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20 April 2019, Volume 33 Issue 2 Previous Issue    Next Issue

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Analysis of Influence of Deep Foundation Pit Construction with Three-row -Pile Isolation Support on Existing Rail Transit ZENG Shiyuan 2019, 33 (2):  103-106.  Abstract ( 499 )   Save With the rapid development of urban underground rail transit, there are more and more deep excavation projects to be constructed adjacent to the existing rail transit system. This paper presents a case history of the support design of a deep excavation near Wuhan Metro No. 2 Line. The effect of the “threerows of pile plus passive retained soil zone method on the existing live operating metro line is evaluated. The results indicated that, both the vertical and lateral deflections of the existing metro structures were less than 10 millimeters. The maximum stress in the metro structures were also within the allowable limits. Based on the evaluation, it is concluded that the safety of the existing metro structures could be warranted. Related Articles | Metrics

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Support System Design for a Deep Excavation in Karst Terrain of  Complicated Geological Conditions QI Deyin1, YU Bei2， XIAO Liping1 2019, 33 (2):  107-110.  Abstract ( 552 )   Save Karst terrain is widely distributed in the southwest of China. Due to its “hard in upper strata and soft in lower strata” soil conditions and large variation in bedrock surface, the karst geology induces negative influences in the engineering projects. In this paper, the supporting system of the deep excavation in the complicated karst geological conditions in Lichuan City is evaluated. To ensure the safety and economy of the project, the additional local reinforcement system in the supporting system was used in resolving the stress concentration issues induced from the significant differences among adjacent soil and rock strata. Both the minimum pile length and the rock socket depth were used in the quality assurance of the soldier pile system. The results were proved to be satisfactory. Related Articles | Metrics

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Interactions of Deep Excavation and Adjacent Underlying Shielded Tunnel Excavation Operations ZHANG Liren 2019, 33 (2):  111-115.  Abstract ( 579 )   Save Shielded tunnel excavation adjacent to the foundation deep excavation might induce the adverse effect to the safety of excavation supporting structures; on the other hand, the foundation and supper structure construction might also affect the deformation of the excavated tunnel. To maintain the safety of the tunnel excavation, the effect of deep excavation on the underlying shielded tunnel was evaluated. These study aspects include: 1) the effect of shielded tunnel excavation on bottom of the foundation excavation area as well as the supporting structures was analyzed by using finite element method. The results indicate that, if the shielded tunnel excavation is directly underneath the deep excavation, the deformation at the bottom of the deep excavation will be greatly affected; whereas, if the shielded tunnel is excavated beside the foundation excavation, the supporting structure of the deep excavation will then be influenced. 2) The influence building structure on the shielded tunnel construction was also investigated and it was concluded that the weight of the superstructure is carried by the pile foundation and the impact on the tunnel excavation is minimal. 3) When the deep excavation and the shielded tunnel is vertically aligned, proper construction sequence is needed to ensure the safe excavation of both the tunnel and the excavation. Related Articles | Metrics

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Construction Monitoring and Analysis of Youth Road Metro Station in Hangzhou WANG Jieguang, JING Guojun, XU Jing, YAO Yejian 2019, 33 (2):  116-120.  Abstract ( 722 )   Save This paper presents a case history of construction monitoring and analysis of foundation excavation of Metro No. 6 Line at Youth Road Station in Hangzhou. The ground subsidence, deflection at the slurry wall and in various soils and the axial force in the supporting system are monitored and analyzed. The results indicated: the deep excavation resulted in the ground subsidence to a wide zone around the excavation and more importantly, the acuminated settlement at the majority of the monitored points exceeded the threshold value. Construction methods that could better control the adjacent ground subsidence are therefore needed in the similar subsurface conditions. The lateral deflection data measured from the ground inclinometer can reflect the local soil conditions; the deflection in various soil depths are closely related to the slurry deflections. The results also recommended that the frequency of axial force monitoring is necessary so that the first layer of internal support system separate with the slurry wall due to the excessive axial force. In addition, the internal support system could be further optimized. Related Articles | Metrics

