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30 December 2021, Volume 35 Issue 6 Previous Issue    Next Issue

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Settlement Analysis of a High Fill Project WU Rui 2021, 35 (6):  649-653.  Abstract ( 283 )   Save This paper presents a case history of ground improvement for Shanxi Coalbed Methane Central Processing Center’s foundations. Based on the site topographic mapping, geological mapping, geotechnical boring program, test pits, insitu tests, and geotechnical sampling results, the site engineering geological and hydrogeological conditions were characterized. An isotopic homogeneous ground deformation model was proposed to predict to site settlement and mitigation plan was also proposed. The results show that the backfill soil layer was unevenly distributed, the degree of compaction criteria were not reached, the void ratios are relatively high and the external drainage system at the site was not functional. The backfill soil softening, and the hydrocompaction induced by the surface water seepage were the main factors causing the settlement and deformation of the backfill soils. The contribution of the underlying loess layer was not significant. Based on the static analysis of the isotropic homogeneous linear deformation body theory, it is concluded that the current settlement within the project area is still ongoing, and the settlement has not stabilized yet, which requires comprehensive engineering treatment. Related Articles | Metrics

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Numerical Simulation Study on DX Pile in Complex Geological Condition TIAN Longlong, XIONG Yucheng 2021, 35 (6):  654-658.  Abstract ( 219 )   Save The DX pile is a new proprietary type of bored reinforced cast-in-place concrete pile with multiple enlarged shaft sections. This paper presents a case history of the installation, analysis, and load testing of long bored DX piles in Guangdong coastal area. The coastal project site is characterized with soft peaty soils and thick silty fine sand with gravel. The commercial finite difference software, FLAC3D, was used to simulate performance of the DX pile under failure load. The stress field distribution, development of settlement at pile, development of plastic zone in the surrounding soils, axial force in the pile and the stress changes in the enlarged shaft sections are evaluated. The loading transfer mechanism and failure mode under axial loading are discussed in the paper. The results are also compared with the test results. Related Articles | Metrics

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Analysis of Wanan Street Rock Fall Hazards and Mitigation Measures WANG Xueqing, LONG Shengjun, HUO Yulong, WANG Yikun 2021, 35 (6):  659-662.  Abstract ( 308 )   Save Unpredicted rock falling has always been an important threat affecting the safety of adjacent residents. At present, the analysis of the trajectory of rock falling is mainly a combination of empirical formulas and kinematic analysis methods. The empirical formula has major limitations. Therefore, in the analysis of Wanan Street rock fall potential, the inversion method is used to estimate the friction coefficient of the rock slope, and at the same time, the trajectory formula of the falling rock during the rebound and oblique throwing process is summarized. Throughout the use of existing kinematics formulas and induction formulas, combined with the topographical characteristics of rock slopes with rock falling potentials in Wanan Street area, the trajectory of rock fall is analyzed, the track of rockfall pattern is described in the paper. Rockfall mitigation and prevention suggestions are also proposed in the paper. Related Articles | Metrics

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Feasibility Study of Constructing a Shielded Tunnel Under Passing the Expressway in Soft Soils ZHOU Jianyong 2021, 35 (6):  663-666.  Abstract ( 202 )   Save With the continuous advancement of urbanization, there are more and more cases of shielded tunnel excavations passing through roads, hospitals, schools and other municipal facilities. This paper presents a shielded tunnel in East China to underpass an existing express highway. The relative position between the existing highway and the proposed under passing tunnel. The engineering geological conditions, site soil and rock stratigraphy and properties, hydrological and geological structures were thoroughly investigated. Based on the site-specific information, Peck formula was used to predict the ground response to the tunnel excavation. The analytical results are also compared with the numerical results by MIDAS. The results demonstrate the deformation pattern of the surrounding rock mass as well as the highway and retaining walls after the tunnel excavation. Based on the above analysis results, it is believed that the impact of shielded tunnel construction on the existing expressways is acceptable.  Related Articles | Metrics

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Soil Improvement Method for Soft Soil over a Liquefiable Soil Layer TANG Wei, GUO Shengjuan, LI Zhaode 2021, 35 (6):  667-669.  Abstract ( 312 )   Save The soft and liquefiable soils are soil strata that are frequently encountered in the engineering projects, however, the soft soil overlying the liquefiable soil is rarely reported. Although many conventional soil improvement methods for soft soils or liquefiable soils exist, but few methods that can improve both soils combined in one site. Deep foundations are frequently used to penetrate both soils. This paper presents a case history of soil improvement method for a weak soil layer overlying liquefiable soil layer. This method has the advantage of matured technique, cost effective and fast construction.  Related Articles | Metrics

