1、 GEOTECHNICAL SPECIAL PUBLICATION NO. 194 SOILS AND ROCK INSTRUMENTATION, BEHAVIOR, AND MODELING SELECTED PAPERS FROM THE 2009 GEOHUNAN INTERNATIONAL CONFERENCEAugust 36, 2009 Changsha, Hunan, China HOSTED BY Changsha University of Science and Technology, China CO-SPONSORED BY ASCE Geo-Institute, US
2、A Asphalt Institute, USA Central South University, China Chinese Society of Pavement Engineering, Taiwan Chongqing Jiaotong University, China Deep Foundation Institute, USA Federal Highway Administration, USA Hunan University, China International Society for Asphalt Pavements, USA Jiangsu Transporta
3、tion Research Institute, China Korea Institute of Construction Technology, Korea Korean Society of Road Engineers, Korea Texas Department of Transportation, USA Texas Transportation Institute, USA Transportation Research Board (TRB), USA EDITED BY Louis Ge, Ph.D., P.E. Boming Tang, Ph.D. WeiHong Wei
4、, Ph.D. Renpeng Chen, Ph.D. Published by the American Society of Civil Engineers Library of Congress Cataloging-in-Publication Data. Soils and rock instrumentation, behavior, and modeling ; selected papers from the 2009 GeoHunan International Conference, August 3-6, 2009, Changsha, Hunan, China / ho
5、sted by Changsha University of Science and Technology, China ; co-sponsored by ASCE Geo-Institute, USA ; edited by Louis Ge. p. cm. - (Geotechnical special publication ; no. 194) Includes bibliographical references and indexes. ISBN 978-0-7844-1046-2 1. Road materials-Congresses. 2. Soils-Congresses
6、. 3. Engineering geology-Instruments-Congresses. 4. Pavements-Congresses. I. Ge, Louis. II. Changsha li gong da xue. III. American Society of Civil Engineers. Geo-Institute. IV. GeoHunan International Conference on Challenges and Recent Advances in Pavement Technologies and Transportation Geotechnic
7、s (2009 : Changsha, Hunan Sheng, China) TE200.S63 2009 624.151-dc22 2009022725 American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia, 20191-4400 www.pubs.asce.org Any statements expressed in these materials are those of the individual authors and do not necessarily represent
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13、s.asce.org/support/reprints/. Copyright 2009 by the American Society of Civil Engineers. All Rights Reserved. ISBN 978-0-7844-1046-2 Manufactured in the United States of America. Geotechnical Special Publications 1 Terzaghi Lectures 2 Geotechnical Aspects of Stiff and Hard Clays 3 Landslide Dams: Pr
14、ocesses, Risk, and Mitigation 7 Timber Bulkheads 9 Foundations cknintut.edu.tw 2Ph.D. Candidate, College of Engineering, National Taipei University of Technology, 1, Sec. 3, Chung-hsiao E. Rd., Taipei, 10608, Taiwan; ABSTRACT: An inclined eight-story reinforced concrete building on a thick soft cla
15、y deposit was leveled by compensation grouting with short gel time grout injected through sleeved pipes. The monitoring system is used to record the injected grout volume, the mat foundations heaved volume after grouting, and the mat foundations settled volume during pore pressure dissipation. The g
16、routing efficiencies improved from negative value to less than 1, and the stress histories of clay soils changed from normally consolidated to over-consolidated. A final compensation efficiency of 9.78% was achieved and the building was successfully leveled. INTRODUCTION Compensation grouting is a t
17、echnique to offset subsidence caused during bored tunneling and underground excavation. The basic principle is to inject grout into the zone between the tunnel and overlying buildings to compensate for the ground loss and stress relief induced by underground excavation (Mair PH (573) 341-7193; FAX (
18、573) 341-4729; E-mail: geyunmst.edu ABSTRACT: Resilient modulus of unbound granular materials is a key design parameter for mechanistic empirical pavement design. But the complexity of the affected factors has made it challenging and difficult for practical designers and researchers to find an appro
19、priate model to describe the entire stress-strain response where the plastic deformation is accumulated during the repeated loading condition. A cyclic plasticity model based on fuzzy sets plasticity theory is presented in this paper to model the resilient modulus and permanent strain behavior of un
20、bound granular materials under repeated loading. The concept of the fuzzy set plasticity is first introduced, followed by its model formulation and numerical simulation. The model was calibrated against a resilient modulus testing data of a typical Missouri soil. The numerical results showed that th
