Browsing by Author "Huang, AB"

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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.
A laboratory study on the undrained strength of a silty sand from Central Western Taiwan
(2004-10-01)
Huang, YT
;
Huang, AB
;
Kuo, YC
;
Tsai, MD
;
土木工程學系
The sand deposit in Central Western Taiwan typically contained significant amounts of fines. The assessment of liquefaction potential using the simplified procedure often involved adjustment in field test results to account for the effects of fines. The available fines content (FC) adjustment methods are highly empirical and may lead to very different conclusions. The need and/or level of FC adjustment should be justified based on cyclic behavior of sand and its relationship with fines. This study made an attempt to provide that reference information for a silty sand commonly found in Central Western Taiwan. A series of isotropic consolidation, undrained monotonic and cyclic triaxial tests were conducted on reconstituted Mai Liao Sand (MLS) with various FCs and densities. Concurrent shear wave velocities were measured using bender elements in some of the cyclic triaxial tests. This paper describes the geological background, the laboratory tests and their implications in the assessment of liquefaction potential for MLS. (C) 2004 Published by Elsevier Ltd.
Chamber calibration of CPT under simulated field conditions
(1998)
Huang, AB
;
Hsu, HH
;
土木工程學系
;
Department of Civil Engineering
An important drawback of calibrating CPT in a chamber is its boundary effects. The lateral boundary of the specimen in a conventional calibration chamber is either stress controlled or rigid. Neither of these two boundary conditions can correctly duplicate the field conditions which lies somewhere in between. In order to eliminate the boundary effects, a new calibration chamber system that enables the field conditions be simulated has been developed. The new chamber wall, 800mm in diameter and 1600mm high, is made of 20 vertically stacked steel rings. The boundary movement induced by the cone penetration is measured at each ring level by an extensometer. The lateral stress at each ring level is determined by the stress-strain relationship of the specimen. A series of CPT calibration tests has been performed in a uniform, dry silica sand using the new system. Results show that the new simulator is capable of eliminating boundary effects, even at a relative density of 84%. The paper describes the design of the new chamber system and presents available test data.
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.
Comparative behavior of laterally loaded groups of bored and driven piles in cohesionless soil
(2003-09-01)
O'Neill, MW
;
Huang, AB
;
土木工程學系
;
Department of Civil Engineering
The lateral load performance of 2 pile groups, one consisting of driven displacement piles, the other of bored piles, is described. The effect of installing the piles is to reduce the soil stiffness within the bored pile group, making the soil less efficient in resisting lateral pile movements than in the driven pile group. Structurally, however, the bored piles were more resistant to flexural loading. The net effect was that the system of bored piles was stiffer than the system of driven displacement piles.
Cone penetration tests under simulated field conditions
(2005-06-01)
Huang, AB
;
Hsu, HH
;
土木工程學系
;
Department of Civil Engineering
Cone penetration tests (CPT) performed in a conventional cavity-wall calibration chamber are inevitably affected by boundary conditions. The authors have developed an axisymmetric field simulator whereby CPT calibration tests can be conducted under substantially reduced boundary effects. The simulator consists of a cylindrical, physical sand specimen and a stack of expandable rings to simulate the soil from beyond the physical boundary. A series of CPT calibration tests has been performed in a clean, uniformly graded quartz sand using this simulator system. For a given relative density, the cone tip resistance (q(c)) was found to be most closely related to mean normal stress. The horizontal stress at the physical boundary increased during CPT under simulated field conditions. This increased horizontal stress had a much more significant and consistent effect on q(c) than the initial horizontal stress existing in the soil prior to CPT. The paper describes the results of CPT in the simulator, and discusses implications for the performance of CPT in a chamber and their interpretation.
