Abstract
The present paper is concerned with the investigation of disturbances in orthotropic thermoelastic medium by using fractional order heat conduction equation with three phase lags due to thermomechanical sources. Laplace and Fourier transform techniques are used to solve the problem. The expressions for displacement components, stress components and temperature change are derived in transformed domain and further in physical domain using numerical inversion techniques. The effect of fractional parameter based on its conductivity i.e., (0 < alpha <1 for weak, alpha = 1 for normal, 1 < alpha <= 2 for strong conductivity) is depicted graphically on various components.
Key Words
orthotropic medium; fractional calculus; Laplace transform; Fourier transform; concentrated load; linearly and uniformly distributed loads
Address
Parveen Lata and Himanshi Zakhmi: Department of Basic and Applied Sciences, Punjabi University Patiala, Punjab, India
Abstract
Light construction waste (LCW) particles are pieces of light concrete or insulation wall with light quality and certain strength, containing rich isolated and disconnected pores. Mixing LCW particles with soil can be one of the alternative lightweight soils. It can lighten and stabilize the deep-thick soft soil in-situ. In this study, the unconfined compressive strength (UCS) and its mechanism of Construction Waste Stabilized Lightweight Soil (CWSLS) are investigated. According to the prescription design, totally 35 sets of specimens are tested for the index of dry density (DD) and unconfined compressive strength (UCS). The results show that the DD of CWSLS is mainly affected by LCW content, and it decreases obviously with the increase of LCW content, while increases slightly with the increase of cement content. The UCS of CWSLS first increases and then decreases with the increase of LCW content, existing a peak value. The UCS increases linearly with the increase of cement content, while the strength growth rate is dramatically affected by the different LCW contents. The UCS of CWSLS mainly comes from the skeleton impaction of LCW particles and the gelation of soil-cement composite slurry. According to the distribution of LCW particles and soil-cement composite slurry, CWSLS specimens are divided into three structures:
Key Words
lightweight construction waste; soft soil; dry density; unconfined compressive strength; strength mechanism
Address
Xiaoqing Zhao, Gui Zhao, Jiawei Li and Peng Zhang: School of Civil and Ocean Engineering, Jiangsu Ocean University, 59 Cangwu Road, Lianyungang, Jiangsu 222005, China
Abstract
Deep excavations for development of subway systems in metropolitan regions surrounded by adjacent buildings is an important geotechnical problem, especialy in Tabriz city, where is mostly composed of young alluvial soils and weak marly layers. This study analyzes the wall displacement and ground surface settlement due to deep excavation in the Tabriz marls using two dimensional finite element method. The excavation of the station L2-S17 was selected as a case study for the modelling. The excavation is supported by the concrete diaphragm wall and one row of steel struts. The analyses investigate the effects of wall stiffness and excavation width on the excavation-induced deformations. The geotechnical parameters were selected based on the results of field and laboratory tests. The results indicate that the wall deflection and ground surface settlement increase with increasing excavation depth and width. The change in maximum wall deflection and ground settlement with considerable increase in wall stiffness is marginal, however the lower wall stiffness produces the larger wall and ground displacements. The maximum wall deflections induced by the excavation with a width of 8.2 m are 102.3, 69.4 and 44.3 mm, respectively for flexible, medium and stiff walls. The ratio of maximum ground settlement to maximum lateral wall deflection approaches to 1 with increasing wall stiffness. It was found that the wall stiffness affects the settlement influence zone. An increase in the wall stiffness results in a decrease in the settlements, an extension in the settlement influence zones and occurrence of the maximum settlements at a larger distance from the wall. The maximum of settlement for the excavation with a width of 14.7 m occurred at 6.1, 9.1 and 24.2 m away from the wall, respectively, for flexible, medium and stiff walls.
Key Words
deep excavation; finite element method; Tabriz Metro Line 2; Marl
Address
Hadiseh Mansouri and Ebrahim Asghari-Kaljahi: Department of Earth Sciences, University of Tabriz, Tabriz, Iran
Abstract
In this paper, the effect of a group of sand columns in the loose soil bed using triaxial tests was studied. To investigate the effect of geotextile reinforcement type on the bearing capacity of these sand columns, Vertical encased sand columns (VESCs) and horizontally reinforced sand columns (HRSCs) were used. Number of sixteen independent triaxial tests and finite element simulation were performed on specimens with a diameter of 100 mm and a height of 200 mm. Specimens were reinforced by either a single sand column or three sand columns with the same area replacement ratio (16%) to evaluate the Influence of the column arrangement. Effect the number of sand columns, the length of vertical encasement and the number of horizontal reinforcing layers were investigated, in terms of bearing capacity improvement and economy. The results indicated that the ultimate bearing capacity of the samples with three ordinary sand columns (OSCs) is eventually about 11% more than samples with an OSC. Also, comparison of the column reinforcing modes showed that four horizontal layers of geotextile achieved similar performance to a vertical encasement geotextile at the 50% of the column height, from the viewpoint of strength improvement, while from the viewpoint of economy, the geotextile needed for encasing the single column is around 2.5 times of the geotextile required for four layers.
