Fei Experimental Study on a Geo Mechanical Model of a High Arch Dam 2010

8/13/2019 Fei Experimental Study on a Geo Mechanical Model of a High Arch Dam 2010

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Experimental study on a geo-mechanical model of a high arch dam

Wen-ping Fei , Lin Zhang, Ru Zhang

State Key Laboratory of Hydraulics and Mountain River Engineering, College of Water Resources and Hydropower, Sichuan University, Chengdu, Sichuan 610065, China

a r t i c l e i n f o

Article history:

Received 7 April 2009

Received in revised form

1 November 2009

Accepted 11 December 2009Available online 4 January 2010

Keywords:

High arch dam

Stability safety factor

Geo-mechanical model

Temperature analogous material

Comprehensive method

a b s t r a c t

This paper presents the complete experimental study on the Geo-Mechanical Model of Jinping high arch

dam to observe the deformation and study the stability of the dam abutment and foundations of the

Jinping first stage hydropower project. The model considers various factors influencing the stability of

dam abutment and foundation during the test, which includes overloading and strength-decreasing of

weak structural planes in the rock mass of the dam foundation. A temperature-analogue material is

employed to simulate the decreasing strength of the weak structural planes. The temperature-analogue

material and model testing technique are developed for the first time. Secondly, the comprehensive

method that considers both overloading and strength-decreasing is applied to the model successfully.

Deformation characteristics, failure patterns and mechanisms of the dam abutment and foundation are

achieved. The safety evaluation based on the experimental model indicates that the whole stability

safety factor of the dam abutment and foundation is 4.75.0.

& 2009 Elsevier Ltd. All rights reserved.

1. Introduction

As is well known, for a high arch dam, the stresses inside the

dam and its foundations are very large, which increases thepossibility of dam failure. For large hydropower projects built on

complex geological structures, the stability of the dam foundation

and abutment is very important. Usually, there are many

unfavorable geological structures in the dam site, and so to

ensure the safe operation of project, the whole stability of the

high dam and its foundation should be carefully considered.

Geological model testing and numerical simulations are usually

the main research methods for solving this kind of geo-mechan-

ical problem[13].

Model testing is one of the most effective and intuitive

methods to solve these types of problems. Geo-mechanical model

testing makes the system into limit equilibrium state near failure

by varying the load or material strengths based on limit

equilibrium theory. The geological mechanical model has a goodintuition of the failure process of arch dam abutment and

foundations.

The complexity and uncertainty of geological conditions, geo-

mechanical and geo-technical engineering problems, however,

will induce a great challenge to the model testing techniques.

Many researchers have contributed to the study of geo-technical

models and have achieved great results[49].

The geo-mechanical model first appeared in the 1960s, when

high dam constructions were developing rapidly, the firstly being

in Italy [4], The experts at the Institute of Structure Model

Experiment and Simulation (ISMES) successfully conducted anumber of geo-mechanical model experiments, such as Italian

Vajont arch dam, with the height of 216.6 m. Using geo-

mechanical model tests and obtaining the minimum safety factor

2, for stability on fissures and faults in the foundation of the

overall model and a greater deformation in its arch crown,

therefore, the measures of grouting and anchor reinforcement in

abutments were decided to be implemented, according to model

test results. The Itaipu gravity dam, also, with the dam height of

196 m, was studied by geo-mechanical model test at ISMES to

define the weakest position in the combined system of the

concrete dam and its foundations and to identify the potential

failure mechanism. The experiment provided a reliable proof for

the improvement of design and reinforcement treatment. Since

the 1970s, geo-mechanical models have been widely used, whichhas expanded the research field of the structural model tests. For

example, Oliveira experimentally obtained the safety factor of an

arch dam in Portugal by keeping constant the material properties,

but increasing gradually the relevant loads applied to the reduced

scale model[5].

