An Expert System for Tunnel Design

An Expert System for Tunnel Design

Y. ICHIKAWA,' 0. AYDAN,2 T. KYOYA,2 H. OSAKA,3 and T. KAWAMOT04

YI , OA, TK, T K . Nagoya University.-HO, Taisei Corporation

n this article, w e describe the development of I d n expert system (€5) for tunnel design and prewnt some applications of the system. The system has been developed by our research group consisting o f2 I people closely involved with the tunnel design under the leadership of Nagoya University. The system consists of four subexpert systems ( 1 ) ES f o r standard tunnel design methods, (2) ES for framed structure method, (3) €5 for theoretical design methods, and (4) ES for numerical analysis design method; a common part to control the overall system; and two data base systems (tunnel data base system and rock mass data base system).

INTRODUCTION

The design of geotechnical engineering structures generally involves various experiences. The reason for this is due to the difficulty of evaluating the true mechanical behavior of the ground at the design stage. This i s well- pronounced in the case of tunnel design. The tunnel design in many cases is carried out with insufficient in- form'ition on the geology and the mechanical behavior of thta ground, and the design is done through some sim- plific,itions regarding the geological structure and the mechanical modeling of the ground on the basis of the experiences of specialists. The decisions vary depending upon the purpose of tunnelling, the objective of designing, the accuracy of available input data, the effect of designing on construction procedures, and social constraints. In addition, the experiences of the designers influcnce the decisions to a great extent.

- AddrPrt correspondence to Y Ichikawa. Department of Ceolec hnical Engi- neering Nagoya University, Chtkusa-ku, Nagoya 464. japan I A5soc idre Professor, Department of Ceotechnicai Engineering ' Reiedrch Associates, Department of Ceotechnical Engineering ' Chiel system Engineer ' Priitewjr Department of Ceo!erhnical Engineering

As expert systems (called ES hereafter) have become popular in recent years, we have started to investigate how to systemize the experiences and decision-making procedures of experts in tunnel design and construction. In the present study, we are mainly concerned with the New Austrian Tunnelling Method (NATM), since the NATM is mostly used in Japan.

The authors have put together a joint research group for the development of expert systems (ES) for the design and construction of tunnels. The project for the development of the tunnel expert system is called the TUX project and was initiated in April 1986. The group con- sisted of 21 researchers and engineers who are closely involved with the design of tunnels, and the work has been carried out with the close collaboration of the members. First, the steps and elements of design were carefully examined and, on the basis of this investigation, the main steps of the design procedures were then categorized. As a result of these studies, the expert system (ES) consisting of four subexpert systems was developed. The subexpert systems are (1 expert system for the tunnel design standards, (2) expert system for the analytic tunnel design methods, (3) expert system for the design of tunnel supports by the framed structure method, and (4) expert system for the numerical analysis. Second, two data base systems for support patterns of existing tunnels and for rock properties were developed using microcomputers.

EXAMINATION OF TUNNEL DESIGN PROCEDURES

There are various kinds of expert systems. The present expert system is aimed at assisting designers who are e'ngaged in tunnel design and construction. The concept of tunnel design and tunnelling has undergone a great change by the introduction of NATM. The construction equipment and procedures were renewed as a result. The main principle of the NATM is associated with the

3 Microcomputers in Civil Engineering 5, 3-18 I19901

8 1990 Elsevier Science Publishing Co , Inc 655 Avenue of the Americas. New York 0885-950719063 50

4 Y. ICHIKAWA ET AL. MICROCOMPUTERS IN CIVIL ENCINEERINC,

effective use of the circuit of investigation-design-construction steps. This principle of the NATM is very log- ical, and it incorporates the experiences of engineers in all steps of the tunnel construction. The Japan Society of Civil Engineers (JSCE) has designated the NATM as the standard tunnelling method [6 ] and construction by the NATM are expected to increase more and more. For further improvement of the NATM in the sense of eco- nomics and rational design, it is necessary to develop more effective numerical and theoretical analysis methods to check the suitability of the employed design, to establish design alteration procedures, and to accumu- late the experiences of engineers. Therefore, provided with data bases of past support patterns and rock mass characteristics, a unified NATM design and construction system is required to be established. This system should incorporate not only the experiences of engineers but also new technical improvements. The ES based on the artificial intelligence concept is thought to be suitable for such a purpose.

