Select

null

2003, 22 (03): -0 doi:
Full Text:

[PDF 118 KB] (540)

+

Show Abstract

Select

STRAIN ENERGY THEOREM OF COSSERAT THEORY AND UNIQUENESS OF ITS SOLUTION

null

2003, 22 (03): -343 doi:
Full Text:

[PDF 234 KB] (1027)

+

Show Abstract

Cosserat continuum theory has been applied widely in geotechnical engineering and other fields，such as composites mechanics，biological mechanics. When dealing with engineering problems with Cosserat Theory，both analytic and numerical methods have been adopted in analysis process. As the solutions obtained with different methods appears with differently forms，the uniqueness of solution is needed to be verified to ensure the results achieved are the answer to problems exactly no matter how different the expressions look from each other and both analytic and numerical methods are effective. Though the number of Cosserat stresses and strains components are more then conditional continuum theory，it has been proved that work done on the Cosserat elastic body is equate to the strain energy gained by the body if no energy dissipated during loading. Moreover，the theorem of uniqueness of solution for Cosserat theory has been proved in this paper，and it provids warrant for the adoption of different analysis methods. Finally，the problem of stress concentration around small hole in plate is analyzed with Cosserat theory by adopting both analytic and numerical methods，and the results are compared and identical with each other.

Select

STUDY ON MATHEMATIC MODEL OF INDEPENDENT MAIN VARIABLE FOR ROCKMASS DYNAMICS SYSTEM

null

2003, 22 (03): -347 doi:
Full Text:

[PDF 215 KB] (692)

+

Show Abstract

It is very important to select or construct reasonable state variables to setting up correct nonlinear dynamics model of rockmass dynamics system. In allusion to the dependence among the state variables in the traditional theories，the independent main variable model of rockmass dynamics system and its algorithm are set up in the article. The example shows that the independent main variable can describe the nonlinear evolution of rockmass dynamics system more accurately.

Select

ON THE DYNAMIC MECHANICS MODEL OF MINING SUBSIDENCE

null

2003, 22 (03): -352 doi:
Full Text:

[PDF 234 KB] (1025)

+

Show Abstract

The strata movement falls into four phases. Different mechanics models are used to simulate the strata movement in different phases. The differential equations are derived for strata movement models in different phases. The boundary conditions of each model and exchange conditions between different models are put forward. The visual computing program is developed to compute movement of strata and surface，position of bed separation，caving height of mined rockmass and caving step length of roof. The model has been proved by comparison with field data.

Select

MULTIPLE POTENTIAL DISCONTINUOUS BIFURCATION MODEL
FOR JOINTED ROCKS AND ITS APPLICATION

null

2003, 22 (03): -358 doi:
Full Text:

[PDF 322 KB] (873)

+

Show Abstract

In the framework of the multiple potential surface elasto-plastic theory，the discontinuous bifurcation model used to simulate the failure of the jointed rocks is presented in this paper. Classical localization analysis is performed to the tangent stiffness tensor，thus the condition for discontinuous bifurcation is derived. Numerical method is formulated to calculate localization directions. With the aid of FEM，analysis is made on several corresponding specimen with initial distributed cracks under tension and compression.

Select

FINITE ELEMENT RESEARCH ON NATURAL FRACTURE
DISTRIBUTION IN UNDERGROUND ROCKS ACCORDING
TO GRIFFITH CRITERION

null

2003, 22 (03): -364 doi:
Full Text:

[PDF 162 KB] (996)

+

Show Abstract

Generally，underground sedimentary stratum consists of several kinds of rocks，with very strong anisotropy and different mechanical property. Moreover，during evolution，the difference of depth，temperature，confined pressure，and the influence of filling，degradation，which probably happened after the fracture forming，make the mechanical property of underground sedimentary stratum changed. The cracking of underground sedimentary stratum is also multiphase in the course of geological history. All these characters of underground sedimentary stratum make it difficult to forecast the distribution of fracture. According to all these characters，comprehensive quantitative method is used to establish mathematic model，analyze the influent factors of cracking，and determine the parameters of model and the steps of modeling. Then the fracture developing probability and fracture characters are predicted. At last，a sample is introduced taking from petroleum industry.

