ISRM International Symposium - 6th Asian Rock Mechanics Symposium

Abstract:

This paper extends the numerical manifold method (NMM) for complete rock slope failure analysis. A fracturing algorithm based on the Mohr-Coulomb criterion with a tensile cutoff is implemented into the NMM code. The developed program is first calibrated through two typical crack problems and then applied to analyze the potential footwall slope instability. Parametric studies are carried out. Numerical results indicate that the developed program can simulate the sliding along pre-existing discontinuities, fracturing through intact rock, as well as kinematics of failed slope, and can reproduce the major failure mechanisms observed in footwall slope collapses. The NMM is promising for such problems and deserves to be further developed to be practically used in rock slope stability analysis and open pit slope design.



1. INTRODUCTION

Open pit mining is a very cost-effective mining method. In open pit mining, pit slopes are formed. With the mining depths steadily increased to 500 meters or even higher, design of open pit slope angles is becoming more and more important. Small change in the overall pit slope angle has significant influence on the overall economy. An ideal design method must be able to i) predict where and under what conditions a failure surface may develop; ii) predict the kinematics of the failed slope. Current design methods can be distinguished into four groups: 1) empirical design method; 2) physical model tests; 3) limit equilibrium methods; 4) numerical methods. Among them, numerical methods have become popular in recent years. Currently existing numerical methods can be generally grouped into two categories: continuum methods (e.g. FDM, FEM, BEM, etc.) and discontinuum methods (e.g. the distinct element method with the commercial codes as UDEC, 3DEC, etc. and the discontinuous deformation analysis (DDA) [1]). Existing continuum codes are able to simulate the location and shape of the failure surface developing in a slope. However, an actual failure surface discontinuity is not formed. Pre-existing fractures are usually not incorporated. Discontinuum codes model the discontinuities presented in rock mass explicitly and have been successfully used to simulate structurally controlled failures. They are, however, difficult to simulate failures through intact rock. Actual slope failure involves both sliding along pre-existing discontinuities as well as fracturing through intact rock. A general method which can simulate the actual slope failure becomes essential. In this paper, the recently developed numerical manifold method (NMM) [2] is explored to account for complete rock slope failure process. Footwall slope is considered. Footwall slopes are often excavated parallel to dip and extensive along both strike and down-dip. When mining continues down-dip, the length of the exposed footwall slope increases and the potential instability of the slope may arise. Footwall slope instability is a relatively common occurrence in open pit mines situated in area of steeply dipping strata particularly where mountainous topography exists. The importance of footwall instability has long been recognized. Failures only occur along the pre-defined discontinuities. In this paper, non-persistent joints are allowed, both sliding along pre-existing discontinuities and fracturing through intact rock will be captured.

ABSTRACT :

Historical reports indicate that underground structures have different behaviors against earthquake with the same magnitude. This finding infers that the earthquake magnitude alone is not sufficient for determination of earthquake intensity. In other words, peak ground acceleration (PGA) that was calculated by attenuation relations is not enough criteria for determination of "design base earthquake" time history because, in addition to PGA, seismic loads frequency affect on the earthquake intensity. The aim of this study is to evaluate the effect of seismic load frequency on the behavior of underground structures. For this purpose, effective parameters on the frequency content of seismic loads were identified and two time histories with different frequency content were compiled. Further, Isfahan-Shiraz tunnel, a railway tunnel in southern part of Iran, located in a disturbed zone was analyzed for two separate time histories that have the same PGA and different frequency content. These analyses reveal that the frequency content of seismic load has significant effect on the earthquake load energy, stress distribution and underground structure stability. Furthermore, loads with higher frequency attenuate faster whereas, generally, loads with low frequency influence more, to compare with high frequency loads, on the structure stability.