Chinese engineers also carried out some research works in this

area[6], in the middle and late of 1970s, presented a report about

material test by geo-mechanical model and carried out 2D and 3D

geo-mechanical model test of discharge sluice of Gezhouba

Erjiang project. In addition, Refs.[79] have carried out research

work in this area successively. Three-dimensional whole geo-

mechanical model tests have been carried out for many high arch

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Contents lists available atScienceDirect

journal homepage: w ww.elsevier.com/locate/ijrmms

International Journal ofRock Mechanics & Mining Sciences

1365-1609/$ - see front matter & 2009 Elsevier Ltd. All rights reserved.

doi:10.1016/j.ijrmms.2009.12.005

Corresponding author. Tel.: +86 2885465866; fax: +86 2885405604.

E-mail address: [email protected] (W.-p. Fei).

International Journal of Rock Mechanics & Mining Sciences 47 (2010) 299306
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dams, the stability against sliding of abutment rock mass, capacity

of overloading, failure mechanism and the actual effectiveness of

foundation reinforcement measures have been studied.

In the past, geo-mechanical model tests were implemented

only by the overloading method, because of the difficulty of

decreasing the strengths of materials, especially using both

overloading and strength-decreasing methods in the same model.

Therefore, for a long time, very little attention has been paid to

the strength-decreasing method because of lacking of appropriatemodel materials, whose strength could be changed according to

requirements during the testing.

Recently, we have successfully developed a new temperature-

analogue material by composing traditional materials, macro-

molecular materials and cementing materials together in some

proportion. At the same time, a temperature varying system is set

up, by which macromolecular materials have been melted

gradually, and then the strength of composite materials have

been decreased gradually.

Under the assumption of constant mechanical properties of

rock, the method of overloading increases the loads of dam

upstream until the failure of dam abutment and foundation. In

normal operation, strength-decreasing method could consider the

safety reserve capacity of rock mass, and decreases the mechan-

ical strength of the rock until the failure of dam abutment and

foundation. Comprehensive method, as proposed in this paper, by

combining the overloading and strength-decreasing methods,

considers not only the possibility of sudden floods, but also the

influence of rock and weak structures on the stability of the

project for long-term operation.

The Jinping First Stage Hydropower Station is an important

cascading hydropower unit located on Yalong River in Sichuan

Province of China. The project (see Figs. 1 and 2) has the

abilities of power generation, silt arrest, and flood control.

The project will build a 305m concrete hyperbolic arch dam

which is the highest in the world. The geological structures

at the dam site are very complex and the height of the slope is

about 1000 m. There are different weak structural planes in rock

mass of the dam foundation such as faults, lamprophyre dikes,

interlayer compressed zones, deep-seated fractures, which are

disadvantageous to the stability of the dam foundation and

abutment.

For this project, we set up the temperature analogous

materials for rock mass, fault intercalations, weak structure

planes and discontinuous joints. For the first time, the compre-

hensive method is applied in the same model.

2. The similarity theory and temperature-analogue material

2.1. Similarity theory

Physical models must satisfy a series of similarity require-

ments in terms of geometry, physical and mechanical properties,

boundary conditions and initial states. According to elasto-

plasticity theory and dimensional analysis, these similarity

requirements can be deduced from force-equilibrium equations,

geometry equations, Hookes law and boundary conditions [10].

Geo-mechanical model test belongs to nonlinear destruction

testing, therefore the following four similarity requirements for

destruction test should be met:

(1) geometric similarity requirement: geometric shape and main

geological structure of prototype and model should meet

geometric similarity requirement;(2) constitutive relationship similarity requirement: deformation

modulus, relationship between stress and strain, compressive

and tensile strength of prototype and model should meet

similarity requirement;

(3) shear-friction resisting strength on geological structure plane

similarity requirement: Shear-friction resisting strength on

main geological structure planes in dam foundation and

abutment of prototype and model (f0 andc0) should meet the

similarity requirement; and

(4) loading similarity requirement: load condition, such as water

pressure, gravity and sand pressure of prototype and model

should meet similarity requirement.

Generally, the first item is a necessary condition, the second and

third items are determined on the conditions of similarity, and the

fourth item is a boundary condition of similarity. Three conditions

are all indispensable. According to above conditions, supposing C

Fig. 1. Developed profile along the dam axis.