Select

EFFECT OF PHYSICAL AND MECHANICAL PROPERTIES OF ROCKS ON STRESS FIELD IN THE VICINITY OF FRACTURES

null

2003, 22 (03): -370 doi:
Full Text:

[PDF 380 KB] (1147)

+

Show Abstract

In this paper，by systematic numerical modeling by the distinct element method with UDEC code， the effect of physical and mechanical properties of rocks including internal friction angle，Young’s modulus，Poisson’s ratio，and cohesion on stress field in the vicinity of fractures are analyzed. It is shown that the variation of all of these properties may cause the change of stress fields in the vicinity of a fault. Meanwhile，the effect of physical and mechanical properties of rocks co-exists with that caused by the change of mechanical properties of fractures and boundary conditions. In the modeling，both the single fracture model and compound fracture model are studied respectively. It is found that the Young’s modulus of rocks has a strong influence on the variation of rock stresses in the case of compound fracture model.

Select

APPROXIMATE METHOD OF PLASTICITY THEORY

null

2003, 22 (03): -378 doi:
Full Text:

[PDF 190 KB] (788)

+

Show Abstract

The new method of plasticity based on e-p curve is of obvious advantages over the classical theory method. However，the analytic solutions can be obtained for only a limited number of problems，and a large number of problems have to rely on numerical method to obtain their solutions. An approximate numerical method of the new method is studied in this paper. Example shows that the approximate method is of a good future.

Select

STUDY ON BREAKING MECHANISM OF ROCKBOLT-END

null

2003, 22 (03): -383 doi:
Full Text:

[PDF 242 KB] (928)

+

Show Abstract

By analysis of rockbolt-end under eccentric load，it is found that the eccentric load is not good for rockbolt-end work and the stress of rockbolt-end is 5 to 7 times larger than that under centred load. Based on rockbolt mechanics model under general condition，the equations and work status of rockbolt-end load are given. The inevitability of eccentric load brought by its gradual breaking is expounded. Finally，the breaking mechanics conditions of rockbolt-end are given，and corresponding practical meanings are interpreted.

Select

STUDY ON SMALL BOREHOLE PRETENSIONED CABLE REINFORCING COMPLICATED ROADWAY

null

2003, 22 (03): -387 doi:
Full Text:

[PDF 208 KB] (1254)

+

Show Abstract

The characteristic and mechanical properties of pretensioned cable with small borehole anchored by resin and grout are summarized. The measurement results of strength，structures of surrounding rocks，and in-situ stresses， the design scheme of cable，underground construction technology and monitoring are introduced， based on a haulageway with large section，soft surrounding rocks，effected by geologic structures and mining in Changcun Coal Mine，Lu’an，Shanxi. The strengthening effect of the cable is appraised，and the techno- economic benefits are analyzed by means of monitoring data.

Select

STUDY AND APPLICATION OF MONITORING FOR SUBSIDING AREA IN A COMPOSITE HARD ROCK ROADWAY

null

2003, 22 (03): -391 doi:
Full Text:

[PDF 300 KB] (953)

+

Show Abstract

The important roles and application prospects of some testing methods are briefly described，including acoustic emission，convergence inspection，stress measurement，subsidence measurement，level measurement in the process of stability and safety monitoring as well as inspecting of subsiding area in a roadway in composite hard rock. In terms of the modern signal analysis technology，the monitoring results and the stability of rock mass are synthetically evaluated，and the location of acoustic origin has been successfully detected according to the acoustic emission regularity. Finally，the key factors to affect the stability of rocks are obtained in subsiding area.

Select

RELIABILITY CALCULATION METHOD BASED ON NUMERICAL
SIMULATION AND BP NETWOORK

null

2003, 22 (03): -395 doi:
Full Text:

[PDF 234 KB] (1116)

+

Show Abstract

Usually it is very difficult to get an analytical equation of limit state for reliability analysis of the stability of tunnel. So，based on numerical simulation，BP network and optimal technique，a reliability analysis method is put forward to calculate the reliability index and test point. This method can simulate the reliability problems with implicit performance functions in actual engineering. On calculation reliability，the deterministic FEM programs can be used directly. Two illustrative examples are presented in this paper. The first example deals with reliability of a frame structure，and the second one studies the stability of a tunnel under the initial stress effect. In the calculation，the Young’s modulus，friction angle and cohesion are treated as random variables and different probability distributions with these random variables and the correlation among them are considered. Comparisons with other methods show that the proposed method is very efficient and reasonably accurate.