1. INTRODUCTION

Underground facilities are an integral part of the infrastructure of modern society and are used for a wide range of applications, including subways and railways, highways, material storage, and sewage and water transport [1]. Underground facilities built in areas subject to earthquake activity must withstand both seismic and static loading. Historically, underground facilities have experienced a lower rate of damage than surface structures. Nevertheless, some underground structures have experienced significant damage in recent large earthquakes, including the 1995 Kobe, Japan earthquake, the 1999 Chi-Chi, Taiwan earthquake and the 1999 Kocaeli, Turkey earthquake [2]. Prediction of ground motions resulting from earthquake is very difficult and it is almost impossible to determine characteristic of ground motion until earthquake actually occurs. Every earthquake causes some unique motions the characteristics of which depend on several factors including disruption mechanism of fault at earthquake source, the wave's propagation media and geological features of earthquake site. Disruption mechanism of fault is complicated and the nature of energy transfer between earthquake source and structure is indeterminate therefore, investigation on all of ground motion characteristics is not possible for common engineering application [3]. For this reason, probable earthquake magnitude is the only parameter used for earthquake risk evaluation for a given special region. Whereas, the effect of seismic load frequency is not considered. It should be noted that the frequency does not play an important role in assessing the shear strength of intact rocks, as shown by Burdine [7], Haimson and Kim [8] and Ray et al. [9]. Further, Chen Feng et al. [10] considered the dynamic response and failure behavior of rocks subjected to dynamic loading with the frequency ranging from 0.5 to 5 Hz and found that the obtained strain rate increase with the increase of load frequency.

ABSTRACT:

At Koyna Hydro-electric Project, an 80MW powerhouse is currently proposed at the left dam foot of Koyna river dam in Maharashtra. The underground powerhouse cavern needed for housing the two turbine units of 2 X 40MW is designed using three-dimensional numerical modelling. Three possible geometries for the powerhouse are designed considering the weaker rock mass layers of Volcanic Breccia existing in the vicinity of the proposed cavern. These configurations are simulated in FLAC3D software. Their stability is analysed using Hoek and Brown rock mass failure criterion. Taking cues from the stability predicted for the three configurations, a final configuration is designed. The final configuration is further subjected to threedimensional modelling and stability analysis. The cavern is expected to have good overall stability. The crown region, since it will be located in stronger Compact Basalt rock layer, will have superior stability. However, the cavern will have weaker sides, where Volcanic Breccia will be exposed. A support plan for the entire cavern is also designed incorporating 100mm thick steel fire reinforced shotcrete (SFRS) and 6.0m long full column grouted resin bolts.



1.0 INTRODUCTION

Koyna Hydro-electric Project of Maharashtra State Government produces electricity of the order of 2000MW in four stages. This environmental friendly and cheap power generation caters to the energy demands of the neighbouring region. As an extension of Stage IV, an 80 MW (2x40 MW) capacity powerhouse is proposed at the Koyna dam foot at the left bank of the Koyna River. Underground powerhouse chambers are proposed for power generation. From the geological survey conducted by Koyna Project authorities, the rock types existing in this vicinity was found to be Deccan Trap Basalts, viz.



2.0 ROCK PROPERTIES AND INSITU STRESS

The intact rock properties tested earlier by CWPRS (Anon (2004) and Anon (2005)) and rock mass parameters such as RMR (Bieniawski (1976)) for compact basalt and volcanic breccia are given in Table 1. The Hoek and Brown rock mass parameters are also evaluated (Hoek and Brown (1980)) and given in the table since they are to be used in the numerical modelling.



3.0 DESIGN STRATEGY

Three optional configurations were initially chosen to comparatively analyze the stability scenario. Depending on their stability, the most stable configuration shall be chosen as the final powerhouse design. The three configurations modelled for their stability analysis has the following salient features.

Configuration 1:

A powerhouse cavern of 21m width, with crown level at 599m RL and springing level at 592.5m RL A valve house of 10m width, with axis at 600 to that of the powerhouse cavern, with crown level at 595.5m RL and springing level at 592.5m RL



Configuration 2:

A powerhouse cavern of 21m width, with crown level at 595m RL, and springing level at 588.5m RL A valve house of 10m width, with crown at 591.5m RL and springing level at 588.5m RL



Configuration 3:

A single powerhouse cavern of 25m width, with crown level at 595m RL and springing level at 588.5m RL, and without a valve house

SYNOPSIS:

As is well known from rock mechanics literature, the mechanical parameters of a rock mass cannot be obtained by conventional laboratory tests due to the difficulties encountered in the preparation of cores from a rock mass containing discontinuities. To overcome these difficulties, researchers have focused on developing empirical equations for predicting stress-strain behavior of a rock mass, including based on measurements of the discontinuity patterns. However, the UCS value of rock mass (UCSRM) can be predicted by decreasing UCSi based on quality of rock mass such as Rock Mass Rating (RMR), Geological Strength Index (GSI), Q value, etc. For this reason, an empirical equation in a unique reducing curve form has limited application in generalizing on the prediction of UCSRM from particularly soft rock mass to hard rock mass. In this study, a new empirical approach is developed to be used for predicting of strength of rock masses from soft to hard rock masses. In addition, a new procedure for defining of the disturbance effect on the strength of rock mass is introduced to the new empirical approach in conjunction with Hoek and Brown failure criterion.



