Abstract
Particle breakage is an unavoidable phenomenon in granular soils, fundamentally representing the transformation of
deformation energy into the surface energy. This paper, based on fractal theory, derives analytical solution for the breakage index
incorporating particle surface energy change. It compares this novel breakage index with the established breakage indices.
Qualitatively, the novel breakage index demonstrates similar trends to the established breakage indices. Quantitatively, the
established breakage indices tend to overestimate the degree of particle breakage. Utilizing the novel breakage index, a particle
breakage model and a particle size distribution (PSD) evolution model were suggested and validated. The surface morphology of
the particle breakage model is found to conform to a hyperbolic paraboloid. The PSD evolution model accurately reflects the
evolution trends of granular soils. Notably, quartz sand exhibits relatively high prediction accuracy, while the prediction
accuracy for rockfill and carbonate sand is slightly limited.
Key Words
fractal theory; particle breakage index; particle breakage model; particle surface energy; PSD evolution
model
Address
Feng Gao, Jungao Zhu: Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering,
Hohai University, Nanjing, Jiangsu 210098, China
Tao Wang: School of Earth Sciences and Engineering, Nanjing University, 163 Xianlin Road, Nanjing 210023, China
Long Wang: Huaneng Lancang River Hydropower Inc., Kunming, Yunnan 650214, China
Fulong Ma and Qixun Luo: Chengdu Engineering Corporation Limited, Power China. Chengdu, Sichuan 610072, China
Abstract
The surface pre-dewatering is usually carried out before the excavation of the tunnel within water-rich fine sand
stratum. Due to the high cost of surface pre-dewatering, the area of the tunnel that has been applied for the first lining may not
continue to pre-dewatering, and the groundwater level will rise again. Under the influence of rising groundwater level, the first
lining of the tunnel may appear large deformation and cracking phenomenon. Taking Xiangshan Tunnel as an engineering case,
the influence of groundwater level rise on tunnel supporting structure was was investigated. Firstly, the main engineering
problems faced in the construction and the corresponding dewatering measures were reviewed. Then the deformation of
surrounding rock, contact pressure, stress and groundwater level in the construction process were monitored and analyzed. The
groundwater level rebound will cause large vertical settlement of the first lining and large extrusion deformation of the tunnel
face. When the groundwater level reaches the arch waist, the minimum principal stress at the first lining arch foot exceeds its
ultimate strength, and it will crack and fail. The increase of surrounding rock moisture content caused by groundwater rebound is
the main reason leading to the failure of the first lining. Reducing the groundwater level, adding steel arch to the damaged
section of the first lining and carrying out radial grouting can effectively solve the problem of first lining cracking. The
experience and lessons learned in the construction process of Xiangshan can provide reference for similar projects in recent
years.
Key Words
groundwater table rebound; deformation characteristics; surrounding rock pressure; tunnels; water-rich fine
sand stratum
Address
Xiaoxu Tian and Zhanping Song: School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China
Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering, Xi'an 710055, China
Hongwei Pan and Jun Li: The First Engineering Co., Ltd of China Railway Beijing Engineering Bureau Group, Xi'an 710199, China
Abstract
Rock Quality Designation (RQD) is an important index for assessing rock mass integrity. In this paper, the RQD of
geological cores drilled from geological exploration boreholes of Qinglonggou Mine is used as the basic data to analyze spatial
correlations of discrete RQD borehole data through statistical methods. The mean RQD profile method was used to test the
smoothness of RQD(x). The normal score method was applied to transform the original RQD(x) data into a standard Gaussian
distribution function to reduce the difference between the extremes of the original RQD(x) and to reduce the heteroskedasticity
of the RQD. A semi-variogram model was established to characterize RQD(x) spatial structure in the 323-South section. Kriging
interpolation method was used for RQD interpolation prediction, based on which a three-dimensional RQD model was
constructed for 323-South mine section. The RQD prediction and modeling results of the 323-South section show that the spatial
variability characteristics of the RQD of the 323-South section are positively correlated with the fault structure, lithology and
weathering conditions.