W.-p. Fei et al. / International Journal of Rock Mechanics & Mining Sciences 47 (2010) 299306300


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is the proportion of physical quantity between prototype and

model, by similarity theory, the following requirements should be

met in destruction model test:

CE Cg CL 1

Cm 1;

CE 1;

Cf 1 2

Cs CE Ct CC 3

CF CgC3L CEC

2L 4

whenCg 1, then

CE CL 5

Fig. 2. Typical geological plan (at the elevation 1590 m).

Table 1

The design of the similarity model.

Items Designs Principles

Law of similarity CE=Cg CL 1. Geometrical similarity

Ce=1,Cf=1, Cm=1 2. Similarity of mechanical and deformation characteristicCE=Cs=Cc=CtCF=Cg CL

3=CE CL2 3. Similarity of shear strength parameter of rock masses, weak

intercalations and faultsIf Cg=1,

CE=CL, CF=CL3 4. Similarity of load and boundary conditions

Geometric

proportion

300 1. To meet the precision demand of the test

2. To consider modeling workload and economic effects synthetically

Simulation

context

1200m 1200m 850m (L W H) 1. Undistorted edge-restraint condition

2. Propitious to dispose system of loading, measuration, and so on

Geological

structures

Left bank: fault f5, lamprophyre dike X

Right bank: faultf13, f14, steep dip joint, and green schist lens

1. To emphasize the major element, and to ignore the minor element

properly

2. To consider the worst-case factor

3. To consider fracture properties

Model materials To mix barite powder, gypsum, adhesives, additive according to certain

proportion

To meet the demand of the similarity theory

W.-p. Fei et al. / International Journal of Rock Mechanics & Mining Sciences 47 (2010) 299306 301


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CF C3L 6

whereCE,Cg,CL,Cs,CcandCF, respectively, represent the similarity

constants for deformation modulus, bulk density, geometry,

stress, cohesive strength and concentrated force proportion, and

Cm, Ce and Cf, respectively, represent the similarity constants for

Poissons ratio, strain and friction coefficient proportion.

Bearing in mind that geo-mechanical model test is a

destructive experiment; the model was designed as mentioned

inTable 1, according to the similarity theory and the condition of

the project synthetically.

According to the scale of project and accuracy requirements of

test, the selected model geometry ratio is CL=300, bulk density

ratio is Cg=1, deformation modulus ratio is CE=300 and strain

ratioCe=1. The 3D model test flume clearance is 4 m 4 m 2.83

m (L W H) which is equivalent to the prototype scale of

project: 1200 m 1200m 850m (L W H). The simulation

domain is large enough to meet the requirement of destructive

test and can fully represent the actual situation of the project.

2.2. Temperature-analogue material

During this test, a comprehensive method is adopted bycombing the overloading method and the strength-decreasing

method, in which a kind of model temperature-analogue material

is developed to accomplish the gradually decreasing process of

shear resistant strength of model material. Because of the

complex geological structure at the dam site, such as the

developing faults, interlayer compression strips, joint fissures,

deep-seated cracks and other structure planes, the stability of the

abutment of arch dam is negatively influenced. The maingeological structure affecting the stability of right-bank abutment

include: faults such as f13 and f14, green schist lens imbedded in

marble rock such as T2423Z, steep dipping fissure with a strike of

nearly SN direction and so on. The main geological structure

affecting the stability of left-bank abutment include: faults such

as f5, f8, f2 and F1, lamprophyre dike such as X, squeezed band

between marble rock layers such as T2423Zand slope-forward joint

fissure and so on. According to the characteristics of geological

structure, this test takes into account of properly decreasing the

shear resisting strength of the main faults and lamprophyre dike

X. Before the test a large number of material tests are carried out

initially, from which the variation relation curve between the

shear strength of materials and temperature T is obtained. The

relation curvetmTof temperature analogous material is showninFigs. 35, respectively, for fault, lamprophyre dike X and green

schist lens.