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Selection of Advance Support Type at Shallow Buried Tunnel Portal in Granite Mountain HUANG Congcong, LIU Zhenping 2021, 35 (6):  670-673.  Abstract ( 225 )   Save The selection of an appropriate advance support type in the shallow buried tunnel portal in the mountain should both consider the construction cost and the safety as well as the risk during the construction. In the construction of the Zhaizibao Tunnel in Fanba Jiangbei Highway Project near Three Gorges, the finite element analysis by using ABAQUS software was used to simulate three different types of advanced support of left side of the tunnel portal excavations in the strongly to completely weathered granite rock mass, namely, no advance support, doublelayer small diameter perforated pilot grouting pipe and large diameter perforating pilot grouting pipe shield. The results show that, in the process of Three Benches excavation, the large diameter perforated pilot grouting pipe shield method had obvious effect in controlling the excessive settlement deformation and development of plastic zone expansion, the predicted settlement deformation characteristics and cumulative value are close to the measured value, while the doublelayer small diameter perforated pilot grouting pipe method had little effect on controlling the deformation and overall failure of the surrounding rock mass. Therefore, the selecting of the advanced support type of large diameter perforated pilot grouting pipe shield method for the left tunnel portal of Zhaizibao Tunnel exit was validated. This project provides a method the design and construction of the advance support for the similar tunnel in the future. Related Articles | Metrics

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Mechanical Effect of Large Diameter Sewage Pipe Jacking Launching Shaft Construction LAI Yinbo 2021, 35 (6):  674-681.  Abstract ( 199 )   Save This paper presents the case history of construction of sewer outfall project of Qianpu wastewater treatment plant in Xiamen. In order to evaluate the mechanical effect of a deep excavation for the pipe jacking launching shaft nearshore under high groundwater table in high permeability sand layer, the numerical simulation and field measurement methods were used to study the internal force and deformation of soldier piles as well as the surrounding soils during the excavation. The results show that, the surface settlement area is mainly distributed outside the long side of the excavated area, and the cumulative maximum deformation value is less than 8.8 mm; The maximum horizontal displacement and bending moment of the retaining wall are 24.6 mm and 852.0 kN·m, respectively. The location of the maximum bending moment varies with the excavation elevation, and the axial force of the diagonal brace is larger, but they are in the allowable stress range. It is worth noting that the maximum horizontal axial force is 2267 kN per meter when the partition wall in front of the tunnel portal is broken, and the stress concentration is formed at the top and bottom of the tunnel after the tunnel portal is broken, and the axial force reaches 4744 kN per meter. Finally, combined with the field measured data, with the excavation retaining wall horizontal displacement gradually increases, and the location of the maximum horizontal displacement moves downward, through the effective control on site, the maximum lateral deflection value can be reduced from 24.6 mm to 18.6 mm. Related Articles | Metrics

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Design and Finite Element Analysis of Ultra High Wind Turbine Tower Foundation WU Xiaoqing, WU Fanghe 2021, 35 (6):  682-685.  Abstract ( 274 )   Save Based on a wind power project in Thailand, this paper introduces the design of an onshore wind turbine foundation of a large capacity and super-high tower. This paper also introduces the finite element analysis on the performance of wind turbine foundation in details, and the results are evaluated. The results show that, with the increase of wind turbine foundation dimensions, the stress characteristics and deformation are different from the conventional foundation design. For the similar wind turbine foundations, there is a certain difference in the assumptions and analytical results when using the traditional theoretical method for the foundation design comparing with the actual results. It is necessary to use finite element calculation to validate the design results, especially for the foundation deformation calculation, structural stress and anchor force analysis.  Related Articles | Metrics

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Dewatering Design Comparisons in Deep Excavations in Thick Sandy Soils PENG Kan 2021, 35 (6):  686-689.  Abstract ( 246 )   Save Longhu Financial Center Outer Loop Building Group Project is located in Zhengdong New District, Zhengzhou City. The entire development consists of 24 land blocks. The total area of the deep excavation is 285,200 m2, and the excavation depth is between 12.5 and 20 meters. The deep excavation project is very large, and the surrounding environmental conditions of the proposed excavated area are complicated. It is necessary to develop a safe, cost-effective and efficient groundwater control measures for the construction in thick sand aquifer layers. Before the implementation of the excavation procedures, a series of single dewatering well tests were conducted to obtain the hydrogeological parameters of the thick phreatic aquifer, to determine the reasonable design of the seepage cut-off wall. Since the groundwater cut-off curtain needs to penetrate the 20 meters thick fine sand layer with high SPT N values, the installations technique of Trench Cutting Re-mixing Deep Wall was used in areas with high environmental restriction requirements. Conventional three-axis cement-soil mixing piles were applied in the other areas. Related Articles | Metrics

