scholarly journals Study on Ground Collapse of Covered Karst Soil Caves by Sudden Drop of Groundwater

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Xuejun Chen ◽  
Ruijian Guo ◽  
Lingming Tang ◽  
Xiaochen Zhang
Keyword(s):  
Groundwater Level ◽  
Early Stage ◽  
Karst Area ◽  
Theoretical Formula ◽  
Karst Collapse ◽  
Stability Coefficient ◽  
Groundwater Drawdown ◽  
Ground Collapse ◽  
The Stability ◽  
Soil Cave

In this study, the ellipsoidal soil cave with vertical collapses in the covering karst area is studied. Based on certain assumptions, the mechanical model of karst collapse caused by groundwater drop was established. Then, based on the negative pressure calculation formula of soil cave cavity according to Boyle–Mariotte’s law, the expression of the stability coefficient of the soil cave was proposed. Subsequently, the feasibility of the theoretical formula was verified. The calculation example analyzed the relationship of groundwater parameters and overburden thickness. The results show that when the initial groundwater level is higher than the top of cave, the law between the stability coefficient of soil cave and groundwater drawdown shows the jumping horizontal broken line. Thus, soil cave tends to collapse when the falling groundwater level drops over the vault; when the initial groundwater level ranges from the bottom to the top of the cave body, the stability coefficient and groundwater drawdown show a negative correlation law, the curve is steep at the early stage and then becomes gentle at the latter stage, and the higher the initial groundwater level in the cave is, the greater stability coefficient of soil cave reduces; when the initial groundwater level is lower than the bottom of the cave, the effect of drawdown is limited. In addition, for the small drawdown or low initial groundwater level, the stability coefficient of soil cave first decreases and then increases with the increases in thickness of overburden, and the thinner the overburden is, the greater the drawdown rate is; when the drawdown or the initial groundwater level is higher, the stability coefficient of soil cave positively relates to the thickness of the overburden layer.

Stability Analysis of Sinkhole Considering Groundwater Level Fluctuation

2012 ◽  
Vol 226-228 ◽  
pp. 1426-1431
Author(s):  
Shan Ming Huang ◽  
Yu Chuan Liu ◽  
Cheng Cheng Wang
Keyword(s):  
Groundwater Level ◽  
Regression Coefficient ◽  
Strength Reduction ◽  
Level Fluctuation ◽  
Regression Curve ◽  
Stability Curve ◽  
Region Of Stability ◽  
Groundwater Level Fluctuation ◽  
The Stability ◽  
Soil Cave

The Method of Finite Element Method Strength Reduction is used to numerical calculate and analyse the subgrade with soil cave, by considering the influence of groundwater level fluctuation in its stability. Nondimensionalize the effect factors, and draw the stability curve to get the regression curve, then make the result regression coefficient directly to the project cases. The result shows that under the weight of the subgrade, the subgrade with soil cave is damaged by that the soil around the soil cave is sheared. The more the value of is, the larger the stability coefficient is, and the higher groundwater level is, the better the stability of the subgrade with soil cave is. With the value increases, the region of stability expands

Observations on some basal failures in sheeted excavations

1970 ◽  
Vol 7 (2) ◽  
pp. 136-144 ◽  
Author(s):  
V. Milligan ◽  
K. Y. Lo
Keyword(s):  
Shear Strength ◽  
Ground Water ◽  
Groundwater Level ◽  
Soil Conditions ◽  
Remedial Measures ◽  
Factors Influencing ◽  
Water Head ◽  
The Stability ◽  
Made In

In excavations below groundwater level, instability of the base may result from the inflow of water into the excavation. The most important factors influencing the stability are the ground water and detailed soil conditions at the site.Construction problems encountered in excavations in clay strata, underlain by pervious water bearing layers, are described. The remedial measures adopted in each case are also discussed. From a study of the observations made in the case records, it is suggested that excavation in intact clays may be carried out to depths exceeding that limited by the ratio of t/h = 0.5, where t is the distance from the bottom of the excavation to the top of the water bearing stratum, and h is the water head at the top of the water bearing stratum, provided that the clay is not disturbed during construction so that the shear strength of the clay is preserved.

scholarly journals Analysis and Calculation of Stability Coefficients of Cross-Laminated Timber Axial Compression Member

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4267
Author(s):  
Qi Ye ◽  
Yingchun Gong ◽  
Haiqing Ren ◽  
Cheng Guan ◽  
Guofang Wu ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Calculation Method ◽  
National Standards ◽  
Test Results ◽  
Average Deviation ◽  
Stability Coefficient ◽  
Cross Laminated Timber ◽  
Stability Bearing Capacity ◽  
The Stability