The research group first examined the tunnelling procedures carefully. The items of that procedure are sum- marized as shown in Figure 1. The tunnel design can be classified into two stages: the design before construction (initial design) and the design during construction. The theoretical bases of both designs are essentially the same. It is, however, difficult to design tunnels rationally on the basis of a small amount of geological and experimental data at the first stage. More accurate designs can be done with the information gained from the per- formance of the tunnel and the observation of the face.

The features of each procedure shown in Figure 1 are explained as follows:

1.

2.

3.

Data lnput (Stage I): The first step is sorting and checking input information for the design. These data generally involve design conditions such as dimensions and the geometry of the tunnel, environmental constraints, geological conditions from past-record surveying, boring and core testing, and ground classifications based on elastic-wave velocity measure- ments. As the amount of data i s too large and ne- cessitates a great deal of labor to handle, the irreducible minimum number of items is required only to be input into the system. Selection of design methods (Stage 1 1 ) : On the basis of information on the ground conditions and the scale and purpose of the tunnel, the suitable design method is selected. Determination of standard support pattern (Stage I l l ) : The support pattern is generally determined from the methods based on either case studies or ground classifications. The determination method based on experimental studies during driving exploration adits or test adits i s rarely applied. Presently in Japan, the classifications of the Japan Roadway Association and

4.

5.

6.

Japan Railways are used. The classifications provide the standard support pattern for the respective tunnel type. Evaluation (Stage IV): The determined support pattern must be checked and evaluated by some stability analyses. We therefore have to discuss the stability of each support member and surrounding rock mass. This procedure i s highly complex, and it requires deep experiential knowledge. Stability analysis (Stage V): The methods for stability analyses are well-established and programmed. This part of the work i s associated with data preparation and the subsequent calculations. Stability analysis methods consist of (1) the stress analysis of support members subjected to loosening loads, (2) the limit equilibrium analysis of the bearing capacity of rock arch, (3) closed-form solutions for the stability of the ground and support members, (4) model tests, and (5) numerical methods (FEM, BEM). Subsidary works (Stage VI): This procedure involves the detailed designs of concrete linings, portals, waterproofing and drainage systems, and so on. The support system previously determined is referred to at this stage. The examination of construction methods, setting the control values for safe construction, and the evaluation of environmental effects are also required.

As noted in Figure 1, there are no directional rela- tionships among the operation stages to indicate a cer- tain flow path. This i s due to the fact that the tunnel design procedure is flexible to incorporate several al- ternative paths effectively depending upon the conditions of each tunnelling problem. This is the usual procedure in experience-based designs. It is difficult to handle this problem by the conventional approach; hence we need to introduce the ES concept.

SYSTEM OUTLINE

The present expert system (TUX) i s mainly concerned with stages I-V, and its structure i s outlined in Figure 2. It consists of a control and commonly referred section and several subexpert systems: ( 1 ES for the standard design methods based on ground classifications, (2) ES for the design methods based on closed-form solutions, (3) ES for a framed structure method based on the frame model and loosening load, and (4) ES for a numerical analysis method using the finite-element method (FEM). The TUX is presently built for use in Japan, and the pre- sentations of conversations between users, knowledge bases, and rules are al l in Japanese.

The development environment is the V A U I Station of the Digital Equipment Corporation (DEC) and the tool for the ES i s OPS5. The computations are done using the existing but renewed programs written in FORTRAN.

VOL 5 NO. I , MARCH 1990 AN EXPERT SYSTEM FOR TUNNEL DESIGN 5

STAGE I: Investigations for Input Data _ - - _ - . _ _ - _ _ _ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - _ _ - _

from Environment Surveying

Determination of Method of Investigation for Groundwater

Ground Classification of Ground Classification of Japan Roadway Association Experimental Construction k

Investigation of Exploration Adits

Roadway Association

_ - _ _ _ _ _ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 1 STAGE IV: Evalu'ation I ____. . . _ _ _ _ _ _ _ _ _ _ _ _ - - - - _ _ _ - - - - - - - - - - - - - - - -