Select

黄宏伟1 胡昕2

null

2003, 22 (03): -400 doi:
Full Text:

[PDF 236 KB] (1108)

+

Show Abstract

In recent years，pipe-jacking method is being used to construct various kinds of underground tubes or tunnels more popularly in urban area or when crossing river. Due to the development of municipal engineering，much more attention should be paid to the effect of pipe-jacking on closer environment. The construction mechanics effects of pipe-jacking with earth pressure balance are analyzed，for instance，the bulkhead pressure，stratum loss，and grouting. Then 3D FEM is employed to calculate additional stress of surrounding soil and surface deformation caused by excessive bulkhead pressure，stratum loss，grouting and their composite operation，respectively. The study illustrates the effect scope either in longitudinal or in transverse section caused by different elements of pipe-jacking，which can help researchers to understand the environment effect of construction in more detail. And at the same time，the quantitative results and some discussions can make for in-situ engineers to make decisions on their own for these effects in advance.

Select

STUDY ON THE FINITE DIFFERENCE METHOD IN CALCULATION OF INTERNAL FORCES OF PRESTRESS-ANCHORED ANTISLIDE PILES

null

2003, 22 (03): -407 doi:
Full Text:

[PDF 287 KB] (1191)

+

Show Abstract

The disadvantages of existing calculation methods for the internal forces of the prestress-anchored antislide pile are pointed out. Based on the principle of the foundation coefficient method in calculating the internal forces of the ordinary antislide pile，the finite difference method is presented to calculate the internal forces of the whole prestress-anchored antislide pile. The corresponding formulae are derived in detail. The pile can be analyzed as a complete entity. It is not necessary to divide the pile into two segments by the sliding surface like the existing methods. The ordinary antislide pile and the prestress-anchored pile are compared by an engineering example. The advantages are showed of the prestress-anchored pile. Meanwhile the example also shows that the finite difference method can obtain the calculation results quickly and precisely and model all sorts of working cases of the pile. Therefore this is a simple and useful method in analyzing the internal forces of the prestress-anchored antislide pile. Monitoring work shows the calculation results are satisfying.

Select

RELATIONSHIP BETWEEN ROCK BURST AND BLASTING

null

2003, 22 (03): -414 doi:
Full Text:

[PDF 291 KB] (1029)

+

Show Abstract

Rock burst records from many large underground projects indicate that there is relationship between rock burst and blasting. The propagation of the explosive stress waves in surrounding rock masses may be simplified as Lamb problem. After blasting，to a peripheral point of underground opening，P wave，Rayleigh wave and S wave reach successively. P wave and Rayleigh wave，especially Rayleigh wave with big amplitude disturbe rocks apparently. P wave and Rayleigh wave will make tensile fissures vertical and parallel to peripheral surface of rocks，respectively. In the stress environment of ，，the appearance of these fissures brings about the failure of rocks by rock burst. The attenuation of P wave and distribution of Rayleigh wave in vertical direction may explain reasonably many rock bust phenomena，such as the space relation between rock burst area and working face，the shape of rock burst fragments and so on.

Select

DAMAGE AND FRACTURE CRITERION FOR MODE I
CRACK OF CONCRETE

null

2003, 22 (03): -420 doi:
Full Text:

[PDF 272 KB] (1096)

+

Show Abstract

Damage theory is used to the concrete fracture criterion. The boundary equations of damage zone under static and dynamic loading are obtained. The new concrete “damage-fracture criterion” is developed by the new concept of allowed damage length. The experimental results and prediction ones from the formula of damage length are in good agreement.

Select

LINK BETWEEN COMPRESSIVE DEFORMATION AND CRACK PROPAGATION IN CEMENT MORTAR

null

2003, 22 (03): -425 doi:
Full Text:

[PDF 184 KB] (819)

+

Show Abstract

The experimental investigation and analysis are presented for exploring the intrinsic link between compressive deformational response and crack behavior of the mortar specimens. Images of the crack propagation on the surface of specimens are recorded synchronously during compressive deformation， and then processed to obtain the cracking process. The identified cracks are then analyzed quantitatively to obtain the measurement of the cracking degree by using the methods in which the effect of the direction of cracking is considered. Theoretical analyses are made for obtaining the intrinsic relation between cracking and non-linear deformational response in conjunction with the experimental observations. The obtained relation provides an effective way to measure the evolution of deformation property of the material caused by damage under compression throughout the measurement of cracking on the surface of the specimen.

