scholarly journals A New Modified Peck Formula for Predicting the Surface Settlement Based on Stochastic Medium Theory

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Zhanping Song ◽  
Xiaoxu Tian ◽  
Yuwei Zhang
Keyword(s):  
Friction Angle ◽  
Surface Settlement ◽  
Calculation Error ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Comparison Results ◽  
Calculation Process ◽  
The Difference ◽  
Shallow Buried Tunnel ◽  
Prediction Approach

Peck method and stochastic medium method are the two most commonly used methods to estimate surface settlement caused by tunnel excavation. However, the Peck method was not suitable for a shallow-buried tunnel, and the calculation process of the stochastic medium theory was complicated. To solve this problem, in this paper, a simple and accurate prediction approach for surface settlement was obtained by improving the Peck method based on the basic idea of stochastic medium theory. In detail, the over-excavation area of the tunnel was divided into n independent units, and the surface settlement caused by the collapse of each unit was calculated, respectively. Then, the total surface settlement can be obtained by superimposing surface settlement induced by each unit. Taking the shallow-buried section of Mulingguan tunnel entrance as a case, the surface settlement calculated by the modified Peck formula and original Peck formula was compared with the observed data, respectively. The comparison results indicated that the surface settlement calculated by the modified Peck formula is closer to the observed data than that calculated by the original Peck formula in the calculation process of surface settlement of shallow-buried tunnel. The table of recommendation for the number of units can be obtained by a discussion of reasonable n values. Finally, the difference between the original Peck formula and the modified Peck formula was analysed, and the results showed that the change rule of the surface settlement is consistent under the tunnel depth, internal friction angle, and ground loss of the tunnel. However, the calculation error of the surface settlements calculated by the original Peck formula is more significant than that calculated by modified Peck formula under the tunnel diameter ratio being less than 1.75. The modified Peck formula is more suitable for calculating the surface settlement under internal angle friction being less than 20° or greater than 40°. The research results expand the scope of application of the original Peck formula and enrich the calculation approach of surface settlement induced by underground excavation in tunnel construction.

scholarly journals Three-Dimensional Ground Settlement Induced by Metro Tunnel Excavation Considering the Influence of Group Piles

2016 ◽  
Vol 2016 ◽  
pp. 1-13
Author(s):  
Zou Jin-feng ◽  
Zhang Yan-jun ◽  
Dan Han-cheng
Keyword(s):  
Three Dimensional ◽  
Ground Surface ◽  
Soil Mass ◽  
Surface Settlement ◽  
Stochastic Medium ◽  
Ground Surface Settlement ◽  
Shear Displacement Method ◽  
Metro Tunnel ◽  
Group Piles ◽  
Prediction Approach

Considering the influence of group piles, a prediction model for three-dimensional ground surface settlement induced by circular metro tunnels excavation in incompressible rock masses is proposed based on the stochastic medium theory and the shear displacement method. The surface settlement caused by the metro tunnel opening is divided into two parts. One part is soil mass settlement caused by the metro tunnel opening and calculated by the stochastic medium theory. The other part is the settlement induced by the friction force between the group piles and the soil mass around the metro tunnel cross section and calculated by the shear displacement method. The three-dimensional prediction of the ground surface settlement is obtained by the linear superposition of the two parts. The validation of the proposed prediction approach is proved by comparing with the measured data and the numerical model of the double tunnels under thePuyuanoverpass where metro tunnels undercrossed group piles. The effects of buried depth, radial convergences, center distance of double tunnels, position and size of piles, and group piles are analyzed and discussed. The improved prediction approach can be applied to calculate the three-dimensional ground settlement, especially for the metro tunnels crossing through group piles.

scholarly journals Plastic failure zone characteristics and stability control technology of roadway in the fault area under non-uniformly high geostress: A case study from Yuandian Coal Mine in Northern Anhui Province, China