3. Loads on the model and loading system

Considering test task and conditions synthetically, water load

and sand load are determined to be simulated in the test.

According to the similarity theory, similarity of load between the

prototype and model must be satisfied. The loads are applied by

using jacking apparatus distributed in different elevations of the

upstream surface of the dam, which are forced by an oil-pressured

instrument. Load-spreading boards are applied to eliminate the

stress concentration (as shown inFig. 6).

7

6

5

4

3

2

1

0

0 10 20 30 40 50 60 70 80

T (C)

m(

1

0-2)

MPa

Fig. 3. tmTcurve of temperature analogous material of fault.

6

5

4

3

2

1

0

0 10 20 30 40 50 60 70 80

T (C)

m(

1

0-2)MPa

Fig. 4. tmTcurve of temperature analogous material of lamprophyre dike X.

4

3.5

3

2.5

2

1.5

1

0.5

0

0 10 20 30 40 50 60 70 80

T (C)

m

(1

0-2)MPa

Fig. 5. tmTcurve of temperature analogous material of green schist lens.

Fig. 6. Loading system on the upstream surface of dam.



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4. The measuring system of the model

The measuring system includes surface displacement mea-

surations and inner deformation measurations. In this test, the

latter give priority to the former which include dam surface

displacement measurations, rock mass displacement measure-

ments and intercalation measurements of interior relative

displacement. Following the principle that it is not only able to

consider the dams comprehensive distributing characteristics ofthe displacement and deformation, but also to monitor local

positions, 63 surface displacement measuring points and 100

inner deformation measuring points are installed.

5. The test method and procedure

A geo-mechanical model test is a rather destructive test, which

mainly includes three kinds: overloading method, strength-

decreasing method and comprehensive method by combining

overloading and strength-decreasing method. Assumption of the

overloading method is that rock mechanical parameters of the

abutment and the foundation are constant and by gradually

increasing upstream water load, till the destruction and destabi-

lization of foundation, the resultant factor of safety is overloading

safety factor. Strength-decreasing considers that the rock mass of

abutment and foundation itself has a proper strength capacity to

know the accurate strength capacity so that you can gradually

reduce the mechanical parameters of rock mass until the

destruction and destabilization of the foundation. The safety

factor thus obtained is a strength-decreasing factor. This method

reflects the influence on the strength index of weak structural

planes by soaking of reservoir water and leakage in long running

of the rock mass. The overloading and strength-decreasing are

adopted in the comprehensive model, this method takes into

account not only unexpected flood projects but also the

probability of mechanical parameter reductions of rock mass

and weak structural planes due to water action in the long-term

project operation.

As the mechanical properties of traditional model materials

cannot be modified, geo-mechanical model destructive testing is

usually completed by the overloading method, because it is very

difficult to achieve this by the strength-decreasing method. In the

past model tests, different membrane, paper, lubricating oil or

chemical coating were usually used to simulate the mechanical

deformation characteristics of the structural planes such as weak

intercalation in foundation rock mass, but the mechanical

parameters of rock mass and intercalation cannot be modified

during the test. If we want to change the mechanical parameters,

we must set up a new model by using modified mechanical

parameters, thus combining the test results of several models to

describe the variation process of mechanical parameters, which is

impractical and uneconomical. To modify mechanical parametersof rock or weak structure plane in the same model, the most

important problem to be solved is a breakthrough on the model

material, which is to develop a new model material to gradually

change model material strength of the rock mass and weak

structural planes.