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Analysis and Mitigation of Settlement of Initial Support of Tunnel Excavation in Saturated Completely Weathered Granite HUANG Yinhai 2021, 35 (6):  690-693.  Abstract ( 299 )   Save This paper presents a case history of mitigating the settlement of initial support of tunnel excavations in the saturated completely weathered granite soils and the factors that inducing the settlement are also investigated. The general guidelines for minimizing the settlement in the initial support are also proposed. Settlement mitigation measures, such as, dewatering around the excavated area, grouting from the ground surface and increasing the stiffness of the initial supporting structures and the construction monitoring system were established based on the theoretical analysis. The comprehensive approaches were applied in the construction and resolved the excessive deformation in the initial support of tunnel excavation in saturated completely weathered granite soils. Related Articles | Metrics

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Sandbag as the Cofferdam in a Deep Water Excavation Project CHEN Ming, WEN Jianpeng 2021, 35 (6):  694-697.  Abstract ( 255 )   Save Based on an upgrading project of a wastewater treatment plant in Beijing and combined with the need of owner’s operation requirements, this paper presents the design conception and the construction technique of the wastewater treatment plant. The entire upgrading project site has a water depth of 10.5 meters and the staged construction divided the original site into two parts by a sandbag cofferdam with one side maintained the normal operation, and the other side was dewatered and excavated. Combined with the results from the finite element analysis software PLAXIS 2D and the construction monitoring data, it is technically feasible to use the sandbag cofferdam as water retaining structure in the deepwater dewatering requirements. This project can provide some guidance or references for projects with similar background and conditions. Related Articles | Metrics

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Combination of Expanded Base Pier and Ground Anchor for Transmission Tower Foundations in Mountain Areas  ZHANG Wenxiang, QIU Haoci, LI Yangsen, CUI Qiang, ZHANG Zhenhua 2021, 35 (6):  698-703.  Abstract ( 327 )   Save The key construction procedures of the composite foundation of the expanded base pier and the rock anchor in mountainous areas include design method, installation and cost comparisons, standardized foundation design and construction procedures. The design method mainly involves the selection of the coefficient of bearing capacity. Based on the numerical simulation and the current test results, the suggestions for the selection of k1 and k2 are proposed in the paper. Under the local geological conditions, loads acting on the proposed foundations and state-of-the-practice construction conditions, the combination of expanded base pier with rock anchor is proved to be cost effective. Through the determination of design principles of expanded base pier part and anchor part, the suggestions of anchor reinforcement arrangement under different diameter of main pier are proposed. In the Luoyuan Bay Power Plant-Bili 220 kV power transmission line project, 17% of the foundations are composite foundation of expanded base pier with rock anchor, the result shows that this composite foundation receives cost, social and environmental benefits. Related Articles | Metrics

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Longnan Expressway Embankment Slope Construction Monitoring Technique CHEN Fang, LIN Chao, TANG Xiaohui, CHEN Yangzheng 2021, 35 (6):  704-707.  Abstract ( 268 )   Save The real time construction monitoring on the embankment slope is critical to the embankment slope stability during the constriction. An embankment slope in Longnan Expressway Project was real-time monitored with various geotechnical instruments. The slope inclinometers were mounted at the top of a retaining wall so that the displacement at the toe of the embankment as well as the lateral movement of the embankment could be measured. The deep settlement benchmarks, piezometers and rainfall gauges were installed at the site so that the groundwater level and precipitation at the site could also be monitored. The results indicate that, the embankment slope lateral deformation during the highway operation varied from 6 to 11 mm, the deflection in the vertical directions varied from 3 to 10 mm. and no obvious trend with time was developed. The deep settlement benchmarks measured deflections were reasonable and no obvious trend was identified. The rainfall range was between 0 and 25 mm. There were no obvious groundwater changes found. It is therefore concluded that the embankment slope is stable.  Related Articles | Metrics