Standard Pattern and Selection of

STAGE V: Stability Analysis - _ _ _ _ - _ - - - - - - - - - - - - - - - - - - - - - - - - _ ___._ .___________________--------- - - - - - -

- - - - - - - - - - - - - - - - - - - - - - - - - _ _ - _ _ _ - - Subsidary Works ___. . _ _ _ _ _ _ _ _ _ - ---_-- - - - -_ - - - - - - - - - - - - - - - - - - - - - - -

-Examination of I I Determination of Control I 1 Examination of I I Design of Waterproofing 1 I Evaluation of Effects I on Environment I [Conslruction Methods 1 I Secondary Concrete Lining I I and Drainage System 1 1

I Design of Portals I

FIGURE 1. The flowchart of the tunnel design procedure by the N-ITM.

CONTROL A N D COMMONLY REFERRED SECTION

The (.ontroI section of the TUX chooses the rules to ex- ecutv each appropriate design method and enables input of arbitrary tunnel shape and support pattern. The commonly referred section consists of a knowledge base to determine material properties of ground and support members. The definitions of tunnel dimensions are shown in Figure 4 and patterns of support systems are given in Table 1 . However, the support system can also be input by users. If we have insufficient information on the properties of the ground and support members, several knowledge bases are available in TUX. As an example, the knowledge base for ground properties is shown in Table 2. Here the smallest unit of the knowledge base corresponds to the knowledge of experts for

each item. The unit of the knowledge base is composed of several rules. If it i s called from other knowledge bases, it first checks whether the required data is available or not. If the data is not available, then it seeks from the auxiliary knowledge base for the required data. A simple example is shown in Figure 3. The knowledge base for determining the group deformation modulus consists of a sequence of knowledge bases, but here the procedure using the modulus of intact rock and jointing index is only presented. In this case, the definition of the formulae to determine the ground modulus is a knowledge base together with their application limits.

ES FOR STANDARD DESIGN METHODS

The classifications of Japan Railways [4, 61 and the Japan Roadway Association [S, 61 provide the standard design methods for tunnels in their respective types. These classifications are outcomes of numerous actual tunnel construction practices. The tables of classification of Japan Railways are shown in Tables 3-5. Table 3 is a ground

6 Y. ICHIKAWA ET AL. kfICROCOMPUTER5 IN CIVll ENGINEERING

Knowledge base for determining the deformation modulus of ground

IF the determination of the elastic modulus of ground is not carried out by using the jointing index,

THEN call the knowledge base for calculation by using the jointing index

-A _ _ _ - _ _ _ - _ _ _ _ _ I

) - - - - - - - I Control and Commonly Referred Section I----- I

i- I I

I - - - - - I

I

I I I I L - - - - - - - -

Selection of Design Method Definition of Ground Conditions

ES for Standard Design Methods Rock Classification of Rock Classification of Roadway Association Japan Railways I Setting Tunnel Shape Setting Tunnel Shape I

Setting Support System Setting Support System 1 _ _ _ _ _ _ - - - - - I

I I

ES for Theoretical Design I Methods I . . ~ ~~

Setting Design Method I ._ - Setting Support Models Setting Ground Model

Execution of Calculation Method

Evaluation of Calculated Results

ES for Framed Structure Method

Setting Calculation Case Construction of Frame Model

Setting Ground Reaction Coefficient Setting Ground Load Executing Calculation

Scheme Evaluation and Displaying

Res u I t s

,-I Commonly Referred Section]-, I

Determination of Properties of 1 1 I

ES for Numerical Design Method

Setting Calculation Case Setting Calculation domain

Setting Properties of Ground

Setting Properties of Support

Setting Initial Stress Setting Excavation Scheme

Mesh Generation Execution of Calculation Evaluation of Calculated

Results

Ground Unit Weight yg

I .

Longitudinal Wave Velocity V; Shear Wave Velocity V?

Strength u! Initial Stress u:

Lateral Stress Coefficient KO Deformation Modulus Elo

Poisson’s Ratio v 9

CRIEPI’s Class Ikeda’s Class

‘ I I I

Shear Wave Vclocity V,’

Deformation Modulus

I - -, - - - - - - - - I_---_------_- I

FIGURE 2. The outline of the tunnel design expert system-TUX.

FIGURE 3. Calling scheme of knowledge bases.

