Advanced Materials Research Vols. 168-170

Abstract: Cracking is the most common damage in the secondary lining concrete because of its continuous thin-walled structure, potential surrounding rock pressure and poor curing conditions. In order to improve the crack resistance of concrete and to reduce the responding costs, seven series modern concretes including ultra-fine pozzolanic powder and different organic fibers are prepared and investigated. The optimized modern secondary lining concrete is determined as the concrete including 0.08% or 0.1% volume fractions of ultra-fine organic fiber (UF), based on the test results of segregation, air voids parameters, primary strengths and multi-factorial crack resistance. The spacing factor and average chord length of concretes including UF are less than 0.1mm, which is positive for mixing UF to enhance the crack resistance of concrete at micro- and meso-scale.

Abstract: Pavement performance evaluation is a reasonable safeguard for the conservation plan and an important basis for investment decisions. In order to obtain a precise and quantitative evaluation result, a general evaluation model based on Extension Theory is established, and a concrete index is raised to indicate the pavement real condition. Practical pavement detection data of Jing-hu highway in Jiangsu Province is used to validate this model. The result shows that the evaluation model based on Extension Theory gives an accurate evaluation on pavement performance, and reflects the pavement condition well. It could provide solid foundation for pavement maintenance orders, and may have a bright future.

Abstract: Prestressed concrete pipe piles have been increasingly used as deep foundation structures for decades. Despite the availability of a limited number of well-instrumented load test results, pile designers would like to know the general performance of such piles in case of lacking adequate experience. An attempt is made in this study to establish a database composed of more than one thousand of pile tests. All piles are founded in silty soil that is one of the competent bearing geomaterials. Short and medium-length piles with slenderness ratios ranging from 20 to 80 are most widely used. The capacity of pile increases with increasing the pile slenderness ratio until a limiting value is achieved. Use of very long piles to reduce settlement is unfavorable and the rebound rates for piles with various lengths are similar. An independent case study is also conducted to witness the success of employing the empiricism-based analyses in the preliminary design of concrete pipe piles.

Abstract: Chemical flooding is a promising method of enhanced oil recovery through improving the oil displacement efficiency. The surfactants can effectively reduce the interfacial tension (IFT) between the injection fluid and the residual oil. Petroleum oxidation soap (POS) as a surfactant has the potential for use in chemical flooding owing to its easily gained, cheap and favorable behavior. This study was an attempt to investigate the interfacial activity of POS as well as the adsorption characteristic on oil sand. The experimental results provided a practical instrument for the application of POS in chemical flooding and a method for broadening its application.

Abstract: A double-row anti-slide pile system can effectively control large landslide thrusts within a large-scale talus landslide. In such a system, the separation of the up-slope and down-slope rows of piles is a key factor that impacts the distribution of their internal forces. Common large-scale talus landslides, which are characterized by a curved slip surface that is gentle in the front and steep in the rear, are discussed in this paper. The mechanical characteristics of double piles positioned at a net separation between rows of 23.8a (where a is the length of the long side of rectangular cross section of a pile), 16.3a, 10.7a, 6a and 2a have been investigated by finite element analyses. Based on this investigation, internal forces of the pile body are found to not change with row separation monotonously. Rather, they are closely related to the pile positions (i.e. within the anti-slide or slide section of the slip surface). When the rear piles are fixed at the anti-slide section of the landslide mass, the landslide thrust on the up-slope side of the rear piles and the slope resistance on the down-slope side increase gradually as the row separation becomes larger. As a result, the comprehensive mechanical effect of double piles tends to worsen. We advise that the optimal net separation between rows of piles is 2a to 4a.

Abstract: Stabilized soil is widely used as road base and sub-base materials, and is sometimes used as covering for waste matter in China. In soil stabilization, the property of a locally available soil are usually modified though chemical stabilization[1]. Cement stabilization and lime stabilization are the two most commonly used methods. Lime-fly ash stabilized soil has been widely applied in road engineering due to its good integrity, great bearing capacity, high stiffness, and water-proofing quality[2-4]. One disadvantage of lime-fly ash stabilized soil is that without any additives, its inherent low initial strength makes it inappropriate for use under low-temperature conditions. Researchers have found that the pozzolanic reactivity among lime, fly ash, and soil contributes to the strength of lime-fly ash stabilized soil. To increase the initial strength of lime-fly ash stabilized soil, many approaches have been used to accelerate the pozzolanic reaction. Sulfate activation is one of the methods that has been widely investigated, specifically, Na2SO4 and CaSO4[5]. PG, another sulfate, has also been investigated. However, existing studies have limited to the investigation of the development of strength of the stabilized soil as road base and sub-base materials. The effect of PG on the durability of stabilized soil has rarely been implicated. This work aims to study the effect of thermally treated PG (400°C) on the properties of durability, in addition to other aspects, of lime-fly ash stabilized soil. Lime-fly ash stabilized soil with different proportions of calcined PG were prepared and cured at normal conditions for 7 d and 28 d. Mass loss and strength loss under different treatments were determined. X-ray diffraction(XRD) patterns and scanning electron microscopy(SEM) photos were examined to gauge whether improvements in the performances of the stabilized soil can be obtained by use of thermally treated PG.

Abstract: The dynamic compression experiments of reinforced concrete are carried out by one-stage light gas gun apparatus which subjects the reinforced concrete to deformation at strain rates of the order of 104/s with confining pressures of 1~1.5GPa. The stress-strain curves of reinforced concrete with different impact velocities are obtained using Lagrangian analysis method. Experimental results indicate that reinforced concrete is non-linear, rate-sensitive and pressure-dependent.

Abstract: This paper presents the results of the experimental program and analytical modeling for performance evaluation of the eccentrically loaded composite short columns confined with Glass Fiber-Reinforced Polymer (GFRP) tube. This test matrix included six specimens, which were tested in the variable eccentricity. Research findings indicated that the strength of the concrete-filled GFRP tubular column was enhanced correspondingly; however, the strength gain caused by the GFRP tube decreased as the ratio of e/d0 was increased. A nonlinear analysis that accounts for the change in eccentricity caused by the lateral deformation was proposed to predict the columns’ strength. A comparison between analytical and experimental results of the present study demonstrated the accuracy and validity of the proposed analysis.

Abstract: According to the geotechnical conditions, A FEM model has been established to analyse the mechanical characteristics of the highway tunnel in the layered rock mass. In this model the layered rock mass and the soften joint are simulated by the transversal isotropic material, the interfaces between layers are simulated by the element of rotational Goodman interface, but the interface between the lining structure and surrounding mass is proposed to simulate by an interface element with thickness, and the supporting of tunnel is simulated by the straight beam element. In the meantime, based on the twin shear strength criterion, the mechanical characteristics of rock, the stiff matrix of element for the layered rock mass, soften joint and interface have been discussed. The analytical model has been demonstrated by comparing the results of layered surrounding rock-mass FEM with the test data in situ.

Abstract: The knowledge of the microstructure is a point of major importance to understand the transport, mechanics, creep and shrinkage properties. The present work proposes a method to quantitatively predict the volume percentage of each of phases in Portland cement pastes. The saturated density of C-S-H is revised as a function of degree of hydration and water to cement ratio (w/c). The computed results are consistent with experimental values for cement paste that performed in this study.