl of Civil Engineering，Beijing Jiaotong University，Beijing 100044，China；
2. China Road and Bridge Corporation，Beijing 100011，China）

Abstract： Local scouring inevitably follows at underwater pile groups， which reduces the buried depth of
the pile foundation and affects the safety of the upper structure. Therefore， the preventing scour measures
for pile groups are worth studying. This work focused on the variation of scour at pile groups in the square
array with spacing of piles，as well as the impact of particles grading and thickness of riprap layer on the
effect of erosion reduction. Laboratory flume experiments were conducted and the observation data were ana⁃
lyzed. The study found that increasing the spacing between piles the local scour depth at pile groups can
be reduced in a limited range. A maximum spacing of which is related with pile Froude number appears
when the equilibrium scour depth can be reduced by 50% ~60% compared with zero spacing of four piles.
During the first 30% of the scouring process，the scour rate is about 30%~50% of less than that at a sin⁃
gle pile. The maximum equilibrium scour depth is located in front of the front row of piles. Riprap com⁃
posed of non-uniform particles with smaller riprap thicknesses can achieve better prevention efficiency than
that of uniform ripraps. An optimal riprap gradation and riprap thickness are impacted by multi-factors，
such as hydrodynamic force，pile diameter，bed sand，and so on，which is worth studying further to meet
the demands of design countermeasure of scour reduction.
Keywords：pile group；scour；riprap gradation；riprap thickness；protection efficiency

（责任编辑：李福田）

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