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Application of Prestressed Ground Anchor with High Pressure Grout in a Large Deep Excavation in Suzhou City HUANG Zhenbo 2019, 33 (2):  121-123.  Abstract ( 692 )   Save Prestressed ground anchors have received wider applications in China recently. When the ground anchor is applied in the deep excavation with high pullout capacity requirements, high pressure jet grout can be applied in the bond zone of the anchor. However, due to underground feature of the grouting zone, it is difficult for the quality assurance and quality control during the construction. Further, the required load tests for the ground anchors are usually not conducted in the practice. As a result, the application of ground anchors for the deep excavation in Suzhou area is relatively rare. This paper presents a case history of a deep excavation support design for the General Children’s Hospital building. High pullout capacity prestressed ground anchor with high pressure jet grout method was used. Both the design and testing required by the code were strictly followed and the results were satisfactory. Related Articles | Metrics

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Application of Pressure Grouted All Flight Auger Cast-in-Place Rock Bearing Concrete Pile in Chengdu Area DENG Yu1, MA Jun2, MENG Baohua2, ZHANG Ning1, LIANG Yao2 2019, 33 (2):  124-128.  Abstract ( 735 )   Save This paper presents a case history of the foundation treatment project of the Huisheng Time Square in east suburban of Chengdu City. Detailed cost comparisons were made between the pressure grouted all flight auger castinplace concrete piles and rotary drilled cast -in-place concrete piles. It was concluded that the grouted auger cast piles is more cost effective in the soft rock with unconfined compressive strength less than 5MPa. Compared with the cast-in-place concrete piles formed by the rotary drilling method, a 17.8% of construction time and a 29% of the construction cost were saved. The selected grouted all flight auger cast-in-place pile were integrity and static loading tested. This paper also summaries the quality control issues. Related Articles | Metrics

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Deep Excavation Support Design of a Metro Station in Thick Sands YAN Chao 2019, 33 (2):  129-132.  Abstract ( 593 )   Save The geological conditions of the thick sand layer are characterized by the high permeability and sensitive to the deformation after unloading. The excavation support design aspects of a metro station in thick sand stratum was summarized by presenting a case history of the supporting structure for the first phase Station for Metro Line #3 in Wuxi City. The deformations of the supporting structures were compared with the construction monitoring data. The necessity of the steel walers, reliability of the steel strut and connection joints, distribution of vertical and horizontal supports, dewatering depth outside of the excavation area and the passive earth pressure inside the excavation area are evaluated. As major control measuring, the deformation a the supporting structures were verified and the results were satisfactory. Related Articles | Metrics

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Design of a Slab Cover Between the Foundation and the Supporting Structure NIU Guanchao1, WANG Hechuan2 2019, 33 (2):  133-136.  Abstract ( 679 )   Save The foundation excavations near the mountainside usually have a large excavation depth. After the foundation construction, if the gap between the foundation and the supporting system can be left open, the supporting system should be permanently stabilized. If the gap needs to be restored to its original appearance, the backfill method will usually be considered first. Excessive lateral earth pressure might adversely affect the safety of the foundation system. This paper presents a cover slab system design over gap between the excavation supporting system and the foundation. Vegetation is planted on the cover so that the site is environmentally friendly. For the backfill portion, the foundation is designed for the lateral earth pressure induced from the backfill soils; for the opening portion, the supporting system is designed for the permanent conditions; for the covered portion, the cover and supporting system have the same design requirement as the foundation system for the stability requirement such as, seismic conditions. Related Articles | Metrics

