FEASIBILITY STUDY OF A 10-GWh TOROIDAL SUPERCONDUCTIVE MAGNETIC ENERGY STORAGE SYSTEM3. CONCEPTUAL DESIGN OF ROCK MASS SUPPORT STRUCTURE

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FEASIBILITY STUDY OF A 10-GWh TOROIDAL SUPERCONDUCTIVE MAGNETIC ENERGY STORAGE SYSTEM3. CONCEPTUAL DESIGN OF

ROCK MASS SUPPORT STRUCTURE

M. Shimizu, Y. Morita, Y. Yukimatsu, T. Tomozawa, Y. Tanabe, N. Takeda, H. Miyazaki, K. Kamemura, M. Yamamoto, T. Uchida, et al.

To cite this version:

M. Shimizu, Y. Morita, Y. Yukimatsu, T. Tomozawa, Y. Tanabe, et al.. FEASIBILITY STUDY OF A

10-GWh TOROIDAL SUPERCONDUCTIVE MAGNETIC ENERGY STORAGE SYSTEM3. CON-

CEPTUAL DESIGN OF ROCK MASS SUPPORT STRUCTURE. Journal de Physique Colloques,

1984, 45 (C1), pp.C1-591-C1-594. �10.1051/jphyscol:19841119�. �jpa-00223588�

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JOURNAL

DE PHYSIQUE

Colloque C I , suppl6ment au no I, Tome

45,

janvier

1984

page (21-591

F E A S I B I L I T Y STUDY OF A

10-GWh

T O R O I D A L SUPERCONDUCTIVE MAGNETIC ENERGY STORAGE SYSTEM

3 , CONCEPTUAL DESIGN OF ROCK MASS SUPPORT STRUCTURE

M. Shimizu, Y. Moritar, Y. yukimatsur, T. Tomozawa*, Y . ~ a n a b e * , N. ~ a k e d a * ~ , H. ~ i ~ a z a k i * * , K. Kamemurar*, M. ~arnarnoto'~, T. Ilchidar**, Y . ~aka~arna***

and T . ~ o k o t a * * *

The Kansai EZeetrie Power Company, Ine., Japan

* f i e I n s t i t u t e of AppZied Energy, Japan

* * ~ a i s e i Corporation, Japan r r r ~ o s h i b a Corporation, Japan

Msume- On examine d ' a b o r d l e s problemes concernant l e s u p p o r t rocheux de l ' a i - mant. L'gtude de l a s t a b i l i t 6 des f o n d a t i o n s pour l e systdme SMES de

10 GWh e s t menee 3. b i e n dans l ' h y p o t h 6 s e d'une e l a s t i c i t e 5 s y m e t r i e a x i a l e pour l e s u p p o r t .

Selon nos c a l c u l s , on c o n s i d e r e que l a f o r c e magnetique a g i s s a n t s u r l ' a i m a n t t o r o i d a l p e u t S t r e contenue p a r l a masse rocheuse des f o n d a t i o n s .

Abstract- Problems concerning rock mass support system a r e examined and rock mass s t a b i l i t y a n a l y s i s f o r t h e conceptual design of t h e 1 0 GWH

SMES

system i s c a r r i e d o u t u s i n g F.E.M. under t h e c o n d i t i o n of axi-symmetrical e l a s t i c i t y .

From t h e r e s u l t s o f c a l c u l a t i o n s , i t i s c o n s i d e r e d t h a t c e n t e r i n g e l e c t r o - magnetic f o r c e of t h e t o r o i d a l c o i l t y p e can be s u p p o r t e d by t h e rock mass.

1. I n t r o d u c t i o n

I n l a r g e - s c a l e SMES system, an e f f e c t i v e support system f o r s t r o n g e l e c t r o m a g n e t i c f o r c e of over 1 0 MPa i s a s e r i o u s problem. From t h e economic p o i n t of view, it i s b e t t e r t o use a rock mass t h a n s t a i n l e s s s t e e l a s t h e support m a t e r i a l . However, t h e allowable magnitude of t h e e l e c t r o m a g n e t i c f o r c e supported by t h e rock mass depends on t h e s t r e n g t h of t h e rock mass.

