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Volume 44,2024 Issue 4 Cover Download Catalog Download

Experimental Study on Reinforced Geogrid of Construction and Demolition Wastes Based on DIC Technology[1-10]

TAN Peng, LI Hai, LI Xiangping, GU Fan, ZHANG Junhui

Abstract: In order to control differential settlement caused by new and old subgrade connections after expressway reconstruction and expansion，this paper proposed a layered treatment structure for the loose steps of the old road with high water content.A layer of construction and demolition waste was laid on the step surface of the old road to wrap the geogrid.The treatment effect was compared with that of sand wrapping and lime mixing，and the digital speckle correlation （DIC） was used to observe the reinforced influence zone，so as to determine the thickness of different layers of the subgrade wrapped by construction and demolition wastes.The particle rotation and displacement were further analyzed，and the reliability and accuracy of the reinforced influence zone determined by DIC observation were verified.The test results show that：① Among the measures to improve the interface strength of reinforced soil in the old road steps，the effect from good to bad is construction and demolition wastes C （particle size of 10?20 mm） > construction and demolition wastes B （particle size of 5?10 mm） > sand > construction and demolition wastes A （particle size of 1?5 mm） > mixed ash of 6% > mixed ash of 4%，and the reinforcement effect increases with the increase in the particle size of the construction and demolition wastes；② The DIC test results show that the area of the reinforced influence zone decreases with the increase in normal stress，and its thickness above the geogrid is greater than t hat below the geogrid.The particles that rotate are mainly concentrated within 3 cm below the geogrid and 5 cm above the geogrid；③ The recommended thickness of the layer wrapped by construction and demolition wastes is determined based on the thickness of the reinforced influence zone：about 20 cm in the middle of the subgrade，about 15 cm in the bottom of the subgrade，and not less than 25 cm in the upper part of the subgrade.

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Latest update time：2024-07-30

Experimental Study on Effect of Temperature on Bound Water Adsorption and Deformation of High Liquid Limit Soil[11-17]

ZI Yinhui, SHEN Xuning, ZHANG Hao, ZHANG Rui, LI Lu

Abstract: In order to study the effect of temperature change on the bound water content adsorbed by high liquid limit clay and the deformation law of high liquid limit clay embankment，the high liquid limit clay in Hainan Province was selected as the primary research object and compared with the low liquid limit sand in Hunan Province.The effect of temperature on the bound water content adsorbed by high liquid limit clay was explored through a nuclear magnetic resonance test.In addition，the effect of temperature on the deformation of high liquid limit clay embankments was analyzed through the consolidation test with a temperature-controlled consolidometer.The molecular dynamics simulation software was used to reveal the mechanism of temperature affecting water adsorption by kaolinite from the microscopic level.The results show that when the temperature rises from 5 ℃ to 45 ℃，the bound water adsorbed by high liquid limit clay decreases by 4.3 percentage points，much greater than that adsorbed by low liquid limit sand （a decrease by 1.4 percentage points）.Under constant temperature and the same load path，the pore ratio of high liquid limit clay changes significantly with the temperature increase.In contrast，low liquid limit sand is almost unaffected，indicating that high liquid limit clay is more temperature-sensitive.The rise in temperature under constant pressure can weaken water adsorption by kaolinite.Under the same heating path，higher pressure indicates more water adsorbed by kaolinite.

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Latest update time：2024-07-30

Stability Analysis of High and Steep Bank Slope of Jinqi Bridge on Wudang‑Changshun Expressway[18-28]

WANG Hao

Abstract: Jinqi Bridge on the Wudang-Changshun Expressway in Guizhou Province crosses the Maotiao River，and the poor geological conditions such as dangerous rock mass and collapse accumulation body on the bank slope of the river are relatively developed，which seriously affects the site selection and safety of the bridge.In order to study the stability of the high and steep bank slope of the bridge，the paper explored the main poor geological conditions in the bridge site through a comprehensive air-ground investigation.By means of numerical analysis，InSAR，and other technologies，the movement range of dangerous rock mass on the bank slope was quantitatively evaluated.The stability and deformation mode of the accumulation body on the bank slope under the action of internal and external dynamics were elucidated.The results show that：① The poor geological conditions in the bridge site are mainly cliff unloading zone，dangerous rock mass，and collapse accumulation body，and the failure mode of dangerous rock mass is pulling-toppling；② The movement distance of W 1，W2，and W 3 dangerous rock mass after failure is about 65 m，57 m，and 320 m，respectively，which affects the Wudangan abutment and Changshun pier；③ The accumulation body on the Wudang bank slope is very stable under normal，rainfall，and rainfall + earthquake conditions.The accumulation body on the Changshun bank slope is stable under normal and rainfall conditions.Under the rainfall + earthquake conditions，the shear plastic zone at the contact surface between the upper accumulation body and the bedrock is completely connected，and the accumulation body is in an unstable state.The failure mode is creep-pulling.The research results can provide a reference for comprehensive investigation and stability analysis of high and steep bank slopes of bridges in deep canyons and steep cliffs in Guizhou Province.

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Latest update time：2024-07-30

Shear Creep Characteristics and Slope Deformation Mechanism of Siliceous Slate[29-36]

LI Jian, YAN Liangyu, YU Kaibing, LI Ming, YAN Tingzhou, ZHAO Jia

Abstract: To study the time-dependent creep effect of siliceous slate and the deformation and failure evolution law of high slope，in this paper，the shear creep test of indoor rock mass was carried out to plot the shear creep duration curves of siliceous slate under different normal stresses，the shear displacement-time curve，and the creep rate-time curve under different normal loads and shear loads.The average creep rate and shear load variation of siliceous slate were studied，and the long-term shear strength parameters of siliceous slate were determined by the steady-state creep rate method.The results show that in the creep test，the sensitivity of cohesion is significantly greater than that of internal friction angle.Finally，the high slope of ZK 33 + 450 siliceous slate on the Shiyan-Wuxi Expressway is used.Based on the Mohr-Coulomb model，the finite difference method was used to analyze the deformation and failure mechanism of the high slope of the typical siliceous slate under shear creep conditions.

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Latest update time：2024-07-30

Working Performance of Rigid Airfield Runway Considering Influence of Cavity Depth[37-46]

DAI Xuan, LI Zhao, CAI Jing, LI Yue, LIU Guoguang, QI Lin

Abstract: In order to analyze the influence of cavity depth on runway safety，a numerical simulation was carried out using the finite difference method.A total of 208 sets of different working conditions were designed by taking into account factors such as different aircraft types，runway dimensions，and cavity depth and area.Based on the runway life model considering the exponential decay of the structural condition，an analytical method was proposed to evaluate the impact of the cavity on the runway life.The results show that the bending and stress of the runway increase gradually with the increase in the cavity depth，but the growth rate is getting slower and slower.There is a coupling effect between the impact of cavity depth and cavity area，and the impact of cavity depth starts to appear when the cavity area is larger.In the cloud diagram of the influence of runway bending and stress，there is a non-sensitive area. The proposed runway bending rate development index and stress development index can be used to evaluate the influence of the trend of the cavity，and with the increase in the cavity area and depth，the above indexes have a peak area.According to different loads，runway structures，and take-off and landing times，the influence diagrams of cavity degree and remaining service life are drawn，which can quickly evaluate and analyze the influence of the cavity，thus guaranteeing the structural safety of the airfield runway.

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Latest update time：2024-07-30