Development of a fibre Bragg grating sensored ground movement monitoring system
(2006-07-01)
Ho, YT
;
Huang, AB
;
Lee, JT
;
土木工程學系
;
Department of Civil Engineering
Monitoring ground movement manually by lowering an inclinometer probe (IP) in a grouted-in-place casing has been in practice for decades. It is possible to install multiple IP units at various depths in an inclinometer casing to allow automated data logging. The high cost and other problems associated with transmitting signals electrically make an automated IP rather impractical for long term and/or massive deployment. In addition to its small size, available technologies allow optical signals to be transmitted over many kilometres and not be affected by electromagnetic interference. The optical fibre Bragg grating (FBG) is one of the many available fibre optic sensor technologies. The authors used FBG as a sensing medium and developed a ground movement monitoring device referred to as the FBG segmented deflectometer (FBG-SD). The FBG-SD, designed to be inserted into the conventional inclinometer casing, measures the relative deflection between the segments. The amount of lateral movement is computed on the basis of the distribution of the segmented deflections. To verify the effectiveness of the new system, the authors performed indoor as well as field experiments where results from FBG-SDs were compared with conventional IP readings. This paper introduces the design principles of the FBG-SD and describes the performance of the system in their indoor and field applications.
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.
Development of an axisymmetric field simulator for cone penetration tests in sand
(1998-12-01)
Hsu, HH
;
Huang, AB
;
土木工程學系
;
Department of Civil Engineering
An experimental system capable of simulating axisymmetric field conditions has been developed. This system, as an improvement over conventional calibration chambers, enables cone penetration tests (CPT) to be calibrated under minimal boundary effects. The new simulator consists of a stack of 20 rings to house the sand specimen. These rings are lined with an inflatable silicone rubber membrane on the inside. The boundary expansion and stress are measured and individually controlled, respectively, at each ring level during the CPT. The soil from physical boundary to infinity is simulated using a nonlinear cavity expansion curve derived from a lateral compression test on the specimen. Results from a series of CPTs show that at relative densities of approximately 80%, the cone tip resistance values agree within 4% as the diameter ratio of the physical specimen over cone varies from 18 to 22. This paper describes unique features of this field simulator, presents available CPT data performed in the simulator, and discusses its implications on future calibration tests.
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.
Effects of construction on laterally loaded pile groups
(2001-05-01)
Huang, AB
;
Hsueh, CK
;
O'Neill, MW
;
Chern, S
;
Chen, C
Full-scale lateral load tests on a group of bored and a group of driven precast piles were carried out as part of a research project for the proposed high-speed rail system in Taiwan. Standard penetration tests, cone penetration tests (CPT), and Marchetti Dilatometer tests (DMT) were performed before the pile installation. The CPT and DMT were also conducted after pile installation. Numerical analyses of the laterally loaded piles were conducted using p-y curves derived from preconstruction and postconstruction DMT and by applying the concept of p multipliers. Comparisons between preconstruction and postconstruction CPT and DMT data and evaluation of the results of computations show that the installation of bored piles softened the surrounding soil, whereas the driven piles caused a densifying effect.
Ground movement monitoring using an optic Fiber Bragg Grating sensored system
(2004)
Huang, AB
;
Ma, JM
;
Zhang, BS
;
Wen, XG
;
Cao, JG
The authors have developed a fiber optic ground movement monitoring system using the optic Fiber Bragg Grating (FBG). A series of FBG's are glued to the outside of flexible plastic elements. These flexible elements are connected together to form a single probe. When the flexible element is bent, the FBG would sense the flexural strain as a result of the bending. Twice integration of the strains along the longitudinal axis of the probe yields the distribution of the displacement of the monitoring probe associated with the bending. The FBG sensored monitoring probe can be inserted in an inclinometer casing or directly grouted in a borehole to monitor ground movement. The sensitivity and range of allowable bending of the monitoring probe can be adjusted according to the need in the field. The new system can be used to monitor stability of natural slopes, man-made retaining structures (including darns or dikes), braced cuts, and tunnel excavations, etc. The FBG based monitoring system has been experimented to monitor the displacement distribution of a laterally loaded pile in Yuin-Lin, Taiwan and stability of a Yellow River dike in Honan, China. This paper describes the principles of the FBG sensored monitoring probe system and presents field applications of the new sensor systems.