( a ) P l a n ( b ) C r o s s s e c t l o n

/ h ' \ > \

^8-Bsection

I ^l-===L

A- A section

Fig.-l Plan and c r o s s s e c t i o n o f conceptual d e s i g n

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19841119

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JOURNAL DE PHYSIQUE

s t r u c t u r e and t h e domain of t h e

model i s d i v i d e d i n t o f i n e e l e m e n t s . P a r t of t h e whole a n a l y t i c a l m o d e l i s shown i n Fig.-3. The t o t a l d i - mensions of t h e a n a l y t i c a l model a r e shown below.

Radius=900m

~ e ~ t h = 4 0 0 m Number of nodes=281 Number of elements=279 T a b l e - 1 Rock p r o p e r t i e s

L ~

A s e r i o u s problem w i t h t h e r o c k

mass support system i s t h e f a c t

Fig.-2 General cross-section

t h a t i n n e r hoop p r e s s u r e i s more

of coil and trench

t h a n lOMPa, r e g a r d l e s s of whether t h e t y p e of system i s a s o l e n o i d o r t o r o i d a l c o i l t y p e , and t h i s

v a r i e s one c y c l e a day. However, g t h e r e a r e no examples i.n which

rock mass p l a y s a r o l e of s u p p o r t -

i n g members a g a i n s t i n n e r p r e s s u r e . ^(Sv/(Sn= 1

Moreover, t h e f a t i g u e c h a r a c t e r i s - t i c s o f rock mass a r e unknown a t p r e s e n t .

;

2. S t a b i l i t y a n a l y s i s

S t a b i l i t y a n a l y s i s was c a r r i e d

out on t h e t o r o i d a l SMES system ( a ) S e t t i n g o f i n i t i a l s t r e s s shown i n Fig.-1. The c r o s s - s e c t i o n

c

The a n a l y t i c a l procedure i s d i -

vided i n t o t h r e e s t a g e s . I n s t a g e 0 ,

i

i n i t i a l s t r e s s , which i s supposed t o b e i n t h e h y d r o s t a t i c s t a t e , i s s e t . I n s t a g e 1, excavation of an open t r e n c h f o r a t o r o i d a l c o i l i s simu- l a t e d and i n s t a g e 2 , t h e e l e c t r o -

magnetic f o r c e a c t i n g on t h e rock m a s s ( c ) E l e c t r o m a g n e t i c f o r c e a c t s

i s c a l c u l a t e d . on s u r f a c e o f s i d e w a l l

shown i n Fig.-2 was modeled f o r a n a l y s i s a s an axi-symmetrical

Fig.-3 Stages of construction and operation simulated by axi-symmetrical F.E.M. model

252m _{* O m}

STAGE1

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STAGE 2

DISPLACEMENT ..--.

^2.0,~,,,, ^scALE

-

^10.01m1

Fig.-4 Calculated displacement around open trench (dotted lines indicate displacement)

The rock p r o p e r t i e s f o r a n a l y s i s shown i n Table-1 a r e supposed t o be s i m i l a r t o t h o s e of h a r d and sound g r a n i t e , t h e seismic l o n g i t u d i n a l v e l o c i t y of which i s about

5

km/sec. These p r o p e r t i e s a r e determined on t h e b a s i s of e x p e r i e n c e which i s gain- ed through many a n a l y s e s o f rock caverns. This t y p e of g r a n i t e i s b e t t e r t h a n t h e medium c l a s s o f rock c l a s s i f i c a t i o n , and i s a v a i l a b l e f o r t h e c o n s t r u c t i o n of SMES systems i n many p a r t s of Japan.

The r e s u l t s o f t h i s a n a l y s i s , which a r e based on t h e s e s u p p o s i t i o n s , a r e shown i n Figs.-&,

5

and

6.

Fig.-4 shows t h e d i s t r i b u t i o n of rock displacement. The a n a l y t i - c a l c o n d i t i o n s i n Fig.-& correspond t o t h o s e i n s t a g e 2 i n Fig.-3.

