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CONTENTS
Volume 12, Number 4, April 2017
 

Abstract
Vast parts of the east of Tabriz city have been covered by Baghmisheh formation marls. These marls can be classified into three types based on their color as identified in yellow, green, and gray marls. Many high-rise buildings and other projects were founded and now is constructing on these marls. Baghmisheh formation marls are classified as stiff soil to very weak rock, therefore they undergo considerable consolidation settlement under foundation loads. This study presents the physical properties and consolidation behavior of these marls. According to the XRD tests, major clay minerals of marls are Illite, Kaolinite, Montmorillonite and Chloride. Uniaxial compressive strength are 100-250, 300-480 and 500-560 kPa for yellow, green and gray marls, respectively. Consolidation and creep behavior of Baghmisheh marls investigated by using of one dimensional consolidation apparatus under stress level up to 5 MPa. The results indicate that yellow marls have high compressibility, settlement and deformation modules. Green marls have an intermediate compressibility and settlement and while gray marls have low compressibility and settlement and from the foundation point of view have high stability. According to the creep test results, all types of marls have not been entered to progressive creep phase up to pressure 5 MPa.

Key Words
Tabriz; consolidation; creep; Baghmishehmarls

Address
(1) Shahrokh Jalali-Milani, Ebrahim Asghari-Kaljahi, Ghodrat Barzegari:
Department of Earth Sciences, University of Tabriz, Iran;
(2) Masoud Hajialilue-Bonab:
Department of Civil Engineering, University of Tabriz, Iran.

Abstract
Geosynthetic reinforced soil retaining walls can be employed as railway embankments to carry large static and dynamic train loads, but very few studies can be found in the literature that investigate their dynamic behavior under simulated wheel loading. A large-scale dynamic test on a reinforced soil railway embankment was therefore carried out. The model embankment was 1.65 meter high and designed to have a soilbag facing. It was reinforced with HDPE geogrid layers at a vertical spacing of 0.3 m and a length of 2 m. The dynamic test consisted of 1.2 million cycles of harmonic dynamic loading with three different load levels and four different exciting frequencies. Before the dynamic loading test, a static test was also carried out to understand the general behavior of the embankment behavior. The study indicated the importance of loading frequency on the dynamic response of reinforced soil railway embankment. It also showed that toe resistance played a significant role in the dynamic behavior of the embankment. Some limitations of the test were also discussed.

Key Words
geosynthetics; reinforced soil embankment; railway; soilbag; large-scale dynamic test

Address
(1) Huabei Liu:
Huazhong University of Science and Technology, Wuhan, Hubei 430074, China;
(2) Guangqing Yang, He Wang, Baolin Xiong:
School of Civil Engineering, Shijiazhuang Tiedao University, Shijiazhuang, Hebei 050043, China.

Abstract
Due to high in-situ stress and brittleness of rock mass, the surrounding rock masses of underground caverns are prone to appear splitting failure. In this paper, a kind of loading-unloading variable elastic modulus model has been initially proposed and developed based on energy dissipation principle, and the stress state of elements has been determined by a splitting failure criterion. Then the underground caverns of Dagangshan hydropower station is analyzed using the above model. For comparing with the monitoring results, the entire process of rock splitting failure has been achieved through monitoring the splitting failure on side walls of large-scale caverns in Dagangshan via borehole TV, micro-meter and deformation resistivity instrument. It shows that the maximum depth of splitting area in the downstream sidewall of the main power house is approximately 14 m, which is close to the numerical results, about 12.5 m based on the energy dissipation model. As monitoring result, the calculation indicates that the key point displacement of caverns decreases firstly with the distance from main powerhouse downstream side wall rising, and then increases, because this area gets close to the side wall of main transformer house and another smaller splitting zone formed here. Therefore it is concluded that the energy dissipation model can preferably present deformation and fracture zones in engineering, and be very useful for similar projects.