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Application of Sleeve-Valve-Pipe Grouting in Historical Building Protection and Soil Improvements LIU Pengfei 2019, 33 (2):  137-140.  Abstract ( 587 )   Save This paper presents a case history of the shielded tunnel excavation of Xi’an Metro No. 6 Line undercrossing the historical Xi’an City Wall at Anding Gate. This project was characterized as complicated surface conditions and undercrossing many historical structures. The subsurface soils of City Wall at the gate were reinforced with Sleeve-Value and Pipe grouting method based on the site geological and hydrological conditions. The grouting reinforcement process was numerically simulated by a commercial geotechnical engineering finite element analysis software MIDAS GTS NX. The results indicate that, for the vertical settlement control purposes, the two rows of sleeve pipes with 1.0 meter square spacing was very effective for the reinforcement depths between 2 and 10 meters below the ground surface. The soil improvement is currently under construction, this construction monitoring data will provide a project reference for the similar constructions. Related Articles | Metrics

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Mass Concreting Construction for Extra-Large-Diameter Manually Excavated Caissons YI Heng, ZENG Lingxi, YANG Xuewen 2019, 33 (2):  141-144.  Abstract ( 544 )   Save Shenzhen Ping’an Financial Center Building is supported by extralarge diameter manually excavated caissons. The foundation has a total of sixteen (16) caissons with a diameter of 5.7 meters and a total of eight (8) caissons with a diameter of 8.0 meters. The minimum distance between Shenzhen Ping’an Financial Center Building and Subway No. 1 Line is only 17 meters. A large quantity of concrete is required for a single caisson and concreting conditions are complicated. No previous concreting experience could be found for the similar diameter caissons. Based on the site construction conditions, the proposed concreting platform design was optimized. This paper presents the concreting methods for the extralarge diameter caissons. These methods include appropriate concrete mix design, quality control for cement and aggregate, construction quality control and temperature monitoring. The results indicated that all twentyfour (24) extralarge diameter caissons are Class I caissons. Related Articles | Metrics

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Foundation Strengthening for a 220 kV High Voltage Power Transmission Tower Foundation  in Yongde, Yunnan Province CHEN Peng1, DAI Xuming2, LIU Wei2, XU Shu1, KE Lei1 2019, 33 (2):  145-150.  Abstract ( 834 )   Save The proposed Yunnan Yongde 220kV power transmission project site was geologically and geotechnically investigated. Based on the site conditions, laboratory test results and site bearing capacity class, the transmission tower foundation strengthening program utilized the pressure grouted ground anchors. The test results indicate that the ground anchor was stable after the loading and no strain softening and pullout failure were observed. The pressure grouted ground anchor can effectively strengthen the foundation. At the later stage of the loading, the strain rate was reduced to zero. The deformation zone underneath the foundation was limited to 6 meters below the footing. The maximum deflection at the bottom of the ground anchor is less than one millimeter, indicating a satisfactory result. Compared with the conventional reinforcement method, this method can meet the restrictive requirements of the field construction, the construction process is not only simple and efficient, but also is very cost effective. Related Articles | Metrics

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Impact of Overburden Thickness over Karstic Bedrock on the Groundwater and Mudflow Intrusion During Tunnel Excavation AN Wensheng1, JI Tongxu2 2019, 33 (2):  151-154.  Abstract ( 445 )   Save Under natural conditions, the karstic bedrock and soil system are generally stable. The human activities, however, disturbs the subtle balance and changes the original geostress and groundwater flow pattern. These changes might result in the development of rock fissures and trigger the geological hazards such as groundwater and mudflow intrusion during the tunnel excavations. This paper presents an approach of establishing a model that the minimum thickness of the bedrock layer that can avoid the groundwater and mudflow intrusion during the tunnel excavation based on practical engineering applications. Various thickness of different filling material during the tunnel excavation were numerically simulated in order to evaluate the possibility of the groundwater and mudflow intrusion of excavation in karstic environment. Throughout the analysis and prediction, a safe tunnel excavation can be warranted. Related Articles | Metrics