Our research groups staff started from the model material and

has made much progress during the years of continuous

exploration in experimental techniques, putting forward a new

method by adopting temperature analogous material to simulate

strength-decreasing properties. Research on temperature analo-

gous material is based on several intercrossing disciplines, which

is done by combining the macromolecular material with the

traditional model material, which is done by adding the macro-

molecular material and cementing material into model material

and at the same time, setting up the system temperature

alteration. During the test, the reduction of mechanical para-

meters of the material is done by heating up and melting down

the macromolecular material, thus the comprehensive method of

testing by combining overloading and strength-decreasing meth-

od is accomplished in the same model. The comprehensive

method has been successfully applied in some engineering

practice, such as the Xiluodu arch dam [11], Shapai arch dam

[12,13], Tongtou arch dam[14]and Baise gravity dam.The method of combination of overloading and strength-

decreasing is applied in this test. At first by decreasing the shear

strength of weak structure in the dam base and abutment,

secondly overloading the dam upstream face by the water

pressure continuously until destabilization and wreck happened

to the dam base and abutment entirely, strength-decreasing is

accomplished through temperature analogous material.

Considering the stress difference of embankment and dam

abutment during the operation, and the influence of floodwater

and rock strength of dam abutment and base, the test is divided

into three steps, which are described as follows:

Step1: Preloading dam body with minor loads, lifting pressure

to the level of normal load to measure and then overloading to

20% above the normal load to measure, to simulate flood

condition according to the statistic results of engineering cases

in China.

Step 2: Maintaining the loading level and rock mass dead-

weight of the former step, warming up rock mass in the dam

abutment and foundation by 10 stages, and measuring the

designated point. At this step the shear strength is reduced at

the half of design value.

Step 3: Maintaining the temperature level and rock mass

deadweight of the former step and continuing to overload on the

dam upstream to measure till the destabilization and wreck happens.

6. Results and analysis of the tests

Test results include the displacement developing process of

embankment surface, abutment and base of dam; the interior

relative displacement developing process of weak intercalations;

the deformation developing process of typical sites of dam

surface; and the failure pattern and process of rock mass.

The test procedure is as follows: the first is strength-

decreasing test, the subsequent is overloading test until the

instability destruction of abutment. The detailed test procedure is

as follows: firstly, to pre-press the model, and then to load with

the normal load level, and on the basis of which, to execute the

strength-decreasing test, that is to reduce about 30 percent shear

resisting strength of abutment rock faults such as f5,f2,f13, andf14,

Kp

5.0

4.0

3.0

2.0

1.0

0.0

-50 -20 10 40 70 100 130

p (nm)

66*

56*

42*74*

28*

Fig. 7. dpKpcurve of typical measuring points along the river.



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lamprophyre dike such as X by heating up the model materials,

furthermore to implement the overloading test until instability

destruction of the abutment.

Through the test, the following relation curves are obtained:

dpKp (between surface displacement and overloading multiple)

curve about radial or tangential displacement and overloading

multiple, curve about strain and overloading multiple at

every measuring point on the typical elevation of dam down-

stream; dpKp curve about river-transverse or between river-

forward displacement and overloading multiple at the measuring

point on two abutments and resisting body (as shown inFig. 7);

DdKp (between inner deformation and overloading multiple)curve about relative displacement and strain and overloading

multiple at the measuring point on the structure zone of

abutment and foundation (as shown in Fig. 8). At the same

time, the destructive process of abutment and resisting body, and

destructive form of the whole model are obtained. The photo of

whole geo-mechanical model test is shown inFig. 9.

6.1. The distribution regularity of the dam displacement

The distribution characteristic of the dam downstream surface

displacement dp is that displacement of the arch crown is rather

large, displacement of the upper arch crown is larger than that of the

lower part. The radial displacement is larger than tangential

displacement, the distribution regularity agrees with the routine

results. Under the normal condition the radial deformation is

basically symmetric, and the deformation direction is toward

downstream. During the strength-decreasing stage, the displacement

of the dam body is small, however, in overloading stage with the

increase of overloading multiple the deformations of left abutment

increases obviously and ultimately a phenomenon happens that

displacement of left abutment is greater than that of right one. It

indicates that at the same time of dam body translation towarddownstream, clockwise rotary movement happens on the dam body,

which is conformed with the characteristics of great difference of

deformation and destruction zone between left bank and right bank.