1. INTRODUCTION

Determination of overall strength of jointed rock masses have been attractive research topic in rock mechanics community due to the difficulties encountered during the preparation of representative undisturbed samples for laboratory studies. The sophisticated and large scaled laboratory equipments are needed to perform experiments on undisturbed jointed rock mass even if the cores can be obtained. Therefore empirical equations have been used as practical tools during pre-design stages of engineering application to be constructed in/on rock masses. To overcome this difficulty, numerous empirical equations have been proposed in the literature and as given in Figure 1 (Yudhbir et al., 1983; Ramamurthy, 1986; Kalamaris and Bieniawski, 1995; Sheorey, 1997; Aydan and Dalgic, 1998; Heok and Brown, 1997 etc.). By using most of the existing empirical approaches, the UCS value of rock mass (UCSRM) can be predicted by reducing UCSi based on quality of rock mass such as Rock Mass Rating (RMR), Geological Strength Index (GSI), Q value, etc (Bieniawski 1989, Hoek and Brown, 1997 and Barton 2002). At this point, the question of “which one is the best for prediction of the strength of a rock mass?” cannot be definitively answered, as each of them tried to represent their original database. Most of the empirical equations consider just RMR, GSI or Joint Parameter-JP as an input parameter. But these characterization schemes may not explicitly include the strength and deformability of rock material may play some important role on the strength behavior of particularly soft rock mass. As can be followed from literature, the lowest strength of rock materials used for the calibration of Hoek and Brown empirical failure criterion is about 39.9 MPa (Hoek and Brown, 1980). Therefore, it is difficult said that the Hoek-Brown failure criterion with its current form has sufficiently a capable of prediction of strength of rock masses composed of particularly softer rock materials.

Abstract:

The stability of slopes can be assessed by a factor of safety, which is usually determined by a limit equilibrium method. In order to evaluate the factor of safety, we need such strength parameters as cohesion and the internal friction angle. In the monitoring of slope stability, displacements are commonly measured. Therefore, the strength parameters should be evaluated from the measured displacements. Sakurai and Nakayama (1999) developed a back analysis procedure for determining the strength parameters from the measured displacements. The back analysis procedure was successfully developed by introducing both an “anisotropic parameter” and “critical shear strain”. Recently, on the basis of this back analysis procedure, a computer code called the “Universal Back Analysis Program for Slope Stability” (UBAPSS) has been completed. In this paper, UBAPSS is briefly described, and a case study is shown to demonstrate its applicability for assessing the slope stability at an open pit coal mine. The surface displacements were measured in the mine by GPS and the data were collected until failure occurred. The strength parameters were determined using the data obtained just one day before the failure occurred. The results of the back analysis indicate that the factor of safety becomes approximately 1.0. This means that the computer code UBAPSS is well applicable to the assessment of the stability of slopes.



1. INTRODUCTION

The stability of slopes can be assessed by a factor of safety, which is usually determined by a limit equilibrium method. In order to evaluate the factor of safety, we need such strength parameters as cohesion and the internal friction angle. However, determining the strength parameters is not an easy task, because soil and rock have numerous geological and geotechnical uncertainties. However, the question of how to evaluate the strength parameters from the measured displacements is raised. To answer this question, Sakurai (1992) developed a back analysis procedure which can determine (1) the mechanism of the slope deformation, whether it is sliding or toppling, (2) the location of sliding planes, and (3) the strength parameters, such as cohesion and the internal friction angle, from the measured displacements, even only from the surface displacements. The back analysis procedure was successfully developed by introducing both an “anisotropic parameter” and “critical shear strain”. Recently, on the basis of this back analysis procedure, a computer code called the “Universal Back Analysis Program for Slope Stability (UBAPSS) has been completed. In this paper, UBAPSS is briefly described, and a case study is shown to demonstrate the applicability of the proposed back analysis procedure for assessing the slope stability at an open pit coal mine, where the surface displacements were measured by GPS and the data were collected until failure occurred. The strength parameters were determined using the data obtained just one day before the failure occurred. The results of the back analysis indicate that the factor of safety becomes approximately 1.0. This proves that the computer code UBAPSS is well applicable to the assessment of the stability of slopes.