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Evaluation and Mitigation Measures of Landslide Hazards in  High Soil Slopes in Western Fujian ZHONG Yuanqing 2019, 33 (2):  155-158.  Abstract ( 448 )   Save This paper presents a case history of the evaluation of a landslide at the high soil slope on the lefthand side of Station K154 in the Xiarong Expressway Expansion Project in Longyan of western Fujian. The landslide hazards on the soil slopes were investigated and the mitigation measures were evaluated. These measures included unloading at the crest, anchoring in the middle of the slope, retaining wall reinforcements at the toe of slope and drainage improvements. The sitespecific stability evaluation with numerical analysis was performed and the results were compared with the construction monitoring data. The result of comparison indicate that the mitigation measures were effective.  Related Articles | Metrics

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Buoyancy Resistance Design of U-shaped Concrete Roadway under a Railway HUANG Zhicai, LI Song, PAN Dan 2019, 33 (2):  159-161.  Abstract ( 1111 )   Save With the development of the highway networks in the urban area, the Ushaped concrete roadway is a useful structure in the transportation engineering applications. When this structure is applied in area with high groundwater, one of the most important aspect is the design for the buoyancy. There is no uniform design method defined in the design code and different consults have significantly different design approach. This paper presents a design approach for the uplift resistance of the Ushaped concrete roadway structure with a case history of a highway alignment underneath a railroad. The aspects of design groundwater level, buoyancy estimation, uplift resistance and the uplift resistance pile are discussed in the paper. The final design approach utilized the selfweight combined with the uplift resistance pile for the buoyancy design. It is concluded that this approach was successful. Related Articles | Metrics

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Treatment of a Roof Collapse in an Extra Long Highway Tunnel Excavation in Liuwei Expressway Project, Guizhou YANG Xiufei 2019, 33 (2):  162-164.  Abstract ( 629 )   Save This paper presents a case history of the treatment of roof collapse in an extra long highway tunnel excavation in Liuwei National Expressway, which connects the Duyun and Shangri-La in Guizhou Province between Liupanshui and Weining. The collapse occurred between Station TZK16+315 and TZK16+330 and a special outside tunnel treatment method was utilized. The collapse mitigation techniques included: 1) Backfill operation should be implemented immediately after the roof collapse and the second concrete lining reinforcement support should be applied in the collapse affected zone; 2) at least three meters thick C15 lean concrete should be backfilled at the collapsed area for the purpose of stabilizing the surrounding rock mass and minimizing the potential collapse. Drainage ditch should be installed around the collapsed area; 3) In the excavation of the collapsed area, the circular excavation around the backfilled lean concrete should be performed. The excavation is similar to S-Ta lining operation. Related Articles | Metrics

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Stability of a Cut Slope with Blasting Excavation SUN Wu, HU Jing 2019, 33 (2):  165-168.  Abstract ( 637 )   Save The excavation of a highcut slope using blasting method in the Highway Bridge Crossing Yangtze River of Hubei Baiyang Project was evaluated using QUAKE/W and SLOPE/W modules in the commercial software Geostudio. The blasting loading in the time domain was input using the actual accelerationtime spectrum. Further, finite element software FLAC3D was used to simulate the real time reaction under the dynamic blasting loading using equivalent triangular loading distribution method. The overall stability of the cut slope, stress, strain distribution, deformation, particle velocity at monitored points and the distribution of the plastic zone were analyzed. The numerical analysis results indicated that, the blasting load could only affect the stability of the cut stability within limited area and the blasting load would not result in the overall slope stability. The numerical analysis results are consistent with the site observations during the construction. Related Articles | Metrics

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Method and Application of Determination of Soil m Values for a Metro Project in Zhengzhou WANG Gang1, LI Weihua1, WANG Shuo2， ZHANG Mengyao1 2019, 33 (2):  169-172.  Abstract ( 710 )   Save  This paper first presents the concept of m value for various soils and its impact on the results of the deep excavation supporting structures. Currently, four different methods of determining the m value are also introduced. This paper also presents the regional geological and geographical conditions with a comparison of differences between east and west sides of Zhengzhou City. The geotechnical parameters of soil and rock material in the No. 5 Line of Zhengzhou Metro are statically analyzed and different method for determining the m values are evaluated. Related Articles | Metrics

