The Use of Geotextiles in Waste Containment Facilities - American

Chapter 23

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on June 15, 2016 | http://pubs.acs.org Publication Date: April 3, 1991 | doi: 10.1021/bk-1991-0457.ch023

The Use of Geotextiles in Waste Containment Facilities S. D. Menoff, J. W. Stenborg, and M. J. Rodgers Chambers Development Company, Inc., Pittsburgh, PA 53215

During the past few years, there has been an increased emphasis on technical advancements in the design and construction of waste containment facilities. This has been in response to the demand for environmentally sound landfill sites. This emphasis has resulted in the increased utilization of geosynthetic materials for waste containment applications. While geomembranes have become the basic element for containment in waste disposal facilities, geotextiles are also utilized to satisfy a number of important design and construction considerations. The p r i n c i p a l a p p l i c a t i o n f o r g e o t e x t i l e s i n waste d i s p o s a l f a c i l i t i e s a r e as f i l t e r s and cushions. They a l s o serve as drainage l a y e r s e i t h e r on t h e i r own o r i n c o n j u n c t i o n w i t h geonets. H i g h - s t r e n g t h g e o t e x t i l e s p r o v i d e s o i l reinforcement t o a l l o w f o r t h e c o n s t r u c t i o n of steeper s i d e s l o p e s , p o t e n t i a l l y i n c r e a s i n g t h e a v a i l a b l e a i r s p a c e . T h i s paper presents an overview o f the design a p p l i c a t i o n s and c o n s t r u c t i o n c o n s i d e r a t i o n s f o r t h e use o f g e o t e x t i l e s i n waste containment facilities. Design O b j e c t i v e s and A p p l i c a t i o n s I n t h e design o f a s o l i d waste d i s p o s a l f a c i l i t y , t h e o b j e c t i v e s a r e t o p r o v i d e f o r t h e containment o f waste and l e a c h a t e i n a manner t h a t ensures long term environmental p r o t e c t i o n , r e g u l a t o r y compliance, and c o s t e f f e c t i v e u t i l i z a t i o n o f manpower, equipment, and space. To achieve these o b j e c t i v e s , l a n d f i l l s a r e l i n e d w i t h one o r more

0097-6156/91/0457-0351$06.00A) © 1991 American Chemical Society

Vigo and Turbak; High-Tech Fibrous Materials ACS Symposium Series; American Chemical Society: Washington, DC, 1991.


352

HIGH-TECH FIBROUS MATERIALS

l a y e r s o f geomembranes. These geomembranes, coupled w i t h n a t u r a l s o i l o r g e o s y n t h e t i c drainage l a y e r s , c o n t a i n and c o l l e c t l e a c h a t e f o r removal and subsequent treatment and d i s p o s i t i o n . The o b j e c t i v e i s t o minimize t h e development of a l e a c h a t e head b u i l d up on t h e geomembrane l i n e r and thereby reduce t h e r i s k t o t h e environment. G e o t e x t i l e s a r e important components o f a g e o s y n t h e t i c containment system i n a waste d i s p o s a l f a c i l i t y . Other components i n c l u d e geomembranes, geonets, and g e o g r i d s . The major a p p l i c a t i o n s o f g e o t e x t i l e s i n l a n d f i l l construction are the following: 1. Cushion G e o t e x t i l e s p l a c e d d i r e c t l y above o r below a geomembrane a c t as a "cushion" which p r o t e c t s t h e geomembrane from damage. Puncture can be a p a r t i c u l a r problem d u r i n g i n s t a l l a t i o n . 2. F i l t r a t i o n G e o t e x t i l e s p l a c e d between two d i f f e r e n t s o i l s o r between a s o i l and a geonet a l l o w l i q u i d t o f l o w p e r p e n d i c u l a r l y t o t h e i n t e r f a c e from one m a t e r i a l t o the o t h e r , w h i l e p r e v e n t i n g t h e movement o f f i n e grained s o i l p a r t i c l e s ( p e r m i t t i v i t y ) . Geotextiles used i n t h i s a p p l i c a t i o n a l s o serve t h e purpose o f separation. 3. Drainage G e o t e x t i l e s a l l o w l i q u i d o r gas t o move a l o n g t h e plane o f t h e m a t e r i a l ( t r a n s m i s s i v i t y ) . Large volumes o f l i q u i d a r e conducted u s i n g g e o t e x t i l e s i n combination w i t h geonets. 4. Reinforcement G e o t e x t i l e s can be used as t h e r e i n f o r c i n g elements i n a s o i l mass p r i m a r i l y through s t r e s s d i s t r i b u t i o n w i t h i n t h e s o i l mass o r d i r e c t s o i l r e i n f o r c e m e n t . Reinforcement a l l o w s s i d e s l o p e s above o r below t h e ground s u r f a c e t o be steepened. Geotextile Classification G e o t e x t i l e s a r e c l a s s i f i e d a c c o r d i n g t o t h e type o f polymer, f i l a m e n t , f i b e r and f a b r i c from which they a r e manufactured. The m a j o r i t y o f g e o t e x t i l e s a r e manufactured from p o l y p r o p y l e n e and p o l y e s t e r . These m a t e r i a l s have been shown t o be r e s i s t a n t t o d e g r a d a t i o n when exposed t o