Abstract:

Constructing mountain roads in harsh terrains is a challenge to the engineering and development of southwestern Saudi Arabia. Al-Baha 32 km-mountain road is constructed at steep slope rock masses, where many rockfalls incidents were experienced. A 100 m long portion of the road, suffers from frequent rockfalls. The rock masses are mainly igneous rocks of medium to low quality. The rock slope-cut has no bench for 20 m, 70°-90° inclination, and 30 m height. Absence of ditches and support systems aggravates the daily road conditions. The RocFall computer program was utilized to perform the risk analysis on such steep man-made and natural rock. Geotechnical parameters such as 1) block size, 2) seeder points of blocks falls, 3) slope angle, 4) restitution coefficients, and 5) slope roughness were used to identify properties of the potential and fallen rock blocks such as: 1) bounce height, 2) kinetic energies (total, translational, and rotational), and 3) translational and rotational velocities. The program modeled the 1) proposed location and energy of the rock blocks barrier's heights and locations, collectors, and 2) proposed slope safer redesign. The results of the study provide a solution to prevent rockfalls, and could be applied at similar conditions.



1 INTRODUCTION

Slope failures, landslides and rockfalls are frequently occurred on mountain roads, at rugged terrains. One of the most difficult terrains in western Saudi Arabia is Al-Baha descent, which is characterized by sharp cliffs and high elevations which reaches above 2,000 m above sea level. The highest elevation at the descent is about 2,200 m (at km 0) above sea level, where the difference in elevation from the highest to lowest elevation is about 1,750 m, the difference is about 450 m at km 32. The descent lies between longitudes 41º25"E and 41º29"E and latitudes 19º47"N and 20º01"N; see Fig. 1. Al-Baha escarpment 50km-road starts southwest of Al-Baha city, and runs through Al-Baha descent. The road connects the highlands where Al-Baha city is located with the lowlands at Al-Mukhwah town. Along this distance, natural slopes in addition to many man-made slope cuts and engineering structures are located. Al-Baha descent includes three distinct geomorphologic terrains: i) a dissected upper plateau of low mountains and hills, ii) a precipitous escarpment, and iii) a low-lying coastal plain (Fig. 2).



2 BRIEF GEOLOGIC HISTORY

The geologic history indicates that the escarpment resulted from a 3000 m lowering of Tihama Coastal Plain during the Tertiary opening of the Red Sea. Al-Baha descent's road is contained almost within a structurally controlled narrow valley, called Wadi Rash. Steep tributaries start from the escarpment ridge, and radiate out from the wadi head and cut deeply into the valley sides and escarpment face. Al-Baha region is underlain predominantly by a north-south trending belt of Precambrian schistose rocks comprised predominantly of fine grained mafic to intermediate extrusives, intrusives and pyroclastics with minor intercalations from clastics and metasediments [1]. The majority of the rocks at the descent area have been subjected to greenschist and amphibolite facies metamorphism [2].

Abstract:

Estimation of mechanical properties of stones is very important because their measurements are cost and timeconsuming. The purpose of this paper is to investigate the relationship between compressive strength and the modulus of rupture of three types of stones as Granite, Calcite and Travertine groups of Iran. In this project all tests were carried out according to ASTM (American society testing of material) standard in laboratory, The obtained results show that the relationship of both properties of direct and is very little between correlation coefficients of linear equations and also nonlinear equations of all stone groups in most of zones of Iran By reason, it is preferred to use of linear equations based on their simplicity and easy application.



1-Introduction

Unconfined compression has the most frequent use of the strength test of rocks, however it properly is not simple to perform, and its results can vary by a factor of more than 2. ASTMC 170-90 is used to measure compressive strength of buildings and decorative stones. The compressive strength c is expressed as the ratio of peak load w to initial cross-sectional area A: c =w/A (1) The flexural strength or "modulus of rupture" is the maximum tensile stress on the bottom of the rock beam corresponding to the peak load. It is calculated from simple beam theory assuming elastic conditions. The flexural strength is found to be two to three times as great as the direct tensile strength. For three points bending of cylindrical rock specimens, with loads applied at L/2 from each end and reactions at the ends, the modulus of rupture is: R=3 w .L /2b.d2 (2) R is modulus of rupture Psi (M Pa),w is the maximum load lbf (N), L is the length specimen, and d is the thickness of the specimen in(or mm) b is width of specimen in(or mm). This paper considers relationship between the compressive strength and the modulus of rupture on three types of stones as Granite group, Calcite and Travertine groups in Iran.



