Browsing by Author "Liao, JJ"

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A field study of induced slope failure in poorly cemented rock
(2003)
Pan, YW
;
Lin, CP
;
Liao, JJ
;
Huang, AB
;
土木工程學系
The paper presents the results of afield study of an induced slope failure and accompanied laboratory and in-situ tests of a poorly cemented soft rock. The project was aimed to examine the full-scale deformation/strength characteristics of soft rock within reservoir bank with geology of poorly cemented rock. Comparison of the results of various tests enabled the clarification of the true properties of the poorly cemented rock. Effect of disturbance was quantitatively investigated. An in-situ study of induced slope failure with well-planed instrumentations looked into the full-size deformation and strength properties of the geomaterial.
Characterization of soft rocks in Taiwan
(2000)
Huang, AB
;
Liao, JJ
;
Pan, YW
;
Cheng, MH
;
Hsieh, SY
A research project was carried out to enhance our capabilities in establishing the engineering properties of the weak sedimentary rocks in northern and central regions of Western Taiwan. Improved field sampling and testing techniques were developed and a series of in situ and laboratory experiments were performed. These included modifications of rock coring procedure, field pressuremeter, PS logging, Lugeon tests and laboratory triaxial tests. A test site was developed where rock cores were taken and a series of field experiments performed. The results from the field and laboratory experiments were analyzed and compared. An interpretation procedure in establishing the rock properties was proposed. This paper describes the experience gained in this series of experiments and discusses its implications in the characterization of the soft rocks.
Computing displacements in transversely isotropic rocks using influence charts
(1999-01-01)
Wang, CD
;
Liao, JJ
;
土木工程學系
;
Department of Civil Engineering
This paper presents a simple graphical method for computing the displacement beneath/at the surface of a transversely isotropic half-space subjected to surface loads. The surface load can be distributed on an irregularly-shaped area. The planes of transverse isotropy are assumed to be parallel to the horizontal surface of the half-space. Based on the point load solutions presented by the authors, four influence charts are constructed for calculating the three displacements at any point in the interior of the half-space. Then, by setting z = 0 of the derived solutions, another four influence charts for computing the surface displacements can also be proposed. These charts are composed of unit blocks. Each unit block is bounded by two adjacent radii and arcs, and contributes the same level of influence to the displacement. Following, a theoretical study was performed and the results showed that the charts for interior displacements are only suitable for transversely isotropic rocks with real roots of the characteristic equation; however, the charts for surface displacements are suitable for all transversely isotropic rocks. Finally, to demonstrate the use of the new graphical method, an illustrative example of a layered rock subjected to a uniform, normal circular-shaped load is given. The results from the new graphical method agree with those of analytical solutions as well. The new influence charts can be a practical alternative to the existing analytical or numerical solutions, and provide results with reasonable accuracy.
Computing displacements in transversely isotropic rocks using influence charts
(1999-01-01)
Wang, CD
;
Liao, JJ
;
土木工程學系
;
Department of Civil Engineering
This paper presents a simple graphical method for computing the displacement beneath/at the surface of a transversely isotropic half-space subjected to surface loads. The surface load can be distributed on an irregularly-shaped area. The planes of transverse isotropy are assumed to be parallel to the horizontal surface of the half-space. Based on the point load solutions presented by the authors, four influence charts are constructed for calculating the three displacements at any point in the interior of the half-space. Then, by setting z = 0 of the derived solutions, another four influence charts for computing the surface displacements can also be proposed. These charts are composed of unit blocks. Each unit block is bounded by two adjacent radii and arcs, and contributes the same level of influence to the displacement. Following, a theoretical study was performed and the results showed that the charts for interior displacements are only suitable for transversely isotropic rocks with real roots of the characteristic equation; however, the charts for surface displacements are suitable for all transversely isotropic rocks. Finally, to demonstrate the use of the new graphical method, an illustrative example of a layered rock subjected to a uniform, normal circular-shaped load is given. The results from the new graphical method agree with those of analytical solutions as well. The new influence charts can be a practical alternative to the existing analytical or numerical solutions, and provide results with reasonable accuracy.
Determination of dynamic elastic constants of transversely isotropic rocks using a single cylindrical specimen
(1997-10-01)
Liao, JJ
;
Hu, TB
;
Chang, CW
;
交大名義發表
;
土木工程學系
A new experimental procedure and its associated interpretation theories are proposed to determine the five dynamic elastic constants of a transversely isotropic rock. Using Christoffel's equations, the elastic constants can be uniquely determined based on ultrasonic wave velocity measurements on a single cylindrical specimen. The new method requires that the orientation of planes of elastic symmetry by parallel to its longitudinal axis. The wave velocity measuring devices (i.e. transducers) can be mounted on the sides or ends of the specimen. The new method has been implemented in the laboratory on a transversely isotropic rock, argillite. Wave velocity measurements were taken on specimens with and without a tensile load applied at the ends. Consistent results were obtained in both cases. This paper describes details of the analytical background and the proposed experimental procedure. Available test results are presented to demonstrate the efficacy of the new method. (C) 1997 Elsevier Science Ltd.
