Papers by Author: Wei Wang

Abstract: The compressive strength development process of recycled coarse aggregate concrete (RCAC) directly affects the safety of the engineering structures, which is an important research topic in the concrete mechanics. According to the statistics of the experimental results, the development mechanism principle of the compressive strength of RCAC gradually increasing with curing time was analyzed. The mathematical property was introduced to reveal the defects of the traditional hyperbolic model of the time-relative compressive strength (TRCS), and to point out that the mathematical nature of the ideal TRCS model should have. A new CES model was presented for TRCS. The mathematical analysis shows that the hyperbolic model is a special case of the CES model, and in another hand the CES model overcomes the defects of the hyperbolic model.

Abstract: Strength characteristics play an important role in mechanic behavior of cement-soil. Laboratory tests on cement-soil with 12% cement ratio and 28 d curing time are conducted by using a new multifunctional triaxial apparatus under fixed spherical pressure condition. Seven series spherical pressures are designed to apply, namely 300 kPa, 400 kPa, 500kPa, 600 kPa, 800 kPa, 1000 kPa, and 1200 kPa. At the same time, seven series consolidation pressures are taken into accounted. Tested data show that: (1) the stress-strain curve of cement-soil is characterized by strain softening, and the soften rate is related to confining pressure; (2) shrinkage or dilatancy of cement-soil volume strongly depend on the value of loaded spherical pressure; (3) failure curve of cement-soil is approximately a line and it agrees with the Mohr-Coulumb criterion. The result of this paper is helpful to the numerical analysis and practical engineering design of cement-soil foundation structures.

Abstract: Mechanism of time effect on vertical ultimate bearing capacity (VUBC) of preformed concrete pile is analyzed. The effect strongly depends on seven parameters of pile engineering. Pile length, area of pile section, soil friction angle, soil consolidation coefficient, soil elastic module and time after pile installation and pile type are them. Considering time effect and soil consolidation, artificial neural network model to predict this time-dependent VUBC is established. Input layer includes seven parameters discussed above. Conjugate gradient method is adopted to train the net. Based on calculation of practical piles, results of the model are found to be in good agreement with field tests, and the efficiency of the present model is signalized.

Abstract: Crack prevention of high-rise building foundation is an interesting and difficult issue to engineers. Reasons for the crack are analyzed first. Then, based on project cases, crack control methods of large volume concrete foundation are studied in terms of active part and passive part. Active part includes optimizing design of concrete, optimizing foundation design and improving confining condition. Passive part includes reducing temperature difference and increasing the fracture strength of concrete. Finally, optimum foundation design is emphasized for crack control of large volume concrete foundation.

Abstract: Building is a complex and opening system, and settlement plays an important role in its safety. Settlement components of building are analyzed and their calculating methods are introduced. Based on growth of building settlement, three aspects of building safety risks induced by excessive settlement are analyzed, namely excessive differential settlement, total incline and disharmony with living environment. Four methods are proposed to reduce and prevent the risks caused by settlement, which include improving calculating method, determining soil mechanical parameter reasonably, predicting time-dependent settlement and optimizing design of the building foundation.

Abstract: Mechanical behavior of municipal solid waste (MSW) is important to geo-environment engineering, and it is necessary to properly understand it. Laboratory direct shear tests were conducted on MSW with 3 short fill ages, namely 1d, 4d and 7d. Three different densities were taken into accounted in each fill age. Experimental data show that MSW’s shear failure still satisfies the Mohr-Coulomb criterion. As to bigger density, shear strength of MSW increases within 1-7d fill age. When density becomes smaller, its shear strength increases within 1-4d fill age but decreases within 4-7d fill age. With fill-age developing, friction angle of MSW increase monotonously, but cohesion force of it first increases and then decreases. Experimented shear stress-displacement curve of MSW can not be well fitted by either hyperbolic model or exponential model. This experimental research is helpful for design and numerical simulation of corresponding MSW landfill.

Abstract: Phosphogypsum-lime-flyash-gravel mixture (PLFG) is usually used to strengthen road foundation of geotechnical engineering. It is important to correctly understand its compressive behavior before corresponding design. In this present paper, triaxial compression test on PLFG was carried out, and its stress-strain curve was investigated. Experiment data show that PLFG is with high bearing capacity and good stiffness. A new composite-exponent model was established, which is available for both hardening and softening type strain-stress curves of PLFG. Finally, comparison between PLFG tested data and new model simulation was performed, and good agreements have been found. This research is helpful for engineering sustainable utilization of phosphogypsum to bring economy and to reduce environmental pollution.

Abstract: Abstract. Recently, more and more concrete structures are demolished and rebuild, and a large amount of demolished concretes are reused as materials for recycled aggregate concrete (RAC). It is very important to correctly describe time-dependent compressive strength of RAC before the design of corresponding RAC structures. In this paper, compressive strength tests of RAC with different curing times are conducted, and a new three-parameter mathematical model for time-strength curve is presented according to exponent function. Approaches to determine parameters of the proposed model are presented based on characterized points of tested time-strength curve. Finally, good agreements have been found between tested data and new model fittings. The result of this paper is helpful to the numerical analysis and practical engineering design of RAC structures.

Abstract: Soil saturation degree plays an important role in mechanic behavior of soil-concrete interface. Laboratory experiments are conducted on soil-concrete interfaces by using improved simple shear apparatus, where three soil saturation degrees and five normal stresses are taken into accounted, respectively. The experiment data show that failure of the interface still satisfies the Mohr-Coulomb criterion under fixed soil saturation degree. With higher soil saturation degree, both shear strength and friction angle of the interface decrease monotonously, but cohesion force of the interface first increases and then decreases after reaching a peak value. When soil saturation degree increases, failure position of the interface moves from concrete surface to soil inner part.

Abstract: Mathematical model for skeleton stress-strain curve under dynamic loading (SSSC) is one important issue to study the dynamic behavior of soft soil. Based on mechanism of developing process, primary mathematical behavior that SSSC model should meet is analyzed. Mathematical investigation on two conventional SSSC models, namely hyperbolic model and exponential model, is conducted. Dynamic stress index is proposed and employed to signalize the shortcomings of two conventional models. A composite tangent-exponent model for SSSC with three parameters is established, which is a monotone increasing and up limited function. The new model can overcome conventional shortcomings. Finally, good agreement between investigated and new model fitted data has been found out.