Cross-laminated timber (CLT) elements are becoming increasingly popular in multi-storey timber-based structures, which have long been built in many different countries. Various challenges are connected with constructions of this type. One such challenge is that of stabilizing the structure against vertical loads. However, the calculations of the stability bearing capacity of the CLT members in axial compression in the structural design remains unsolved in China. This study aims to determine the stability bearing capacity of the CLT members in axial compression and to propose the calculation method of the stability coefficient. First, the stability coefficient calculation theories in different national standards were analyzed, and then the stability bearing capacity of CLT elements with four slenderness ratios was investigated. Finally, based on the stability coefficient calculation formulae in the GB 50005-2017 standard and the regression method, the calculation method of the stability coefficient for CLT elements was proposed, and the values of the material parameters were determined. The result shows that the average deviation between fitting curve and calculated results of European and American standard is 5.43% and 3.73%, respectively, and the average deviation between the fitting curve and the actual test results was 8.15%. The stability coefficients calculation formulae could be used to predict the stability coefficients of CLT specimens with different slenderness ratios well.

Evaluating second-order effects in rigid wall-flexible roof diaphragm buildings

2020 ◽  
Vol 36 (4) ◽  
pp. 1864-1885
Author(s):  
John Lawson ◽  
Maria Koliou
Keyword(s):  
Rigid Wall ◽  
The United States ◽  
Second Order ◽  
Order Effects ◽  
Building Stock ◽  
Stability Coefficient ◽  
Multistory Buildings ◽  
Flexible Diaphragm ◽  
Second Order Effects ◽  
The Stability

When evaluating seismically induced second-order effects in buildings, engineers and researchers are most familiar with these concerns in the context of multistory buildings with rigid diaphragms. However, similar concerns are valid for short single-story concrete or masonry-walled buildings with larger flexible diaphragms, which is a significant portion of the building stock in the United States. These rigid wall-flexible diaphragm (RWFD) buildings may have significant diaphragm drifts causing induced second-order effects. The stability coefficient currently found in ASCE 7 has traditionally been used by practitioners to evaluate the relative risk of P-delta instability in multistory buildings, but this indicator can be adapted for use in RWFD buildings. Using numerical studies following the Federal Emergency Management Agency (FEMA) P-695 collapse assessment methodology to evaluate the risk of collapse for a set of RWFD archetype buildings, a modified stability coefficient for RWFD buildings is found to capture the trend toward P-delta collapse and can act as a reasonable indicator without the need for heavy computational efforts.

Stability Coefficient of Interlocking Compressed Earth Block Masonry under Axial Compression

2020 ◽  
Author(s):  
Tianya Wang ◽  
Yihong Wang ◽  
Guiyuan Zeng ◽  
Jianxiong Zhang ◽  
Dan Shi
Keyword(s):  
Compressive Strength ◽  
Axial Compression ◽  
Design Guidelines ◽  
Stability Coefficient ◽  
Strength Failure ◽  
Compressed Earth Block ◽  
Out Of Plane ◽  
The Stability ◽  
Earth Block ◽  
Plane Deformations

To investigate the effects of the height-thickness ratio (β) on the mechanical properties and stability coefficients (φs) of interlocking compressed earth block (ICEB) masonry members under axial compression, four groups of specimens with different β of 3.75, 6.75, 11.25, and 14.25 were tested, thereby assessing their stress process, failure mode, compressive strength, and in- and out-of-plane deformations. All the specimens underwent brittle failure under axial compression: the compressive strength was found to decrease in a range from 5.6% to 43% with increasing β, whereas the initial stacking defects and the in- and out-of-plane deformations increased. The specimens became less stable, and we noticed that the overall damage was caused by strength failure and not instability failures. Because the stability coefficient of ICEB-based masonry components cannot be calculated as those of more conventional brickwork, we combined our results with well-established masonry design guidelines and derived an interlocking improvement coefficient.

scholarly journals Application of Roadway Backfill Mining in Water-Conservation Coal Mining: A Case Study in Northern Shaanxi, China

2019 ◽  
Vol 11 (13) ◽  
pp. 3719 ◽  
Author(s):  
Yihe Yu ◽  
Liqiang Ma
Keyword(s):  
Water Resources ◽  
Coal Mining ◽  
Groundwater Level ◽  
Water Conservation ◽  
Coal Pillar ◽  
Normal Growth ◽  
Mining Area ◽  
Backfill Mining ◽  
Northern Shaanxi ◽  
The Stability

The mining induced subsidence and strata deformation are likely to affect the stability of the aquiclude, resulting in loss of water resources in the mining area. In order to reduce the disturbance of coal mining to the overlying strata and to preserve the water resources in the coal mining area, the roadway backfill mining (RBM) method was trialed in Yuyang coal mine in Northern Shaanxi, China. Based on pressure arch theory and ultimate strength theory, a mechanical model was developed to analyze the stability of coal pillars. Then the maximum number of vacant roadways between the mining face and the backfilling face was determined according to the stability of coal pillar and filling body. The method to calculate aquiclude subsidence and deformation was also proposed. Furthermore, as indicated by FLAC3D numerical simulations, the maximum tensile stress subjected by the aquiclude was 0.14 MPa, which is smaller than its tensile strength; the horizontal deformation was 0.24 mm/m, which is also smaller than the critical deformation of failure. Field monitoring data demonstrated a maximum of 2.76 m groundwater level drop in the mining area after mining. The groundwater level was determined to be 4.45~10.83 m below surface, ensuring the normal growth of surface vegetation and realizing the water-conservation coal mining (WCCM).

