Long term additional load on a shield tunnel in soft clay due to clay consolidation with water leakage

Marine clay is a problematic construction material, which is often encountered in Malaysian coastal area. Previous researchers showed that lime stabilization effectively enhanced the engineering properties of clay. For soft clay, both strength and consolidation characteristics are equally important to be fully understood for design purpose. This paper presented the effect of lime on compaction, strength and consolidation characteristics of Pontian marine clay. Compaction, unconfined compression, direct shear, Oedometer and falling head permeability tests were conducted on unstabilized and lime stabilized samples at various ages. Specimens were prepared by compaction method based on 95 percent maximum dry density at the wetter side of compaction curve. It was found that lime successfully increased the strength, stiffness and workability of Pontian marine clay; however, the permeability was reduced. Unconfined compressive strength of stabilized soil was increased by 49 percent at age of 56 days whereas compressibility and permeability was reduced by 48 and 67 percent, respectively. From laboratory tests, phenomenon of inconsistency in engineering characteristics was observed for lime stabilized samples below age of 28 days. This strongly proved that lime stabilized soil underwent modification phase before stabilization phase which provided the long term improvement.

Download Full-text

A Water Leakage Risk Assessment Model for Shield Tunnel Based on Kalman Filter Data Fusion Method

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/861/7/072050 ◽

2021 ◽

Vol 861 (7) ◽

pp. 072050

Author(s):

Wang Jiaxu ◽

Xue Yadong ◽

Li Xuhui ◽

Chen Yuelong ◽

Fu Yanbin

Keyword(s):

Risk Assessment ◽

Kalman Filter ◽

Data Fusion ◽

Assessment Model ◽

Shield Tunnel ◽

Fusion Method ◽

Risk Assessment Model ◽

Water Leakage

Download Full-text

Behaviour of friction piles in soft sensitive clays

Canadian Geotechnical Journal ◽

10.1139/t80-023 ◽

1980 ◽

Vol 17 (2) ◽

pp. 203-224 ◽

Cited By ~ 14

Author(s):

R. Blanchet ◽

F. Tavenas ◽

R. Garneau

Keyword(s):

Precast Concrete ◽

Soft Clay ◽

Load Test ◽

Pile Groups ◽

Test Program ◽

Shear Creep ◽

Soft Clays ◽

The North ◽

Effective Stress Analysis

During the construction of heavy structures, such as bridges and overpasses, on soft clays on the north shore of the St. Lawrence Valley, a detailed load test program on friction piles was performed to establish the characteristics of the most suitable type of pile and to study its long-term behaviour. Three types of piles, timber, steel pipe with closed end, and precast concrete Herkules H-420 piles, were tested. Four timber piles driven in a group and submitted to a 712 kN load served to study the long-term settlement of a small group of piles. Three deep settlement gauges were installed in the centre of this group for measuring settlements in clay at various depths.This test program was completed by the instrumentation of two bridge piers in order to verify the behaviour of larger groups of piles.The paper presents the results of the test piles, the long-term behaviour (4 years) of the bridge pier foundations resting on friction piles in soft clay, and the interpretation of the results.This study shows that the pore pressures induced by pile driving are related to the pre-consolidation of the clay and that they are much larger for tapered piles. It is demonstrated that the effective stress analysis method proposed in 1976 by Meyerhof determines adequately the ultimate pile bearing capacity, but that the effect of the timber pile taper doubles the skin friction.The settlement analysis of pile groups shows that settlements are due to the reconsolidation of the clay and shear creep deformations in the clay close to the pile wall.

Download Full-text