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J. H. Wang
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Civil Engineering, Building, Construction & Architecture Engineering Transportation

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LONG-TERM SETTLEMENT BEHAVIOR OF MULTI-STORY BUILDINGS ON SOFT SUBSOIL IN SHANGHAI J. J. Chen; J. H. Wang; S. L. Shen; H. B. Zhou
Lowland Technology International Vol 7 No 1, June (2005)
Publisher : International Association of Lowland Technology

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The soft deposit in Shanghai is a multilayered formation due to different sedimentary environments and eras. This soft deposit has high compressibility, and the buildings on it undergo long-term settlement. Most of the multistory buildings in Shanghai are built on natural soft subsoil with a shallow foundation. This paper presents the settlement behavior of 50 multi-story buildings based on long-term observed data. According to the characteristics of the soil profile in various areas, the subsoil condition is categorized into four zones: “hard” Zone, “normal” Zone, “soft” Zone, and “very-soft” Zone. The results of observations of settlement on these four types of subsoil over a long term are presented and compared. Statistical analysis is employed to analyze the observed settlement of various subsoils, including final settlement and the developing process of settlement. In order to investigate the effect on settlement behavior of the thickness of very soft clay layers in the four zones, the relationship between the thickness ratio of soft clay layer Rs and the long-term settlement of buildings is obtained through an analysis of all records. With the increase of Rs, the final settlement and settlement duration increase; however, the settlement during construction decreases. These results can be applied in research on the settlement mechanism and can be used to judge the possible settlement range and provide a design scheme for multi-story buildings in the soft clay region.
PERFORMANCE OF DEEP EXCAVATED RETAINING WALL IN SHANGHAI SOFT DEPOSIT Z. H. Xu; W. D. Wang; J. H. Wang; S. L. Shen
Lowland Technology International Vol 7 No 2, Dec (2005)
Publisher : International Association of Lowland Technology

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This paper presents a field case of deep excavated pit of a building foundation in soft deposit of Shanghai lowland area. The details of the project are described at first. Then, the design method and construction process are presented. The wall displacements, axial force of struts, and displacement of the steel lattice columns were monitoredand the results are presented and compared with the calculated results in design. Field measured data show that the ratio between the maximum lateral displacement and the excavated depth was controlled within 0.62%. Monitored data also show that the axial force in the second level struts was the largest among the three levels struts while the axial force in the first level strut was the smallest. The design method described in this paper is used to predict the diaphragm wall deformations. The prediction is consistent well with the measured data. However, there are some discrepancies of the axial forces in the struts between the calculated values and the measured values. Factors affecting effectiveness of the supporting system were investigated. The larger the thickness of the wall and the larger the stiffness of the struts, the smaller displacement of the wall will result. The rate of reduction of the wall displacement decreases with the increaseof the thickness of the wall and the stiffness of the struts. There exists a threshold value of the depth ratio of the diaphragm wall, which has a significant influence on the lateral displacement. In this field case the threshold value of depth ratio is 0.3.
UNCERTAINTY OF EMPIRICAL PREDICTION MODEL FOR WALL DEFLECTION OF DEEP EXCAVATION IN SHANGHAI SOILS H.J. Fan; L.L. Zhang; J. H. Wang
Lowland Technology International Vol 13 No 1, June (2011)
Publisher : International Association of Lowland Technology

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Empirical and semiempirical methods are simple models for estimating the maximum wall deflection induced by an excavation by practicing engineers for preliminary design. Various factors, such as excavation geometry, wall stiffness, strut spacing, ground condition, dewatering, etc, may affect deformation behavior of an excavation. It is impossible and not practical to incorporate all these factors in a prediction model for excavation-induced wall deflection. Hence, the prediction model of wall deflection is subject to model uncertainty, which is necessary to be quantified. In this paper, a database of 25 well-documented case histories of braced excavations in Shanghai is established. The model uncertainties of two semiempirical models for wall deflection, i.e., the KJHH model (Kung et al. 2007) and the C&O method (Clough and O’Rourke 1990) are quantified using the Bayesian updating approach. A model bias factor is defined as the ratio of the observed maximum wall deflection over the estimated value by the prediction model. With the information of the case histories, the uncertainty of the model bias factor is reduced. It is found that the posterior mean of the bias factor of the KJHH model is closer to 1.0 than that of C&O method and the uncertainty of the KJHH model is smaller than that of C&O method. Keywords
Co-Authors H. B. Zhou H.J. Fan J. J. Chen L.L. Zhang S. L. Shen W. D. Wang Z. H. Xu