Key Words
geological hazard modeling; geostatistics; rock mass quality prediction; RQD; spatial variability
Address
Xingdong Zhao, Lei Deng and Ye Bai: School of Resources and Civil Engineering, Northeastern University, Shenyang 110819, Liaoning, China
Abstract
Controlled low-strength material (CLSM) has been developed to enhance the stability of underground structures and
overcome the drawbacks of traditional backfill materials, such as compacted sandy soils. The objective of this study is to
develop CLSM reinforced with basalt fibers (BF) and to evaluate the flowability, setting time, and strength characteristics of BFreinforced
CLSM. Basalt fibers are incorporated into CLSM with four fiber lengths and three fiber contents to form BFreinforced
CLSM specimens. Flow and Vicat needle tests are performed to evaluate the fluidity and setting times of BFreinforced
CLSM. Uniaxial compression tests and splitting tensile tests are conducted on 3 and 28 days after curing. The results
reveal that the incorporation of BF into CLSM reduces the fluidity as well as the initial and final setting times. After 3 days of
curing, BF-reinforced specimens with fiber lengths of 18 and 24 mm exhibit higher uniaxial compressive strength than
unreinforced specimens; however, at 28 days, the reinforcement effect is marginal. The splitting tensile strength of all reinforced
specimens, at both 3 and 28 days, exceeds that of the unreinforced specimens. In particular, at 28 days, the splitting tensile
strength of all reinforced specimens generally increases with fiber length. Therefore, the use of BF in CLSM can enhance early
compressive strength and improve both early-age and long-term tensile strength in underground structures backfilled with
CLSM.
Address
Dong Geon Son: School of Civil, Environmental and Architectural Engineering, Korea University,
145, Anam-ro, Seongbuk-gu, Seoul 02841, South Korea
Yong-Hoon Byun: Department of Agricultural Civil Engineering, Kyungpook National University,
80 Daehak-ro, Buk-gu, Daegu 41566, South Korea
Abstract
Accurate prediction of ground surface settlement is essential in urban shield tunneling projects to prevent damage to
nearby structures. While empirical and data-driven models have been widely used, they often neglect support mechanisms such
as grouting and slurry injection, or require extensive datasets that are not always available to obtain promptly. This study
proposes a simple and practical algorithm for predicting the maximum surface settlement induced by shield tunneling. The
algorithm was developed using the parametric results from three-dimensional numerical modeling of the excavation and support
process of shield Tunnel Boring Machines (TBMs). The results indicated that the stiffness of the weaker support material plays a
dominant role in controlling settlement, particularly when the face pressure is maintained above the active earth pressure. For the
purpose of incorporating the effects of support mechanisms, three gap parameters were defined at the tunnel face, shield annular
gap, and tail void, and were modified based on stress states and support stiffness. Correction coefficients were introduced to
quantify the contribution of each support phase at specific ground type. The proposed algorithm requires only a limited number
of input variables, such as ground properties and face pressure, making it suitable for field application. The model was validated
against field measurements with prediction errors within 2 mm. This study provides a physically grounded and computationally
efficient framework that improves predictive accuracy while addressing limitations of traditional methods in shield tunneling
settlement analysis.
Key Words
earth pressure; numerical analyses; settlement; tunnel; tunnelling
Address
Jun-Beom An and Gye-Chun Cho: Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology,
291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea
Seok-Jun Kang: Department of Geosciences, Texas Tech University, Lubbock, TX 79409, United States
Abstract
This study presents a numerical analysis approach to determine the freezing range of tunnels in cold regions. The
analysis utilizes numerical methods to analyze the temperature distribution inside the tunnel and the temperature distribution of
the surrounding ground. Based on the numerical analysis results, a regression equation is proposed to estimate the freezing
range. In South Korea, more than 70% of the land consists of mountainous areas, leading to an increasing trend in tunnel
construction due to limited land availability for road and railway development. Consequently, the importance of maintenance
and management of tunnel structures has been emphasized. Tunnels operating in cold regions, particularly in well-known areas
like Gangwon Province, are susceptible to freezing-related damages such as icicle formation, ice accumulation, and blockage of
drainage pipes. Therefore, this study aims to determine the freezing range of tunnels in cold regions using numerical analysis
methods. The research findings confirm the temperature distribution inside the tunnel and the ground surrounding the tunnel
under various structural and environmental conditions. By utilizing the results of the numerical analysis, regression equations are
derived to estimate the freezing rate along the longitudinal direction of the tunnel and the depth of ground freezing around the
tunnel. These research outcomes can serve as a useful indicator for assessing the freezing prevention measures and facilitating
efficient maintenance and management of tunnels in cold regions.
Key Words
cold region; freezing range; heat transfer analysis; tunnel freezing
Address
Hwan-Hee Yoon and Young-Su Kim: KECC, Korea Engineering Consultants Corp. Institute of Technology, 21 Sangil-ro 6-gil Gangdong-gu,
Seoul 05288, Republic of Korea
Ha-My Tran and Hyuk-Sang Jung: Dongyang University, Dept. of Railroad Construction and Safety Engineering,
145 Dongyangdae-ro, Punggi-eup, Yeongju-si, Gyeongsangbuk-do 36040, Republic of Korea
Joon-Shik Moon: Kyungpook University, Dept. of Civil Engineering,80 Daehak-ro, Buk-gu, Daegu, Republic of Korea
open access