Vol. 42 No.2 June 2011

Field Measurements on Piled Rafts with Grid-Form Deep Mixing Walls on Soft Ground

Kiyoshi Yamashita, Junji Hamada and Takeshi Yamada

ABSTRACT: Piled raft foundations have been used for many buildings including tall buildings in excess of 150 m in height in Japan, since a piled raft was first used to the four-story building in 1987. This paper offers recent two case histories for an advanced type of piled rafts. The piled rafts combined with grid-form deep cement mixing walls were employed for a seven-story building and a twelve-story building to cope with liquefiable loose sand as well as to reduce consolidation settlements of soft cohesive soil below the loose sand. The high-modulus grid-form soil-cement walls confine the liquefiable loose sand so as not to cause excessive shear deformation to the loose sand during earthquakes. To confirm the foundation design, field measurements were performed on the foundation settlements and load sharing between raft and piles from the beginning of construction to 72 and 27 months after the end of construction for the former and the latter buildings.

KEYWORDS: Piled raft, Grid-form deep mixing wall, Soft ground, Field measurements, Settlement, Load sharing

DOI: 10.14456/seagj.2011.17

Vol. 42 No.2 June 2011

Static Axial Reciprocal Load Test of Cast-in-place Nodular Concrete Pile and Nodular Diaphrgm Wall

K. Watanabe, H. Sei, T. Nishiyama and Y. Ishii

ABSTRACT: In recent years, both tension force and compression force occur in foundation such as pile foundation or wall foundation due to earthquake and wind loads with increasing building height and building weight. In addition, tension loads on foundation can increase also as groundwater table rises. This trend is noticeable especially in urban central areas of Japan. From these backgrounds, it is necessary to develop new types of foundations for high-rise superstructures. New types of foundation are nodular cast-in-place concrete pile or nodular diaphragm wall with one- or two-bell shaped enlargements to increase both bearing capacity and tension resistance. The main purpose of this study is to confirm the resistance of nodular cast-in-place concrete pile and nodular diaphragm wall in clayey soils. The paper reports the investigation of construction methods of nodular cast-in-place concrete pile and nodular diaphragm wall, and the results of static axial reciprocal load tests carried out to develop the nodular cast-in-place concrete pile and nodular diaphragm wall. According to the ultrasonic measurement during the construction of piles or wall and the investigation of pile shape or wall shape after the load tests, the nodular cast-inplace concrete pile and nodular diaphragm wall were constructed as designed. As a result of load tests, the nodular cast-in-place concrete pile and nodular diaphragm wall have large tension and compression resistance. The tension resistance at the nodular part and under-reamed part shows a large value.

KEYWORDS: Nodular Cast-in-place Concrete Pile, Nodular Diaphragm Wall, Reciprocal Load Test, Bearing Pressure, Clayey Soil

DOI: 10.14456/seagj.2011.18

Vol. 42 No.2 June 2011

Vertical Load Test and Settlement Analysis of Cast-in-place Concrete Nodular Piles Supporting a High-Rise Building

N. Suzuki and T. Seki

ABSTRACT: This paper describes full-scale pile load tests and 3D FEM settlement analyses regarding cast-in-place concrete nodular piles for design of a high-rise building foundation. The nodular piles have bulbs on its shaft in order to increase pile resistance.
A compressive & tensile load test and a tensile load test were carried out in the site of the high-rise building for design purpose. Each bulb of the test piles was installed in medium gravel layer and dense gravelly sand layer. Although load condition included repeated loading and long-term loading (4 days), the measured test results showed that resistance of the bulb was sufficient in both layers. Furthermore, concerning settlement behaviour of the bulb, it was attempted to normalize relationship between bearing pressure and settlement. As a result, the authors’ normalization method worked well to evaluate settlement behaviour of the bulb.

With regard to analysis, 3D FEM analyses of pile group under sustained loading and earthquake loading were conducted. These analyses were based on the analyses of the two pile load tests. In the pile group analyses, settlement of the foundation and distributions of loads on the pile head were evaluated for design. The influence of load dispersion due to stiffness of the footing beams were considerably large and marked particularly under earthquake loading.