2020 ◽  
Vol 12 (1) ◽  
pp. 406-424 ◽  
Author(s):  
Yaoguang Huang ◽  
Aining Zhao ◽  
Tianjun Zhang ◽  
Weibin Guo
Keyword(s):  
Numerical Methods ◽  
Numerical Solutions ◽  
Stress Test ◽  
Pressure Coefficient ◽  
Stability Control ◽  
Failure Zone ◽  
Plastic Failure ◽  
Comparison Results ◽  
High Geostress ◽  
The Difference

AbstractIn order to explore the effective support method for deep broken roadway, based on the in situ stress test results, the analytical and numerical solutions of the stress and the range of plastic failure zone (PFZ) in a circular roadway subjected to non-uniform loads were obtained using analytical and finite difference numerical methods based on the elastoplastic theory, respectively. Their comparison results show that the analytical and numerical methods are correct and reasonable. Furthermore, the high geostress causes the stress and range of PFZ in roadway roof and floor to increase sharply while those in roadway ribs decrease. Moreover, the greater the difference of horizontal geostress in different horizontal directions is, the larger the range of PFZ in roadway roof and floor is. The shape of PFZ in roadway varies with the ratio of horizontal lateral pressure coefficient in x-direction and y-direction. Finally, according to the distribution characteristics of PFZ and range of PFZ under the non-uniformly high geostress, this paper has proposed a combined support scheme, and refined and optimized supporting parameters. The field monitoring results prove that the roadway deformation and fracture have been effectively controlled. The research results of this paper can provide theoretical foundation as well as technical reference for the stability control of deep broken roadway under non-uniformly high geostress.

scholarly journals Ground Movement Analysis Based on Stochastic Medium Theory

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
Meng Fei ◽  
Wu Li-chun ◽  
Zhang Jia-sheng ◽  
Deng Guo-dong ◽  
Ni Zhi-hui
Keyword(s):  
Distribution Function ◽  
Back Analysis ◽  
Movement Analysis ◽  
Measured Data ◽  
Ground Movement ◽  
Pile Driving ◽  
Normal Distribution Function ◽  
Stochastic Medium ◽  
Medium Theory ◽  
Vertical Ground

In order to calculate the ground movement induced by displacement piles driven into horizontal layered strata, an axisymmetric model was built and then the vertical and horizontal ground movement functions were deduced using stochastic medium theory. Results show that the vertical ground movement obeys normal distribution function, while the horizontal ground movement is an exponential function. Utilizing field measured data, parameters of these functions can be obtained by back analysis, and an example was employed to verify this model. Result shows that stochastic medium theory is suitable for calculating the ground movement in pile driving, and there is no need to consider the constitutive model of soil or contact between pile and soil. This method is applicable in practice.

scholarly journals Determination of land surface reflectance using the AATSR dual-view capability

2014 ◽  
Vol 7 (7) ◽  
pp. 7451-7494
Author(s):  
L. Sogacheva ◽  
P. Kolmonen ◽  
T. H. Virtanen ◽  
E. Rodriguez ◽  
A.-M. Sundström ◽  
...  
Keyword(s):  
Land Surface ◽  
Atmospheric Correction ◽  
Correlation Coefficients ◽  
Absolute Error ◽  
Surface Reflectance ◽  
Imaging Spectrometer ◽  
Comparison Results ◽  
Moderate Resolution ◽  
The Difference ◽  
Along Track

