TITLE:
Experimental Study of Dynamic Characteristics on Composite Foundation with CFG Long Pile and Rammed Cement-Soil Short Pile
AUTHORS:
Jihui Ding, Yanliang Cao, Weiyu Wang, Tuo Zhao, Junhui Feng
KEYWORDS:
Blasting Vibration; CFG Pile; Rammed Cement-Soil Pile; Combined Pile Composite Foundation; Dynamic Characteristics
JOURNAL NAME:
Open Journal of Civil Engineering,
Vol.4 No.1,
February
26,
2014
ABSTRACT:
Based on the idea of
optimization design of pile type, the two kinds of the typical pile type are selected,
which containing flexibility pile (e.g. rammed cement-soil pile is for short
RCSP), and rigid pile (e.g. cement-flyash-gravel pile is for
short CFGP). The three kinds of the composite foundation are designed, which
are CFGP, CFG long pile and CFG short pile (for short CFGLP-CFGSP), CFG long-short
pile and rammed cement-soil short pile (for short CFGLP-RCSSP). Natural
earthquake is simulated by using the engineering blasting; the dynamic
characteristics and dynamic response of the composite foundation are studied through field
test. CFGLP-RCSSP is closed to linear relation. The bearing capacity of the
four composite foundation of the CFGP, CFGLP-CFGSP, and CFGLP-RCSSP in the site
are 225 kPa, 179 kPa, and 197 kPa, separately increases
150%, 98.8% and 119% compared to the natural foundation. The vibration main
frequency is mainly depended on properties of foundation soil and piles between
vibration source and measuring point, pilling load value. Horizontal vibration
main frequency greater than the vertical vibration main frequency and the
vertical vibration main frequency close to the first-order natural frequency of
composite foundation. With the pilling load increasing, the CFGLP-RCSSP pile
composite foundation combined frequency decreased. Under the same blast energy,
the acceleration peak on the CFG pile composite foundation is less than
CFGLP-CFGSP the corresponding values, as the load increases, the peak acceleration
gently. CFG pile composite foundation is favorable on seismic. The distribution
of peak acceleration is consistent within 4 m from pile top in the CFGLP_RCSSP composite foundation. The maximum of
the horizontal acceleration peak along the pile body occurs at a distance of
pile top 4 m or the pile top, and
that of vertical acceleration peak occurred at a pile top.