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Stability Evaluation of Slopes in High Altitude Low Temperature and High Seismic  Intensity Areas Using the Cloud Model TANG Xinneng, LI Yuansong, RAN Xiaoqing, CAO Zexin 2019, 33 (2):  173-176.  Abstract ( 532 )   Save Considering the particularity and randomness of the influencing factors on the stability of rock slopes in areas with low temperature, high altitude and high seismic intensity, an evaluation method for the rock slope stability in these areas is proposed using the normal cloud model theory approach. With the understanding of engineering geology features, topographic conditions, engineering environments, eleven potentia  stability influence factors, such as, degree of weathering of rock and soils, seismic intensity, coefficient of freeze resistivity and vegetation coverage, were selected for the slope stability evaluation. The normal cloud model and the weight of each factor were used to determine the degree of certainty and the slope stability class. This approach was applied to the evaluation of the rock slope stability between stations K53 and K78 in Wu-Yu Expressway Project. The satisfactory evaluation results were obtained, and the results are consistent with the construction observations. Related Articles | Metrics

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Evaluation of Shear Strength Influence Factors in the Deep Excavation Support GAO Meiling1, LIU Dapeng2 2019, 33 (2):  177-180.  Abstract ( 643 )   Save Although the deep excavation support is a temporary project, the safety of the excavated area throughout the entire foundation excavation and construction is not only directly related to the excavation support itself, but also may result in the damage to adjacent buildings and/or utilities. Further, it might pose a threat to the loss of properties and even public and construction workers lives. Therefore, the importance of the deep excavation support design should be properly recognized by the designers as well as the owners. The shear strength is the most critical factor in the deep excavation support design. The three factors, such as, groundwater level, freezethaw effect and earth excavation sequence, that could impact the shear strength are evaluated in this paper based on a practical project. Typical issues that encountered in the foundation excavation and correspondent countermeasures are analyzed in the paper. Related Articles | Metrics

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Finite Element Simulation of Tunnel Excavation in Soft Rock Mass with High Geo-Stress GONG Weifeng1, WANG Dongying2,3 2019, 33 (2):  181-186.  Abstract ( 549 )   Save The stability of the excavated tunnels in the high geostress soft rock mass is usually poor. Geohazards with large tunnel deformations, such as, collapse and roof squeeze, are frequently encountered in the tunnel excavation projects in these problematic rock mass. It is critically important to select an appropriate construction method. This paper presents the analytical results of a tunnel excavation support in the high geostress soft rock mass, and the analytical model was calibrated with the observed construction results. The following conclusions can be made: 1) Stepped excavation method is an appropriate construction method for the tunnel excavation in the soft rock mass with high geostresses. It has the advantage of small tunnel deflection and is reliable in the construction safety; 2) The plastic zones within the soft rock mass are initiated at the middle portion of the side walls and develop upward to the crown of the tunnel; 3) The deformations at the bottom and crown of the tunnel are toward the excavated area, whereas, larger stresses could be found a the middle portion of the tunnel walls and the deformation of these areas are toward the rock mass. Larger vertical stresses are also encountered at the middle portion of the side walls and horizontal stress concentrations are encountered at the bottom and the crown of the excavated tunnel. The supporting structures have large tensile stress at the middle portion of the side walls and larger compressive stresses could be found at the crown and bottom areas that supporting the tunnel. Related Articles | Metrics