6.2. The surface displacement of abutment and resisting body

The overall distribution rule of surface displacement of abutment

and resisting bodydpis as follows: the displacement of left bank is

larger than that of right bank. The displacement on the middle-upper

part is larger than that of lower part. In general, the displacement

along the river is toward downstream, and the displacement across

the river is toward streambed. The largest displacement of right bank

appears in the transverse Section 5, and largest displacement of left

bank appears in the transverse Section 1, the second is in thetransverse Section 5, and in other sections the displacement is very

small, which indicates that the deformation tendency is conformed

with the geological tectonic characteristics of both banks.

6.3. The displacement of fault, lamprophyre dike and weak tectonic

zone

The general distribution rules of relative displacement of fault,

lamprophyre dike X, squeezing zone g, deep fissure SL and green

schist lens in both abutments and resisting body Dd are as

follows: the maximum value ofDdis in transverse section V near

to abutment, followed by Dd in transverse sections II1 and I, and

the minimum value is in transverse section III far away from

abutment, which indicates the displacement direction is along thetectonic zone. In general, Dd of left bank is greater than that of

right bank. On the left bank, Dd in fault f5 fault is greatest,

followed by Dd in fault f2 and lamprophyre dike X, and Dd in

interlayer squeezing zoneg, faultF1, deep fissure SL is smaller. In

elevation,Ddin the middle part is greater than that on the upper

part, which proves that the effect of reinforcing treatment by

concrete backer on the left abutment is very obvious. The upper

Ddof faultf14,f13on the right bank is larger, nearly equating to Dd

of green schist lens. Therefore, the fault f5 of left abutment,

lamprophyre dike X beside the river, faults f2 and f13, f14of right

abutment, the green schist lens, steep dip joint with SN strike,

have a great impact on the stability of the abutment.

6.4. Strain distribution characteristic of the dam body

Tensile and compression strain of dam downstream is

coincident with convention, and the measurement point at all

the elevation of arch abutment is mainly in compression state,

especially, the arch-toward and beam-toward pressure strain on

1670 m elevation is very large, which is due to the geological

condition of lower part of the left abutment, especially fault f5,

lamprophyre dike X, interlayer squeezing zone g. According to the

relative curve of strain and overloading multiple on the over-

loading stage, when the Kp is 3.84.5, process curves at all

measuring points have a obvious break, which is similar with the

process curve of displacement. It should be noted that, due to the

limitation of material characteristic of dam, the stress of dam

model cannot be converted to that of dam prototype.

5

4

3

2

1

00 80 160 240 320 400

(10-1mm)

Kp

66# 65# 95#

Fig. 8. DdKpcurves of typical measuring points in fault f5.

Fig. 9. The whole geo-mechanical model.



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6.5. Failure patterns and features

The failure pattern and feature of left bank is: fault f5extends

along the river from arch abutment top of downstream to around

the transverse profile VI, the total length is about 330m; the

lamprophyre dike X outside the faultf5cracks from the elevation

of 18851710 m; the rock of arch abutment cracks from the top to

the elevation 1960 m, and the upstream crack is very obvious and

extends to the bottom of dam; the fault f2 in the middle-lower

part, interlayer squeezing zone g and rock mass around arch

abutment from the elevation 16501750 m is seriously damaged.

Due to the reinforcement treatment by using concrete backer

between the elevation 1750 and 1885 m, this part of rock mass

around abutment is slightly damaged, which shows that left

abutment reinforcement treatment has an obvious effect, but it is

worth noting that in the part of upstream arch abutment below

the elevation 1750m, there are several horizontal cracks due tothe dislocation effect of interlayer squeezing zone g. If the

concrete backer extents more deeply and becomes wider, the

damage can be relieved. Because the fault F1and deep fissures SL

are far away from arch abutment, the stability of the abutment is

hardly influenced. The damage extent and degree of left bank is

more serious than that of right bank, which is mainly due to the

complex geological structure condition of left bank (see Fig. 10).