Determination of dynamic elastic constants of transversely isotropic rocks using a single cylindrical specimen
(1997-10-01)
Liao, JJ
;
Hu, TB
;
Chang, CW
;
土木工程學系
;
Department of Civil Engineering
A new experimental procedure and its associated interpretation theories are proposed to determine the five dynamic elastic constants of a transversely isotropic rock. Using Christoffel's equations, the elastic constants can be uniquely determined based on ultrasonic wave velocity measurements on a single cylindrical specimen. The new method requires that the orientation of planes of elastic symmetry by parallel to its longitudinal axis. The wave velocity measuring devices (i.e. transducers) can be mounted on the sides or ends of the specimen. The new method has been implemented in the laboratory on a transversely isotropic rock, argillite. Wave velocity measurements were taken on specimens with and without a tensile load applied at the ends. Consistent results were obtained in both cases. This paper describes details of the analytical background and the proposed experimental procedure. Available test results are presented to demonstrate the efficacy of the new method. (C) 1997 Elsevier Science Ltd.
Development of a multiple-purpose borehole testing device for soft rock
(2002-09-01)
Huang, AB
;
Fang, CK
;
Liao, JJ
;
Pan, YW
;
土木工程學系
The authors developed a versatile in situ testing device specifically for soft rock. The main purpose of this device was to provide design parameters for shallow or deep foundations in soft rock. The new. device, referred to as the Borehole Testing Device (BTD) consisted of four radial curved platens at the top and a circular steel plate at the bottom. The BTD was designed to be used in a 200-mm-diameter borehole. Driven by a high stress pressure-meter and a hydraulic piston, the BTD, can be used to perform a borehole jacking test, plate-loading test, and borehole sheaf test in the same borehole. A multistage testing procedure was proposed to perform the BTD test. This paper describes the design and operation of the BTD and presents a set of test data to demonstrate the capabilities of the BTD.
Developments in the characterization of soft rocks in Taiwan
(2003)
Huang, AB
;
Liao, JJ
;
Pan, YW
;
Cheng, MH
;
土木工程學系
Local Experience has indicated that the weak sedimentary rocks in northern and central regions of Western Taiwan were poorly cemented. Sampling in these types of rock formations has been difficult and test results on recovered samples were often scattered. The authors have been developing improved field sampling and testing techniques to enhance our capabilities in characterizing the soft rocks. These included modifications of rock coring procedure, development of a high stress pressuremeter, a borehole testing device, and laboratory triaxial tests with local strain measurements. These techniques have been applied for various construction and research projects. The paper describes the development of these new or modified techniques and experience gained in the characterization of the soft rocks in this region.
Direct tensile behavior of a transversely isotropic rock
(1997-07-01)
Liao, JJ
;
Yang, MT
;
Hsieh, HY
;
土木工程學系
;
Department of Civil Engineering
The tensile behavior of a transversely isotropic rock is investigated by a series of direct tensile tests on cylindrical argillite specimens. To study the deformability of argillite under tension, two components of an electrically resistant type of strain gage with a parallel arrangement, or a semiconductor strain gage, are adopted for measuring the small transverse strain observed on specimens during testing. The curves of axial stress vs axial strain and vs average volumetric strain ape presented for argillite specimens with differently inclined angles of foliation. Experimental results indicate that the stress-strain behavior depends on the foliation inclination of specimens with respect to the loading direction. The five elastic constants of argillite are calculated by measuring two cylindrical specimens in the manner recommended by Wei and Hudson. Based on theoretical analysis results, the range of the foliation inclination of the specimens tested is investigated for feasibility obtaining the Jive elastic moduli. A dipping angle of the foliations (theta) of 30-60 degrees with respect to the plane normal to the loading direction is recommended. The final failure modes of the specimens are investigated in detail. A sawtoothed failure plane occurs for the specimens with a high inclination of foliation with respect to the plane perpendicular to the loading direction. On the other hand, a smooth plane occurs along the foliation for specimens with low inclination of foliation with respect to the plane normal to the loading direction. A conceptual failure criterion of tensile strength is proposed for specimens with a high inclination of foliation. (C) 1997 Elsevier Science Ltd.