Auxiliary knowledge base for determining the deformation modulus of ground from

the deformation modulus of rock, by using

- IF

THEN IF

THEN IF

THEN IF

THEN

IF

THEN -

ie jointing index coefficient the elastic modulus of rock is not known, call the input knowledge base the wave velocity of ground is no1 known, call the input knowledge base the wave velocity of rock is not known, call the input knowledge base the elastic modulus of rock, wave velocity of ground and rock exist calculate the modulus from J, = (V;/V;)* E& = J, x El , the elastic modulus of rock, wave velocity of ground and rock do not exist, there is no jointing index value

Input knowledge base for the deformation modulus of rock

the uniaxial strength of rock exists

uniaxial compression test results I --

VOL 5 , NO. 1, MARCH 1990 AN EXPERT SYSTEM F O R T U N N E L DESIGN 7

TABLE 1 DATA FOR SUPPORT PATTERN

Class Name of Data kern

Exc.ivation conditions

Rockbolt pattern 1

Rockbolt pattern 2 (Two type rockbolt installation pdtterns are possible)

Shotcrete

Steel ribs

Con( rete lining

Allowed dtiplacement

Excavation method Face advancement; length of a

Rockbolt installation type Rockbolt length Rockbolt number Rockbolt diameter Rockbolt transverse spacing Rockbolt longitudinal spacing Pull-out capacity

Rockbolt installation type Rockbolt length Rockbolt number Rock bol t diameter Rockbolt transverse spacing Rockbolt longitudinal spacing Pull-out capacity

Definition method for shotcrete

Shotcrete thickness (upper) Shotcrete thickness (lower)

Steel rib type Area of the cross section (upper) Area of the cross section (lower) Installation spacing

Thickness of arch and wall sections Thickness of invert

Allowed displacement (upper) Allowed displacement (lower) Allowed displacement (invert)

round

thickness

classification by considering the uniaxial strength of the intact ground material. Table 4 is a grading of ground by considering the elastic longitudinal wave velocity of ground and the ratio of the uniaxial strength of ground to the overburden stress. Table 5 shows the required support patterns for various grades of ground and the type of tunnel. As the classification of Japan Roadways Association is also similar to that of Japan Railways, the details of this classification wil l not be given in this article.

A subexpert system was developed for the standard design methods of Japan Railways and Japan Roadway Association by using the classification tables mentioned above. The system consists of ground classifications and the determination of the tunnel shape and support pattern corresponding to each ground grade. There are several tunnel standard cross sections provided by each respective authority; see Figure 4. The support system is determined from the dimensions of the tunnel cross section and ground grade together with the information on excavation conditions and the installation patterns of support members. These relations are al l installed in the system as a knowledge base.

ES FOR THEORETICAL DESIGN METHODS

There are several simple closed-form solutions suggested for the tunnel designs by NATM. Of these, the methods of Egger [ l ] , Einstein and Schwartz [21, and Oka [81 are installed in this system. TUX first selects the calculation method following the input conditions given in Table 6.

TABLE 2 KNOWLEDGE BASE FOR DETERMINING G R O U N D PROPERTIES

kern Data to be Determined Determination Method

Ground properties Unit weight Longitudinal velocity V,, Shear velocity V, Ground strength

Initial stress Lateral stress coefficient

Deformation modulus

Poisson’s ratio

CRIEPl’s class

Ikeda’s class

Roc h Properties Strength Deformation modulus Wave velocity

Input of test value Input of measured value Input of measured value Input of test value Modification of rock strength by jointing index Determination from CRlEPl classification Overburden x unit weight (y x H) Input of measured value Estimation from Poisson’s ratio Input of measured value Modification of elastic modulus of rock by jointing index Modification of dynamic elasticity by Kujundzic’s

Estimation from CRlEPl classification Input of measured value Use of dynamic Poisson’s ratio Estimation from Ikeda’s classification 0.3 Input of user decision Estimation from wave velocity Input of user decision Rock name and wave velocity

Input of test value Input of test value Input of measured value

method

8 Y. ICHIKAWA ET AL. MICROCOMPUTERS IN CIVIL ENClNEERlNC

TABLE 3 GROUND CLASSIFICATION

Ground Class Geological Class and Name 01 Rock

A 1 . Paleozoic and Mesozoic (slate, sandstone, chert, tuff brecia, limestone)