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Comparative Study of Different Data Process Methods for the Atterberg Limits Determination GUO Jiapeng, CHEN Zhitao 2019, 33 (2):  187-190.  Abstract ( 742 )   Save The process of Atterberg Limit determination of Zhengzhou silty cohesive soils is first demonstrated in this paper. The existing data processing methods of analytical method and Excel spreadsheet method are briefly introduced and a new method that using the AutoCAD method for the graphical Atterberg Limit solutions is also presented. After the comparative study, following conclusions could be made: The analytical method requires establishing formulas in Excel spreadsheet and the initial process is relatively tedious. However, it can be repetitively used after the initial establishment; the AutoCAD graphical method is more straight forward more accurate and easier to understand, compared with the hand drawing method. However, this method has no repetitive and new graphics are need each time. The graphical method within the Excel spreadsheet is just between the above methods. The manual operation is still necessary for the intersect point established by the regression method. Based on the results of Atterberg Method obtained by the analysis method, except for the difference of 0.2% between the plastic limit and that obtained by the Excel graphical method, the remaining data and its error are within 0.1%. It is concluded that three data processing methods can meet the precision requirements. Related Articles | Metrics

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Effect of Abandoned Mining Caverns on the Railway Tunnel Structures ZHANG Qian 2019, 33 (2):  191-193.  Abstract ( 796 )   Save  With the development of China’s highspeed railway construction, more and more highspeed railway projects are aligned over areas with unfavorable geological conditions, such as, abandoned mining caverns. The stability of the railroad over mining caverns becomes increasingly more important and need to be addressed. This paper presents a case history of the ground subsidence and cavern collapse evaluation for a railway tunnel near the abandoned mining caverns in Zhang Jihuai Highspeed Railway Project. Based on the analogy analysis, the ground subsidence area of an abandoned Du Ye manganese ore mining caverns and its influence zone as well as the tunnel deformation are numerically simulated by the FLAC 3D finite element software. The results indicate that, the deformations of the abandoned mining caverns were concentrated in the upper crown area and area along the bedrock dip direction; areas outside the deformation concentration has little deflections. The influence distance for the abandoned mining cavern on the railway tunnel is conservatively taken as 221 meters and the deformation of the tunnel induced by the mining caverns are within the allowable limits. Related Articles | Metrics

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Numerical Analysis of Pile Installation Effect of Tapered Pile with Equal Wall Thickness HE Jie, CHEN Yujin, XIONG Meng 2019, 33 (2):  194-197.  Abstract ( 462 )   Save The Particle Flow Code PFC2D is a generalpurpose distinct element modeling software. This paper presents the simulation of the equal wall thickness tapered pile installation process by static pressin method. The following conclusions can be made: the maximum radial deformation magnitude around the pile increased with the pile installation depth. With the increase of the pile penetration, at the soil radial deformation at the same pile location increased to a maximum value and then decreased. The location of the maximum radial deflection moved downward with the increase of pile penetration depth. Compared with the equal-diameter piles, a higher normal stress acting on the shaft surface of the tapered pile and this higher normal stress increased the pilesoil interactions. The soil surrounding the tapered pile moved downward during the pile installation. With the increase of pile penetration, the porous ratio gradually decreased and the zone soils with porous ratio change increased.  Related Articles | Metrics

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Failure Criteria for Side Wall Stability of Rock Caverns YANG Zhigang 2019, 33 (2):  198-200.  Abstract ( 481 )   Save The foundation for the underground space is an integral part of a complicated system consisting of rock mass, underground rock cavern and building structures above the ground. The stability of the underground space foundation should evaluate stability of rock mass underneath the rock cavern as well as the stability of surrounding rock mass. The failure criteria should include the “failure criteria of rock foundation” and the “failure criteria of surrounding rock mass”.  For the failure criteria of rock foundation, it includes two portions: the bearing capacity of rock mass excluding the influence of rock cavern and the settlement of foundation including the impact of rock cavern. The first portion is focused on the strength failure mode for the maximum bearing capacity that the rock mass could carry. The second portion is concentrated to deformation failure mode for the tolerable settlement for buildings above the ground. For the failure criteria of surrounding rock mass are for the examination of the stress and strain at the rock mass. The analytical method, the stereographic projection graphical analysis method and the numerical simulation method can be used in the stability analysis. Among all locations, the stability criteria for the rock mass at the side walls of the cavern are established for four different categories based on the structural characteristics, the stress level of rock mass and the rock joints: Uniform rock cavern; rock carven with similar rock properties; rock cavern in jointed rock mass and rock cavern. Related Articles | Metrics

