M.S.C.E., E.I.T, Staff geotechnical engineer at URS Corp.

Transcription

1 TWO DIMENSIONAL MODEL STUDY ON INFILTRATION CONTROL AT A LATERAL PIPE JOINT USING ACRYLAMIDE GROUT H. Gukan Ozguel 1, H. A. González 2 and C. Vipulanandan 3, Membe, ASCE ABSTRACT One of te callenges faced in maintaining te aging sewe systems is te infiltation, wic is caused by te deteioation of te sewe systems. In tis study, A table top lateal joint model was used to investigate gout movement toug soil, wen sealing sewe pipe leaks at lateal joints by gouting. Acylamide cemical gout was injected toug a leaking lateal joint into a coase sand (d 10 =0.5 mm), using 3 psi (21 kpa).te volume of infiltation was measued befoe and afte gouting to detemine te effectiveness of gouting. Te volume infiltation was measued at 1 min, 1 and 24 s. afte gouting using an extenal wate pessue up to 3 psi (21kPa). At te end of te test, te sape of te gout bulb aound te joint was mapped. A matematical model was developed to detemine te sape of te gouted egion aound te lateal joint, and veified wit te expeimental data. Te amount of gout used to contol te leak aound te joint was compaed to te ecommendation of ASTM F 2304 INTRODUCTION Infiltation is caused by ain wate and/o goundwate tat ente toug te defects in te sewe systems. Infiltation educes te effective capacity of a sewe system by adding exta flow and by depositioning fine paticles inside te systems. Numbe of factos suc as oot penetation, gound movement, joint displacement, constuction flaws, and unsealed connections lead to infiltation [CIRIA, 1997]. Infiltation inceases te cost of teating wastewate, adds to te flooding poblems and sanitay sewe oveflows (SSO). 1 M.S.C.E., E.I.T, Staff geotecnical enginee at URS Cop. gukan_ozguel@uscop.com 2 M.S.C.E. Student, Dept. of Civil and Envionmental Engng. Univ. of Houston, Houston, Tx, Gad. Asstnt Cnt fo Innovative Gouting Mat. And Tecnol. (CIGMAT) 3 Caiman, Pof. Dept. of Civil. and Envion. Engng., Univ. of Houston, Houston, Tx, and Di. of Cnt fo Innovative Gouting Mat. and Tecnol. (CIGMAT), , (pone # (713) ; Fax (713) cvipulanandan@u.edu) 1

2 Today te fedeal egulations on te waste wate systems ae moe stingent. USEPA, in conjunction wit municipal and ote industy epesentatives, ave developed a famewok fo a dynamic management appoac fo collection systems called te capacity, management, opeation, and maintenance (CMOM) appoac. Te CMOM appoac is an infomation based appoac to set pioities fo activities and investments (Gatuan, 2003). EPA (Sept., 2002) egulated tat seweage system utilities expeiencing SSOs o oveflow violations at wastewate teatment plants sould begin implementing te CMOM as soon as possible. Futemoe, te EPA (1970) ecommended infiltation limits at a ate not to exceed 200 gal/in.diam/mi/day (185.2 cm.diam/km/day). Cemical gouting is among te most common metods to educe te infiltation at sewe pipe joints. Lateal joints ae pipeline connections tat banc off te main sewe and connect building sewes to te public sewe main. Tese connections ente mainlines at angles anging fom 30 to 90 degees to te axial flow diection of te main lines. Te standad ASTM F Standad Pactice fo Reabilitation of Sewes Using Cemical Gouting descibes te pocedues fo testing and sealing individual sewe pipe joints wit appopiate cemical gouts using te packe metod [ASTM F 2304, 2003]. Among te gouting mateials, acylamide and acylic based gel gouts ave low initial viscosity, and quick and contollable setting time, and tey ae used fo suc leak contol applications [Kaol, 1990]. Accoding to ASTM F 2304 (2003) no joint sall be consideed sealed unless, a minimum of ¼ gal/in. of pipe diamete of gout is pumped unde pessue. Cemical gout sall be pumped to efusal wit a volume not to exceed ½-gal/in. diamete. Te point of efusal is a point at wic, duing injection, gout flows toug te joint failue into te suounding soil and as gelled. At tis point, te injection pessue apidly spikes an additional 8 (55kPa) to 12 psi (83 kpa) above te pio pessue in a sot peiod of 1 to 5 seconds [ASTM F 2304, 2003]. OBJECTIVES Te objectives of tis study wee (1) to investigate te gout movement toug te unsatuated ganula media suounding te pipe joint using a 2D model; (2) to veify te pefomance of acylamide gout in contolling leaks at te lateal joints; and (3) Develop a matematical model to epesent te gouted sand bulb aound te joint MATERIALS AND TESTING Sand Commecially available sand was used fo tis study. Te sand ad d 10, and d 50 of 0.5 mm 0.95 mm, espectively. Fo tis sand te coefficient of unifomity and gadation wee 2.17 and 0.9, espectively. Gout A commecially available AV-118 Duiflex N-metylolacylamide (NMA) gout (Avanti Gout Intenational, Webste Texas) was used in tis study. 2

