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Analysis of load and adaptability of disc cutters during shield tunneling in soft–hard varied strata

《结构与土木工程前沿（英文）》 2023年 第17卷 第4期   页码 533-545 doi: 10.1007/s11709-023-0946-1

摘要： The disc cutters of shield machines exhibit unsatisfactory adaptability and performance during the soft–hard varied strata tunneling process. To analyze the rotation state, cutting performance, and adaptability of disc cutters during shield tunneling in soft–hard varied strata, the Holmquist Johnson Cook and Federal Highway Administration constitutive models are introduced to numerically simulate the failure process of materials on the excavation face and to calculate the load of disc cutters. Additionally, the parameters of the models are modified based on laboratory disc cutter excavation test results. The results of numerical calculation can reflect the load level and the behavior of the disc cutters during operation. The tangential loads of the disc cutters during the cutting of four typical soft-strata excavation face models are numerically calculated, thus providing reference values for the starting torque of the disc cutters. A greater penetration is suggested for soft-strata tunneling to allow the disc cutters to rotate smoothly and continuously as well as to guarantee a better cutting effect. The disc cutters in the center of the cutterhead should be specified with a lower starting torque to prevent uneven wear, rotation stagnation, cutterhead clogging, and other adverse phenomena.

关键词： shield tunneling     disc cutter load     laboratory excavation test     numerical calculation     soft–hard varied strata    

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Field and laboratory experimental studies on hard-rock tunnel excavation based on disc cutter coupled

《结构与土木工程前沿（英文）》   页码 1370-1386 doi: 10.1007/s11709-023-0947-0

摘要： The tunnel boring machine (TBM) is typically used in hard-rock tunnel excavation. Owing to the unsatisfactory adaptability of TBM to the surrounding rock, when crossing high-strength and high-wear strata, the TBM can easily cause defects, such as abnormal wear on cutters and overload damage to bearings, thus affecting the construction efficiency and cost. Therefore, high-pressure waterjet technology should be applied to assist in rock breaking for efficient TBM tunneling. In this study, the effects of water pressure, nozzle diameter, and nozzle speed on cutting are investigated via laboratory experiments of cutting hard rock using high-pressure waterjets. The penetration performance of the TBM under different water pressures is investigated via a field industrial penetration test. The results show that high-pressure waterjets are highly efficient for rock breaking and are suitable for industrial applications, as they can accommodate the advancing speed of the TBM and achieve high-efficiency rock breaking. However, during the operation of high-pressure waterjets, the ambient temperature and waterjet temperature in the tunnel increase significantly, which weakens the cooling effect of the cutterhead and decreases the construction efficiency of the TBM. Therefore, temperature control and cooling measures for high-pressure waterjets during their long-term operation must be identified. This study provides a useful reference for the design and construction of high-pressure water-jet-assisted cutterheads for breaking road headers.

关键词： tunnel boring machine     hard-rock cutting     free face     disc cutter     rock-cutting efficiency    

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Numerical and experimental analyses of methane leakage in shield tunnel

《结构与土木工程前沿（英文）》   页码 1011-1020 doi: 10.1007/s11709-023-0956-z

摘要： Tunnels constructed in gas-bearing strata are affected by the potential leakage of harmful gases, such as methane gas. Based on the basic principles of computational fluid dynamics, a numerical analysis was performed to simulate the ventilation and diffusion of harmful gases in a shield tunnel, and the effect of ventilation airflow speed on the diffusion of harmful gases was evaluated. As the airflow speed increased from 1.8 to 5.4 m/s, the methane emission was diluted, and the methane accumulation was only observed in the area near the methane leakage channels. The influence of increased ventilation airflow velocity was dominant for the ventilation modes with two and four fans. In addition, laboratory tests on methane leakage through segment joints were performed. The results show that the leakage process can be divided into “rapid leakage” and “slight leakage”, depending on the leakage pressure and the state of joint deformation. Based on the numerical and experimental analysis results, a relationship between the safety level and the joint deformation is established, which can be used as guidelines for maintaining utility tunnels.