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Cross Section Design of an Inclined Shaft of Jiaozhou Bay Second Subsea Tunnel#br# CHEN Libao, LI Bo 2021, 35 (6):  708-711.  Abstract ( 293 )   Save This paper presents a case history an inclined shaft at Huangdao end of Qingdao Jiaozhou Bay Second Subsea Tunnel. The design aspects of the longitudinal profile and the cross section of the inclined shaft for the long tunnel are introduced. Considering the needs of the auxiliary construction, hazard prevention and rescue and operation services of the inclined shaft, the design procedure of the longitudinal profile and cross section of the inclined shaft meeting the requirements is proposed. The longitudinal slope of the inclined shaft is a combined slope of 10% (200 m) + 3% (60 m). The speed limit during construction is 5 km per hour and 20 km per hour during operation. The design of inclined shaft cross section needs to meet the needs of building clearance with different functions during the construction, emergency rescue and operation services. After the completion, it will be retained as a service and emergency rescue tunnel, which will greatly improve the emergency rescue capacity in case of emergencies and provide convenience for the later operation and the maintenance of the tunnel. Related Articles | Metrics

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Vibration Influence of Cast-in-Place Concrete Pile by Impact Method on the Adjacent Bridge Piers CHEN Junzhou 2021, 35 (6):  712-717.  Abstract ( 288 )   Save This paper presents a case history of the vibration influence of the proposed magnetic levitation bridge under passing the existing Shanghai-Kunming railway viaduct. The peak particle velocity (PPV) of the target soil was selected as the target of the vibration control. The shaft of the cast-in-place reinforced concrete pile was installed by impact punching method in this project. To study the pile construction induced vibration on the adjacent existing bridge piers, vibrations from three typical installation impact conditions, namely, shallow layer punching, mid layer punching and deep layer punching, were numerically investigated by using FLAC3D software. The PPV values generated from different stroke and installation depth were evaluated. The results showed that the stroke had a great influence on the PPV values. With the increase of the stroke, the PPV in the radial, tangential and vertical directions gradually increased. During construction, the impact of construction vibration on the existing railway bridge piers could be reduced by reducing the stroke. The overlying soil had less effect on the transmission of vibration and the induced PPV at the ground surface was reduced with the deeper punching position. As the impact depth increased, the horizontal vibration of the soil was stronger than the vertical vibration. The research results will provide a scientific basis for the impact assessment of vibration safety in the construction of cast-in-place piles near the railway line and the optimization of pile installation procedures. Related Articles | Metrics

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Application of Strength Reduction Method in Analysis of Basal Stability for Deep Excavations in Soft Clay XU Jian, CUI Xiaokai 2021, 35 (6):  718-722.  Abstract ( 159 )   Save In this paper, the excavation process of a deep excavation supporting project in the soft soils was investigated by using the strength reduction method. The influence of the embedded depth and the shear strength change of the deep excavation supporting structure on the uplift instability is also studied. The analysis results are compared with the results from Terzaghi foundation bearing capacity and Prandtl foundation bearing capacity estimation methods. The results show that: (1) with the increase of the insertion ratio D / h of the supporting structure, the factor of safety against the uplift stability in deep excavation also increases gradually, but the improvement of the factor of safety of the against the uplift failure is limited; (2) with the decrease of the shear strength of the soft soil, the uplift stability factor of safety in the deep excavation decreases nonlinearly; (3) the analytical results based on Terzaghi and Prandtl models are larger than the results from the strength reduction method, which overestimates the uplift resistance against the soft soil stability. Related Articles | Metrics

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Numerical Stability Analysis of Rock Mass at the Crest of a Tunnel CHEN Chunling, XU Pei 2021, 35 (6):  723-727.  Abstract ( 384 )   Save Hidden caves have an important impact on the safety of the tunnel excavation. The FLAC3D software was used to investigate the influence of karst rock cavities with different diameters and distance to the tunnel crest on the rock mass surrounding the tunnel. The results show that the safe distance of the karst rock cavity to the tunnel from the groundwater intrusion is about 6 meters, and the deformation around the tunnel due to the rock cavity is mainly in the vertical displacement. When the distance between the cavity and the tunnel is greater than 2 to 3 times the radius of the karst cavity, the influence on the tunnel will be weakened. When the distance between the two increases by every 2 meters, the volume of the plastic zone φ decreases to approximately 15.3%~12.4%, while the volume of the plastic zone outside the boundary decreases approximately 8.5%~6.7%. After these statistical analyses, the linear relationship between the settlement and displacement of the tunnel crest and the size distribution of the karst rock cavity is obtained, which provides references for the design and construction of similar projects. Related Articles | Metrics