23.

MENOFFETAL.

The Use ofGeotextiles in Waste Containment Facilities 353

m u n i c i p a l s o l i d waste l e a c h a t e . P o l y e t h y l e n e g e o t e x t i l e s have been r e c e n t l y i n t r o d u c e d i n t o the market, however, they are not r e a d i l y a v a i l a b l e i n the U n i t e d S t a t e s . The two types of g e o t e x t i l e s used i n most g e o t e c h n i c a l a p p l i c a t i o n s are woven and non-woven. Non-woven g e o t e x t i l e s are used most o f t e n i n waste containment a p p l i c a t i o n s because experience has shown t h a t they perform b e t t e r as f i l t e r s and cushions i n c o n j u n c t i o n w i t h o t h e r l a n d f i l l components. The f i l a m e n t s used i n non-woven f a b r i c s are bonded i n one of t h r e e ways: chemical bonding, thermal bonding, or mechanical bonding by needle punching. The most common bonding procedure i s needle punching. Landfill Application 1. Cushion A l a n d f i l l can o n l y be considered e n v i r o n m e n t a l l y sound when l e a c h a t e can be c o l l e c t e d and removed, thereby p r e v e n t i n g contamination of the surrounding hydrogeologic regime. To e f f e c t i v e l y c o l l e c t l e a c h a t e , the i n t e g r i t y of the geomembrane l i n e r system must be preserved. S i n c e h i g h d e n s i t y p o l y e t h y l e n e (HDPE) geomembranes are s u s c e p t i b l e t o damage d u r i n g and a f t e r i n s t a l l a t i o n , g e o t e x t i l e s are p l a c e d adjacent t o the l i n e r t o a c t as a cushion a g a i n s t p o s s i b l e puncture. The p r o p e r t i e s most important i n t h i s a p p l i c a t i o n are b u l k d e n s i t y and thickness. In g e n e r a l , non-woven g e o t e x t i l e s i n the range of 10 t o 16 ounces per square y a r d have proven adequate f o r most cushion a p p l i c a t i o n s . The e v a l u a t i o n of the e f f e c t i v e n e s s of cushion m a t e r i a l s i s b e s t accomplished through a l a b o r a t o r y t e s t i n g program which i n c l u d e s s t a t i c l o a d t e s t i n g t o s i m u l a t e a c t u a l l a n d f i l l conditions. 2. F i l t r a t i o n When d e s i g n i n g a f i l t e r system u s i n g g e o t e x t i l e s , the same c r i t e r i a are used as i f d e s i g n i n g w i t h aggregates. Flow estimates and c a p a c i t y c a l c u l a t i o n s are e s s e n t i a l l y the same. The advantage over t y p i c a l aggregate systems i s the s a v i n g of v a l u a b l e l a n d f i l l a i r s p a c e and c o n s t r u c t i o n time. Three c o n d i t i o n s must be met f o r a g e o t e x t i l e t o be c o n s i d e r e d an effective f i l t e r : i t must p r o v i d e adequate drainage c a p a b i l i t y ( p e r m i t t i v i t y ) , prevent p i p i n g of the s o i l , and p r o v i d e the r e q u i r e d d u r a b i l i t y a g a i n s t chemical or b i o l o g i c a l a t t a c k . These c o n d i t i o n s are g e n e r a l l y met u s i n g a non-woven p o l y e s t e r o r


354

fflGn-TECH FIBROUS MATERIALS p o l y p r o p y l e n e g e o t e x t i l e , e s p e c i a l l y when f i n e g r a i n e d s o i l s a r e present. Although e i t h e r woven o r non-woven g e o t e x t i l e s can be used i n f i l t e r a p p l i c a t i o n s , i n d u s t r y experience has shown t h a t t h e performance o f non-woven g e o t e x t i l e s i s g e n e r a l l y superior.