Key Words
high geostress; underground cavern group; splitting failure; in-situ monitoring; energy dissipation; opening displacement

Address
(1) Zhi-shen Wang, Yong Li, Wei-shen Zhu, Yi-guo Xue, Bei Jiang:
Geotechnical & Structural Engineering Research Center, Shandong University, No. 17923 Jingshi Rd., Jinan, Shandong Province, P.R. China;
(2) Yong Li:
School of Civil Engineering, Shandong University, No. 17922 Jingshi Rd., Jinan, Shandong Province, P.R. China;
(3) Yan-bo Sun:
Shandong Luqiao Group CO. LTD, No. 330 Jingwu Road Jinan, P.R. China.

Abstract
The research reported herein is concerned with the model testing of piles socketed in soft rock which was simulated by cement, plaster, sand, water and concrete hardening accelerator. Model tests on a single pile socketed in simulated soft rock under axial cyclic loading were conducted and the bearing capacity and accumulated deformation characteristics under different static, and cyclic loads were studied by using a device which combined oneself-designed test apparatus with a dynamic triaxial system. The accumulated deformation of the pile head, and the axial force, were measured by LVDT and strain gauges, respectively. Test results show that the static load ratio (SLR), cyclic load ratio (CLR), and the number of cycles affect the accumulated deformation, cyclic secant modulus of pile head, and ultimate bearing capacity. The accumulated deformation increases with increasing numbers of cycles, however, its rate of growth decreases and is asymptotic to zero. The cyclic secant modulus of pile head increases and then decreases with the growth in the number of cycles, and finally remains stable after 50 cycles. The ultimate bearing capacity of the pile is increased by about 30% because of the cyclic loading thereon, and the axial force is changed due to the applied cyclic shear stress. According to the test results, the development of accumulated settlement is analysed. Finally, an empirical formula for accumulated settlement, considering the effects of the number of cycles, the static load ratio, the cyclic load ratio and the uniaxial compressive strength, is proposed which can be used for feasibility studies or preliminary design of pile foundations on soft rock subjected to cyclic loading.

Key Words
simulated soft rock; model tests; static load ratio; cyclic load ratio; number of cycles; cyclic secant modulus

Address
School of Civil Engineering, Wuhan University, No. 16 Luojiashan Road, Wuchang District, China.

Abstract
The high positive correlation between plastic strain of loaded coal-rock and AE (acoustic emission) characteristic parameter was studied and proved through AE experiment during coal-rock uniaxial compression process. The results show that plastic strain in the whole process of uniaxial compression can be gained through the experiment. Moreover, coal-rock loaded process can be divided into four phases through analyzing the change of the plastic strain curve : pressure consolidation phase, apparent linear elastic phase, accelerated deformation phase, rupture and development phase, which corresponds to conventional elastic-plastic change law of loaded coal-rock. The theoretical curve of damage constitutive model is in high agreement with the experimental curve. So the damage evolution law of coal rock damage can be indicated by both acoustic emission and plastic strain. The results have great academic and realistic significance for further study of both AE signal characteristics during loaded coal-rock damaged process and the forecasting of coal-rock dynamic disasters.

Key Words
loaded coal-rock; plastic strain; acoustic emission; unloading modulus; damage

Address
(1) Peijian Jin:
School of Municipal & Environmental Engineering, Jilin Jianzhu University, Changchun, Jilin 130118, China;
(2) Enyuan Wang, Dazhao Song:
College of Safety Engineer, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China.

Abstract
The binary mixture consists of two types of granular media with different physical attributes and sizes, which can be characterized by the percentage of large granules by weight (P) and the particle size ratio (α). Researchers determine that two thresholds (PS and PL) exist for the peak shear strength of binary mixtures, i.e., at P ≤ PS, the peak shear strength is controlled by the small granules; at P ≥ PL, the peak shear strength is controlled by the large granules; at PS ≤ P ≤ PL, the peak shear strength is governed by both the large and small granules. However, the thresholds of binary mixtures with different α values, and the explanation related to the inner details of binary mixtures to account for why these thresholds exist, require further confirmation. This paper considers the mechanical behavior of binary mixtures with DEM analysis. The thresholds of binary mixtures are found to be strongly related to their ZL coordination numbers for all values of α, where ZL denotes the partial coordination number only between the large particles. The arrangement structure of the large particles is examined when P approaches the thresholds, and a similar arrangement structure of large particles is formed in both 2D and 3D particle systems.