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Strength and Durability of the Cast-in-Place Concrete Pile using Manufactured Sand LV Jinhui 2021, 35 (6):  728-731.  Abstract ( 691 )   Save The experience of applying manufactured sand in the highway construction in Gansu Province is still rarely reported. According to the investigation of manufactured sand from many venders in Gansu Province, a comparative study between the manufactured sand concrete and the natural sand concrete in the strength and the durability was investigated. The results show that: The 28-day strength of the manufactured sand concrete can reach the same grade as that of the natural sand concrete for C40、C50、C60, and the strength of manufactured sand concrete is slightly higher than that of natural sand concrete. In terms of the durability index, the dry shrinkage rate of C40~C60 with manufactured sand concrete is lower than that of the natural sand concrete. Under the same grade of frost resistance, the relative dynamic elastic modulus of the manufactured sand concrete is greater than that of the natural sand concrete. The fluoride and carbonation resistance in the manufactured sand concrete are basically at the same level as those of the natural sand concrete. Related Articles | Metrics

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Application of Stereographic Projection in the Stability Evaluation of Rock Slopes CHEN Yuanyong, TANG Youshan, ZHANG Xian 2021, 35 (6):  732-736.  Abstract ( 239 )   Save Under the influence of fault and rock joints, the local rock slope failures at south portion of Jinduicheng Mine are frequently occurred. The failure modes include rock sliding, rock burst and rock fall. The lithology of the south bank of the rock slope consists of quartzite, slate and Anshan siltstone. The stability of rock slopes in different rock lithology is significantly different. Based on the geotechnical investigation result for the rock slope, the rock slope stability of south portion was evaluated using stereographic projection method and the potential locations of the instability of these rock slopes were predicted. The quartzite rock slope is mainly encountered in the west side. The single step sliding failure mode was identified by L1 structural plane. The combination of rock joints of L1 and L2 would lead to a wedge failure mode. The middle portion of slope consists of slate rock. The joint L1 is daylighting with the rock slope at a small angle so that the sliding failure potential existed. The Anshan siltstone rock slope is found at the east portion. The L2 joint set is less than the slope angle of the step so that the broken siltstone at the surface sliding failure might be occurred along this plane. Related Articles | Metrics

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Safety Hazards of the Shielded Tunnel Excavation Under Passing an Expressway Bridge YIN Jian 2021, 35 (6):  737-740.  Abstract ( 272 )   Save This paper presents a case history of safety hazards evaluation of the shielded tunnel excavation under pass the existing highway bridge in the Suzhou Rail Transit No. 6 Line under passing the Changtai Expressway at location between Xujiabang and West Zhongxin Avenue stations. The influence of the relative location between the shielded tunnel and the expressway bridge on the safety hazards was evaluated by the three-dimensional finite element method and the stress and deformation of bridge piers induced by the tunnel excavation were simulated. The numerical simulation results indicate that, the deformation of the bridge piers is mainly in the traffic (longitudinal) direction with a maximum deflection of 3.3 mm. The maximum differential settlement is 0.39 mm. If the shielded tunnel excavations could use the zoned method and the control of amount of grouting, the bridge pier deformation could be controlled within the tolerable range.  Related Articles | Metrics

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Settlement and Deformation of Deep Excavation Estimation Based on Stochastic Medium Theory GAN Binlin, LIANG Yahua, BI Shuqi, BIAN Chao, YANG Yonghua, LI Huan 2021, 35 (6):  741-745.  Abstract ( 218 )   Save The simplified stochastic medium theory and the settlement empirical formula were used to estimate the ground settlement in the deep excavation of Nahong Overpass Station of Nanning Rail Transit Project. The feasibility and accuracy of prediction ground subsidence are validated by the monitored data. The settlement of surrounding buildings causing by the deep excavation and the relationships among the building settlement, the ground deformation and the horizontal displacement of supporting structure of the deep excavation were analyzed. The results indicate that the predicted value by the stochastic medium theory is consistent with the characteristics of the monitored data, but the monitored value is less than the predicted value. The settlement characteristics of the building are consistent with the surrounding ground deformation, but it is relatively lagging with time. Both the deep excavation and the internal support construction will lead to deforming of the surrounding environment, causing fluctuations in the cumulative settlement of the surrounding ground and buildings. Related Articles | Metrics

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Study and Numerical Simulation of a Reinforced Earth Embankment over Soft Soils HUANG Wenbin, , LIU Dong, 2021, 35 (6):  746-750.  Abstract ( 232 )   Save The finite element method w used to analyze the deformation development in the process of a reinforced earth embankment over soft soils. The results show that the embankment reinforcement can effectively control the lateral deformation of soft soil, improve the ability of “contracting” of horizontal displacement in consolidation stage, uniformize the embankment settlement. In the embankment filling stage, the excess pore pressure in the underlying soft soil in the reinforced earth embankment is obviously higher than that of underlying the unreinforced embankment. However, with the consolidation of soft soil gradually tends to be consistent between the reinforced and the unreinforced embankments. The safety factor of embankment is obviously improved after the soil reinforcement. The failure modes are different between the reinforced and unreinforced embankments due to the characteristics among the soil reinforcement, soil-geogrid interface and embankment soils. The embankment filling rate has a significant effect on the unreinforced embankment. If the reinforced earth is placed in the embankment, construction rate can be improved. Related Articles | Metrics