3. Drainage G e o t e x t i l e s alone can be used as a drainage medium, although they a r e most f r e q u e n t l y used i n c o n j u n c t i o n w i t h a geonet t o produce a geocomposite. The advantage o f a geocomposite i s t h a t g e o t e x t i l e prevents s o i l s from c l o g g i n g t h e drainage channels o f t h e geonet. When choosing a geonet f o r a l a n d f i l l a p p l i c a t i o n , one must c o n s i d e r t h e overburden p r e s s u r e , s t r a n d r o l l o v e r , or t h e i n t r u s i o n o f adjacent m a t e r i a l s i n t o t h e geonet channels. F a c t o r s t h a t impact t h e l o n g term performance o f a geocomposite i n c l u d e creep, response t o e l e v a t e d temperatures, and t h e p o t e n t i a l f o r b i o l o g i c a l o r mechanical c l o g g i n g . 4.

Reinforcement The l i m i t e d a v a i l a b l e a i r s p a c e i n e x i s t i n g l a n d f i l l s makes i t necessary t o l o o k f o r i n n o v a t i v e ways t o use the a v a i l a b l e space. One way i s t o i n c r e a s e t h e s l o p e s o f t h e l a n d f i l l . By i n c o r p o r a t i n g g e o t e x t i l e s such as h i g h t e n s i l e s t r e n g t h wovens, s t e e p e r s l o p e s can be b u i l t . The f a b r i c p r o v i d e s t e n s i l e s t r e n g t h t o t h e bottom o f t h e embankment and may a l s o i n t e r r u p t r o t a t i o n a l - t y p e f a i l u r e . Areas o f concern when a n a l y z i n g s o i l s f o r reinforcement i n c l u d e s o i l creep, p l a s t i c s o i l deformation, and s t r e s s r e d i s t r i b u t i o n . Because these s o i l a n a l y s e s a r e dependent on a number o f f a c t o r s , a r e l a t i v e l y h i g h f a c t o r o f s a f e t y o f i s recommended.

Construction Considerations The c o n s i d e r a t i o n s p r e v i o u s l y d i s c u s s e d r e l a t e t o t h e g e o t e x t i l e once i t i s i n p l a c e and f u n c t i o n i n g as designed. During c o n s t r u c t i o n and i n s t a l l a t i o n , o t h e r c o n s i d e r a t i o n s t h a t become important i n c l u d e i n s t a l l a t i o n d u r a b i l i t y , f i e l d seam s t r e n g t h , anchor t r e n c h adequacy, and u l t r a - v i o l e t l i g h t degradation. I n s t a l l a t i o n o f a g e o t e x t i l e l a y e r begins by u n r o l l i n g a panel o f m a t e r i a l down t h e s l o p e o r a c r o s s t h e area intended t o cover. A s e r i e s o f panels a r e p l a c e d and j o i n e d a t t h e i r edges t o form one continuous l a y e r o f m a t e r i a l . The edges o f adjacent panels a r e overlapped and sewn o r heat welded t o g e t h e r . Experience has shown t h a t sewing i s t h e p r e f e r r e d method o f j o i n i n g g e o t e x t i l e



