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美国科罗拉多矿业大学卢宁教授系列报告

发布日期:2019-04-01访问次数:字号:[ ]

 

报告人:卢宁,美国科罗拉多矿业大学土木工程系教授

时间:201948-9日,每天上午9:00-10:00,下午2:00-3:00

地点:中以楼五楼会议室

联系人:黄冠华,任东阳(13051268875

卢宁教授简介:

Ning Lu is   professor of civil and environmental engineering at Colorado School of Mines   (CSM) and the director of the joint CSM/US Geological Survey Geotechnical   Research Laboratory in Golden, CO. He is a recipient of the ASCE 2007 Norman Medal, of the ASCE 2010 Croes Medal, of the ASCE 2017 Ralph B. Peck Award, and of the ASCE 2017 Maurice Biot Medal, as   well as a fellow of ASCE, Engineering   Mechanics Institute, and Geological   Society of America. His primary research interests are flow and stress   laws in multiphase porous media, rainfall-induced instability of natural and   engineered slopes, geologic hazards, energy storage in porous media, and   subsurface nuclear waste isolation. He is the senior author of the widely   used textbook Unsaturated Soil Mechanics   (John Wiley and Sons, 2004) and the textbook Hillslope Hydrology and Stability (Cambridge University Press,   2013). Both books are translated into Chinese and published by The Chinese   Higher Education Press.

48日上午9:00-10:00

Lecture #1: What   Is the Range of Soil Water Density? Critical Reviews With a Unified Model

Abstract. Critical   reviews are provided on the experimental and theoretical methodologies on   soil water density to identify their limitations, flaws, and uncertainties.   Some recent findings on intermolecular forces, interfacial interactions, and   soil water retention mechanisms are synthesized to clarify molecular-scale   physicochemical mechanisms governing the soil water density. A unified model   to quantify soil water density variation is presented.

48日下午2:00-3:00

Lecture   #2: Soil Sorptive Potential: Unitary Definition of Matric Potential

Abstract. In nature, soil-water interaction involves two   physical mechanisms: capillarity and adsorption. As such, matric potential or   the negative of matric suction should reflect both mechanisms.  However,   the common definition of matric potential, being the pressure difference   between pore water and pore air pressure, overlooks the adsorption, leading   to poor predictions on when soil water freezes, when change phase occurs   between liquid and vapor, and why soil water density could be as high as 1.8   g/cm3.  The adsorption can be fully captured in a new concept   called soil sorptive potential, leading to a general definition of matric   potential. This new definition of matric potential provides thermodynamic   ways to bridge the long-standing gap between pore water pressure and soil   sorptive potential, and to accurately quantify soil freezing curve   (constitutive relationship between soil water content and temperature below 0   oC), soil water density (soil water density as a constitutive function   of soil water content), and soil water cavitation (soil water phase   transition between liquid and vapor).

49日上午9:00-10:00

Lecture #3: Separating External and   Internal Particle Surface Areas of Soil

Abstract. Specific surface area (SSA) of soil is an intrinsic   property governing many soil properties. SSA can be physically divided into   two categories: external or particle surface area and internal or   intra-crystalline surface area. Even though each of them is well known to   play different roles in physical, chemical, and biological processes, few   methods have been developed to quantitatively distinguish between them. Using   a recent theoretical advancement of an augmented Brunauer-Emmet-Teller (BET)   adsorption equation for soil, the writers develop a procedure based on   measured water adsorption isotherm to quantify the external and internal   SSAs. Extensive adsorption isotherms of water, ethylene glycol monomethyl   ether, and nitrogen of a variety of silty and clayey soils are used to   validate the procedure. Practical implications of SSA are also provided by   linking the importance of the internal SSA to swelling behavior, and the   importance of the external SSA to adsorption of non-polar materials. The   demonstrated procedure to quantify external and internal SSAs should provide a pressing and powerful   method to understand physical, chemical, and biological processes in soils.

49日下午2:00-3:00

Lecture #4:   Effective Stress Principle in Soil

Abstract. Since the early 2000s, suction stress has been   conceptualized as a unitary way to quantify effective stress in soil, i.e., effective stress equal to total stress minus suction stress. Suction stress is the part of effective stress   due to soil-water interaction. When soil   is saturated, suction stress is the pore water pressure, whereas when soil is unsaturated, suction stress is a   characteristic function of soil called the suction stress characteristic   curve (SSCC). Two physicochemical soil-water retention mechanisms are   responsible for the SSCC: capillarity and adsorption. These two mechanisms   are explicitly considered to develop a closed-form equation for the SSCC and   effective stress. The SSCC data from the literature for a variety of soils ranging from clean sand to   silty and clayey soils are used to validate the equation, and indicate that the equation can well represent the   data. Additional validation is achieved using experimental data of the soil   shrinkage curves and the elastic modulus functions. The equation can be   reduced to the Lu et al.’s previous closed-form equation for SSCC when   capillarity dominates soil-water retention, can be reduced to the Bishop’s   effective stress equation when capillarity is the sole soil-water retention mechanism, and can be reduced to the   Terzaghi’s classical effective stress equation when soil is saturated.

 





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