scholarly journals Galloping Stability and Aerodynamic Characteristic of Iced Transmission Line Based on 3-DOF

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Xiaohui Liu ◽  
Ming Zou ◽  
Chuan Wu ◽  
Bo Yan ◽  
Mengqi Cai
Keyword(s):  
Wind Speed ◽  
Transmission Line ◽  
Angle Of Attack ◽  
Wind Tunnel Test ◽  
Simulation Method ◽  
Theoretical Formula ◽  
Aerodynamic Load ◽  
Line System ◽  
Critical Wind Speed ◽  
The Stability

A new calculation method of critical wind speed based on three degrees of freedom (3-DOF) is proposed for galloping problem of iced transmission line. Based on the quasistatic theory, the aerodynamic load of iced transmission line is obtained, which considers the influence of transverse and torsional motion on the relative wind angle of attack. Finally, the equivalent galloping model of 3-DOF iced transmission line is established. At the initial angle of attack, the aerodynamic load is expanded by Taylor, and the unsymmetrical linear aerodynamic coefficient matrix is obtained. The Routh–Hurwitz criterion is used to judge the stability of iced transmission line system, and then the critical wind speed is calculated. The in-plane and out-plane frequencies corresponding to the first-order mode of the transmission line are solved by the analytical method and numerical simulation method. The results obtained by the two methods are compared and verified. The influence of dimensionless transmission line parameter λ on the in-plane and out-of-plane frequencies is discussed. The aerodynamic coefficients of the iced transmission line are measured by wind tunnel test and the aerodynamic characteristics are analyzed. According to the theoretical formula, the critical wind speed is calculated by MATLAB. The critical wind speed determined in this paper is compared with the critical wind speed determined by Den Hartog and Nigol theory. The influences of torsional vibration frequency, ice thickness, and ice shape on critical wind speed are analyzed. The research results of this paper have important theoretical significance for the stability judgment of iced transmission lines.

Study on Evaluation of High Slope Stability and Countermeasures Based on GEO-SLOPE

2014 ◽  
Vol 988 ◽  
pp. 371-376
Author(s):  
Nian Qin Wang ◽  
Qing Tao Wang ◽  
Qi Pang ◽  
Qian Xue
Keyword(s):  
Slope Stability ◽  
Limit Equilibrium ◽  
Optimization Analysis ◽  
High Slope ◽  
Stability Coefficient ◽  
Anchor Cable ◽  
Before And After ◽  
The Stability ◽  
Reinforcement Measures

Based on the theory of limit equilibrium, by the GEO-SLOPE software,analyzed the stability before and after reinforcement of a high Loess-bedrock slope. The results and conclusions show: (1)Analyzed and Optimized the high Loess-bedrock slope through SLOPE/W module, optimizing the engineering quantity of the anchor cable frame in the local and saving the investment; (2)When taken reinforcement measures, conducted the SLOPE/W model again, the stability coefficient is 1.459, the effect testified by projects is obvious; (3)Aiming at the optimization analysis, proposed countermeasures system, with reference for reinforcement of a high Loess-bedrock slope.

PERFORMANCE OF THE ANALYTICAL PLOTTER

1963 ◽  
Vol 17 (2) ◽  
pp. 205-211
Author(s):  
T. J. Blachut
Keyword(s):  
Early Stage ◽  
Statistical Treatment ◽  
Measuring System ◽  
Stage Of Development ◽  
Pointing Accuracy ◽  
Analytical Accuracy ◽  
The Stability ◽  
Extensive Experimental Data ◽  
Mean Square Errors ◽  
Very High

In spite of the lack of extensive experimental data at this, in a sense, early stage of development, some very interesting indications of the eventual performance of the Analytical Plotter can be seen. The accuracy of the measuring system is very high; monocular grid measurements gave mean square errors of 2.5 - 3.5 μ. The stability is even better, repetition of readings being constant within 2 to 3 μ, that is, within the pointing accuracy. The accuracy of the complete system may be improved by using experimental corrections and proper statistical treatment of redundant observations. Complete relative and absolute orientations can be carried out in 10 to 15 minutes or less with analytical accuracy. Further economical advantages result from the use of the inherent computer capabilities to solve auxiliary problems and to carry out pertinent “real time” operations, such as automatic control of the plotting table.

Sign in / Sign up

Export Citation Format

Share Document