Pengcheng Fu

... 20006. Larson, CD, Sami, N. and Luhr, DR 2000. Structured approach to managing quality of pavement distress data: Virginia Department of Transportation experience. Transportation Research Record , 1699: 72–80. [CrossRef] View all references, McQueen and Timm 20058 ...

ABSTRACT Hydraulic fracturing has become an increasingly important technique in stimulating reservoirs for gas, oil, and geothermal energy production. In use commercially since the 1950's, the technique has been widely lauded, when combined with other techniques, for enabling the development of shale gas resources in the United States, providing a valuable and extensive source of domestic energy. However, the technique has also drawn a degree of notoriety from high-profile incidents involving contamination of drinking water associated with gas extraction operations in the Marcellus shale region. This work highlights some of the insights on the behavior of subsurface hydraulic fracturing operations that have been derived from field and laboratory observations as well as from numerical simulations. The sensitivity of fracture extent and orientation to parameters such as matrix material heterogeneity, presence and distribution of discontinuities, and stress orientation is of particular interest, and we discuss this in the context of knowledge derived from both observation and simulation. The limitations of these studies will also be addressed in terms of resolution, uncertainty, and assumptions as well as the balance of fidelity to cost, both in computation time (for numerical studies) and equipment / operation cost (for observational studies). We also identify a number of current knowledge gaps and propose alternatives for addressing those gaps. We especially focus on the role of numerical studies for elucidating key concepts and system sensitivities. The problem is inherently multi-scale in both space and time as well as highly coupled hydromechanically, and, in several applications, thermally as well. We will summarize the developments to date in analyzing these systems and present an approach for advancing the capabilities of our models in the short- to long-term and how these advances can help provide solutions to reduce risk and improve efficiency of hydraulic fracturing operations. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

ABSTRACT Hydraulic fracturing has been an enabling technology for commercially stimulating fracture networks for over half of a century. It has become one of the most widespread technologies for engineering subsurface fracture systems. Despite the ubiquity of this technique in the field, understanding and prediction of the hydraulic induced propagation of the fracture network in realistic, heterogeneous reservoirs has been limited. Recent developments allowing the modeling of complex fracture propagation and advances in quantifying solution uncertainties, provide the possibility of capturing both the fracturing behavior and longer term permeability evolution of rock masses under hydraulic loading across both dynamic and viscosity dominated regimes. We present a framework for leveraging these advances in practical workflows for analyzing prospective and operating geothermal / hydrothermal sites. We will demonstrate the first phase of this effort through illustrations of fully three-dimensional, 2-way coupled hydromechanical simulations of hydraulically induced fracture network propagation and discuss preliminary results regarding the mechanisms by which fracture interactions and the accompanying changes to the stress field can lead to deleterious or beneficial changes to the fracture network.

ABSTRACT We propose a weighted Nitsche framework for small-sliding frictional contact problems on three-dimensional interfaces. The proposed method inherits the advantages of both augmented Lagrange multiplier and penalty methods while also addressing their shortcomings. Algorithmic details of the traction update and consistent linearization in the presence of Nitsche terms are provided. Several benchmark numerical experiments are conducted and the results are compared with existing studies. The results are encouraging and indicate accurate satisfaction of the non-interpenetration constraint, stable tractions and asymptotic quadratic convergence of the Newton–Raphson method.

ABSTRACT Modeling hydraulic fracturing in the presence of a natural fracture network is a challenging task, owing to the complex interactions between fluid, rock matrix, and rock interfaces, as well as the interactions between propagating fractures and existing natural interfaces. Understanding these complex interactions through numerical modeling is critical to the design of optimum stimulation strategies. In this paper, we present an explicitly integrated, fully coupled discrete‐finite element approach for the simulation of hydraulic fracturing in arbitrary fracture networks. The individual physical processes involved in hydraulic fracturing are identified and addressed as separate modules: a finite element approach for geomechanics in the rock matrix, a finite volume approach for resolving hydrodynamics, a geomechanical joint model for interfacial resolution, and an adaptive remeshing module. The model is verified against the Khristianovich–Geertsma–DeKlerk closed‐form solution for the propagation of a single hydraulic fracture and validated against laboratory testing results on the interaction between a propagating hydraulic fracture and an existing fracture. Preliminary results of simulating hydraulic fracturing in a natural fracture system consisting of multiple fractures are also presented. Copyright © 2012 John Wiley & Sons, Ltd.

This paper systematically studies the effects of asphalt foam characteristics and pulverized asphalt pavement (PAP) material attributes on foamed asphalt mix strength. A fracture face image analysis procedure was employed to quantify asphalt dispersion, which was key to establishing ...

Knowledge of the temperature sensitivity of foamed asphalt stiffness is very important in mix and structural design, field non-destructive testing and advanced research. However, this subject has not been studied extensively, especially the effects of the stress state on the ...

ABSTRACT Full-depth reclamation-recycling-or deep in situ recycling-of damaged pavement with foamed asphalt and an active filler (e.g., portland cement or lime) to provide a stabilized base for a new hot-mix asphalt or chip-sealed wearing course, is a pavement rehabilitation-upgrading strategy of increasing interest worldwide. However, the process is not a fix-all solution that can be used in every instance to rehabilitate failed or close-to-failed pavements, and a thorough project investigation needs to be undertaken to identify candidate projects as well as problems that need to be corrected before rehabilitation-upgrading can be considered. This paper provides guidelines for undertaking such an investigation and is applicable to projects with both thin (multiple chip seals) and thick (multiple lifts of thin asphalt concrete) surfacings.

... 20006. Larson, CD, Sami, N. and Luhr, DR 2000. Structured approach to managing quality of pavement distress data: Virginia Department of Transportation experience. Transportation Research Record , 1699: 72–80. [CrossRef] View all references, McQueen and Timm 20058 ...

Resilient modulus of foamed asphalt materials is stress state dependent, but the field stress state cannot be fully characterized by any available laboratory test alone. Test results of the triaxial resilient modulus test and the flexural beam test, each of which characterizes one ...

This paper investigates laboratory test methods for resilient modulus of foamed asphalt mixes. By comparing test results from different laboratory test methods, the effects of various stress states are identified. The indirect tensile resilient modulus test and the free-free ...

ABSTRACT Most highway agencies contract their automated pavement condition survey (APCS), and therefore technical competence of the service providers is critical to the success of APCS projects. However, technical evaluation of APCS service providers presents unique challenges primarily because the technologies are being advanced by the service providers themselves at a fast pace and their details are often outside the skill set of practicing pavement engineers and managers. This paper presents California’s experience gained in evaluating multiple service providers at a recent APCS demonstration conducted by the California Department of Transportation and technically supported by the University of California Pavement Research Center. Service provider’s data were assessed on an item-by-item basis instead of the conventional approach of aggregating different distresses and comparing a composite index. Problems and errors were identified for each data item and will be used to help the winning service provider improve their data quality in the subsequent statewide survey. This paper also documents a number of technological and methodological innovations, including 1) use of several independent methods for the same measurement to improve the credibility of ground truth data, 2) synchronization of profile measurements and pavement images to strengthen the credibility of the determined ground truth, and 3) development of a comprehensive pavement condition information viewer using open standards. Detailed evaluation results of georeference information, rut depths, mean profile depths and roughness are also presented to demonstrate the evaluation procedure and innovations.