KEYWORDS: Cast-in-place concrete nodular pile, Load test, FEM analysis, Pile group efficiency

DOI: 10.14456/seagj.2011.19

Vol. 42 No.2 June 2011

Extended Use of Spring Hammer Rapid Load Testing

K. Matsuzawa and T. Matsumoto

ABSTRACT: Instruction As one of rapid load test methods, Spring Hammer test (SH test) method has been developed (Matsumoto et al., 2004) and used in practice. A simplified interpretation method of dynamic signals called Non-Linear Damping interpretation (NLD) is basically used for the SH rapid pile load test to derive a static response of the tested pile. In this paper, details of the Spring Hammer test method including NLD interpretation method is mentioned first. Second, validation of the SH test method is demonstrated through comparisons of static and the SH rapid load tests on relatively short piles and on circular rigid plates. Three case studies of the SH rapid load tests are then presented. The SH tests were conducted on perfect end-bearing piles (H-steel pile having end plate) in cases 1. In this SH tests, the NLD interpretation method did not work well to obtain the static behaviours of the piles due to the influence of wave propagation phenomena even though the pile lengths were relatively short compared to the loading durations. Hence, an extended NLD interpretation method is proposed for perfect end-bearing piles in case 1. In case 2, the SH test was carried out for estimating bearing characteristics of a pile group supporting a small bridge in service which was planned to be renewed, in order to make a decision whether existing pile foundations also were to be re-constructed or not. In case 3, the results of the SH plate load tests are compared with the static plate load tests on a saturated loam layer and on an improved soil. This paper discusses the applicability and limitation of the SH rapid load test methods through the case studies.

KEYWORDS: Rapid load test, Bearing capacity, Wave propagation, Case study, Pile, Rigid plate

DOI: 10.14456/seagj.2011.20

Vol. 42 No.2 June 2011

Push-up Load Tests Using Uncrushable Particles and Its DEM Analyses

SuriyahThongmunee, Shun-ichi Kobayashi and Tatsunori Matsumoto

ABSTRACT: In this study, push-up load tests of soil plugs having various aspect ratios in a steel pipe pile and its DEM analyses were carried out. Uncrushable uniform spherical particles (alumina balls) were used to model soil plugs. In order to obtain physical properties of the alumina ball, element tests of alumina balls, including one-dimensional compression tests and direct shear tests, shear tests between the model soil and the model pile and so on, were carried out. Then, DEM analyses of the one-dimensional compression tests and direct shear tests were carried out by matching the DEM results with the results of the element tests to obtain the analysis parameters to be used in DEM simulations of the push-up load tests. Thereafter, the push-up load tests and its DEM simulations were carried out. The results showed that the maximum push-up force increases with increase in aspect ratio and that hardening and softening behaviour of the push-up force occurs. These behaviours were totally in accordance with the experimental results. Finally, the experimental results in this paper are compared with the push-up load tests of the crushable sand plugs obtained in previous study, in which the push-up force increased monotonically with increasing push-up displacement. Possible influence of crushability of particles on the plugging behaviour during push-up loading is discussed, based on the comparison.

KEYWORDS: Push-up load test, Uncrushable spherical particle, Crushable particle, Plugging behaviour, 3D-Discrete Element Method

DOI: 10.14456/seagj.2011.21

Vol. 42 No.2 June 2011

On Design and Construction of Pile Group Foundation of Taipei 101

Ching-Han Yu

ABSTRACT: The evenly distributed cast-in-place reinforced concrete group piles with socketed length into soft bedrock of 15 to 33 m were designed as the foundation for Taipei 101. The high-rise building is extremely sensitive to the foundation settlement. Besides, the bearing behavior of a cast-in-place bored pile is largely determined by the way it was installed. Accordingly, the design of pile group foundation for Taipei 101 was based on a series of full scale pile trial installation as well as comprehensive instrumented pile load tests with compressive and pull-out load up to 40 MN and 22 MN respectively. The characteristic t-z curve for each subsurface stratum was evaluated and used to predict the pile load-settlement behavior for the specific soil stratification of each pile located, thus each pile length was determined according to the anticipated loads during service. Besides, the pile group effects, including bearing capacity reduction and settlement increase, were considered in the foundation design. The creep behaviors for piles embedded into bedrock were also analyzed by using the measured results of pile load tests. The superstructures, basement, mat, piles and retaining diaphragm walls were modeled into one integral system for the structural design of foundation, thus the estimation of foundation behavior under various load combinations were conducted using the above mentioned model with the sub-grade reaction under foundation mat. Based on the investigation of trial installations, the construction specification was proposed for the installation of reverse circulation piles. For piles under the main tower, the measures of bottom cleaning and post-grouting were employed to improve the pile bottom sediments and increase end bearing capacity. Both the conventional static and STATNAMIC dynamic loading tests were employed to verify the bearing capacities and behaviors of production piles. Results of the proof load tests met the design requirements well as compared with the simulation using pile ultimate load test results.