Abstract. In this study, a method is presented to retrieve the surface reflectance using reflectance measured at the top of the atmosphere for the two views provided by the Along-Track Scanning Radiometer (AATSR). In the first step, the aerosol optical depth (AOD) is obtained using the AATSR dual view algorithm (ADV) by eliminating the effect of the surface on the measured radiances. Hence the AOD is independent of surface properties and can thus be used in the second step to provide the aerosol part of the atmospheric correction which is needed for the surface reflectance retrieval. The method is applied to provide monthly maps of both AOD and surface reflectance at two wavelengths (555 and 659 nm) for the whole year of 2007. The results are validated vs. surface reflectance provided by the AERONET-based Surface Reflectance Validation Network (ASRVN). Correlation coefficients are 0.8 and 0.9 for 555 and 659 nm, respectively. The standard deviation is 0.001 for both wavelengths and the absolute error is less than 0.02. Pixel-by-pixel comparison with MODIS (MODerate resolution Imaging Spectrometer) monthly averaged surface reflectances show a good correlation (0.91 and 0.89 for 555 and 659 nm, respectively) with some (up to 0.05) overestimation by ADV over bright surfaces. The difference between the ADV and MODIS retrieved surface reflectance is smaller than ±0.025 for 68.3% of the collocated pixels at 555 nm and 79.9% of the collocated pixels at 659 nm. An application of the results over Australia illustrates the variation of the surface reflectances for different land cover types. The validation and comparison results suggest that the algorithm can be successfully used for the both AATSR and ATSR-2 (which has characteristics similar to AATSR) missions, which together cover 17 years period of measurements (1995–2012), as well as a prototype for The Sea and Land Surface Temperature Radiometer (SLSTR) to be launched in 2015 onboard the Sentinel-3 satellite.

scholarly journals Ionospheric Peak Parameters Retrieved from FY-3C Radio Occultation: A Statistical Comparison with Measurements from COSMIC RO and Digisondes Over the Globe

2019 ◽  
Vol 11 (12) ◽  
pp. 1419
Author(s):  
Han Wang ◽  
Jia Luo ◽  
Xiaohua Xu
Keyword(s):  
Solar Activity ◽  
Correlation Coefficient ◽  
Radio Occultation ◽  
Elevation Angle ◽  
Activity Period ◽  
Time Interval ◽  
Comparison Results ◽  
Standard Deviations ◽  
The Difference ◽  
Solar Activity Period

In this study, two ionospheric peak parameters (ICPs), NmF2 and hmF2, derived from the global navigation satellite system (GNSS) radio occultation (RO) ionospheric electron density profiles (EDPs) obtained by Feng-Yun 3C (FY-3C) mission are compared with those derived from the observations of the Constellation Observing System for the Meteorology, Ionosphere, and Climate (COSMIC) mission and the measurements from 24 digisonde stations distributed around the world during the year from 2014 to 2017. The FY-3C derived ICPs and the COSMIC-derived ICPs are provided by the National Satellite Meteorological Centre (NSMC) and the COSMIC Data Analysis and Archive Center (CDAAC), respectively. The correlation and bias analyses are carried out in the comparison under the collocation criterion with the time interval of 1 h and the space interval of 3° in latitude and 5° in longitude. When comparing the ICPs derived from the two RO missions, the difference in the azimuth of occultation planes (DAOPs) between the matched pairs is limited to be within 20°. The comparison results are analyzed for different solar activity periods, and solar elevation angle (SEA) is taken for the first time as a factor that represents the comprehensive impacts of latitude zones, seasons, and local time of the observations. The results are shown as follows: (1) Both the COSMIC RO-derived and the digisonde-observed ICPs are in good agreement with the FY-3C RO-derived ones. The correlation coefficient (CC) between the NmF2 and hmF2 derived by COSMIC RO and FY-3C RO is 0.965 and 0.916, respectively, while the correlation coefficient between the NmF2 and hmF2 derived by digisonde and FY-3C RO is 0.924 and 0.832, respectively. The quality of FY-3C RO-derived ICPs are reliable enough for further applications. (2) The CC of NmF2 is, in general, higher than that of hmF2 when comparing FY-3C RO with other observations, and the overall MAB and MRB of FY-3C RO-derived ICPs during the higher solar activity period are higher than the ones during the lower solar activity period. The difference between the two RO missions is much smaller than that one between FY-3C RO and digisonde. (3) For a certain solar activity period, the standard deviations of the absolute bias (SDAB) and the standard deviations of the relative bias (SDRB) of FY-3C RO-derived ICPs compared with digisonde-derived ones generally increases with the increase of SEA, while the SDAB and SDRB of FY-3C RO-derived ICPs both get the minimum values for the AOP interval near to 90°.