21、e fuzzy set model is capable of mimicking and simulating the resilient and permanent responses of unbound granular materials under repeated loading. INTRODUCTION Pavement design is a process intended to find the most economical methods for the pavement, taking into account the properties of the soil
22、 foundation and the traffic to be carried during the service life of the road. And resilient modulus of unbound granular materials is a key parameter for mechanistic empirical pavement design. With the laboratory resilient modulus testing data, many computational modeling, which correlate the resili
23、ent modulus to different confining pressure and deviator stress, can be calibrated (Werkmeister et al., 2004). However, the complexity of the affected factors has made it challenging and difficult for practical designer and 9researchers to find an appropriate model to describe the entire stress-stra
24、in response where the plastic deformation is accumulated during the repeated loading condition. And the disadvantages of traditional design have become more obvious during the last decades as a consequence of the growth of transportation needs and the urge for using recycled materials. So developing
25、 reliable and versatile constitutive models to describe the appropriate characterization of the unbound granular materials has been challenging tasks. Over the years, many constitutive models have been proposed and developed, which employ analytical methods focusing on the realistic stress-strain be
26、haviors of unbound granular materials under repeated load cycles including the resilient behavior, plastic response and permanent deformation based on theory of plasticity (e.g. Lekarp, 1997; Jacobsson, 1998; Frost et al., 2004; Garcia-Rojo and Herrmann, 2005). In the mean time, the selection of the
27、 most appropriate material model has been used in the analytical design of the pavement. A cyclic plasticity model based on fuzzy sets plasticity theory is presented in this paper to model the resilient modulus and shakedown behavior of unbound granular materials under repeated loading. The concept
28、of the fuzzy set plasticity is first introduced, followed by its model formulation. The model developed here is capable of simulating realistic stress-strain behaviors of unbound granular materials under repeated load cycles including nonlinear dilatancy behavior, material memory, accurate reverse l
29、oading feature, non-proportional loading, and long-term cyclic effects. The resilient modulus calculated from each load cycle is recorded and calibrated through a set of common Missouri subgrade soils and unbound granular base materials in accordance with the AASHTO T 307 test method. MODEL FORMULAT
30、ION As previously mentioned, many elastoplastic constitutive models, normally with a great number of constants and parameters, have been developed to describe the complex behavior of the granular materials. The determination of these parameters naturally requires more extensive laboratory test data
31、and site investigation plans compared to what simpler models need. Nevertheless, the stress-strain state of the pavement structure can be modeled more realistically using the advanced models. With that in mind, we intend to assess whether the fuzzy set plasticity model can mimic more realistic stres
32、s-strain behavior of granular material under repeated loading. The original fuzzy set plasticity model consists of deviatoric and locking fuzzy surfaces to account for material responses under purely deviatoric shearing and isotropic compression/extension condition. In this study, the model has been
33、 simplified and only deviatoric component of the original fuzzy set model was used for the simulation. Further and detailed information about fuzzy set plasticity can be found at Ge and Sture (2008). The fuzzy surface in compression is expressed as which represents a three-stress-invariant yield sur
34、face. p is the mean stress and is one third of first stress invariant I1. r is the multiplication of q and g, where q is defined in a way similar to second deviatoric stress invariant J2, and g is the Willam-Warnke function (Willam and Warnke, 1974). For proportion loading, g is 1, so that . GEOTECH
35、NICAL SPECIAL PUBLICATION NO. 19410At each stress state, the value of the membership function will be explicitly defined and the plastic modulus on the loading surfaces can be found at Ge and Sture (2008), which is given as follows. where M and d are model parameters, is the plastic modulus. Althoug