Select

DISCUSSION ABOUT SHEAR STRENGTH AND COMPRESS-SHEAR RUPTURE CRITERION OF TWO PHASE STUFF OF SAND GROUT-LIMESTONE

null

2003, 22 (03): -429 doi:
Full Text:

[PDF 260 KB] (1075)

+

Show Abstract

Contraposing the sand grout-limestone’s cylinder specimen taking from a gravity dam engineering，the uniaxial compression test of limestone and the straight shear test of two phase stuff gumming face of sand grout-limestone are made by RMT-150 multifunctional rigidity servo testing machine.Via the tests，the elastic modulus，Poisson’s ratio of limestone and shearing strength，intensive parameters of two phase stuff gumming face are obtained. Thereby，the compress-shear rupture criterion is presented to estimate dam stability besed on the idea of stress intensity factor. The relationship among gumming face strength，specimen size and elastic modulus，and that expression between the shear modulus and elastic modulus of limestone are found，which can be valuable reference for practical engineering.

Select

NONLINEAR CHAOTIC MODEL OF LANDSLIDE FORECASTING

null

2003, 22 (03): -434 doi:
Full Text:

[PDF 175 KB] (1050)

+

Show Abstract

According to the nonlinear characteristics of landslide displacement time series，the nonlinear chaotic model is presented applying the forecasting method of chaotic time series. Then the adding-weight one-rank local-region algorithm is proposed and applied in the forecasting calculation of the displacement monitoring data obtained in Maoping landslide of Qingjiang. The results show that the forecasting method based on nonlinear chaotic model is not only accurate but also of less calculation amount and easy to handle. Thus a new forecasting method is provided for the landslide displacement.

Select

EXTENSION CLASSIFICATION PREDICTION METHOD
FOR THE STABILITY OF ROCK-MASS SLOPES

null

2003, 22 (03): -438 doi:
Full Text:

[PDF 164 KB] (983)

+

Show Abstract

Based on the matter-element model and the classified analysis method，an extension classification prediction method for the stability of rock-mass slopes is proposed. In the method，the stability types and the influence factors on rock-mass slopes are used to set up the classical and limited matter elements. A simple forecasting model of the stabilyty types of rock-mass slopes is established by applying the correlated functions of matter elements and extension sets. The predicting results of the stability of rock-mass slopes are obtained by applying the classified analysis. The analyzing results of an example show that the proposed method is available.

Select

STUDY OF COMBINED EVALUATION METHOD FOR SAFETY OF OPEN-PIT SLOPE AND ENVIRONMENT

null

2003, 22 (03): -442 doi:
Full Text:

[PDF 246 KB] (851)

+

Show Abstract

The stiffness resisting deformation and strength resisting failure induced by open-pit excavation are two problems. Therefore，different influence mechanisms are produced. Slope rockmass is safe if the strength condition is satisfactory. But，surrounding environment will be broken if stiffness is not sufficient. In the light of old mining area surrounding city，the safety definition should assure mining and environment safe. Otherwise，economical benefit may be a negative value. The analysis is made on these problems. Then，synthetic analysis on slope stability and ground deformation combined history-case is carried out and corresponding analytical methods are given.

Select

FINITE ELEMENT ITERATION METHOD FOR STABILITY SAFETY FACTOR OF SLOPES AGAINST SLIDING

null

2003, 22 (03): -446 doi:
Full Text:

[PDF 306 KB] (1073)

+

Show Abstract

The contact surface between landslide body and rock foundation is simulated by rectangle element for plane problems or cubic element for three dimensional problems with small thickness. A nonlinear iterative computation method is suggested to meet Mohr-Coulomb criterion for the stresses on the surface of sliding. On the basis of the nonlinear iterative method， a finite element iteration method of safety factor against sliding of the landslide body is presented to meet the limit equlibrium condition. This method can be used for 2D and 3D problems and the results include displacement field and the stress field. An example of the safety factor against a broken-line slide plane is analyzed. It demonstrates that the method suggested in this paper is effective，rational and reliable.