Ground movement monitoring using an optic Fiber Bragg Grating sensored system
(2005)
Ho, YT
;
Huang, AB
;
Ma, JM
;
Zhang, BS
;
Cao, JG
The authors have developed a fiber optic ground movement monitoring system using the optic Fiber Bragg Grating (FBG). A series of FBG's are glued to the outside of flexible plastic elements. These flexible elements are connected together to form a single probe. When the flexible element is bent, the FBG's sense the flexural strain as a result of the bending. Twice integration of the strains along the longitudinal axis of the probe yields the distribution of the displacement of the monitoring probe associated with the bending. The sensitivity and range of allowable bending of the monitoring probe can be adjusted according to the need in the field. The FBG based monitoring system has been experimented to measure the displacement distribution of a laterally loaded pile in Yuin-Lin, Taiwan. This paper describes the principles of the FBG sensor monitoring probe system and presents a case of field application of the sensor system.
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.
Local displacement measurement and physical modeling
(2003)
Huang, AB
;
Wu, CT
;
Hsu, HH
;
土木工程學系
;
Department of Civil Engineering
The importance and value of local displacement measurement in physical modeling and/or field tests have been well recognized. This paper describes two cases where local displacement was monitored for cone penetration tests (CPT) in a calibration chamber and model foundation load tests. In the CPT chamber calibration tests, local displacement measurement was used as part of a scheme to minimize boundary effects. In the model foundation load tests, the local displacement measurement was used to monitor the distribution of displacement in the rock mass. This paper describes the techniques implemented in these two cases and discuses their performances.
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.
Site characterization of a dynamically compacted silty fine sand
(1998)
Huang, AB
;
Chang, JW
;
Chen, DDS
;
Yeh, CC
;
土木工程學系
A reclaimed land of approximately 2400 hectares is under construction as part of an industrial development at Mail Liao Township, on the West Coast of Taiwan. Silty fine sand dredged offshore was placed hydraulically to reach a final grade of 3 m above sea level. The foundation soil consists of similar material that extends to several hundred meters below sea level. The new sand fill and the underlying foundation soil was dynamically compacted to increase the sand density within top 10 m. Earlier attempts to estimate pile shaft frictions using CPT data according to existing methods were 30 to 70% below those measured in pile load tests at Mai Liao. A new method to predict the shaft friction that considers the characteristics of the silty fine sand at Mai Liao and the effects of dynamic compaction is proposed. The new method was developed based on a series of laboratory experiments that include CPT chamber calibration tests. According to comparisons with four pile load tests, the new method provides a reasonable and slightly conservative prediction for the shaft friction of driven PC piles. The average error was - 12%.
The behavior of a compressible silty fine sand
(1999-02-01)
Huang, AB
;
Hsu, HH
;
Chang, JW
;
土木工程學系
;
Department of Civil Engineering
Publications associated with sands are often limited to clean (i.e., little fines content), uniform, uncemented silica or quartz sand. On the other hand, the importance of mineral content, particle shapes, as well as gradation to the behavior of sand has long been recognized. Although systematic studies of sands ether than clean quartz sand have been limited, there is increasing attention being paid to sands with an appreciable fines content. Because of a major construction project, extensive field and laboratory experiments were performed on a silty fine sand from Mai-Liao, which is located on the central west coast of Taiwan. Results show that Mai-Liao Sand (MLS), a silty sand, can be significantly more compressible than clean quartz sand under static load. The particles of MLS have moderate strength, and significant crushing can be induced by triaxial shearing. As a result, MLS has low dilatancy and a relatively small range of peak friction angles. Cone penetration tests in MLS were conducted in a calibration chamber. Analyses of the data indicate that interpreting cone tip resistance in MLS using methods developed based on clean quartz sand without considering the differences of compressibility can be unrealistic. This paper documents results of the experimental studies on MLS.