23. MENOFFETAL.

The Use of Geotextiles in Waste Containment Facilities 355

p a n e l s . The g e o t e x t i l e m a t e r i a l and seams must be s t r o n g enough t o " s u r v i v e " t h e i n s t a l l a t i o n o f subsequent g e o s y n t h e t i c s and n a t u r a l s o i l l a y e r s and remain i n t a c t t o f u n c t i o n as intended by d e s i g n . The most c r i t i c a l d e s i g n c r i t e r i a i s f o r t h e g e o t e x t i l e t o remain i n t a c t as a s o i l l a y e r i s being p l a c e d over i t . As f i e l d seaming progresses, t h e o u t e r edge o f t h e panels must be anchored t o h o l d i t i n p l a c e and prevent movement i n t o t h e c e l l as o t h e r l a y e r s o f m a t e r i a l a r e p l a c e d over t h e g e o t e x t i l e l a y e r . The g e o t e x t i l e i s u s u a l l y p l a c e d i n an anchor t r e n c h w i t h o t h e r g e o s y n t h e t i c l a y e r s such as geomembranes o r geonets. The anchor t r e n c h uses h o r i z o n t a l o r v e r t i c a l embedment t o h o l d t h e m a t e r i a l by f r i c t i o n o r simple b u r i a l i n a shallow trench. F r i c t i o n c o n s i d e r a t i o n s o r f r i c t i o n angles f o r g e o s y n t h e t i c m a t e r i a l s a r e a concern when d e s i g n i n g access i n t o o r p l a c i n g t h e f i n a l cover system over t h e waste containment area and i n anchor t r e n c h d e s i g n s . G e o t e x t i l e s have r e l a t i v e l y low f r i c t i o n angles when i n c o n t a c t w i t h geomembranes such as HDPE. G e o t e x t i l e s i n c o n t a c t w i t h s o i l have r e l a t i v e l y h i g h f r i c t i o n angles. The d e s i g n e r must u s u a l l y c o n s i d e r t h e s t a b i l i t y o f a composite l a y e r o f s o i l and g e o t e x t i l e on an HDPE l i n e r . When working below ground s u r f a c e w i t h i n t h e c e l l , t h e g e o t e x t i l e i n t h e anchor t r e n c h p r o v i d e s a means o f h o l d i n g t h e l a y e r as waste i s p l a c e d i n t h e c e l l . The most c r i t i c a l time f o r design i s immediately a f t e r c o n s t r u c t i o n . As t h e area i s f i l l e d w i t h waste m a t e r i a l , the p o t e n t i a l f o r p u l l o u t o f l i n e r components from t h e anchor t r e n c h i s g e n e r a l l y reduced. F r i c t i o n a l c o n s i d e r a t i o n becomes a concern as waste i s p l a c e d above the surrounding ground s u r f a c e and an "above-grade" s i d e s l o p e i s c r e a t e d . The f i n a l cover system i s c o n s t r u c t e d over t h e t o p and s i d e s l o p e s o f t h e f a c i l i t y . When g e o s y n t h e t i c components a r e used i n t h e f i n a l cover system, t h e maximum s l o p e p e r m i t t e d because o f r e l a t i v e l y low f r i c t i o n between g e o t e x t i l e s and HDPE l i n e r i s about 6:1 ( h o r i z o n t a l : v e r t i c a l ) . F i n a l cover systems c o n s t r u c t e d e n t i r e l y o f s o i l a r e u s u a l l y s t a b l e over t h e l o n g term on s l o p e s as steep as 3:1. R e i n f o r c i n g g e o t e x t i l e s can be used t o steepen s i d e s l o p e s and p r o v i d e long-term s t a b i l i t y when g e o s y n t h e t i c components a r e used i n f i n a l cover systems. Q u a l i t y C o n t r o l and Q u a l i t y Assurance The i n s t a l l a t i o n o f any c o n s t r u c t i o n product a c c o r d i n g t o the d e s i g n p l a n s and s p e c i f i c a t i o n s i s always important. However, i t i s extremely c r i t i c a l when g e o s y n t h e t i c s a r e used i n a waste containment a p p l i c a t i o n . Q u a l i t y c o n t r o l and q u a l i t y assurance a r e i n t e g r a l p a r t s o f a l l geosynthetic i n s t a l l a t i o n s .