A frame-independent comparison metric for discrete motion sequences

2020 ◽  
Vol 234 (9) ◽  
pp. 1764-1774
Author(s):  
Ping Zhao ◽  
Yong Wang ◽  
Lihong Zhu ◽  
Xiangyun Li
Keyword(s):  
Moving Frame ◽  
Kinematic Synthesis ◽  
Reference Motion ◽  
Comparison Results ◽  
Synthesis Of Mechanisms ◽  
Rotational Part ◽  
The Difference ◽  
Four Bar Linkage ◽  
The Given ◽  
Discrete Motion

To evaluate the kinematic performance of designed mechanisms, a statistical-variance-based metric is proposed in this article to measure the “distance” between two discrete motion sequences: the reference motion and the given task motion. It seeks to establish a metric that is independent of the choice of the fixed frame or moving frame. Quaternions are adopted to represent the rotational part of a spatial pose, and the variance of the set of relative displacements is computed to reflect the difference between two sequences. With this variance-based metric formulation, we show that the comparison results of two spatial discrete motions are not affected by the choice of frames. Both theoretical demonstration and computational example are presented to support this conclusion. In addition, since the deviation error between the task motion and the synthesized motion measured with this metric is independent of the location of frames, those corresponding parameters could be excluded from the optimization algorithm formulated with our frame-independent metric in kinematic synthesis of mechanisms, and the complexity of the algorithm are hereby reduced. An application of a four-bar linkage synthesis problem is presented to illustrate the advantage of the proposed metric.

scholarly journals Application of element decomposing method for solving integer problems

2018 ◽  
Vol 192 ◽  
pp. 01022
Author(s):  
Ekkaphon Jaiyen ◽  
Komgrit Leksakul
Keyword(s):  
Simplex Method ◽  
Input Data ◽  
Second Phase ◽  
Np Hard ◽  
B Method ◽  
Large Size ◽  
Comparison Results ◽  
Integer Problem ◽  
The Difference

This research objective is to solve the integer problems by using an algorithm that applied to the element decomposing method (EDCM). Integer problem is a NP-hard when the problem is large-size, more time needed to solve the problem. The EDCM cuts a structure into several elements and reconnects elements at “nodes”. This process can disconnect other nodes that not connected with the element. Moreover, it appropriately need in optimization solutions for applications, in which can give answers faster by cutting the nodes in finding the answers. There’s 2 phases of step on this research. The first phase is input data and simplex method, while the second phase is creating and developing the algorithm from EDCM application. The comparison results show how two methods are carried out between EDCM and B&B Method. The results from two methods are focused on the value and solution step by step. According to the problem, it can be solved within the number of variables 2-15. The value of the difference in the answer is on average at 0.00% and solution step used for solving problem is less on average at 40.89 %.

A method of estimating surface settlement above tunnels constructed in soft ground

1983 ◽  
Vol 20 (1) ◽  
pp. 11-22 ◽  
Author(s):  
R. K. Rowe ◽  
K. Y. Lo ◽  
G. J. Kack
Keyword(s):  
Elastic Modulus ◽  
Elastic Anisotropy ◽  
Soft Soil ◽  
Surface Settlement ◽  
Initial Stresses ◽  
Rigid Base ◽  
Factors Affecting ◽  
Plastic Failure ◽  
Ground Loss ◽  
The Difference