2. Intrusive rocks (granite, diorite, etc.) 3. Semi-intrusive rocks (porhyrites, micro-

4. Extrusive rocks (basalt) 5 . Metamorphic rocks (schists, phyllite,

B 1. Easily cleavaged metamorphic rocks

granite, diabase)

hornfels)

2 . Thinly layered paleozoic and mesozoic rocks

C 1 . Mesozoic rocks (shale)

andesite)

shale)

2. Extrusive rocks (rhyolite, quartzite,

3. Tertiary rocks (silisceous sandtone and

Tertiary paleogenic and neogenic rocks (shale, sandstone, brecia, tuff, tuff brecia)

E Neogenic rocks (mudstone, siltstone, sandstone, tuff)

F Neogenic soils (consolidated clays)

C Slide debris and top soil

D

Then, the ground is modeled as brittle, perfectly plastic or strain-softening plastic type. The material constants of these models are determined in the commonly referred section. The tunnel shape is approximated by a circle and the support pattern is modified for that shape. The material properties of support members are also determined in the commonly referred section. Once the required data is ready, the stress state, tunnel wall displacements, and the plastic zone radius of the surrounding ground are calculated. Then, the check on the ap- propriateness of the support pattern is carried out by comparing the strengths of support members wi th the calculated results. The comparison method is shown in Figure 5.

ES FOR FRAMED STRUCTURE DESIGN METHOD

As a design method of the support system, a framed structure modeling is employed, in which loads are determined from the loosening load concept. This subexpert system is coded as shown in Figure 2. Here the state variables are the data for each excavation step and the hardening state of shotcrete in relation to the tunnel face advance. In setting up the calculation, the conditions for the installation timing of the support members,

TABLE 4 GROUND CLASSIFICATION STANDARDS FOR DESIGN

Ground Class

Soil

Hard Rock Medium Hard Rock Soft Rock F,G Classes Ground Grade A.8 Classes c Class D Class E Class Clav Sandv

V p 2 5.2 V p 2 5.0 V p 2 4.2

5.2 > V p 2 4.6

4 .6 > V p 2 3.8

V N

I V N

/ / I N

5.0 > V p 2 4 .4

4.4 > V p 2 3.6

4.2 > V p 2 3.4

3.4 > V p S 2.6

l l N 3.8 > V p 2 3.2 3.6 > V p 2 3.0 2.6 > V p 2 2.0 5 2 4 YH

IN 3.2 > V p 2 2.5 3.0 > V p 2 2.5 2.6 > V p 2 2.0 u c 4 2 - 2 2 Y H

or 2.0 > V p 2 1.5 U C - 2 2 Y H

2.5 > V p 2.5 > V p 1.5 > V p o r u c 2 2 - Y H

2.6 > V p 2 2 . 6

2.6 > V p 2 1.5

5 2 4 Y H

2.6 > V p 2 1.5 (Jc 4 2 - 2 2 U C - 2 2 YH YH

1.5 > V p or m c 2 2 - YH

VOL 5, NO. I, MARCH 1990 AN EXPERT SYSTEM FOR TUNNEL DESIGN 9

TABLE 5 STANDARD SUPPORT PATTERN

(a) Single Railway Tunnel

Shotcrete Thickness (crnj Steel Ribs Rockbolts Ground C, rade

V Y 5 Arch 2 and 0-5 5

111,v Arch 2 and 8 1.5 10 11 v Arch and Sidewall 2 and 10 1.2 10 l h Arch and Sidewall 3 and 12 1 .o 10 100 H

0.8-1 .O 10 10 100 H I , Arch and Sidewall 3 and 14 - I I Arch and Sidewall 3 and 8 0.8-1 .O 15 100 H

Location Length (mj and Number Spacing (m) Arch and Sidewall lnvert Type -

(b) Double Railway Tunnel

Steel Ribs Rockbolts Shotcrete Thickness (cm) Ground

V V 5 I L N Arch 2 and 0-7 5 I l l y Arch 2 and 10 1.5 10 /I,, Arch and Sidewall 3 and 14 1.2 10 I* Arch and Sidewall 3 and 18 1 .o 15 125 H I , Arch and Sidewall 3 and 12 or 4.5 and 8 0.8-1.0 15 15 150 H 1' Arch and Sidewall 3 and 10 0.8-1 .O 20 125 H

