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| 1 | Laboratory model study of newly deposited dredger fills using improved multiple-vacuum preloading technique显示文摘Problems continue to be encountered concerning the traditional vacuum preloading method in field during the treatment of newly deposited dredger fills.In this paper,an improved multiple-vacuum preloading method was developed to consolidate newly dredger fills that are hydraulically placed in seawater for land reclamation in Lingang Industrial Zone of Tianjin City,China.With this multiplevacuum preloading method,the newly deposited dredger fills could be treated effectively by adopting a novel moisture separator and a rapid improvement technique without sand cushion.A series of model tests was conducted in the laboratory for comparing the results from the multiple-vacuum preloading method and the traditional one.Ten piezometers and settlement plates were installed to measure the variations in excess pore water pressures and moisture content,and vane shear strength was measured at different positions.The testing results indicate that water dischargeetime curves obtained by the traditional vacuum preloading method can be divided into three phases:rapid growth phase,slow growth phase,and steady phase.According to the process of fluid flow concentrated along tiny ripples and building of larger channels inside soils during the whole vacuum loading process,the fluctuations of pore water pressure during each loading step are divided into three phases:steady phase,rapid dissipation phase,and slow dissipation phase.An optimal loading pattern which could have a best treatment effect was proposed for calculating the water discharge and pore water pressure of soil using the improved multiple-vacuum preloading method.For the newly deposited dredger fills at Lingang Industrial Zone of Tianjin City,the best loading step was 20 kPa and the loading of 40-50 k Pa produced the highest drainage consolidation.The measured moisture content and vane shear strength were discussed in terms of the effect of reinforcement,both of which indicate that the multiple-vacuum preloading method has a better treatment effect not only in decreasing the moisture content and increasing the bearing capacity,but also in increasing the process uniformity at different depths of foundation. | Jingjin Liu Huayang Lei Gang Zheng Haizuo Zhou Xuelian Zhang | 2017 | Journal of Rock Mechanics and Geotechnical Engineering2017，9，5： | 7 |
| 2 | Effect of defects and remediation measures on the internal forces caused by a local thickness reduction in the tunnel lining显示文摘This study presents a case history of a tunnel lining with an insufficient thickness.The effect of the defects resulting from the insuf-ficient thickness of the secondary lining and their locations on the internal forces are discussed based on numerical analysis.The results show that defects increase the number of inflection points in the defect region.The increased maximum bending moment is located on the air side of the secondary lining around the defect region.The defects near the crown of the secondary lining have the most significant influence on the internal forces of the primary and secondary linings,while the defects near the sidewall of the secondary lining have a limited influence on the internal forces of the lining.A remediation measure consisting of the installation of a tertiary lining is proposed and its efficiency is analyzed.The tertiary lining significantly reduces the bending moment of the secondary lining and the axial force of the primary lining.The effect of the thickness and location of the tertiary lining on the tunnel performance is discussed. | Ping Lu Dongwang Qiao Chunxiao Wu Shun Wang Xiaopei He Wenjun Zhang Haizuo Zhou | 2022 | Underground Space2022，7，1： | 1 |
| 3 | Neural network and support vector machine models for the prediction of the liquefaction-induced uplift displacement of tunnels显示文摘Tunnels buried in liquefiable deposits are vulnerable to liquefaction-induced uplift damage during earthquakes.This paper presents support vector machine(SVM)and artificial neural network(ANN)models to predict the liquefaction-induced uplift displacement of tunnels based on artificial databases generated by the finite difference method.The performance of the SVM and ANN models was assessed using statistical parameters,including the coefficient of determination R^(2),the mean absolute error,and the root mean squared error.Applications for the above-mentioned approaches are compared and discussed.A relative importance analysis was adopted to quantify the sensitivity of each input variable.The precision of the presented models is demonstrated using centrifuge test results from previous studies. | Gang Zheng Wenbin Zhang Wengang Zhang Haizuo Zhou Pengbo Yang | 2021 | Underground Space2021，6，2： | 1 |
| 4 | A 3D sliced-soil-beam model for settlement prediction of tunnelling using the pipe roofing method in soft ground显示文摘The pipe roofing method is widely used in tunnel construction because it can realize a flexible section shape and a large section area of the tunnel,especially under good ground conditions.However,the pipe roofing method has rarely been applied in soft ground,where the prediction and control of the ground settlement play important roles.This study proposes a sliced-soil-beam(SSB)model to predict the settlement of ground due to tunnelling using the pipe roofing method in soft ground.The model comprises a sliced-soil module based on the virtual work principle and a beam module based on structural mechanics.As part of this work,the Peck formula was modified for a square-section tunnel and adopted to construct a deformation mechanism of soft ground.The pipe roofing system was simplified to a threedimensional Winkler beam to consider the interaction between the soil and pipe roofing.The model was verified in a case study conducted in Shanghai,China,in which it provided the efficient and accurate prediction of settlement.Finally,the parameters affecting the ground settlement were analyzed.It was clarified that the stiffness of the excavated soil and the steel support are the key factors in reducing ground settlement. | Yu DIAO Yiming XUE Weiqiang PAN Gang ZHENG Ying ZHANG Dawei ZHANG Haizuo ZHOU Tianqi ZHANG | 2023 | Frontiers of Structural and Civil Engineering2023，17，12： | 0 |
| 5 | Estimation of hydraulic parameters from pumping tests in a multiaquifer system显示文摘The hydrogeologic conditions in Tianjin,China,are characterized by a system of multiple alternating aquifers and aquitards and a high groundwater level.Generally,the groundwater system to a depth of 70 m includes one phreatic aquifer and three semiconfined aquifers(AqI–AqIII).The distribution of aquifers varies greatly.Accurate estimates of aquifer parameters from pumping tests are essential in geotechnical engineering practice.In this study,the applicability of different models for estimating hydraulic parameters in a multiaquifer system is analyzed.To avoid errors in the graphic-analytical process and to enhance the efficiency and accuracy,a hybrid algorithm,called GALMA(a genetic algorithm(GA)combined with the Levenberg–Marquardt(LM)algorithm),is used with the Neuman and Witherspoon model and ratio method.The estimated values in the second and third semiconfined aquifers(AqII and AqIII)from various solutions are compared with the measured data.Further validations based on the prediction of the drawdown values are performed via a three dimensional numerical simulation. | Da Ha Gang Zheng Haizuo Zhou Chaofeng Zeng Huihui Zhang | 2020 | Underground Space2020，5，3： | 0 |
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