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Bearing Capacity of a Shallow Strip Foundation-Comparison of Results between German Standard and Chinese Standard CHEN Chuantao, XU Caiwei, 2021, 35 (6):  751-753.  Abstract ( 437 )   Save The Terzaghi basic bearing capacity formula with superposition method is used by the German Standard DIN4017 and Chinese Standard GB 50007-2011 to estimate the bearing capacity of a shallow strip foundation on homogeneous soil; the bearing capacity coefficients in DIN4017 are obtained with the conventional failure modes by Prandtl (Nq and Nc) and from the experimental results (Nr), in addition, the characteristic value of the bearing capacity could be estimated with the additional safety factor. The settlement-control of the foundation is considered by Chinese Standard; hence the characteristic bearing capacity is obtained using the semi-empirical value of the coefficients; the comparison between the results of case study shows that the bearing capacity estimated by DN4017 and GB 50007-2011 are comparable and both methods are proved to be conservative.  Related Articles | Metrics

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Simulation of the Dynamic Breakage of a Single Coral Sand Particle under Impact Loads LUO Shangyi, ZHANG Haotian, GAO Kanghua, HOU Geyuan, YANG Jun, ZHANG Xin 2021, 35 (6):  754-758.  Abstract ( 336 )   Save The particle flow code in two dimensions (PFC2D) software was used to construct a numerical model for analyzing the effects of dynamic impact loads on coral sands with random internal pore distributions. The evolution law of particle breakage was described combining of the force chain distributions, crack development and fragmentation patterns. The results indicate that the single-grain dynamic breakage strength in the coral sand follows the Weibull distribution pattern. Under impact loads, the force chains of a coral sand particle will first appear around the internal pore-end and loading-end. Most of the mesoscopic cracks form along these force chains, and the force chains will weaken around cracks. The cracks often appear in the tensile stress concentration zones and the primary crack will grow along the loading axis. The secondary cracks, which are formed by the crack deflection towards the internal pores, will extend towards the edges of the specimen and merge with adjacent cracks to penetrate the specimen, breaking it into multiple breakages. At higher loading rates, more cracks initiate from the internal pores and increase at a much faster rate. Crack penetration is also more common.  Related Articles | Metrics

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Experimental Study on Mechanics Properties of Clay Polluted with Different Concentrations of CuSO4 WANG Xiaoping, WU Yan, XIE Liwen, SUO Qiaoqiao, GAO Haifei, HU Kun 2021, 35 (6):  759-763.  Abstract ( 301 )   Save In order to study the influence of heavy metal ions intrusion on the soil engineering properties, the typical clay layer in Jingjiang City of Jiangsu Province was selected. Soil samples with five concentrations of CuSO4 solutions (0%, 0.5%, 1%, 2% and 3%) were prepared. Direct shear test, triaxial test, unconfined compressive strength test and compression test were used to investigate the difference of mechanical properties before and after CuSO4  contaminated soil samples, and the corresponding environmental tests and X-Ray powder Diffraction (XRD) tests were used to compare the results The results show that the minimum shear strength of the soil sample appears at the concentration of 0.5% CuSO4  in direct shear test and triaxial test, and the minimum value of unconfined compressive strength appears in the concentration range of 0.5%~1% CuSO4 . The cohesion and unconfined compressive strength of the two tests decrease first and then increase, showing a “concave” type change. The extreme value of the cohesion change appears at 0.5%. The results of triaxial test show that the internal friction angle decreases, while the direct shear test value oscillates. The acidic CuSO4  solution would dissolve the cementitious substances in soil samples, and Cu2+ would destroy the original electric double layer structure, resulting in the thinning of the bound water film and the reduction of the strength. The CuSO4  solution with high concentration had a single electric layer structure and produces colloidal substances. Related Articles | Metrics