(cJ Shinkansen Railway Tunnel

- Grade Location Length (rnj and Number Spacing ( r n j Arch and Sidewall lnvert Type

- ~ _ _

Rockbolts Shotcrete Thickness (crn) Steel Ribs Ground

v-I 5 I\. N Arch 2 and 0-8 5 lily Arch 2 and 12 1 5 10 11 ii Arch and Sidewall 3 and 16 1.2 10 /I, Arch and Sidewall 3 and 20 1 .o 1 5 125 H 1 5 Arch and Sidewall 3 and 14 or 4.5 and 8 0.8-1 .O 15 15 150 H / I Arch and Sidewall 3 and 12 0.8-1 .O 20 125 H

Crade Location Length (mj and Number Spacing (rn) Arch and Sidewall lnvert Type

CL FIGURE 4. Definition of dimensions of a tunnel.

10 Y. ICHIKAWA ET AL.

No 1

2

3

4

5

MICROCOMPUTERS IN ClVlL ENCINE€RINC

Calculation conditions support members are subjected to their ultimate resistances tunnel wall displacement is allowed up to the limit of the allowed displacement rockbolt loads with a prestress equal to the pull-out capacity, shotcrete and steel ribs to behave elastically rockbolts without prestress, shotcrete and steel ribs to behave elastically rockbolts, shotcrete and steel ribs to behave elastically

TABLE 6 SETTING OF DESIGN CASES

Calculation Initial Stress Behavior Method

~

Non-hydrostatic Elastic Einstein

Hydrostatic Elastic-perfectly Einstein plastic Egger

Elastic-strain Egger softening Oka plastic

Elastic-brittle Egger plastic

the excavation method, and the presence of the primary and secondary linings are determined. Element divisions of support members, their material properties, and boundary conditions are also set. To determine the ground reaction coefficient, the system provides a knowledge base with various experimental data. The loads acting on the support members are determined from the classification of Terzaghi (101 with the help of the classification of the Central Research Institute of Electric Power Industry of Japan. The calculated results are the displacement, the axial and shear forces, and the moment of support members.

ES FOR FINITE-ELEMENT ANALYSIS (FEM)

Under the more complex situation, i.e., when the overburden is shallow and/or adjacent structures are

FIGURE 5. Analyzed cases (theoretical design methods).

1.0 % d w Ln < w 2 r d e: m

e: i-. Ln

Y

I AI.I.OWARLE BEARING

CAPACITY LlMlT

0

present or the opening is very large, numerical methods are used for the stability analysis. In TUX, a general finite-element program is installed. This program treats the rock mass as an elastic medium under a plain-strain condition and takes into account the effect of the face advancing. This conditions involve the variations of support patterns and the material properties of the support members in relation to the release rate of the initial stress. The mesh generation, the modeling of ground and support members, the setting of the analysis domain, and the presentation of the calculated results are all done automatically. The analyzed cases are the same as those in the case of the framed structure ES. When the overburden is shallow, the inclination of the ground surface i s also taken into account. The material properties of ground and support members are determined from the knowledge base of the commonly referred section of the system. In determining the initial stress state, the value of Poisson's ratio i s assigned by using a rule of experiences. A knowledge base is also available for the stress release rate, which was determined from three-dimen- sional FEM analyses, for simulating the effect of the face advancing. The ground, rockbolts, steel ribs, shotcrete, and concrete lining are represented by four-noded iso- parametric elements, line elements, and four-noded is- oparametric elements with the use of the reduced in- tegration technique, respectively. The calculated results are displayed and output as the distributions of displacements, stress in ground and support members, and safety factor.

It is difficult to write down the rules of experience for the evaluation of the results of the finite-element analysis, since the procedure of evaluation is generally per- formed by observing the distributions of stress and displacement and safety factor contours. Presently, the evaluation scheme for the finite-element calculations is still being installed in TUX.