Direct tensile behavior of a transversely isotropic rock
(1997-07-01)
Liao, JJ
;
Yang, MT
;
Hsieh, HY
;
交大名義發表
;
土木工程學系
The tensile behavior of a transversely isotropic rock is investigated by a series of direct tensile tests on cylindrical argillite specimens. To study the deformability of argillite under tension, two components of an electrically resistant type of strain gage with a parallel arrangement, or a semiconductor strain gage, are adopted for measuring the small transverse strain observed on specimens during testing. The curves of axial stress vs axial strain and vs average volumetric strain ape presented for argillite specimens with differently inclined angles of foliation. Experimental results indicate that the stress-strain behavior depends on the foliation inclination of specimens with respect to the loading direction. The five elastic constants of argillite are calculated by measuring two cylindrical specimens in the manner recommended by Wei and Hudson. Based on theoretical analysis results, the range of the foliation inclination of the specimens tested is investigated for feasibility obtaining the Jive elastic moduli. A dipping angle of the foliations (theta) of 30-60 degrees with respect to the plane normal to the loading direction is recommended. The final failure modes of the specimens are investigated in detail. A sawtoothed failure plane occurs for the specimens with a high inclination of foliation with respect to the plane perpendicular to the loading direction. On the other hand, a smooth plane occurs along the foliation for specimens with low inclination of foliation with respect to the plane normal to the loading direction. A conceptual failure criterion of tensile strength is proposed for specimens with a high inclination of foliation. (C) 1997 Elsevier Science Ltd.
Displacements and stresses due to a vertical point load in an inhomogeneous transversely isotropic half-space
(2003-07-01)
Wang, CD
;
Tzeng, CS
;
Pan, E
;
Liao, JJ
;
土木工程學系
We present the solutions for displacements and stresses subjected to a vertical point load in a continuously inhomogeneous transversely isotropic half-space with Young's and shear moduli varying exponentially with depth. Planes of transverse isotropy are assumed to be parallel to the horizontal surface. The solutions for the half-space are obtained by superposing the solutions of two full spaces, one with a point load in its interior and the other with opposite traction of the first full space along the z = 0 plane. The Hankel transform in a cylindrical co-ordinate system is employed for deriving the solutions. However, the resulting integrals for displacements and stresses involve polynomial, exponential function, and Bessel function that cannot be given in closed form; hence, numerical techniques are adopted in this work. In order to check the accuracy of numerical procedures, the comparisons are carried out with the homogeneous solutions of Liao and Wang, and the calculated results agree with those to nine decimal places. Furthermore, two illustrative examples are presented to elucidate the effect of inhomogeneity, and the type and degree of rock anisotropy on the vertical surface displacement and vertical normal stress in the inhomogeneous isotropic/transversely isotropic rocks subjected to a vertical concentrated force acting on the surface. The calculated results show that the induced displacement and stress are decisively influenced by the inhomogeneity, and the degree and type of material anisotropy. The proposed solutions can more realistically simulate the actual stratum of loading problem in many areas of engineering practice. (C) 2003 Elsevier Ltd. All rights reserved.
Elastic solutions for a transversely isotropic half-space subjected to a point load
(1998-06-01)
Liao, JJ
;
Wang, CD
;
土木工程學系
;
Department of Civil Engineering
We rederive and present the complete closed-form solutions of the displacements and stresses subjected to a point load in a transversely isotropic elastic half-space. The half-space is bounded by a horizontal surface, and the plane of transverse isotropy of the medium is parallel to the horizontal surface. The solutions are obtained by superposing the solutions of two infinite spaces, one acting a point load in its interior and the other being free loading. The Fourier and Hankel transforms in a cylindrical co-ordinate system are employed for deriving the analytical solutions. These solutions are identical with the Mindlin and Boussinesq solutions if the half-space is homogeneous, linear elastic, and isotropic. Also, the Lekhnitskii solution for a transversely isotropic half-space subjected to a vertical point load on its horizontal surface is one of these solutions. Furthermore, an illustrative example is given to show the effect of degree of rock anisotropy on the vertical surface displacement and vertical stress that are induced by a single vertical concentrated force acting on the surface. The results indicate that the displacement and stress accounted for rock anisotropy are quite different for the displacement and stress calculated from isotropic solutions. (C) 1998 John Wiley & Sons, Ltd.