36、h the value of is 1 at fully elastic state and 0 at the fully plastic state, the assignment of the value in elastoplastic state is deterministic and can be arbitrarily defined as needed. A linear variation with respect to stress state was adopted in this study. A classical flow rule incorporating cu
37、rrent stress state and state parameter is used (Been and Jefferies, 1985). where A and dare model parameter and Mcis the stress ratio q/p at critical state condition and is identical to the model parameter a1. =0. is the current stress ratio q/p. The resilient behavior is often expressed in terms of
38、 the resilient modulus , indicate “change in”, and 11, 12, and 0a, = major and minor principal stress and recoverable axial strain, respectively. And regarding the combined effects of stress level and test material density, the shear modulus values have been used (Iwasaki and Tatsuoka, 1977). where
39、G0and p0are initial shear modulus and mean stress. m is a stress exponent depending on the shear strain level. Since modeling the resilient modulus of unbound granular material under repeated loading is the main task of this research, laboratory test on loose sandy soils and unbound granular base ma
40、terials were used for model calibration and verification purposes. RESULTS AND DISCUSSION Table 1 lists the model parameters that were used in the fuzzy set plasticity model, which was calibrated against the resilient modulus testing data on a Missouri subgrade soils (Petry et al., 2008). The stress
41、 paths for the investigation of the resilient modulus due to sequences of varied amplitude loading are presented on the p-q stress space shown in Figure 1. All loading procedures are limited to pulse series where the confining pressure remains constant, as can be seen from the slopes of the stress p
42、aths. The confining pressure for these stress paths O1- A1- B1- C1- D1- E1, O2- GEOTECHNICAL SPECIAL PUBLICATION NO. 194 11A2- B2- C2- D2- E2, and O3- A3- B3- C3- D3- E3are selected as 2 psi, 4 psi, and 6 psi, respectively. The initial void ratios were reported 0.41. Fig. 2 shows the resilient modul
43、us versus deviator stress response while Fig. 3 presents the permanent axial strain versus number of cycles. Table 1. Model parameters used in the simulation K G0M d d a0 a1 m A 5800 4809 2520 0.98 0 10.57 1.03 0.54 0.071 0 2 4 6 8 10 12 14 16 18 2002468101214161820p (psi)q (psi)a1a0O1A1C1B1E1O2A2B2
44、C2E2D2D1O3A3B3C3D3E3Fuzzy Set SurfaceFIG. 1. Stress paths for varied amplitude loading. GEOTECHNICAL SPECIAL PUBLICATION NO. 194120 2 4 6 8 10 120200040006000800010000120001400016000q (psi)ResilientModulus(psi)CS = 2 psiCS = 4 psiCS = 6 psiFuzzy Set ModelFIG. 2. Resilient modulus vs. deviator stress
45、. In Fig. 2, the fuzzy set model shows a good match against the three stress paths. It is seen that the resilient modulus increases after the confining pressure p increased. And it is also shown that the resilient modulus decreases when the deviator stress is increased. The results in Fig. 3 show th
46、at, after a number of cycles at each stress level, the rate of accumulation of permanent strain is decaying towards a zero rate. An increase of applied deviator stress results in more permanent axial strain. CONCLUSIONS A simplified fuzzy set plasticity model was developed and its capability and per
47、formance was assessed through one of the AASHTO T 307 tests on common Missouri subgrade soils and unbound granular base materials. After comparing with these test data, the simplified fuzzy set plasticity model perform fairly well in modeling resilient modulus of unbound granular materials under rep
48、eating loading. More work need to be done to fully assess the resilient and permanent deformation behaviors of unbound granular materials under complex loading/unloading conditions. The fuzzy set plasticity model can be verified against more factors affecting the resilient response, such as: stress
49、level, density, particle size, stress history, number of load cycles. GEOTECHNICAL SPECIAL PUBLICATION NO. 194 130 50 100 150 200 250 300 350 400 450 50000.010.020.030.040.050.060.070.08No. of cyclesPerm. axial stainP=6psiP=4psiP=2psiFIG. 3. Permanent axial strain vs. Number of loading cycles. ACKNOWLEDGMENTS This study was financially supported by the Fund of China Scholarship Council (20073020) and the Scientific Research Fund of Hunan Provincial Edu