EVALUATION OF TUX

The TUX has the function of carrying out an automatized design as it generates the necessary data for the tunnel design from the experiential knowledge. To activate TUX, the minimum amount of data are the purpose of use (roadways, railways, etc.), the rock name, the elastic wave velocity of ground, the type of the standard tunnel cross section, the overburden, the inclination of the ground surface, and the pull-out capacity of each bolt. If these data are supplied, TUX deduces the tunnel shape and the support pattern, then it carries out the stability analysis. Still the current system i s not convenient for inexperienced users, but it can be used as a tool for the education of inexperienced users under the supervision of the expert engineers.

During the development of TUX, we have thoroughly discussed what the true features of expert systems should

VOl 5, NO. 7, MARCH 1990

be. 1 he merits of expert systems of the TUX type can be sumrnerized as follows:

1. Deduction ability: Since the ES has its o w n deduction svstem to deal wi th the rules of experience, there is no need to prepare another special routine for this purpose. This feature i s particularly important when no fixed procedure i s available for the problem.

2. Object-orientated structure: We can closely examine the contents of each unit of knowledge base in the ES. This, in turn, enables the coding of the program iii segments independently, which implies that an object-oriented coding technique is easy to imple- ment.

3. Easy understanding: The description of rules is close to human language so that i t is not difficult to read and understand the codes.

4. Certainty factor and fuzzy theory: It i s possible to iricorporate the decision-making procedure by the use of the certainty factor concept of fuzzy theory. 1 he certainty factor and fuzzy set theory have been introduced by lmazu [3] and Shimizu 191 for the rock classification expert system, respectively. These ap- proaches will be applied to the evaluation of the cal- c ulated results.

As it i s clear from the above statements, the case of extending the system is the most important feature of the ES. This becomes particularly important in further development of the large-scale expert systems such as the extended TUX involving the management and measure- ments in tunnelling.

A revision of TUX in the future i s considered to be closely dependent on the development of the tunnel data base system. W e have presently developed two data base systems for support patterns of existing tunnels and for rock properties, using personal computers, which are independent of TUX.

The tunnel data base system was developed with the objective of checking the design with reference to experience gained in the existing tunnels under similar ground and environmental conditions. Table 7 gives the details of this data base system. The rock property data base system was developed with the purpose to refer to the properties of ground. The details of this data base are given in Table 8. Presently, the data gathered from 96 tunnels in Japan have been stored in the tunnel data base, while the rock property data base has 1300 data items. The data collection is still continuing.

EXAMPLE

W e present an example of the application of our system to a tunnel design problem. When the system is acti- vated, a screen shown in Figure 6 is displayed and the user is asked to input data and other related information. Once the selection of one of the standard design meth-

A N EXPERT SYSTEM FOR TUNNEL DESIGN 11

TABLE 7 ITEMS OF TUNNEL DATA BASE SYSTEM ~ ~~~

Content Item

Tunnel

Geologic Conditions

Design Conditions

Instability

Monitoring

Tunnel number, tunnel name, location, tunnel type, tunnel length, length by NATM, existence of adjacent constructions, existence of junctions, dates of commencement and completion of tunnel, referred article

Geologic age, geologic class, upper and lower elastic wave velocities, rock name, rock classification and classes, max. amount of seepage period, expansibility, flowability, unusual loads, existence of faults and fractured zones, existence of landslides, overburden

Excavation methods, excavation types, diameter of excavation, excavation area excavation advance length, rockbolt (length, number, spacing)

spacing), shotcrete (thickness, strength), existence of Bernold sheets, existence of steel-fibre, concrete lining (invert, arch, side-walls)

Contents of instability, auxiliary methods

Max. displacement, max. crown convergence, pull-out resistance of bolts

Steel ribs (upper-half, lower-half,

ods is made, the system asks the user to select the method for the stability analysis of the tunnel. If, for example, the user has selected the theoretical design method of Egger 111, the system wi l l calculate and dis- play results as shown in Figures 7 and 8. When the calculation is over, the system will again ask the user i f he/ she wishes the system to conduct the stability analysis by other methods. For the same problem, if the ES for frame structure design method is selected, the calculated results will be displayed and output. Figure 9 shows the applied load and resulting bending-moment distribution. If the user continues the stability analysis and se-

TABLE 8 ITEMS OF ROCK-MASS DATA BASE SYSTEM

Content Item

Rock Construction name, location, geologic

Ceol og ic

Test Data

age, formation name, rock name

Classification name and classes, V, and V, of rock mass, V, and V, of intact rock

Excavation method, support pattern name, excavation area, unit weight, compressive strength, elastic modulus ( E s o ) , Poisson's ratio, friction angle, cohesion, N-value, RQD, referred article

Conditions

-> b

-> d

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7.