关键词： shield tunnel     harmful gas leakage     numerical analysis     laboratory test    

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Laboratory assessment of Alaska aggregates using Micro-Deval test

Jenny LIU,Sheng ZHAO,Anthony MULLIN

《结构与土木工程前沿（英文）》 2017年 第11卷 第1期   页码 27-34 doi: 10.1007/s11709-016-0359-5

摘要： Aggregates suitable for use in asphalt concrete (AC) pavement construction must meet durability criteria. Thus, it is critical to select appropriate tests to properly characterize aggregate durability. In Alaska, durability tests currently being used for aggregates in AC pavement include Los Angeles (LA) abrasion test, sulfate soundness test and Washington degradation test. However, there have long been concerns arising over Washington degradation test used as an acceptance tool, motivating pavement practitioners to seek more suitable alternatives. This paper presents a study to investigate the feasibility of using Micro-Deval test, commonly used in other states, to evaluate the durability of Alaskan aggregates in AC pavement as well as its potential to replace Washington degradation test. Micro-Deval test, Washington degradation test and other tests currently specified in Alaska were conducted on aggregates from 16 batches representing statewide sources. Based on the testing results, it is found that using Micro-Deval test for durability assessment of Alaska aggregates was feasible and reproducible, and a high potential was revealed to use Micro-Deval test to replace Washington degradation test in Alaska. It is recommended that Micro-Deval test be considered as an additional test for a certain period, but in the long run should be used along with current LA abrasion and sulfate soundness tests to provide a more desirable durability assessment of Alaska aggregates used in AC pavement.

关键词： aggregate durability     Washington degradation test     Micro-Deval test    

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Seepage failure by heave in sheeted excavation pits constructed in stratified cohesionless soils

Serdar KOLTUK, Jie SONG, Recep IYISAN, Rafig AZZAM

《结构与土木工程前沿（英文）》 2019年 第13卷 第6期   页码 1415-1431 doi: 10.1007/s11709-019-0565-z

摘要： In this study, experimental and numerical investigations are performed to clarify the seepage failure by heave in sheeted excavation pits in stratified cohesionless soils in which a relatively permeable soil layer ( ) lies above a less permeable soil layer ( ) between excavation base and wall tip. It is shown that the evaluation of base stabilities of excavation pits against seepage failure by using Terzaghi and Peck’s approach leads to considerably lower critical potential differences than those obtained from the model tests. On the other hand, a relatively good agreement is achieved between the results of the model tests and the finite element (FE) analyses. Further investigations are performed by using axisymmetric excavation models with various dimensions and ground conditions, and a comparison between the results obtained from Terzaghi and Peck’s approach and finite element analyses is given.

关键词： seepage failure by heave     cohesionless stratified soil     model test     Terzaghi and Peck’s approach     FE analysis    

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Prediction of characteristic blast-induced vibration frequency during underground excavation by using

Tae Un PAK; Guk Rae JO; Un Chol HAN

《结构与土木工程前沿（英文）》 2022年 第16卷 第8期   页码 1029-1039 doi: 10.1007/s11709-022-0861-x

摘要： Blast-induced vibration produces a very complex signal, and it is very important to work out environmental problems induced by blasting. In this study, blasting vibration signals were measured during underground excavation in carbonaceous shale by using vibration pickup CB-30 and FFT analyzer AD-3523. Then, wavelet analysis on the measured results was carried out to identify frequency bands reflecting changes of blasting vibration parameters such as vibration velocity and energy in different frequency bands. Frequency characteristics are then discussed in view of blast source distance and charge weight per delay. From analysis of results, it can be found that peak velocity and energy of blasting vibration in frequency band of 62.5–125 Hz were larger than ones in other bands, indicating the similarity to characteristics in the distribution band (31–130 Hz) of main vibration frequency. Most frequency bands were affected by blasting source distance, and the frequency band of 0–62.5 Hz reflected the change of charge weight per delay. By presenting a simplified method to predict main vibration frequency, this research may provide significant reference for future blasting engineering.

关键词： wavelet analysis     blast-induced vibration     frequency characteristics     underground excavation    

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Laboratory diagnosis for malaria in the elimination phase in China: efforts and challenges

《医学前沿（英文）》 2022年 第16卷 第1期   页码 10-16 doi: 10.1007/s11684-021-0889-7

摘要： Malaria remains a global health challenge, although an increasing number of countries will enter pre-elimination and elimination stages. The prompt and precise diagnosis of symptomatic and asymptomatic carriers of Plasmodium parasites is the key aspect of malaria elimination. Since the launch of the China Malaria Elimination Action Plan in 2010, China has formulated clear goals for malaria diagnosis and has established a network of malaria diagnostic laboratories within medical and health institutions at all levels. Various external quality assessments were implemented, and a national malaria diagnosis reference laboratory network was established to strengthen the quality assurance in malaria diagnosis. Notably, no indigenous malaria cases have been reported since 2017, but the risk of re-establishment of malaria transmission cannot be ignored. This review summarizes the lessons about malaria diagnosis in the elimination phase, primarily including the establishments of laboratory networks and quality control in China, to better improve malaria diagnosis and maintain a malaria-free status. A reference is also provided for countries experiencing malaria elimination.