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The Application of TEM in Urban Geological and Environment Survey ZHANG Zhaobin, ZHANG Peng, QI Songsong, ZHANG Kaiwei, LIU Peng, NIU He 2021, 35 (6):  764-767.  Abstract ( 291 )   Save Combined with the theoretical model and actual case analysis of the pseudo magnetotelluric interpretation by using transient electromagnetic method, the anomalies in the urban geological survey could be identified. In the karst rock cavity investigation, the cover soils are characterized by the low electrical resistance layer, the dissolution rock belt is represented by a resistivity gradient belt, the filling material dissolved cave show the abnormal low resistance body. The electrical structure of the landfill is characterized by the low resistivity landfill zone surrounded by high resistance impervious area, no low resistance channel gradient belt, the landfill anti-seepage effect is good. Related Articles | Metrics

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Property Tests of Fly Ash and State-of-the-Art Review of Fly Ash Utilization ZHU Zewei, CHEN Zhongqing, WU Zaosheng, WEI Wei, XIE Jianxiang 2021, 35 (6):  768-771.  Abstract ( 345 )   Save Fly ash is the byproduct from the combustion of pulverized coal. As a typical solid waste, the resource utilization and mechanical properties are widely interested. A series of testing, such as, X-Ray Fluorescence (XRF) test, activity test, laser particle size test and scanning electron microscope test, were performed to investigate the performance of Class II and III fly ash in Shaoxing from three different aspects including silicon aluminum oxide content, activity index and particle size distributions. The research progress of resource utilization of the fly ash is also reviewed. The results show that the content and activity index of Si-Al oxide in Class II fly ash are higher than those in Class III fly ash, and the grading of Class II is better with a large number of glass beads with smooth surface and irregular melt; Currently, the applications of fly ash are, in soil performance improvement, geopolymer preparation and concrete admixture, ash brick and ceramist products.  Related Articles | Metrics

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Study of Testing Method and Influence Factors of Viscosity Coefficient of Soft Soil LIU Yang, SUN Qian, WANG Xiaowen 2021, 35 (6):  772-776.  Abstract ( 460 )   Save Viscosity coefficient is a very important physical and mechanical index of soft soils. The accurate determination of the viscosity coefficient of the soft soil plays an important role in describing the creep and rheological properties of the soft soil and establishing the corresponding constitutive model. The previous methods had either limitations or disputes on their applicability, therefore, a new method to determine the viscosity coefficient is proposed by using the direct shear test according to the definition of viscosity coefficient, and the study on the influence of the shear displacement, vertical stress, consolidation, and the moisture content for the viscosity coefficient of the soft soil was investigated. The results show that the viscosity coefficient of the soft soil increases with the increase of the shear displacement and presents a logarithmic correlation; increases with the increase of the vertical stress, and presents a linear correlation; and decreases with the increase of moisture content, consolidation makes the viscosity coefficient of the soft soil larger. Related Articles | Metrics

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Experimental Study of Adhesion Strength Between Rock Anchor Grout and Rock for a Slope Stability Project LIU Hui, WANG Xiandong, SHENG Guangqi 2021, 35 (6):  777-780.  Abstract ( 586 )   Save The nominal adhesion strength between the rock anchor grout and heavily weathered slate rock mass Lower Series of Silurian Period was back-analyzed from the in-situ critical testing on four rock anchors. The influence of the grout length on the nominal adhesin strength was evaluated and the critical grout length in the similar geological conditions was also proposed. The influence of the borehole installation, and grouting procedures on the nominal adhesion strength was also investigated. Related Articles | Metrics

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Application of Transient Electromagnetic Method in Advanced Detection of Geohazards in Shallow Buried Highway Tunnel in Saturated Completely Weathered Granite Soils LIANG Yanfeng, SHEN Menglong, SONG Gang, CHENG Xu, 2021, 35 (6):  781-786.  Abstract ( 331 )   Save The Mabiejiao Tunnel in the Jinghai Expressway project has the characteristics of shallow burying, unsymmetric pressure, rich groundwater, and extremely soft rock mass.  The exposed geomaterials during the tunnel excavation consist of silty clay and completely weathered granite saprolite with individual less weathered sphere boulders. The stability of the surrounding rock is poor and small disturbance in the tunnel excavation could easily induce the liquefaction of the surrounding rock mass. Construction related geo-hazards, such as, rushing of mud and groundwater at the excavation surface and at the bottom of supported surface, rock collapse at the crest of arch and side walls, are frequently occurred. This paper presents a case history of applying the transient electromagnetic method to collect groundwater information at the supporting area and the ground surface in the Mabeijiao Hunnel of Jinghai Expressway. The collected data could be used in providing advanced hazard prediction and providing design and construction guidance of the shallow buried highway tunnel excavation in saturated completely weathered granite saprolite soils. The collected data could also minimize the impact of adverse factors on the tunnel excavations.  Related Articles | Metrics