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Numerical Analysis of Spudcan Punchthrough on Hard Crust Layer Overlying Clay CHEN Yangbin1, SUN Yongfu2, HOU Fang3, GUO Lei4, LIU Tao1, ZHENG Jingbin1 2019, 33 (2):  201-205.  Abstract ( 712 )   Save The soil profile of “hard crustoverclay” is prevalent in offshore area of Chengdao, where mobile jackup rigs are used frequently. Different to sand and clay soils, the “hard crust” mainly consists of silty sand or silt. Therefore, the existing numerical method and design formula may not be suitable for analyzing the potential for spudcan punchthrough in this type of soil profile. In this paper, large deformation finite element method is used to simulate centrifuge tests that have been carried out for spudcan penetration in hard crust layer overlying clay. In the numerical analysis, the hard crust is modelled as sand or stiff clay layer, using MohrCoulomb (MC), modified MohrCoulomb (MMC) and modified Tresca models. The results show that when the hard crust is modelled as sand layer, the penetration resistance of spudcan in “hard crustoverclay” is significantly underestimated by MC and MMC models. By contrast, the numerical analyses, where the hard crust is modelled as stiff clay layer, provide a better prediction for the peak resistance in the hard crust as punchthrough happens. For the hard crust soil used in the centrifuge tests of this study, which was collected from Chengdao Sea with an effective unit weight of 11 kN/m3, an equivalent undrained shear strength of about 80kPa is suggested. Related Articles | Metrics

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Experimental Studies of Shear Strength and Volumetric Strain Characteristics of Shredded Tire Chips-Loess Soil Mixtures DU Zhenjiang, LIU Wuchao, YANG Yongqi, SU Huayang 2019, 33 (2):  206-209.  Abstract ( 448 )   Save The influence of the dimensions of shredded tire chips on the shear strength and volumetric strain characteristics of shredded tireloess soil mixtures were studied throughout the largescale directshear tests. The shear strength and volumetric strain parameters were affected by the mixture content and dimensions of the shredded tire, density of the tested samples and the magnitude of the applied normal stress. The experimental test results indicated that the frictional properties at the contact surface among the shredded tire chips were improved by the loess soils and the properties of the mixtures were enhanced. It is concluded that the engineering properties of loess soils can be improved by adding the shredded tire chips. Related Articles | Metrics

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Evaluation of Formulas for Estimating the Shear Strength of Unsaturated Granitic Residual Soils CHEN Zhidong1, ZHANG Lingshuai1, CHEN Minhua1, LU Zhao1,2,3, CHEN Xiaoliang3， CHEN Rui3 2019, 33 (2):  210-214.  Abstract ( 603 )   Save The granitic residual soils are widely distributed in southern China and these soils are generally unsaturated in nature. However, the mechanical properties of the unsaturated granitic residual soils are rarely reported. This paper presents the undrained directed shear test result of the unsaturated granitic residual soils. The tested shear strength values were compared with three different formulas for the shear strength estimations. The comparative results indicate that the Oberg formula had the best estimation results. Further, this formula can predict the shear strength by only providing the degree of saturation at failure, therefore, it can be easily applied in the practical engineering projects. Related Articles | Metrics