关键词： malaria     laboratory diagnosis     quality control     malaria elimination     China    

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Optimized determination of airborne tetracycline resistance genes in laboratory atmosphere

Lu Song, Can Wang, Yizhu Wang

《环境科学与工程前沿（英文）》 2020年 第14卷 第6期 doi: 10.1007/s11783-020-1274-5

摘要： Abstract • Sampling parameters with high efficiency was determined. • Operational process to detect airborne ARGs was optimized. • Providing research basis to control airborne ARGs of a laboratory atmosphere Antibiotic resistance genes (ARGs) have been detected in various atmospheric environments. Airborne ARGs transmission presents the public health threat. However, it is very difficult to quantify airborne ARGs because of the limited availability of collectable airborne particulate matter and the low biological content of samples. In this study, an optimized protocol for collecting and detecting airborne ARGs was presented. Experimental results showed that recovery efficiency tended to increase initially and then declined over time, and a range of 550–780 copies/mm2 of capture loading was recommended to ensure that the recovery efficiency is greater than 75%. As the cell walls were mechanically disrupted and nucleic acids were released, the buffer wash protects ARGs dissolution. Three ratios of buffer volume to membrane area in buffer wash were compared. The highest concentrations of airborne ARGs were detected with 1.4 µL/mm2 buffer wash. Furthermore, the majority of the cells were disrupted by an ultrasonication pretreatment (5 min), allowing the efficiency ARGs detection of airborne samples. While, extending the ultrasonication can disrupt cell structures and gene sequence was broken down into fragments. Therefore, this study could provide a theoretical basis for the efficient filter collection of airborne ARGs in different environments. An optimized sampling method was proposed that the buffer wash was 1.4 µL/mm2 and the ultrasonication duration was 5 min. The indoor airborne ARGs were examined in accordance with the improved protocol in two laboratories. The result demonstrated that airborne ARGs in an indoor laboratory atmosphere could pose the considerable health risk to inhabitants and we should pay attention to some complicated indoor air environment.

关键词： Airborne tetracycline resistance genes     Filter sampling     Capture loading     Membrane pretreatment     Indoor laboratory atmosphere    

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Erratum to: Optimized determination of airborne tetracycline resistance genes in laboratory atmosphere

Lu Song, Can Wang, Yizhu Wang

《环境科学与工程前沿（英文）》 2020年 第14卷 第6期 doi: 10.1007/s11783-020-1289-y

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Toward autonomous mining: design and development of an unmanned electric shovel via point cloud-based optimal trajectory planning

《机械工程前沿（英文）》 2022年 第17卷 第3期 doi: 10.1007/s11465-022-0686-2

摘要： With the proposal of intelligent mines, unmanned mining has become a research hotspot in recent years. In the field of autonomous excavation, environmental perception and excavation trajectory planning are two key issues because they have considerable influences on operation performance. In this study, an unmanned electric shovel (UES) is developed, and key robotization processes consisting of environment modeling and optimal excavation trajectory planning are presented. Initially, the point cloud of the material surface is collected and reconstructed by polynomial response surface (PRS) method. Then, by establishing the dynamical model of the UES, a point to point (PTP) excavation trajectory planning method is developed to improve both the mining efficiency and fill factor and to reduce the energy consumption. Based on optimal trajectory command, the UES performs autonomous excavation. The experimental results show that the proposed surface reconstruction method can accurately represent the material surface. On the basis of reconstructed surface, the PTP trajectory planning method rapidly obtains a reasonable mining trajectory with high fill factor and mining efficiency. Compared with the common excavation trajectory planning approaches, the proposed method tends to be more capable in terms of mining time and energy consumption, ensuring high-performance excavation of the UES in practical mining environment.