Key Words
thresholds; granular mixtures; partial coordination number; porosity; direct shear test; DEM

Address
State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China.

Abstract
Preventing water seepage and inrush into mines where close multiple-seam longwall mining is practiced is a challenging issue in the coal-rich Ordos region, China. To better protect surface (or ground) water and safely extract coal from seams beneath an aquifer, it is necessary to determine the height of the mining-induced fractured zone in the overburden strata. In situ investigations were carried out in panels 20107 (seam No. 2-2upper) and 20307 (seam No. 2-2middle) in the Gaojialiang colliery, Shendong Coalfield, China. Longwall mining-induced strata movement and overburden failure were monitored in boreholes using digital panoramic imaging and a deep hole multi-position extensometer. Our results indicate that after mining of the 20107 working face, the overburden of the failure zone can be divided into seven rock groups. The first group lies above the immediate roof (12.9 m above the top of the coal seam), and falls into the gob after the mining. The strata of the second group to the fifth group form the fractured zone (12.9-102.04 m above the coal seam) and the continuous deformation zone extends from the fifth group to the ground surface. After mining Panel 20307, a gap forms between the fifth rock group and the continuous deformation zone, widening rapidly. Then, the lower portion of the continuous deformation zone cracks and collapses into the fractured zone, extending the height of the failure zone to 87.1 m. Based on field data, a statistical formula for predicting the maximum height of overburden failure induced by close multiple seam mining is presented.

Key Words
close multiple-seam mining; overburden structure; failure zone; in situ investigations

Address
(1) Jianguo Ning, Jun Wang, Yunliang Tan, Lisheng Zhang:
A State Key Laboratory of Mining Disaster Prevention and Control, Co-founded by Shandong Province and the Ministry of Science and Technology, Shandong University of Science and Technology, 579 Qianwangang Road, Qingdao, China;
(2) Lisheng Zhang;
Gaojiangliang Colliery, Haohua Cleaned Coal Co., Ltd, Erdos City, Inner Mongolia, China.

Abstract
The anchor block is a specially designed concrete member intended to withstand pullout or thrust forces from backfill material of an internally stabilized anchored earth retaining wall by passive resistance of soil in front of the block. This study presents small-scale laboratory experimental works to investigate the pullout capacity of a concrete anchor block embedded in air dry sand and located at different distances from yielding boundary wall. The experimental setup consists of a large tank made of fiberglass sheets and steel framing system. A series of tests was carried out in the tank to investigate the load-displacement behavior of anchor block. Experimental results are then compared with the theoretical approaches suggested by different researchers and codes. The appropriate placement of an anchor block and the passive resistance coefficient, which is multiplied by the passive resistance in front of the anchor block to obtain the pullout capacity of the anchor, were also studied.

Key Words
anchor block; retaining wall; passive resistance coefficient; pullout capacity; cohesionless soil

Address
Department of Civil Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka 1000, Bangladesh.

Abstract
The present study deals with the Pressure-settlement behavior of square and rectangular skirted footing resting on sand and subjected to a vertical load through a laboratory experimental study. A series of load tests were conducted in the model test tank to evaluate the improvement in pressure-settlement behavior and bearing capacity of square and rectangular model footings with and without structural skirt. The footing of width 5 cm and 6 cm and length/width ratio of 1 and 2 was used. The relative density of sand was maintained at 30%, 50%, 70%, and 87% respectively. The depth of skirt was varied from 0.25 B to 1.0 B. All the tests were carried out using a strain controlled loading frame of 50 kN capacity. The strain rate for all test was kept 0.24 mm/min. The results of present study reveal that, the use of structural skirt improves the bearing capacity of footing significantly. The improvement in bearing capacity was observed almost linearly proportional to the depth of skirt. The improvement in bearing capacity of skirted footings over footing without skirt was observed in the range of 33.3% to 68.5%, 68.9% to 127% and 146.7% to 262% for a skirt depth of 0.25 B, 0.50 B and 1.0 B respectively. The skirted footings were found more effective for sand at relative density of 30% and 50% than at relative density of 70% and 87%. The bearing capacity was found to increase linearly with footing width for footings with and without skirts. This observation was found to be consistent for footings with different skirt depths and for relative density of sand i.e., 30%, 50%, 70%, and 87%. The obtained results from the study for footing with and without skirts were comparable with available solutions from literature.