Select

SWELLING TESTS ON BENTONITE AND SAND-BENTONITE MIXTURE

null

2003, 22 (03): -451 doi:
Full Text:

[PDF 272 KB] (1010)

+

Show Abstract

The swelling characteristics of bentonite and sand-bentonite mixture were studied by laboratory tests, which were conducted on an oedometer apparatus. A general relationship between swelling strain and overburden pressure is proposed by the test results. It is shown by the test results that the swelling characteristics are related to the sample compaction conditions, and the swelling deformation takes place due to the interaction between montmorillonite and water.

Select

EVALUATION OF DYNAMICAL SETTLEMENT OF UNFREE-FIELD

null

2003, 22 (03): -456 doi:
Full Text:

[PDF 209 KB] (879)

+

Show Abstract

In order to study the effect of layered ground on dynamical deformation of unfree field，which is a very complex and hard to deal with，firstly the concept of unfree field is explained and a sand layered subsoil is suggested as an example of unfree field. According the different causes to induce the deformation of subsoil and structures，the total settlement or the deformation is divided into the volume compresion of soil under recycled shear force，added settlement by dynamical action from the up-structures，and the settlement from soil deformation by modulus degeneration of dynamical nonlinearity. A cone model is introduced to analyze the scattered source and research the interaction of structures and multi-layers-subsoil. The solving process is given to analyze and evaluate the settlements，and satisfied actory results are obtained.

Select

ANALYSIS ON INTERNAL FORCE AND DEFORMATION OF SUPPORT STRUCTURE FOR FOUNDATION PIT

null

2003, 22 (03): -462 doi:
Full Text:

[PDF 219 KB] (1001)

+

Show Abstract

The coupling method of finite-infinite element is suggested to analyze the internal force and deformation of support structure for foundation pit. In order to simulate the actual situation，a new kind of interface element with thickness is installed in the interface between soil and structure. It is verified by a practical project that the new model can consider the space effect of deformation of retaining wall due to excavation and the time effect due to rheology of foundation. The deformation and internal force of support structure at any time and place can be calculated based on the program.

Select

INFLUENCE OF THE CHANGE OF IMPACT VELOCITY ON IMPACT DEFORMATION FIELD OF METEORITE

null

2003, 22 (03): -467 doi:
Full Text:

[PDF 381 KB] (949)

+

Show Abstract

Aiming to meteorite impact affair of Cangshan，the popular nonlinear program ANSYS/LS-DYNA is used to analyze how the change of impact velocity affect the emergence，development and evolvement of the impact deformation field of meteorite. The relationship curves between impact velocity and deformation field are obtained，which can be an important base of the research for meteorite impact.

Select

STUDY ON THE TECHNIC METHODS OF INCREASING
DETECTION DISTANCE OF TSP-202 SYSTEM

null

2003, 22 (03): -472 doi:
Full Text:

[PDF 190 KB] (1000)

+

Show Abstract

The technic methods to increase the detection distance of TSP-202 system is studied with the theories of the geological tectonics and the explosion seismology. According to the different tectonics and lithology，it is stressed how to adopt the detection parameters based on practical conditions. Then，the effective technique is put forward for the method.

Select

UNDERSTANDING AND CONSIDERATION TO THE STRUCTURE DESIGN OF METRO STATION IN HARD ROCK STRATUM

null

2003, 22 (03): -476 doi:
Full Text:

[PDF 278 KB] (1188)

+

Show Abstract

Combining with the design and construction of the trial section of Qingdao Metro，some problems are analyzed，such as the depth，structure type，construction method of bored station in hard rock stratum. The suggestions are proposed for the next stage design for Qingdao Metro.

Select

INTERACTION ANALYSIS ON WALE AND RETAINING
PILES IN DEEP FOUNDATION PIT

null

2003, 22 (03): -481 doi:
Full Text:

[PDF 266 KB] (1072)

+

Show Abstract

A semi-spatial model is presented to analyze the behavior of retaining piles in deep excavation. Based on free support assumption at the bottom of the piles，the analytical formula is derived to calculate the bending moments and deformations of the piles. The formula can account for the top-beam and strut-wale effects. Finally， the spatial effect of this kind of structure and influence of the wale are shown through a case study.

