Pile foundations are an integral part of many civil engineering structures. The seismic behavior of pile foundations is a very complex problem with interactions between soils (solid skeleton, pore water, and pore air), piles, and superstructure. This... (more)

Pile foundations are an integral part of many civil engineering structures. The seismic behavior of pile foundations is a very complex problem with interactions between soils (solid skeleton, pore water, and pore air), piles, and superstructure. This complexity is further exacerbated when weak soils such as soft clays and liquefiable loose sands surround the pile foundation. The behavior of pile foundations in liquefiable sands has been studied extensively; however, similar investigations for soft clays or seismic response of piles in improved soils have been rarely performed. The current seismic design practice calls for avoiding inelastic behavior of pile foundations by restricting their lateral displacements because it is difficult to detect damage to foundations following an earthquake. Limiting the lateral displacement of a pile foundation is relatively easy to achieve in competent soils. In the case of weak soils, the current practice is to use an increased number of more ductile, larger diameter piles that are difficult to design and expensive to construct. An innovative, and perhaps more cost-effective, solution to this problem is to improve the soil surrounding the pile foundation. For structures undergoing seismic retrofit with existing pile foundations in weak soils, in certain instances, improving the soils may be the only option to improve the seismic behavior of the foundation. This technique is not widely used in seismic regions due to lack of fundamental understanding of the behavior of improved and unimproved soils and the interactions between them as well as with the piles during earthquakes. As a first step in a long term objective of understanding and improving the seismic behavior of pile foundations in all weak soils, the proposed research will focus on soft clays. Soft clays are quite prevalent in earthquake prone areas of the U.S., but have received little attention from the research community.

Following are some of the unanswered research questions that have to be addressed before ground improvement can be used as a viable option to enhance the seismic response of pile foundations in soft clays in routine design practice: (1) What are the effective techniques for improving soft clays around pile foundations for both seismic design and retrofit? (2) How can we analyze, simulate, and design pile foundations in soft clays with ground improvement for earthquake loads? (3) How do individual piles and pile groups, with and without ground improvement, behave during seismic events and how can we validate our analysis and simulation tools and designs? And (4) how can we translate our understanding into a useful design methodology to benefit the broader earthquake engineering community?

The intellectual merit of this work is that the above mentioned research questions will be systematically addressed using a multidisciplinary team consisting of structural and geotechnical engineers and industrial partners who have extensive experience in ground improvement techniques and seismic design of pile foundations. Innovative centrifuge and full-scale field tests using NEES facilities and equipment, simplified analysis methods, and sophisticated fully coupled simulation techniques will be utilized to understand and improve the seismic behavior of pile foundations in soft clays. The research results will be translated into a useful design methodology and tools that will benefit the entire earthquake engineering community immediately as well as influence the long term practices. Simple analysis methods will serve the immediate needs of the industry while sophisticated simulation techniques are expected to show the limitations of the simple analysis methods and impact the long term industry practices. (hide)

Equipment	Component	Equipment Class	Facility
Data Acquisition Infrastructure	All DAQ Systems Combined	DAQ Infrastructure	University of California, Davis
Data Acquisition Infrastructure	RESDAQ-Main Data Acquisition System	Other Utilities	University of California, Davis
Data Acquisition Infrastructure	VIDDAQ - multi-camera high speed video DAQ	Other Utilities	University of California, Davis
Data Acquisition Infrastructure	WIDAQ - Wireless Sensor Manager Data Acquisition System	Other Utilities	University of California, Davis
Data Acquisition Infrastructure	data viewer	Other Utilities	University of California, Davis
Geotechnical Centrifuge	Geotechnical Centrifuge	Geotechnical Centrifuge System	University of California, Davis
Horizontal Shaking Table	Soil Container FSB1	Soil Container	University of California, Davis
Hydraulic Power Infrastructure	Auxialiary Hydraulic Power Supply	Hydraulic Power Infrastructure	University of California, Davis
LAN Infrastructure	All LAN Infrastructure	LAN Infrastructure	University of California, Davis
NI DAQ	NI SCXI-1520 101	DAQ Infrastructure	University of California, Los Angeles
NI DAQ	NI SCXI-1520 102	DAQ Infrastructure	University of California, Los Angeles
NI DAQ	NI SCXI-1520 104	DAQ Infrastructure	University of California, Los Angeles
NI DAQ	NI SCXI-1520 201	DAQ Infrastructure	University of California, Los Angeles
NI DAQ	NI SCXI-1520 202	DAQ Infrastructure	University of California, Los Angeles
NI DAQ	NI SCXI-1520 203	DAQ Infrastructure	University of California, Los Angeles
NI DAQ	NI SCXI-1520 301	DAQ Infrastructure	University of California, Los Angeles
NI DAQ	NI SCXI-1520 302	DAQ Infrastructure	University of California, Los Angeles
NI DAQ	NI SCXI-1520 303	DAQ Infrastructure	University of California, Los Angeles
Q330	277	DAQ Infrastructure	University of California, Los Angeles
Q330	290	DAQ Infrastructure	University of California, Los Angeles
Q330	291	DAQ Infrastructure	University of California, Los Angeles
Q330	293	DAQ Infrastructure	University of California, Los Angeles
Q330	297	DAQ Infrastructure	University of California, Los Angeles
Q330	404	DAQ Infrastructure	University of California, Los Angeles
Q330	405	DAQ Infrastructure	University of California, Los Angeles
Telepresence Equipment	Video Server 2400 (private viewing)	Video Server	University of California, Davis
Telepresence Equipment	Video Server 2400 (public viewing)	Video Server	University of California, Davis
Telepresence Equipment	Video Server 2401 (private viewing)	Video Server	University of California, Davis
Telepresence Equipment	Video Server 2401 (public viewing)	Video Server	University of California, Davis
nees@UCLA mobile field laboratory	Linear inertial shaker	Field Shaker System	University of California, Los Angeles
nees@UCLA mobile field laboratory	Mobile command center	LAN Infrastructure	University of California, Los Angeles
nees@UCLA mobile field laboratory	National Instruments data acquisition system	DAQ Infrastructure	University of California, Los Angeles

Chunyang Liu; Hoda Soltani; Juan Pinilla; Muralee Muraleetharan; Amy Cerato; Gerald Miller, "Centrifuge Investigation of Seismic Behavior of Pile Foundations in Soft Clays" (view)

Chunyang Liu; Hoda Soltani; Juan Pinilla; Muralee Muraleetharan; Amy Cerato; Gerald Miller, "Centrifuge Investigation of Seismic Behavior of Pile Foundations in Soft Clays" (view)

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