Key Words
pressure-settlement; rectangular skirted footing; sand; bearing capacity; relative density

Address
(1) Vishwas Nandkishor Khatri:
Department of Civil Engineering, Indian Institute of Technology (Indian School of Mines) Dhanbad-826004, Jharkhand, India;
(2) S.P. Debbarma, Rakesh Kumar Dutta:
Department of Civil Engineering, National Institute of Technology, Hamirpur – 177005, Himachal Pradesh, India;
(3) Bijayananda Mohanty:
Department of Civil Engineering, National Institute of Technology, Mizoram-796012, India.

Abstract
The objective of this paper is to experimentally study the consolidation of saturated silty clay subjected to repeated heating-cooling cycles using a modified temperature-controlled triaxial apparatus. Focus is placed on the influence of the water content, confining pressure, and magnitudes and number of thermal loading cycles. The experimental results show that the thermally induced pore pressure increases with increasing water content and magnitude of thermal loading in undrained conditions. After isothermal consolidation at an elevated temperature, the pore pressure continues to decrease and gradually falls below zero during undrained cooling, and the maximum negative pore pressure increases as the water content decreases or the magnitude of thermal loading increases. During isothermal consolidation at ambient temperature after one heating-cooling cycle, the pore pressure begins to rise due to water absorption and finally stabilizes at approximately zero. As the number of thermal loading cycles increases, the thermally induced pore pressure shows a degrading trend, which seems to be more apparent under a higher confining pressure. Overall, the specimens tested show an obvious volume reduction at the completion of a series of heating-cooling cycles, indicating a notable irreversible thermal consolidation deformation.

Key Words
silty clay; magnitudes of thermal loading; isothermal consolidation; pore pressure; water content

Address
School of Civil Engineering, Beijing Jiaotong University, Beijing, 100044, P.R. China.

Abstract
Rock is a heterogeneous material, which introduces complexity in the analysis of rock slopes, since both the existing discontinuities within the rock mass and the intact rock contribute to the degradation of strength. Rock failure is often catastrophic due to the brittle nature of the material, involving the sliding along structural planes and the fracturing of rock bridge. This paper proposes an advanced discretization method of rock mass based on block theory. An in-house software, GeoSMA-3D, has been developed to generate the discrete fracture network (DFN) model, considering both measured and artificial joints. Measured joints are obtained from the photogrammetry analysis on the excavation face. Statistical tools then facilitate to derive artificial joints within the rock mass. Key blocks are searched to provide guidance on potential reinforcement measures. The discretized blocky system is subsequently implemented into a discontinuous deformation analysis (DDA) code. Strength reduction technique is employed to analyze the stability of the slope, where the factor of safety can be obtained once excessive deformation of slope profile is observed. The combined analysis approach also provides the failure mode, which can be used to guide the choice of strengthening strategy if needed. Finally, an illustrated example is presented for the analysis of a rock slope of 20 m height inclined at 60° using combined GeoSMA-3D and DDA calculation.

Key Words
rock slope; stability analysis; block theory; strength reduction technique; discontinuous deformation analysis (DDA); artificial joints

Address
(1) Shuhong Wang:
Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, School of Resources and Civil Engineering, Northeastern University, Shenyang, 110819, China;
(2) Shuhong Wang, Runqiu Huang:
State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, 610059, China;
(3) Pengpeng Ni:
GeoEngineering Centre at Queen's-RMC, Department of Civil Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada;
(4) Seokwon Jeon:
GeoEngineering Centre at Queen's-RMC, Department of Civil Engineering, Queen's University, Kingston, Ontario, K7L 3N6, Canada.

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