Select

DISCUSSION ON COMPACTION GROUTING IN SHANGHAI AREA

null

2003, 22 (03): -487 doi:
Full Text:

[PDF 150 KB] (1305)

+

Show Abstract

In this paper，two types of grouting methods，compaction grouting and splitting grouting，are differentiated. The analysis is made on diverse grouting methods used in Shanghai in present. The discussion is also made about the necessity of the development of compaction grouting in Shanghai and the problem that should be solved.

Select

MULTI-ATTRIBUTE DECISION-MAKING ANALYSIS ON SELECTING RETAINING SCHEME OF DEEP FOUNDATION PIT

null

2003, 22 (03): -490 doi:
Full Text:

[PDF 239 KB] (953)

+

Show Abstract

The selection of retaining scheme for deep foundation pit is presented. The selection involves multiple objectives such as technology，economics，environment，and risk. The decision relevant information such as attribute weights and the values of alternatives about some attributes may be not known exactly. Rather，they are to be expressed as a set of linear inequalities such as rankings and/or bounds. To cope with such decision-making question with incomplete information，a mathematical programming model based multi-attribute decision-making approach is used，which can obtain a satisfactory retaining scheme by checking dominance of alternatives. A practical example is given to show the feasibility and effectiveness of the presented method.

Select

STUDY ON BEARING BEHAVIOR OF SQUEEZED BRANCH PILE

null

2003, 22 (03): -494 doi:
Full Text:

[PDF 210 KB] (688)

+

Show Abstract

It is proved by loading test that the loading transfer behavior of squeezed branch piles has changed because at different places of the pile body are located many branches or disks. The loading transfer behavior of squeezed branch pile is studied and analyzed based on static loading test，and the modified coefficients used for calculation of limit bearing capacity with empirical formula are proposed and used in this test. It is shown that the calculated results and test data are in good agreement. The effect factors of squeezed branch piles are analyzed at the same time.

Select

INCREASING AND DISSIPATION REGULARITY OF THE PORE WATER PRESSURE UNDER THE DYNAMIC COMPACTION ACTION TO THE ALLUVIAL AND DILUVIUM SOIL OF YELLOW RIVER

null

2003, 22 (03): -500 doi:
Full Text:

[PDF 193 KB] (821)

+

Show Abstract

The increasing and dissipation regularity of the pore water pressure with depth and broadness under the different hammering energy of the downstream alluvial and diluvium soil of Yellow River is studied by experiment. The experiment results show that increasing and dissipation rate of the pore water pressure under the action of hammering energy of the alluvial and diluvium soil of Yellow River is comparatively high. The influence depth and width of the hammering energy are of the tendency in direct proportion with the magnitude of the hammering energy. This kind of soil is suitable for being compacted by the method of dynamic compaction. The stratum of this area is mainly composed of silty clay，and the increasing and dissipation of the pore water pressure are relativity slow below the groundwater level，under the hammering energy. The recovery of the soil strength will need more time. During the application of dynamic compaction method，the low energy and long resting time method should be considered.

Select

TESTING STUDY OF PERMEABILITY OF THE ORIGINAL
CLAY，RECOMPOSED CLAY AND IMPROVED CLAY
WITH STABILIZER ZDYT-1

null

2003, 22 (03): -505 doi:
Full Text:

[PDF 197 KB] (1400)

+

Show Abstract

According to the results of undisturbed and disturbed samples of Xiaoshan clay and the clay improved with stabilizer ZDYT-1 in different stabilizer mixing ratio and time through the laboratory test，the permeability of the clay is analyzed for reference to practical engineering. The testing study results are valuable for preventing water curtain of deep excavation and consolidating soft clay.

Select

CALCULATION PROCEDURE FOR P-S CURVE OF PILES

null

2003, 22 (03): -509 doi:
Full Text:

[PDF 275 KB] (1283)

+

Show Abstract

With the parameters of common soil laboratory test data，c，f，g，t-u，the defomation modulus Eo of foundation is established by the relation between Eo and N from plate loading tests. In addition，according to the transmission law of pile load value，the calculation procedure of pile P-S curve is put forward. The calculation procedure has been applied into practice and satisfactory results are obtained.

Select

THEORY STUDY AND ENGINEERING APPLICATION OF LARGE DIAMETER AND SUPER-LONG PILE UNDER WATER

null

2003, 22 (03): -514 doi:
Full Text:

[PDF 97 KB] (745)

+

Show Abstract