The failure pattern and feature of right bank is: fault f13along

the river cracks from the arch abutment top to the elevation

1940m, and the total crack length is about 150 m;f14cracks from

arch abutment downstream to the extension length of about

135 m; the rock mass from arch abutment downstream to

transverse profile I, between the elevation 1670 and 1885 m, is

seriously damaged, several cracks can be found, which have a

nearly same strike as the deep dip joint with SN strike; especially

in the steep outcrop of green schist lens, there are several cracks

along the layer, which connect to fissures with SN strike. There is

an obvious destruction tendency of shear sliding toward down-

stream. Thus it can be seen that fault f13,f14, steep dip joint with

SN strike, and green schist lens on the right bank, have a great

impact on the stability of abutment (seeFig. 11).

7. Conclusions and suggestions

This test aims at the complex geological structural conditions

in the foundation of the high arch dam of the Jinping First Stage

Hydropower Station, by using temperature-analogue material and

state of the art technology of test simulation, while considering

not only the overloading on arch dam upstream but also the

influence of strength softening of the fault and weak structural

planes in both abutments of the dam. Adopting comprehensive

method by combining overloading and strength-decreasing

methods, the whole stability of arch dam abutment and founda-

tion is studied, which can be concluded as follows:

(1) According to the comprehensive analysis on test results

obtained, the strength-decreasing coefficient is found

K1=1.3, overloading coefficient K2=3.63.8. According to the

similarity theory [15], the comprehensive safety factor of

abutment stability is Kc=K1K2=4.75.0. This meets the

requirements of the whole stability of the dam abutment

and foundations, while, not considering the influence of

seepage pressure and seismic loads.

(2) The impact degrees on stability by the faults, lamprophyre

dikes and weak structure zones in both abutments and

resisting body are not the same. For example, on the left

dam abutment, fault f5, lamprophyre dike X beside the river,

and fault f2 have a greater impact on the stability of

abutment; on the right dam abutment faultf13,f14, the green

schist lens, and SN directional steep dip joint have a greater

impact on the stability of abutment.

(3) The destruction zone of Left Bank extends along the river from

arch abutment top of downstream to around the transverse

profile VI, the total length is about 330 m which is slightly

greater than the height of the dam. The destruction zone of

Right Bank along the river extends from the arch abutment

top of downstream to around the transverse profile I. The total

crack length is about 150 m, nearly half of the dam height. The

smeared crack pattern is resulted from the complex founda-

tion conditions, especially the strike of faults and joints.

Therefore, reinforcing treatment must be implemented in the

range of left dam abutment to transverse profile VI, and right

dam abutment to transverse profile I. At the same time,

drainage hole should be constructed for the whole stability of

both abutments and resisting body.(4) Reinforcing treatment has a large effect on the stability of both

abutments, i.e. concrete reinforcement choke plugs settle on

the elevation at 16651710m of the downstream of right arch

abutment, however, it does not crack in the final destruction

stages, which indicates the obvious reinforcement effect.

(5) The emphasis of this research is on the stability of abutment,

but test result shows that the overall design of the dam

structure is reasonable. Because of the complex geological

conditions of left abutment, deformation of the middle-upper

part of left abutment is lack of coordination, it is necessary to

strengthen further treatment to left abutment. The relative

displacement of tectonic zone under the foundation is rather

small, and the displacement curve has no obvious inflection

points and sharp increasing trend.

Fig. 10. Failure pattern of left abutment.

Fig. 11. Failure pattern of right abutment.



8/8

ARTICLE IN PRESS

(6) By the comprehensive method proposed in this paper,

strength-decreasing is aimed to simulate the softening of

discontinuities due to groundwater and long-term operation,

and overloading is aimed to simulate the flood load case.

Nevertheless, seismic load, uplift load, and water load on the

riverbed are neglected. Also, gravity scale effect and con-

struction process are not considered.

Acknowledgments

The work is supported by the China National Natural Science

Fund (CSNF) under nos. 50879050 and 50620130440, joint

support from CNSF and Yalongjiang Development under no.

50639100, international cooperation program under no.

2007DFB60100. The authors wish to offer their gratitude and

regards to everyone who has been a part and support to this

project in all means.

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