Elastic solutions for a transversely isotropic half-space subjected to buried asymmetric-loads
(1999-02-01)
Wang, CD
;
Liao, JJ
;
土木工程學系
;
Department of Civil Engineering
Elastic closed-form solutions for the displacements and stresses in a transversely isotropic half-space subjected to various buried loading types are presented. The loading types include finite line loads and asymmetric loads (such as uniform and linearly varying rectangular loads, or trapezoidal loads). The planes of transverse isotropy are assumed to be parallel to its horizontal surface. These solutions are directly obtained from integrating the point load solutions in a transversely isotropic half-space, which were derived using the principle of superposition, Fourier and Hankel transformation techniques. The solutions for the displacements and stresses in transversely isotropic half-spaces subjected to linearly variable loads on a rectangular region are never mentioned in literature. These exact solutions indicate that the displacements and stresses are influenced by several factors, such as the buried depth, the loading types, and the degree and type of rock anisotropy. Two illustrative examples, a vertical uniform and a vertical linearly varying rectangular load acting on the surface of transversely isotropic rock masses, are presented to show the effect of various parameters on the Vertical surface displacement and vertical stress. The results indicate that the displacement and stress distributions accounted for rock anisotropy are quite different for those calculated from isotropic solutions. Copyright (C) 1999 John Wiley & Sons, Ltd.
Elastic solutions for stresses in a transversely isotropic half-space subjected to three-dimensional buried parabolic rectangular loads
(2002-12-10)
Wang, CD
;
Liao, JJ
;
土木工程學系
;
Department of Civil Engineering
In many areas of engineering practice, applied loads are not uniformly distributed but often concentrated towards the centre of a foundation. Thus, loads are more realistically depicted as distributed as linearly varying or as parabola of revolution. Solutions for stresses in a transversely isotropic half-space caused by concave and convex parabolic loads that act on a rectangle have not been derived. This work proposes analytical solutions for stresses in a transversely isotropic half-space, induced by three-dimensional, buried, linearly varying/uniform/parabolic rectangular loads. Load types include an upwardly and a downwardly linearly varying load, a uniform load, a concave and a convex parabolic load, all distributed over a rectangular area. These solutions are obtained by integrating the point load solutions in a Cartesian coordinate system for a transversely isotropic half-space. The buried depth, the dimensions of the loaded area, the type and degree of material anisotropy and the loading type for transversely isotropic half-spaces influence the proposed solutions. An illustrative example is presented to elucidate the effect of the dimensions of the loaded area, the type and degree of rock anisotropy, and the type of loading on the vertical stress in the isotropic/transversely isotropic rocks subjected to a linearly varying/uniform/parabolic rectangular load. Copyright (C) 2002 John Wiley Sons, Ltd.
Elastic solutions of displacements for a transversely isotropic half-space subjected to three-dimensional buried parabolic rectangular loads
(2002-09-01)
Wang, CD
;
Liao, JJ
;
土木工程學系
;
Department of Civil Engineering
This paper presents the closed-form solutions for estimating the displacements in a transversely isotropic half-space subjected to three-dimensional buried linearly varying, uniform, and parabolic rectangular loads. The loading types include an upward linearly varying load, a downward linearly varying load, a uniform load, a concave parabolic load, and a convex parabolic load on a rectangle. The planes of transverse isotropy are assumed to be parallel to the horizontal surface of the half-space. The presented solutions are obtained from integrating of the point load solutions in a Cartesian co-ordinate system for the transversely isotropic half-space. The solutions for a transversely isotropic medium subjected to parabolic rectangular loads are never mentioned in the literature. The parabolic loads might be more realistic than linear variable or uniform loads acting on foundations. The buried depth, the dimensions of loaded area, the type and degree of material anisotropy, and the loading type for transversely isotropic half-spaces influence these solutions. An illustrative example is presented to investigate the effect of the type and degree of rock anisotropy, and the loading types on the displacement. The proposed solutions can provide reasonably results to estimate the induced displacements in the isotropic/transversely isotropic geomaterials subjected to three-dimensional buried parabolic rectangular loads for practical purposes. (C) 2002 Elsevier Science Ltd. All rights reserved.
Estimating coefficients of volume compressibility from compression of strata and piezometric changes in a multiaquifer system in west Taiwan
(2004-09-01)
Liu, CH
;
Pan, YW
;
Liao, JJ
;
Hung, WC
;
土木工程學系
This paper estimates the coefficients of volume compressibility from variation in compressible! layer thickness and changes in piezometric heads by using detail ground surface surveys and a multilayer monitoring well at a selected site (Shigang) within the Choshui River alluvial fan in west Taiwan. The paper integrates various types of in situ monitoring tools, including leveling surveys, continuous global position system (GPS) stations, multilevel layer compression and groundwater pressure head-monitoring wells, to investigate the situation and progress of the subsidence problem in the region. The results from the cross-analyses of the measured data show that surface settlement caused by the compression of strata is between the depths of 60 and 210 m where the clayey stratum within 120-180 m was most pronounced and contributes up to 53% of the total compression. The results indicate that the clayey stratum is under normal consolidation. The results also reflect the fact that 20% of settlement contribution comes from the sandy stratum within 90-120 m; the elasto-plastic behavior of this sandy stratum is clear. The coefficients of volume compressibility of the clayey and sandy stratum analysed from the stratum's compression records; they were 6.38 x 10(-8) and 5.71 x 10(-9) m(2)/N, respectively. Ultimately, this parameter estimation would permit to control and predict land subsidence based on change in pressure head which are related to groundwater extraction. (C) 2004 Elsevier B.V. All rights reserved.