2- Sample preparation

Taken samples from the quarries have been cut in cutting workshops and sent to the laboratories for the tests. ASTM standard is considered during sampling as shown in table1. Based on standard codes, physical and mechanical tests should be done on each sample and mean value of tests should not be more than 10%.



3- Methodology for selecting the scientific name of stones

To prevent various names of stones, which use in different classifications, determination of the Dunhan System is applied for notation of sedimentary stones, and regarding the volcanic stones, it is also considered the main and subsidiary materials names and also the tissue name of the stones. Based on obtained results from these tests all decorative stones can be divided into four groups as follows:

3-1- Granite groups:

Granite is a volcanic rock, which consists mainly of quartz and feldspar grains. Granite color varies from pink to gray with homogeneous texture. Usually, one or several mafic minerals associated with granite.

Synopsis:

The appropriate assessment of the strength of a jointed rock mass is a fundamental requirement for the successful design of structures built in or on rock. Due to the complexity of the rock mass, a large number of empirical methods are developed, for its estimation. Its analytical treatment has been tackled mainly by the plane of weakness theory. In this study, an extended plane of weakness theory is applied to a well documented jointed rock physical model. For the failure mechanisms observed in the experiment, the non linear strength envelope provided by this extended plane of weakness theory fits well to the experimental data.



1 INTRODUCTION

Rock mass strength estimation belongs to the problems that are too complex to be tackled easily with analytical methods. Complexity is mainly due to fracturing, anisotropy inhomogeneity, and the variety of pertinent modes of failure. Therefore, empirical correlations, that do not need theoretical treatment, are usually employed. They come from the systematic observation of the factors that affect the strength. Analytical methods for the estimation of jointed rock strength have been developed, for the case of sparsely jointed rock masses. The most widely known analytical method for such a purpose is the plane of weakness theory, presented by Jaeger [1]. This method has been extended in order to take into account the roughness of joint surfaces. This extended method is presented and then, both the original and extended theories of weakness plane are applied to a jointed rock physical model.



2 THE EXTENDED THEORY OF WEAKNESS PLANE

The original theory of weakness plane (Jaeger, [1]) allows for the analytical evaluation of the anisotropic or equivalent isotropic strength of jointed rock. This theory uses the Mohr - Coulomb failure criterion for the joints. However, this linear criterion is unable to describe adequately the shearing behaviour of rock joints, which are rarely smooth, and their strength is a non linear function of the existing normal stress. Experiments ondiscontinuities have shown that for low normal stresses, the surface roughness causes expansion with shear movement, while for higher normal stresses there is failure of asperities and suppression of any expansion.



3 EXPERIMENTAL EVIDENCE ON DISCONTINUOUSSPECIMENS

Various researchers, such as for example, Goldstein et al. [5], Hayashi [6], Lama [7], Brown [8], Einstein and Hirschfield [9], experimented on artificial specimens made by blocks, usually of plaster, arranged in such a way to form a jointed structure. By this procedure, the jointed structure of the specimen is considered to represent the rock mass. For low values of confining stress, shear failures of joints or in intact material, were observed. For higher lateral stresses, the failure was due to the formation of many almost parallel shear planes, mainly within the intact material. The strength of the specimens depended on joint dip, except from the case of high lateral pressures, where the strength of the specimen was nearly equal to that of the intact material. The behaviour of specimens was brittle for low lateral pressures and ductile for higher.

ABSTRACT:

In tunneling a reliable prediction of advance rates is essential for calculating budget and construction time. Estimation of penetration rate is expressed as the basis for predicting advance rate in underground excavation using Tunnel Boring Machine. In this study the obtained data from 10KM of excavated Zagros tunnel project in Iran were subjected to statistical analyses using MATLAB for ANN modeling. When the neural network has been successfully trained, its performance is tested on a separate testing data set. Finally, the penetration rate was predicted by the trained neural network. The results show that the developed ANN method is efficient for predicting the PR in Zagros tunnel. The ANN model for next 0.5 KM which is recently excavated is well compatible with the real calculated PR of TBM in the field with 79% confident level. Result of sensibility analysis on the effect of Thrust and Torque on the PR shows that the maximum PR in given ground condition occurred in the optimum limits of Thrust and Torque.



