Analysis of the Soil Loss and Settlement of Silty Clay with Different Subclassifications
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ORIGINAL PAPER
Analysis of the Soil Loss and Settlement of Silty Clay with Different Subclassifications Ming-lei Hou . Wan-tao Ding . Xiang-gang Wang . Ke-qi Liu . Lei Chen
Received: 13 September 2019 / Accepted: 28 May 2020 Springer Nature Switzerland AG 2020
Abstract There is an ever-growing demand for the construction of silty clay stratum tunnels; therefore, effectively controlling the surface settlement caused by tunnel construction has become an important task. Since the physical indexes of silty clay greatly influence strength and deformation, based on the physical and mechanical indexes of 3192 groups in three areas, quantitative and determinative indexes for the subclassification of silty clay are proposed using K-means clustering and the tracking records of the actual project. Then, the soil loss and settlement of different subclassifications of silty clay are studied through the standard Gauss error function. Empirical formulas for calculating the width of the settlement trough and the soil loss rate are proposed. The dispersion of the settlement parameters with different subclassifications indicates that the soil properties of the silty clay strata vary greatly with subclassification, and the influence range of the surrounding soil disturbance caused by excavation also varies. In addition, the change in the soil loss rate with the propulsion of the tunnel face in the same monitoring section is discussed. For subgrade V, the increasing M. Hou W. Ding (&) K. Liu L. Chen Research Center of Geotechnical and Structural Engineering, Shandong University, Jinan 250061, China e-mail: [email protected] X. Wang Shandong Highway Engineering Construction Group Co., Ltd, Jinan 250102, China
soil loss rate reaches a maximum when the tunnel face reaches the monitoring sections. For subgrades VI1 and VI2, this rate changes mainly during the timeframe spanning from 5 days before excavation to 5 days after excavation. A numerical simulation was also carried out to validate the applicability of the Peck formula for silty clay tunnels. The numerical prediction and field measured data show that when the coverto-diameter ratio is between 1 and 3, it is reasonable to use the Peck formula to analyze the surface settlement of a silty clay tunnel. This paper can provide guidance based on experience for the subclassification of the soil surrounding rock and for the prediction of the ground surface settlement. Keywords Silty clay stratum Subclassification of silty clay Peck formula Settlement trough width Soil loss rate
1 Introduction In recent years, with the rapid development of urban subway tunnels, the shallow mining method has been commonly used to construct tunnels in weak strata. Due to the poor bearing capacity and low shear strength of the weak stratum, the control of surface settlement is particularly important; however, the control standards are not unified and there is a lack of technical specifications with regional adaptability.
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