A technique suitable for the analysis of lined tunnels constructed in soft soil is described. This technique permits consideration of the soil-lining interaction, lining weight, and plastic failure within the soil. Particular attention is given to the simulation of loss of ground including the annular void created by the difference between the tunnelling machine and lining diameters. The analysis is used in a parametric study to identify potentially significant factors affecting the prediction of surface settlement due to tunnel construction. Consideration is given to the effects of elastic modulus; the distance between the tunnel and the underlying rigid base stratum; plastic failure; initial stresses; ground loss (including the annular void); and the injection of clay grout into the tailpiece void. The results of this analysis indicate that elastic anisotropy, ground loss, and clay grout injection are all important factors that are not usually considered in analyses. In particular, a parameter called the gap is defined in the paper and is used in an attempt to incorporate practical tunnelling experience into the calculation of surface settlement. Furthermore, it is shown that in predicting surface settlements underestimation of the true elastic modulus below the tunnel may decrease the predicted surface settlement and lead to overestimation of the invert heave. Underestimation of the modulus above the tunnel may also decrease the predicted surface settlement for situations where there is limited ground loss and extensive plastic failure.

scholarly journals Performance of Slurry Shield Tunnelling in Mixed Strata Based on Field Measurement and Numerical Simulation

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Jian Cui ◽  
Wang-Hao Xu ◽  
Yong Fang ◽  
Li-Ming Tao ◽  
Chuan He
Keyword(s):  
Measurement Data ◽  
Tunnel Boring Machine ◽  
3D Models ◽  
Surface Settlement ◽  
Engineering Practice ◽  
Silty Clay ◽  
Pressure Balance ◽  
Shield Tunnelling ◽  
The Difference ◽  
Slurry Shield

There are severe challenges for slurry pressure balance tunnel boring machine (TBM) tunnelling in sandy cobble soil of Beijing, Chengdu, and Lanzhou in China. And the problems caused by tunnelling from silty clay to sandy cobble stratum are more serious. With the change of stratum, the key parameters and surface settlement will change correspondingly. Controlling the key parameters and predicting the surface settlement accurately and efficiently is important for hazard mitigation and risk management. In this study, based on the Tsinghuayuan Tunnel project in Beijing, the key parameters and surface settlement while tunnelling from silty clay to sandy cobble stratum are studied. Firstly, the difference of key parameters while tunnelling in two different strata is analyzed. The analysis shows that immediate responses to changes in the stratum are recommended in order to ensure construction efficiency. Then, a refined 3D finite difference model is developed to simulate the slurry TBM tunnelling in different strata. For refined simulation, three key parameters obtained from measurement data were applied to the 3D models, and the simulation results were compared with the field data. Results show that the refined model has good performance in terms of the accuracy and efficiency. This study provides a good engineering practice reference for slurry TBM tunnelling in mixed strata.

Accurate Prediction Approach of 3D Trimming Line for Auto Panel Part

2013 ◽  
Vol 535-536 ◽  
pp. 235-238 ◽  
Author(s):  
Yi Dong Bao ◽  
Yang Sang ◽  
Hou Min Wang
Keyword(s):  
Inverse Analysis ◽  
Layer By Layer ◽  
Adjacent Element ◽  
Analysis Theory ◽  
Comparison Results ◽  
Distorted Mesh ◽  
One Step ◽  
Experimental Values ◽  
Prediction Approach ◽  
Auto Panel

It is difficult to obtain 3D trimming line using traditional prediction methods for auto panel parts. An initial geometrical development method with element layer is proposed based on one step inverse analysis theory for this problem. The flange mesh can be unfold onto the die surface layer by layer according to nodal adjacent element relation, then the above development mesh is smoothed by mesh smoothing method with sliding constraint surface in order to delete overlap and distorted mesh, the 3D initial mesh can be obtained for one step inverse analysis method. The accurate 3D trimming line of auto panel part can be achieved by plasticity iteration of one step inverse analysis. A typical real part of 3D trimming line prediction is selected to prove this method, the comparison results between the simulated and experimental values show that this method has enough precision and can handle complex parts, satisfies the engineering practical demands.

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