Maximum displacement on t h e rock w a l l i s approximately 22mm towards t h e t o r o i d a l c e d t e r i n s t a g e 2.

Fig.-? shows t h e d i s t r i b u t i o n o f t h e s t r e s s o f t h e rock mass i n s t a g e 2. Maximum compressive s t r e s s ( 2 . 3 m a ) occurs n e a r t h e middle o f t h e i n s i d e w a l l of t h e t r e n c h and~maximum t e n s i l e s t r e s s (0.26 M P ~ ) occurs n e a r t h e bottom of t h e t r e n c h when c e n t e r i n g e l e c t r o m a g n e t i c f o r c e a c t s .

This d i s t r i b u t i o n of t e n s i l e s t r e s s i s shown i n Fig.-6. The t e n s i l e s t r e s s calcu- l a t e d i s l e s s t h a n t h e t e n s i l e s t r e n g t h of t h e rock mass. The rock mass i s t h e r e - f o r e kept s t a b l e a g a i n s t s h e a r and t e n s i l e f a i l u r e when energy i s s t o r e d .

Under t h e c o n d i t i o n s o f d a i l y charging and d i s c h a r g i n g , however, t h e number of l o a d i n g c y c l e s i s 18,250 t i m e s i n 50 y e a r s which corresponds t o t h e l i f e span of a pumped hydro s t o r a g e s t a t i o n .

Hence, t h e f a t i g u e of t h e rock mass due t o t h e low c y c l e change i n t h e l o a d should be considered. However, r e s e a r c h i n t o rock mass f a t i g u e was s t a r t e d only r e c e n t l y . There remain many problems t o b e s o l v e d through p r o g r e s s i n r e s e a r c h on t h e f a t i g u e of rock mass. The e v a l u a t i o n o f s a f e t y f a c t o r s , f o r example.

3. Construction method

Open t r e n c h f o r SMES systems may b e c o n s t r u c t e d by even c o n v e n t i o n a l t e c h n i q u e s such a s t h e New A u s t r i a n Tunneling Method u s i n g s h o t c r e t e , r o c k b o l t s f o r rock mass s t a b i l i t y , smooth b l a s t i n g t e c h n i q u e s which do not r e s u l t i n damage t o rock masses, and t h e bench c u t method.

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JOURNAL DE PHYSIQUE

STAGE 2

PRINCIPAL STRESS

^o2.5MPa

'CALE

10.01m1

Fig.-5 Calculated principal stress distribution due to electromagnetic force

Fig.-6

Calculated tensile zone

4.

Conclusion

From t h e r e s u l t s of c a l c u l a t i o n , it i s considered t h a t c e n t e r i n g e l e c t r o m a g n e t i c f o r c e of t h e t o r o i d a l c o i l t y p e can be supported by a rock mass. It w a s shown t h a t t h e c a l c u l a t e d s t r e s s i s lower t h a n t h e s t r e n g t h of t h e rock mass when c=5 MPa and 4=45', and t h a t t h e rock mass i s s t a b l e a g a i n s t t h e e l e c t r o m a g n e t i c f o r c e .

A f t e r t h e survey on t h e c o n s t r u c t i o n o f an open t r e n c h of 80m wide and 45m deep, it became c l e a r t h a t t h e c o n s t r u c t i o n of a 10 GWH SMES rock mass support system i s probably p o s s i b l e even with e x i s t i n g t e c h n i q u e s .

F r o m t h i s p o i n t , we w i l l have t o attempt a s t u d y on rock p r o p e r t i e s , emphasizing t h e f a t i g u e of rock masses. The d e s i g n o f new, improved rock mass support systems t o s h a r e p a r t of t h e hoop s t r e s s of c o i l s , should be s t u d i e d .

Reference

M. Shimizu e t a l . : Conceptual design on lOGWH SMES, Proceedings of 29th confer- ence on cryogenic e n g i n e e r i n g i n Japan, 1983, May.