Key Words
geosynthetics; stone columns; loose soil bed; geotextile encasement; horizontal geotextile layers
Address
Mohammad Shamsi and Ali Ghanbari: Department of Civil Engineering, Kharazmi University of Tehran, No.49 Mofattah Ave, Tehran, Iran
Javad Nazariafshar: Department of Civil Engineering, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran
Abstract
For quality control and the economical design of grouted sand, the prior establishment of the unconfined compressive strength (UCS) estimating formula is very important. This study aims to develop an empirical UCS estimating formula for grouted sand based on the physical properties of sands and the UCS of cured pure grout. Four sands with varying particle sizes were grouted with both microfine cement and Ordinary Portland cement. Grouted specimens were prepared at three different relative densities and at three different water-to-cement ratios, and unconfined compression tests were performed. The results demonstrate that UCS of grouted sand can be expressed as the power function of the UCS of cured pure grout: UCSgrouted sand / 1 MPa = Asoil x (UCSpure / 1 MPa)N. Because the exponent N strongly depends on the combination of pore area and pore size, N is expressed as the function of porosity (n) and specific surface (Sa). Additionally, because Sa determines the area of the sand particle that cement particles can adsorb and n determines the number of cementation bondings between sand particles, Asoil is also expressed as the function of n and Sa. Finally, the direct relationship between Asoil and N is also investigated.
Key Words
grouting; microfine cement; unconfined compressive strength; specific surface; porosity
Address
Changho Lee: Department of Marine and Civil Engineering, Chonnam National University, Yeosu 550-749, Republic of Korea
Hongyeop Nam and Woojin Lee: School of Civil, Environmental and Architectural Engineering, Korea University, Seoul 136-713, Republic of Korea
Hyunwook Choo : Department of Civil Engineering, Kyung Hee University, Yongin 17104, Republic of Korea
Taeseo Ku: Department of Civil and Environmental Engineering, National University of Singapore, 117576 Singapore
Abstract
The elastic modulus is an important parameter to characterize the property of rock. It is common knowledge that the strengths of rocks are significantly different under tension and compression. However, little attention has been paid to the bi-modularity of rock. To validate whether the rock elastic moduli in tension and compression are the same, Brazilian disc, direct tension and compression tests were conducted. A horizontal laser displacement meter and a pair of vertical and transverse strain gauges were applied. Four types of materials were tested, including three types of rock materials and one type of steel material. A comprehensive comparison of the elastic moduli based on different experimental results was presented, and a tension-compression anisotropy model was proposed to explain the experimental results. The results from this study indicate that the rock elastic modulus is different under tension and compression. The ratio of the rock elastic moduli under compression and tension ranges from 2 to 4. The rock tensile moduli from the strain data and displacement data are approximate. The elastic moduli from the Brazilian disc test are consistent with those from the uniaxial tension and compression tests. The Brazilian disc test is a convenient method for estimating the tensile and compressive moduli of rock materials.
Address
Jiong Wei: Department of Engineering Mechanics and CNMM, School of Aerospace Engineering, Tsinghua University,
NO. 30, Shuangqing Road, Haidian District, Beijing, People\'s Republic of China
Leilei Niu: Center of Rock Instability and Seismicity Research, School of Resources and Civil Engineering, Northeastern University,
NO. 3-11, Wenhua Road, Heping District, Shenyang, People\'s Republic of China
Jae-Joon Song and Linmao Xie: Department of Energy Resources Engineering, Research Institute of Energy and Resources, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, Republic of Korea
Abstract
This study aims to evaluate the applicability of a grout material that is mixed with carbon fiber, biogrout, ground granulated blast furnace slag (GGBS) powder and cement. Uniaxial compressive strength tests were performed on homo-gel samples at days of 1, 3, 7, 14 and 28. In addition, the variation of permeability with the mixing ratios was measured. Based on the uniaxial compressive strength test, it was confirmed that the uniaxial compressive strength increased by 1.2times when carbon fiber increased by 1%. In addition, as a result of the permeability test, it was found that when the GGBS increased by 20%, the permeability coefficient decreased by about 1.5times. Therefore, the developed grout material can be used as a cutoff grouting material in the field due to its strength and cut-off effect.
Address
Daehyeon Kim and Kyungho Park: Department of Civil Engineering, Chosun University, 309 Philmoondae-ro, Dong-gu, Gwangju, 61452, Republic of Korea