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Application of Total Station Triangulation Method in Surface Settlement Observation LIN Lixiang 2019, 33 (2):  215-219.  Abstract ( 657 )   Save This paper introduces the application of the total station triangulation method in the ground settlement observation in the excavation of an under passing tunnel at Tianlin Road project. The error in the elevation survey was estimated. The frequent comparisons of elevation results observed from geometric level method and from triangulation method resulted a reliable conclusion that the triangulation method is acceptable in the ground settlement observation. Related Articles | Metrics

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Relationship between Optimal Moisture Content and Coarse Grain Content in Granular Soils XIONG Yi 2019, 33 (2):  220-224.  Abstract ( 1020 )   Save  This paper briefly introduces the Proctor Test principles on granular soils. Factors that are potentially affecting the laboratory compaction test results, such as, gradation, material properties, sample preparation methods and methods of compaction, are evaluated in detail. The effect of coarse gain soil content in the granular soil samples on the Proctor Test results are summarized from test results from five different sources. Combined from the rest results as well as the literature review, the following conclusions can be made: 1) The critical factor that affecting the optimum moisture content is not the size of the coarse grains but the content of the coarse grain soils; 2) linear relationships are existed between the optimum moisture content and coarse grain coarse, the optimum moisture content and fine grain content; 3) the linear relationships are formulized.    Related Articles | Metrics

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The Effect of Sodium Hexametaphosphate Concentration on the Results of Grain Size Distribution Analysis for Soft Clay Samples WU Jiaqi1, BI Qingtao1, CAO Shichao1, HOU Rui1， DING Bingdong2 2019, 33 (2):  225-227.  Abstract ( 878 )   Save The influence of different concentration of sodium hexametaphosphate solutions on the laboratory grain size distribution analysis results (densitometer method) on the soft clay samples from a ground improvement project in estuary area of Bohai. The test results indicate that, the concentration of sodium hexametaphosphate solutions have a significant impact of the test results. The sodium hexametaphosphate solution should be used in the laboratory gain size distribution test. For the soft clay sample from estuary area of Bohai, the dispersion solution should use 10 ml sodium hexametaphosphate solution with a concentration between 6% and 8%. With the appropriate concentration, the test results demonstrate a good stability. The content of finegrained group increased with the increase of sodium hexametaphosphate concentration and tended to be stable. The content of powder first decreased and then increased, and the content of clay first increased and then decreased. Related Articles | Metrics

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Application of Pressuremeter Tests in the Geotechnical Investigations of a Metro Station WANG Pei1， WEI Li1， WANG Xiaoyan2， LI Fang3 2019, 33 (2):  228-231.  Abstract ( 532 )   Save  In-situ pressuremeter tests were conducted the metro station site in Tianjin City. The initial pressure, creep pressure and limit pressure along with their deformation were obtained. These values were used to derive the atrest earth pressure (K0) and coefficient of lateral subgrade reaction (Kh). The test derived values were also compared with the suggested values based on soil classifications. It is concluded that the pressuremeter can be used to determine the lateral atrest earth pressure and the coefficient of lateral subgrade reaction, but the measured values are different from the conventional estimated values. Related Articles | Metrics

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Centrifuge Tests for Peak Penetration Resistance of Spudcan Footings in Hard Crust Layer Overlying Clay JING Shaodong1, CHEN Xiao2, SUN Yongfu3, ZHANG Minsheng2, KOU Hailei2, WANG Dong2 2019, 33 (2):  232-235.  Abstract ( 752 )   Save The “hard crust layerclay” layered soil is spread widely in shallow waters near Chengdao, Dongying. When they are installed in such stratigraphy, the spudcan footings of jackup rigs are vulnerable to punchthrough failure. A number of centrifuge tests were conducted to explore the penetration resistance profile of spudcans in hard crust layer overlying clay. The approaches recommended in the ISO guidelines and other two representative approaches are compared, in terms of the magnitude of peak resistance and its corresponding depth. It is found that hard silty sand layer can be regarded as a strong clay layer under undrained conditions, then the peak resistance may be estimated through previous approaches for “stiffoversoft” clays. Related Articles | Metrics