1 INTRODUCTION

Since the first Tunnel Boring Machine (TBM) was built, the performance analysis and the development of accurate prediction models of the machines have been the ultimate goals of many research works [1-9]. A reliable prediction of TBM performance is needed for time planning and budget control of projects. Both penetration rate (PR) and advance rate (AR) are estimated in performance prediction of TBM. Penetration rate is defined as the distance excavated divided by the operating time during a continuous excavation phase, while advance rate is the actual distance mined and supported divided by the total time [10]. The AR includes downtimes for TBM maintenance, machine breakdown and tunnel failure. Even in stable rock, the rate of advance is considerably lower than the net rate of penetration and utilization coefficients (U%=(AR/PR)×100) is estimated about 30-50% mainly due to a TBM daily maintenance. When low quality rocks are excavated, the penetration rate could potentially be very high. However it demands a strong support pattern and face to rock jams and gripper bearing failure which results a relatively low advance rate with utilization coefficients about 5- 10% [11]. According to the literature, important parameters in TBM performance could be categorized in two major parts as follows:

1. Ground Condition: It includes characteristic parameters of intact rock and rock mass properties. Mostly reported important properties of intact rock in TBM performance are Uniaxial Compressive Strength (UCS), Brazilian Tensile Strength (BTS) and Point load index (Is50). In terms of Rock Mass properties, discontinuity spacing (Js), Rock Quality Designation (RQD), the angle between the tunnel axis and the planes of weakness (Discontinuity Dip and Dip Direction), rock mass quality using classification system such as RMR, Q and GSI have significant impact on TBM performance.

2. TBM operational parameters such as value of thrust, torque, Round Per Minute (RPM) and disc specifications have great influence on TBM performance. Tarkoy (1973) presented a model to predict penetration rate of TBM using only total hardness of intact rocks.

Abstract:

Although application of concrete faced rock fill dams (CFRD) have a rather long history, these have begun to be widespread lately in Turkey. These dam types are preferred generally due to being secure, comply with land conditions, their construction being practical and economic. The geological situation of the dam location is a significant factor for rock fill dams. Concrete faced rock fill dams are constructed up to now successfully at great heights. Since the whole of the concrete faced rock fill dams are dry, the earthquake do not form cavity water pressure in the rock fill cavities. Because of this property, concrete faced rock fill dams is resistant to earthquake. In this study the properties of concrete faced rock fill dams are briefly explained and Dim Dam (Antalya) is given as an example. Dim Dam is one of the most important concrete faced rock fill dams which construction continues. The dam is located on the Dim creek 13 km northeast of Antalya province Alanya town. The dam is being constructed for the purpose of energy, irrigation and fresh water and its height from the foundation is 134.50 m and crest length is 365 m. Bahçeli formation formed by Upper Permian aged schist with limestone blocks and Quaternary aged alluvium are outcropped in the dam location. Upstream face slope of the dam is 1.40 horizontal / 1 vertical, downstream face slope is 1.50 horizontal / 1 vertical. The impermeability of the dam is provided by the concrete coating on the upstream face.



1. ADVANTAGES OF CONCRETE FACED ROCK FILL DAM

Dams with concrete faced have been started to be constructed intensively in the entire world in recent years. The main reasons for preferring them are summarized in articles hereunder.

- Since the filling slopes are hillsideer than clay - core fillings, the body filling volume is less and it is possible to shorten the length of their discharge installations (spillway and derivation structures).

- Since zones numbered 1 (clay) and 2 (semi-permanent) do not exist, it is possible to continue work during rainy days and no damage is caused on agricultural lands - In case any problems that may increase leakage occurs on the front face, its repair is easy.

- The reservoir water load on the front face is safer since it is transferred to the base rock in the downstream of the dam axis.

- Under the reservoir water load + earthquake loads, high safety numbers are obtained since the material parameters do not change.

Furthermore, since there is no water movement within the dam, no space water pressure increases occur under earthquake vibrations and no decrease tendency is observed at sliding strength.

- Injection works can be performed in parallel with the filling construction. Base improvement requirement and cost cover the region only under the heel plate, therefore it is less than the other dam types.

- It is possible to construct ramps in any direction within the dam body. This minimizes the access ways in the dam.