356

HIGH-TECH FIBROUS MATERIALS

I t i s important t h a t t h e g e o t e x t i l e s used i n t h e c o n s t r u c t i o n o f any s p e c i f i c l a n d f i l l meet t h e d e s i g n s p e c i f i c a t i o n s . A q u a l i t y c o n t r o l program i s needed a t the manufacturing p l a n t t o assure t h e manufacturing process i s not v a r i e d and a c o n s i s t e n t product adhering t o t h e s p e c i f i c a t i o n i s produced. Samples should be taken on a r e g u l a r b a s i s d u r i n g manufacturing ( t y p i c a l l y once every 50,000 sq. f t . ) and t e s t e d t o e v a l u a t e t h e a p p r o p r i a t e g e o t e x t i l e p r o p e r t i e s . The manufacturer i s generally responsible for providing c e r t i f i c a t i o n s that each r o l l o f g e o t e x t i l e conforms t o t h e s p e c i f i c a t i o n . The manufacturer must a l s o m a i n t a i n d e t a i l e d r e c o r d s o f q u a l i t y c o n t r o l documentation. When c o n s i d e r i n g a g e o t e x t i l e manufacturer, o n l y one w i t h a r e c o r d o f c o n s i s t e n t l y producing a q u a l i t y product and a c a r e f u l l y implemented q u a l i t y c o n t r o l program should be c o n s i d e r e d . A f u l l time q u a l i t y assurance m o n i t o r i n g team should be a s s i g n e d t o a l l i n s t a l l a t i o n s o f g e o t e x t i l e s and o t h e r g e o s y n t h e t i c components. A q u a l i f i e d p r o f e s s i o n a l engineer experienced i n g e o s y n t h e t i c s should s u p e r v i s e a l l c o n s t r u c t i o n q u a l i t y assurance programs and c e r t i f y a l l q u a l i t y assurance documents. A p r e - c o n s t r u c t i o n meeting should be h e l d p r i o r t o the s t a r t o f c o n s t r u c t i o n t o review a l l q u a l i t y assurance procedures. The agreement o f a l l p a r t i e s i n v o l v e d should i n c l u d e sampling frequency and q u a n t i t i e s , t e s t i n g procedures, and any s i t e s p e c i f i c problems t h a t may a r i s e . C a r e f u l a t t e n t i o n must be p a i d t o any s p e c i a l i n s t a l l a t i o n requirements, e s p e c i a l l y when combinations o f g e o t e x t i l e s , geomembranes and geonets a r e b e i n g used. G e o t e x t i l e must be checked by f i e l d i n s p e c t i o n personnel t o ensure t h a t o v e r l a p p i n g and seaming procedures a r e as s p e c i f i e d . G e o t e x t i l e s must be maintained i n a c l e a n c o n d i t i o n t o prevent c l o g g i n g o f openings. The p a s t few years have seen an i n c r e a s e d emphasis on t e c h n i c a l advancements i n t h e d e s i g n and c o n s t r u c t i o n o f waste containment f a c i l i t i e s . C o n c u r r e n t l y , t h e need f o r e n v i r o n m e n t a l l y sound l a n d f i l l a i r s p a c e has a c c e l e r a t e d . These two f a c t o r s have r e s u l t e d i n t h e i n c r e a s e d u t i l i z a t i o n o f g e o s y n t h e t i c m a t e r i a l s f o r waste containment a p p l i c a t i o n s . While t h e use o f geomembranes as b a r r i e r l a y e r s i s obvious, g e o t e x t i l e s have a l s o been u t i l i z e d t o s a t i s f y a number o f s i g n i f i c a n t d e s i g n and c o n s t r u c t i o n concerns. The p r i n c i p a l a p p l i c a t i o n s o f g e o t e x t i l e s i n waste d i s p o s a l f a c i l i t i e s a r e as f i l t e r s and c u s h i o n s . They can a l s o serve as drainage l a y e r s e i t h e r on t h e i r own o r i n c o n j u n c t i o n w i t h geonets. F i n a l l y , h i g h - s t r e n g t h g e o t e x t i l e s can p r o v i d e s o i l reinforcement t o allow f o r the c o n s t r u c t i o n of steeper s l o p e s , thereby maximizing t h e a v a i l a b l e a i r s p a c e . T h i s


23. MENOFF ETAL.

The Use of Geotextiles in Waste Containment Faci

paper provides an overview of the design applications and construction considerations for the use of geotextiles in waste containment facilities.


Summary The increased use of geotextiles in waste containment applications improves the environmental integrity of the landfill liner, leachate collection and final cover systems; reduces construction costs; and can provide additional airspace for waste disposal. LITERATURE CITED 1.

Bell, J . Richard Ph.D., P . E . , M. ASCE, "Design and Construction Using Geosynthetics" ASCE Continuing Education, 1989.

2. O'Leary, Philip, "Solid Waste Landfills", Waste Age, 1986. 3.

Lundell, C. M. & Menoff, S. D., "The Design and Construction of Landfill Containment Systems with Geosynthetic Components", presented at Geosynthetic '89, San Diego, 1989.

4.

Lundell, C. M. & Menoff, S. D., "The Use of Geosynthetics as Drainage Media at Solid Waste Landfills", presented at National Solid Waste Management Association, Waste Tech, Boston, 1988.

5.

Richardson, G. N. and Koerner, R. M., "Geosynthetic Design Guidance for Hazardous Waste Landfill Cells and Surface Impoundments", 1988.

6.

Giroud, Jean-Pierre, "Geotextile and Geomembranes Definitions, Properties and Design", Industrial Fabrics Association International, 1984.

RECEIVED July 31,

1990


The Use of Geotextiles in Waste Containment Facilities - American

Recommend Documents