关键词： autonomous excavation     unmanned electric shovel     point cloud     excavation trajectory planning    

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Bridging the gap between laboratory and field moduli of asphalt layer for pavement design and assessment

Huailei CHENG; Liping LIU; Lijun SUN

《结构与土木工程前沿（英文）》 2022年 第16卷 第3期   页码 267-280 doi: 10.1007/s11709-022-0811-7

摘要： Asphalt pavement is a key component of highway infrastructures in China and worldwide. In asphalt pavement design and condition assessment, the modulus of the asphalt mixture layer is a crucial parameter. However, this parameter varies between the laboratory and field loading modes (i.e., loading frequency, compressive or tensile loading pattern), due to the viscoelastic property and composite structure of the asphalt mixture. The present study proposes a comprehensive frequency-based approach to correlate the asphalt layer moduli obtained under two field and three laboratory loading modes. The field modes are vehicular and falling weight deflectometer (FWD) loading modes, and the laboratory ones are uniaxial compressive (UC), indirect tensile (IDT), and four-point bending (4PB) loading modes. The loading frequency is used as an intermediary parameter for correlating the asphalt layer moduli under different loading modes. The observations made at two field large-scale experimental pavements facilitate the correlation analysis. It is found that the moduli obtained via laboratory 4PB tests are pretty close to those of vehicular loading schemes, in contrast to those derived in UC, IDT, and FWD modes, which need to be adjusted. The corresponding adjustment factors are experimentally assessed. The applications of those adjustment factors are expected to ensure that the moduli measured under different loading modes are appropriately used in asphalt mixture pavement design and assessment.

关键词： asphalt mixture layer     stiffness modulus     loading mode     UC/4PB/IDT     FWD     frequency    

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Influencing factors and control measures of excavation on adjacent bridge foundation based on analytic

Shuangxi FENG, Huayang LEI, Yongfeng WAN, Haiyan JIN, Jun HAN

《结构与土木工程前沿（英文）》 2021年 第15卷 第2期   页码 461-477 doi: 10.1007/s11709-021-0705-0

摘要： Many uncertain factors in the excavation process may lead to excessive lateral displacement or over-limited internal force of the piles, as well as inordinate settlement of soil surrounding the existing bridge foundation. Safety control is pivotal to ensuring the safety of adjacent structures. In this paper, an innovative method is proposed that combines an analytic hierarchy process (AHP) with a finite element method (FEM) to reveal the potential impact risk of uncertain factors on the surrounding environment. The AHP was adopted to determine key influencing factors based on the weight of each influencing factor. The FEM was used to quantify the impact of the key influencing factors on the surrounding environment. In terms of the AHP, the index system of uncertain factors was established based on an engineering investigation. A matrix comparing the lower index layer to the upper index layer, and the weight of each influencing factor, were calculated. It was found that the excavation depth and the distance between the foundation pit and the bridge foundation were fundamental factors. For the FEM, the FE baseline model was calibrated based on the case of no bridge surrounding the foundation pit. The consistency between the monitoring data and the numerical simulation data for a ground settlement was analyzed. FE simulations were then conducted to quantitatively analyze the degree of influence of the key influencing factors on the bridge foundation. Furthermore, the lateral displacement of the bridge pile foundation, the internal force of the piles, and the settlement of the soil surrounding the pile foundation were emphatically analyzed. The most hazardous construction condition was also determined. Finally, two safety control measures for increasing the numbers of support levels and the rooted depths of the enclosure structure were suggested. A novel method for combining AHP with FEM can be used to determine the key influencing aspects among many uncertain factors during a construction, which can provide some beneficial references for engineering design and construction.

关键词： deep foundation pit excavation     adjacent bridge foundation     influencing factors     analytic hierarchy process     finite element    

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Shanghai center project excavation induced ground surface movements and deformations

Guolin XU, Jiwen ZHANG, Huang LIU, Changqin REN

《结构与土木工程前沿（英文）》 2018年 第12卷 第1期   页码 26-43 doi: 10.1007/s11709-017-0439-1

摘要： Empirical data on deep urban excavations can provide designers a significant reference basis for assessing potential deformations of the deep excavations and their impact on adjacent structures. The construction of the Shanghai Center involved excavations in excess of 33-m-deep using the top-down method at a site underlain by thick deposits of marine soft clay. A retaining system was achieved by 50-m-deep diaphragm walls with six levels of struts. During construction, a comprehensive instrumentation program lasting 14 months was conducted to monitor the behaviors of this deep circular excavation. The following main items related to ground surface movements and deformations were collected: (1) walls and circumferential soils lateral movements; (2) peripheral soil deflection in layers and ground settlements; and (3) pit basal heave. The results from the field instrumentation showed that deflections of the site were strictly controlled and had no large movements that might lead to damage to the stability of the foundation pit. The field performance of another 21cylindrical excavations in top-down method were collected to compare with this case through statistical analysis. In addition, numerical analyses were conducted to compare with the observed data. The extensively monitored data are characterized and analyzed in this paper.