Dis

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for

the

anal

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by

ES fo

r th

eore

tical

des

ign

met

hod.

egger’s m e t h o d

i

I r&l ,,.’ ,

FIGURE 8. Displayed calculation results (Egger’s design method). Case 1 : support members are subjected to their ultimate resistances. Case 2: rockbolt loads with a prestress equal to the pull-out capacity, shortcrete, and steel. Case 4: rockbolts without prestress, shortcrete, and steel ribs to behave elastically.

FIGURE 9. Displayed calcuation results (framed structure design method).

H

UNIT mz: 11.7 t f

fQlf€-)c> b H DISTRIBUTION OF BENDING MOMEN

H

UNIT &Z: 11-6 t f m

a b

VOL. 5, NO. I , MARCH 1990 AN EXPERT SYSTEM FOR TUNNEL DESIGN 17

led3 the finite-element routine, the system automatically generates the finite-element mesh and gets results of dis-

FIGURE 10. Displayed finite-element mesh and calculation results (numerical analysis design method-FEM).

MESH S C A L E

0 20 m

a

tributions of displacements, stresses, and safety contours at each excavation step. Figure 10 shows the mesh and the calculated safety factor contours for the upper-half excavation and the subsequent lower-half excavation. The results by FEM can be obtained within 30 minutes for all excavation steps.

b

C

MICROCOMPUTERS IN ClVlL ENGINEERING 18 Y. ICHIKAWA ET AL.

i ACCUMULATION I & I ACCUMULATION USE

E X P E R T DATA ARRANGEMENT

B A S E S Y S T E M EXPER

1 I I E M E ~

I< NOW LE DGE

EXPEnlENCE * .

R E S E A R C H - I R E S E A R C H I-'

J

C E

FIGURE 11. Relation between the expert system and the design-construction-research cycle.

numerical analysis. Of course, there are several ap- proaches how to position the ES in civil engineering. One of these is that the ES can be considered to act as an effective connection tool among design-construction-research (Figure 1 1). By starting to develop an expert system for the purpose of design and construction, we were able to sort out the rules of experience up to this extent. We intend to improve the current system by including the management and monitoring procedures in tunnel I ing.

The present research work was jointly carried out from April 1986 to March 1989 by Nagoya University and private construction companies under the Grant in Aids for Developmental Scientific Research (Grant 61 3020601, the Japan Ministry of Education (Monbusho) (71. The authors wish to extend their sincere thanks and gratitude to the members of the research team listed in Table 9 for their continuous contributions and the Japan Digital Equipments Corporation (DEC) for their coop- eration and help.

CONCLUSIONS REFERENCES

We have developed an automatized tunnel design system (called TUX-tunnel expert system) based on the ES concept. It can be used by anyone who does not have sufficient knowledge in theoretical, framed structure, or

TABLE 9 NAME A N D AFFILIATIONS OF RESEARCH TEAM

Name Affiliation

T. Kawamoto Nagoya University Y. lchikawa Nagoya University- T. Kyoya Nagoya University 0. Aydan Nagoya University M. Sezaki Miyazaki University T. Yamabe Saitama University T. Akagi Toyota Technical College H. Osaka Taisei Co. K. Kamemura Taisei Co. T. Shinokawa Sat0 Kogyo Co. Y . Goto Tokyu Construction Co. T. Tsuruhara oyo co. S . Tsuchiyama T. Kitagawa Nishimatsu Gumi Co. T. lchijo Nishimatsu Construction Co. Y. Mitarai Kurnagai Gumi Co. Y. Takahashi Kajima Co. H. Nitta Okumura Co. Y. lshizuka Shimizu Construction Co. S . Kadota Fujita Co. M. Kusabuka Hazama-Gumi Ltd.

Chubu Electric Power Co.

1.

2.

3 .

4.

5.

6.

7.

8 .

9.

10.

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An Expert System for Tunnel Design