No abstract

Professor in Geotechnical Engineering Program, School of Engineering and Technology, Asian Institute of Technology, Thailand (bergado＠ ait.ac.th).iii) M. Eng. Graduate, ditto. iv) Doctoral Graduate, ditto. v) Regional Technical Manager of PLAXIS Asia. The manuscript for this paper was received for review on January 29, 2010; approved on December 7, 2010. Written discussions on this paper should be submitted before November 1, 2011 to the Japanese Geotechnical Society, 4-38-2, Sengoku, Bunkyo-ku, Tokyo 112-0011, Japan. Upon request the closing date may be extended one month. ABSTRACT A new kind of Deep Cement Mixing (DCM) pile called StiŠened Deep Mixing Pile (SDCM) is introduced to mitigate the low ‰exural strength and unexpected failures of DCM piles. A jet grouting method with a jet pressure of 22 MPa, was utilized in the installation of DCM piles. The SDCM pile consists of a DCM pile with a precast reinforced concrete core pile inserted at its center. Pile and embankment load tests were conducted, and then the results of theˆeld load tests were simulated by a 3Dˆnite element method (FEM) to back-analyze and conˆrm the related design parameters. These parameters were then used further in numerical experiments. Theˆeld test results showed that the settlements and lateral movements of the SDCM pile using a prestressed concrete core pile with area ratio (A core /A DCM ) of 0.17 and a length ratio of 0.85 was less than those of the DCM pile by 40z and 60z, respectively. Moreover, the SDCM pile foundation increased the bearing capacity by as much as 2.2 times. The average lateral pile capacity of the SDCM piles was 15 times higher than the DCM piles. A strength reduction factor of 0.40 was obtained at the concrete core and the DCM interface from the full scale pullout test. The behavior of both the DCM and SDCM piles was conˆrmed from the subsequent 3D FEM simulations. From the 3D FEM simulations, the length of the concrete core pile had more in‰uence on the settlements of the SDCM pile than its cross-sectional area. However, both the length and cross-sectional area of concrete core pile aŠected the lateral resistance of the SDCM pile.

No abstract

A resistivity-undrained shear strength equation was proposed in this work to investigate the relationship between the undrained shear strength and electrical resistivity of soft Bangkok clay. The field vane shear and screw driving sounding tests were used to evaluate the undrained shear strength of the soft Bangkok clay from 10 field investigations of the canal-side roads. Meanwhile, the electrical resistivity was collected by the low-cost nondestructive resistivity survey method. The relationship between the measured resistivity corresponding to the undrained shear strength was expressed as a linear equation of S u = 7.061ρ with a high statistical correlation (96.20%) between the undrained shear strength and resistivity. The validation between the predicted undrained shear strength from the equation and the measured undrained shear strength from the field sites confirmed the statistically significant relation of data and the reliability of the proposed equation. By using this equation, it successfully predicted the undrained shear strength of the soft Bangkok clay at a depth of 4.00-10.00 m below the ground surface of canal-side roads (zones C, D, and E in the zonation map). The proposed new equation from the resistivity survey in this work, therefore, serves as an alternative tool to fast estimate the shear strength of soft soil in the large area for the preliminary evaluation of road construction.

No abstract

No abstract