关键词： deep excavation     foundation pit     soft clay     top-down method     field observation     ground surface movements     ground deformations    

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Partitioning of heavy metals during municipal solid waste incineration on a laboratory fluid bed furnace

LI Jianxin, YAN Jianhua, CHI Yong

《能源前沿（英文）》 2007年 第1卷 第3期   页码 359-364 doi: 10.1007/s11708-007-0054-2

摘要： The content of heavy metals in the main physical compositions of municipal solid waste (MSW) is analyzed. The effects of temperature, chlorine and water on the partitioning of heavy metals are studied using a laboratory fluidized-bed (FB) furnace with simulated MSW composition. The experimental results show that temperature and chloride content in the feed have significant influence on the volatility of heavy metals, especially those of lower boiling point such as Hg, Cd and Zn. The influence of water is slight.

关键词： partitioning     municipal     volatility     significant influence     temperature    

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Undrained seismic bearing capacity of strip footing adjacent to a heterogeneous excavation

《结构与土木工程前沿（英文）》 2023年 第17卷 第4期   页码 566-583 doi: 10.1007/s11709-023-0905-x

摘要： The analysis of the bearing capacity of strip footings sited near an excavation is critical in geotechnics. In this study, the effects of the geometrical features of the excavation and the soil strength properties on the seismic bearing capacity of a strip footing resting on an excavation were evaluated using the lower and upper bounds of the finite element limit analysis method. The effects of the setback distance ratio (L/B), excavation height ratio (H/B), soil strength heterogeneity (kB/cu), and horizontal earthquake coefficient (kh) were analyzed. Design charts and tables were produced to clarify the relationship between the undrained seismic bearing capacity and the selected parameters.

关键词： excavation     finite element limit analysis     heterogeneous soil     strip footing     undrained bearing capacity    

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标题 作者 时间 类型 操作

Analysis of load and adaptability of disc cutters during shield tunneling in soft–hard varied strata

期刊论文

Field and laboratory experimental studies on hard-rock tunnel excavation based on disc cutter coupled

期刊论文

Numerical and experimental analyses of methane leakage in shield tunnel

期刊论文

Laboratory assessment of Alaska aggregates using Micro-Deval test

Jenny LIU,Sheng ZHAO,Anthony MULLIN

期刊论文

Seepage failure by heave in sheeted excavation pits constructed in stratified cohesionless soils

Serdar KOLTUK, Jie SONG, Recep IYISAN, Rafig AZZAM

期刊论文

Prediction of characteristic blast-induced vibration frequency during underground excavation by using

Tae Un PAK; Guk Rae JO; Un Chol HAN

期刊论文

Laboratory diagnosis for malaria in the elimination phase in China: efforts and challenges

期刊论文

Optimized determination of airborne tetracycline resistance genes in laboratory atmosphere

Lu Song, Can Wang, Yizhu Wang

期刊论文

Erratum to: Optimized determination of airborne tetracycline resistance genes in laboratory atmosphere

Lu Song, Can Wang, Yizhu Wang

期刊论文

Toward autonomous mining: design and development of an unmanned electric shovel via point cloud-based optimal trajectory planning

期刊论文

Bridging the gap between laboratory and field moduli of asphalt layer for pavement design and assessment

Huailei CHENG; Liping LIU; Lijun SUN

期刊论文

Influencing factors and control measures of excavation on adjacent bridge foundation based on analytic

Shuangxi FENG, Huayang LEI, Yongfeng WAN, Haiyan JIN, Jun HAN

期刊论文

Shanghai center project excavation induced ground surface movements and deformations

Guolin XU, Jiwen ZHANG, Huang LIU, Changqin REN

期刊论文

Partitioning of heavy metals during municipal solid waste incineration on a laboratory fluid bed furnace

LI Jianxin, YAN Jianhua, CHI Yong

期刊论文

Undrained seismic bearing capacity of strip footing adjacent to a heterogeneous excavation

期刊论文