Improved design and data interpretation of a multi-purpose borehole testing device for soft rock
(2006-06-01)
Pan, YW
;
Liao, JJ
;
Huang, AB
;
Chang, JC
;
Liao, HJ
The authors previously developed a multi-purpose borehole testing device (BTD). The purpose of the BTD was designed for obtaining mechanical properties including anisotropic elastic modulus and interface shear strength properties for soft rock that may be easily disturbed during sampling. Since the creation of the previous BTD, a few minor problems were experienced during in situ testing operation. In the present work, improvements both in equipment design and data interpretation were made. Improved design of BTD successfully reduced the chance for pressure meter test (PMT) membrane breakage, allowed larger expansion of borehole jack test (BJT), improved the waterproof of the bottom compartment and made easy for the whole equipment setup. The refined design has improved the in situ performance of BTD. New approach of data interpretation was also proposed. A series of BTD tests, including BJTs, borehole plate loading tests and borehole shear tests were carried out to demonstrate the capability of the refined borehole test device. (c) 2005 Elsevier Ltd. All rights reserved.
Loading behavior of shallow foundation on poorly cemented sandstone
(2004)
Liao, JJ
;
Chang, JC
;
Pan, YW
;
Huang, AB
;
Lin, CP
This paper aims to investigate the load bearing behavior and failure mechanism of a shallow foundation on poorly cemented rock. A series of laboratory material and model tests with specimens made of artificial soft rock were conducted. The results of material tests show that the properties of the artificial material are quite close to natural poorly cemented sandstone. The results of model bearing test indicate that a load-settlement curve can be roughly divided into the incipient stage, the linear stage, the yielding stage, and the final stage. The failure zones and mechanism were also identified. Failure zones were divided into the active zone, the transitional zone, and the passive zone. It was found that the bearing behavior on poorly cemented sandstone is distinct from the cases on hard rock or soil, with both plasticity and brittle characteristics. The bearing capacity formulas commonly used for soil or hard rock is not necessarily suitable for the case of poorly cemented soft sandstone.
Monitoring displacement distribution within the rock mass during a plate load test
(2003)
Huang, AB
;
Liao, JJ
;
Pan, IW
;
Lin, CP
;
土木工程學系
A fiber optic sensor system has been developed specifically for monitoring displacements within geomaterials. Optic fiber Bragg gratings were fixed to the sides of a slender piece of plastic rod as a means for displacement measurements. An attempt was made to monitor the local displacements within an artificial soft rock sample in a laboratory model plate load test. Two 8 mm diameter fiber optic sensored Delrin rods were inserted into the rock mass at various depths below the model foundation. The amount and distribution of the displacements caused by the plate load were measured through the flexural strains occurred in the fiber optic sensors. Initial results have indicated that the technique was capable of detecting relative displacements at least for the case of a model plate load test. Reasonable relationship between moduli and strains could be derived from these displacement measurements and estimated average stresses based on Boussinesq theory. This paper describes the laboratory set up of the sensor system; present the results of the plate load test and discusses the implications in the use of fiber optic sensors for field local displacement measurements.
Pressuremeter tests in poorly cemented weak rocks
(1999)
Huang, AB
;
Pan, IW
;
Liao, JJ
;
Wang, CH
;
Hsieh, SY
A series of pre-bored pressuremeter tests (PMT) were performed in relatively young, weak rock deposits at several test sites in Taiwan. Equipment used included the Menard type tri-cell pressuremeter and Cambridge high-pressure dilatometer. The test data were interpreted using some of the existing empirical and a newly developed analytical procedure. According to the interpretations of PMT data, the tested weak rock should behave as a highly overconsolidated cohesive material. This is contrary to some of the available laboratory experimental results. A 3-surface numerical scheme has been developed to simulate pressuremeter expansion in weak rock with unload-reload cycles. Preliminary results have indicated that the numerical scheme is capable of capturing the important features of pressuremeter expansion in a weak sandstone.