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Consolidated Undrained Shear Tests of Qingyang Unsaturated Undisturbed Loess Soil Samples YANG Xueqiang, GAO Zhenyu, SUI Jun, ZHANG Hong, LIU Pan, LIN Jinhong 2021, 35 (6):  787-791.  Abstract ( 406 )   Save A series of consolidated undrained triaxial shear tests were conducted on Qingyang undisturbed loess samples with different confining pressure and matrix suction combinations. The test results reveal that 1) with increasing in suction or confining pressure, the shear strength and initial shear modulus are both increased for the undisturbed loess samples. 2) increasing in the matric suction will cause the increase of apparent cohesion c″=c′+(ua-uw) tanφ″, the matric suction in the range of s=0~100 kPa will lead to an obvious increase in the apparent cohesion, whereas s>100 kPa will lead to a slow increase in the apparent cohesion in the undisturbed loess samples. This also shows that internal frictional angle φ″ induced by the matrix suction is not a constant and it decreases nonlinearly as the matrix suction increases. 3) the shear interlocking effect among particles increases with the increase of matric suction. This will induce an increase of the effective friction angle. 4）the apparent cohesion c″ =2 kPa of undisturbed loess in saturated state with suction s=0, this shows that runoff in the field occurs frequently for Qingyang loess being saturated and gradually lost the matrix suction under the continuous rainfall conditions. Related Articles | Metrics

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Influence Factors in Free Swelling Ratio Tests and Mechanism of Expansion and Shrinkage#br# XIANG Tianbing, CHENG Yun, YANG Weiqing, GAO Kunli 2021, 35 (6):  792-797.  Abstract ( 363 )   Save A typical expansive soil in Mengzi, Yunnan Province was selected for the free expansion rate test, and the influences of stirring times and grain size distribution of in the range of <0.5mm, 0.5～0.25mm, 0.25～0.075mm and <0.075mm were analyzed. The test results show that the number of stirring times has a certain influence on the test results, and the grain size distribution has a significant influence on the test results. In order to ensure the reliability of the free swelling ratio test results and enhance the comparability, it is recommended that the number of stirring times should be taken two times, and the grain size distribution should be controlled within the range of 0.5～0.25mm, so as to provide a reference for engineering testing staff. Finally, the mechanism of the swelling and shrinkage of the expansive soil is analyzed from micro and mesoscopic point of view. It is considered that the intrusive water molecules cause the expansion of crystal lattice and the thickening of the bound water film on the surface, which are the internal reasons for the swelling of expansive soil. Related Articles | Metrics

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In-Situ Monitoring and Analysis of Settlement in Tidal Zone Soft Soils Improved by Blasting Method XIA Junwo, ZHANG Jinrong, WANG Jun, ZHANG Liujun, QIN Wei, HU Yonggang, ZHANG Zhizhou, XIANG Aihua, FU Peiqi, PAN Chaohao 2021, 35 (6):  798-800.  Abstract ( 337 )   Save The soil improvement by blasting method has the advantages of simple construction process, short construction period and cost effective. The vertical settlement of soft soils improved by this method is one of the indicators for the treatment effect. This method is widely applied in strengthening soft soils in the coastal tidal zone. However, the vertical deformation pattern of improved soils is rarely reported. To investigate the settlement of the improved soils in the tidal zone, a long-term settlement observation program for highway project by using the settlement plates was implemented. The results indicate that the settlement of the roadway embankment stabilized after 50 days after the blasting treatment. The observed maximum settlement value in 172 days was 0.307 m and the settlement plate No. 1 was stabilized in during observation period. Related Articles | Metrics

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Rectangular Pipe Jacking Construction LI Qixu, GONG Jianwu, HUO Zhen 2021, 35 (6):  801-804.  Abstract ( 298 )   Save With the development and utilization of urban underground space, shallow buried rectangular pipe jacking engineering is widely used. The surface deformation caused by pipe jacking construction has an impact on the safety of superstructures. Based on the model test method, a laboratory model is designed to simulate the jacking process of rectangular pipe jacking, and the law of soil disturbance and deformation is analyzed. The test results show that the transverse influence range of ground settlement mainly occurs at twice the pipe jacking width from the pipe jacking center line, and the surface uplift mainly occurs directly above the pipe jacking. The subsequent pipe jacking construction will continuously disturb the soil layer in the jacked area, and the ground deformation monitoring shall be strengthened during the construction process. In addition to preventing excessive ground settlement, it is also necessary to prevent surface uplift damage caused by back soil effect in shallow buried rectangular pipe jacking. The research results can provide a reference for the design and construction of relevant rectangular pipe jacking project. Related Articles | Metrics