KEYWORDS: Pile load test, Performance-based design, Pile Group, Creep behavior of pile, Pile bottom cleaning and post-grouting

DOI: 10.14456/seagj.2011.22

Vol. 42 No.2 June 2011

Pile Raft Foundations for Tall Buildings

H.G. Poulos, J.C. Small and H. Chow

ABSTRACT: Piled raft foundations are increasingly being recognised as an economical and effective foundation system for tall buildings. This paper sets out some principles of design for such foundations, including design for the geotechnical ultimate limit state, the structural ultimate limit state and the serviceability limit state. The advantages of using a piled raft will then be described with respect to two cases: a small pile group subjected to lateral loading, and then the design of the Incheon Tower in South Korea. Attention will be focused on the improvement in the foundation performance due to the raft being in contact with, and embedded within, the soil.

KEYWORDS: Piled rafts, Design, Lateral load, Case studies

DOI: 10.14456/seagj.2011.24

Vol. 42 No.2 June 2011

Capacity versus Deformation Analysis for Design of Footings and Pile Foundations

Bengt H. Fellenius

ABSTRACT: Measurements of settlement of a piled raft supporting a 40 grain elevators and of five furnaces on piled foundations showed that the settlements were unrelated to deformation due to load transfer from individual piles to the soils and instead governed by compression below the pile toe level. Full-scale static loading tests on footings and pile toes in sand showed that the soil response is not that of building up to an ultimate value, but instead due to gradually increasing compression of the soil below the footing or pile toe. Pile toe movements from 26 piles founded in sand, although showing a scatter of soil deformation response, confirm the results of the footing test. The findings are used to reaffirm the principle that design of a piled foundation requires the analysis of the interaction between load transfer, soil settlement, and pile toe load-movement response.

KEYWORDS: Footings, pile toe, capacity, settlement, design, field measurements

DOI: 10.14456/seagj.2011.23

Vol. 42 No.2 June 2011

Foundation Design of the 151 Story Incheon Tower in a Reclamation Area

Ahmad Abdelrazaq, Frances Badelow, Sung Ho-Kim, Harry G. Poulos

ABSTRACT: A 151 storey super high-rise building located in an area of reclaimed land constructed over soft marine clay in Songdo, Korea is currently under design. This paper describes the design process in developing the foundation system of the super-tall tower, which is required to support the large building vertical and lateral loads and to restrain the horizontal displacement due to wind and seismic forces. The behaviour of the foundation system due to these loads and foundation stiffness influence the design of the building super structure, displacement of the tower, as well as the raft foundation design. Therefore, the design takes into account the interactions between soil, foundation and super structure, so as to achieve a safe and efficient building performance.

The site lies entirely within an area of reclamation underlain by up to 20m of soft to firm marine silty clay, which overlies residual soil and a profile of weathered rock. The nature of the foundation rock materials are highly complex and are interpreted as possible roof pendant metamorphic rocks, which within about 50m from the surface have been affected by weathering which has reduced their strength. The presence of closely spaced joints, sheared and crushed zones within the rock has resulted in deeper areas of weathering of over 80m present within the building footprint.

The foundation design process described includes the initial stages of geotechnical site characterization using the results of investigation boreholes and geotechnical parameter selection, and a series of detailed two- and three-dimensional numerical analysis for the Tower foundation comprising over 172 bored piles of varying length using finite element and boundary element methods. The effect of the overall foundation stiffness and rotation under wind and seismic load is also discussed since the foundation rotation has a direct impact on the overall displacement of the tower.

KEYWORDS: Foundation Design, 151 Story Incheon Tower, Reclamation Area

DOI: 10.14456/seagj.2011.25