3 Two-Dimensional (2D) Lateal Model A two-dimensional (2D) model was designed to investigate te gout movement aound a lateal pipe joint duing gout injection. It was a cambe wit intenal dimensions of 12 in (310mm) ig, 24 in (620mm) long, and 2 in (50mm) wide (Fig. 1). It was made wit plexiglass, and was eld togete wit stainless steel ods. Rubbe gaskets and Teflon tape wee used to ensue watetigtness. A ole was opened at te cente of te bottom plate allowing a vetical connection of 2 in (50mm) diamete pipe extending into te cambe tat epesented a 2 in. diamete lateal joint. Te opening aea between te pipe and bottom plate was 1.38 in 2 (8.9 cm 2 ). Once te cambe was filled wit sand two metallic plates wee placed ove it to simulate insitu conditions. Te desied soil density was easily acieved by pouing te sand tamping it in 4 layes. Afte tat, wate was injected into te cambe using vaious injection pessues and te infiltation at te pipe joint wee measued using test tubes. An infiltation test using te 2D model is sown in Fig. 1. Infiltation was measued befoe and afte gouting at vaious wate pessues tat wee gadually inceased fom 2 psi (14 kpa) to 4 psi (28 kpa). Te gout was injected fom te bottom at a 3 psi (21 kpa) pessue toug te leaking joint. Te movement of te gout duing injection was ecoded up to 5 sec. using a Sony-Mavica video camea. Te Gout movement was investigated using tis video at 0.25 sec incements. Clamps wee used to pevent te bending of watetigt cambe body. Te injection setup fo te 2D model is sown in te Fig. 2. TEST RESULTS AND DISCUSSION (a) Infiltation Study Te cambe was filled wit 450 ci (7500 cc)of sand. Te sand s unit weigt was 90.5pcf (14.2 kn/m 3 ). Te pemeability of te sand was 1.5 x 10-3 in/sec(4 x 10-3 cm/sec). Infiltation at te leaking joint in te 2D model inceased almost linealy wit inceasing wate pessue. Te infiltation was 540 gpd/in. diamete and 1440 gpd/in.diamete at 2 psi (14 kpa) and 4 psi (28 kpa) wate pessues espectively. Infiltation values vesus applied pessue ae sown in te Fig. 3. infiltations wee above limit of 200 gpd/in.diam of pipe set by EPA (1977). (b) Exfiltation Study (i) Ungouted Joint Wate was injected into te cambe using 3 psi (21 kpa), 5 psi (30 kpa), 7 psi (117 kpa), and 10 psi (690 kpa) pessuesat te leaking joint and te wate movement was ecoded. Te obsevations sowed tat te movement of wate font toug te unsatuated soil suounding te pipe joint was ellipsoid like as sown in Fig. 4. 3

4 2 pipe Cambe filled wit sand Infiltation Flow Figue 1. Te 2D Model Duing Infiltation Testing Pessue Gauge Scews to Apply Vetical Pessue Gout Cambe Lateeal Cambe Clamps to pevent bending Ai Pessue Line Figue 2. 2D Lateal Model Gout Injection Setup 4

5 Te movement of wate in te semi-mino () and semi-majo () axes inceased wit injection time and injection pessue. Te effect of injection pessue and injection time on te movement of wate in te semi-mino () and semi-majo () diections ae sown in Fig. 5. and Fig. 6. espectively. Te aveage atio of semi-mino to semi-majo axis was (/) 0.6 and emained constant wit vaying injection pessue and time. Te vaiation of / atio wit vaious injection pessues is sown in Fig. 7. Te movement of acylamide gout inside te cambe wen injected at 3 psi is sown in Fig. 8. Te / atio fo te gout anged fom 0.55 to 0.65 (ii) Gouted Joint Using 3 psi (21 kpa) injection pessue, a total of 0.14gal (500 cm 3 ) of acylamide gout was injected into te cambe wit a flow ate of 14 cm 3 /sec (0.86 in 3 /sec). Te sape of te gouted sand aound te lateal joint is sown in Fig. 9. At te end of gouting te gout movement on te semi-majo () and semi-mino () axes wee 6.25 in (15.9 cm) and 3.5 in (8.9 cm) espectively (/ = 0.56). Even toug tee was a sligt diffeence on te sape of te gouted sand on te igt and left side of te cambe, measued and values wee same. Te Infiltation flow was measued afte gouting using up to 6 psi (42 kpa) wate pessue, but te joint was totally sealed, and te infiltation flow was zeo. Te ASTM F 2304 ecommends injecting a gout volume of 1 / 4 gal pe in of pipe diamete, tat would ave esulted in pumping 0.5 gal of gout (1.9 L) fo te joint wit a cicumfeence of 2π in. In tis study, oweve, te model tickness was 4 in (bot sides). Hence, following te ASTM ecommendation 0.3gal (1.2 L) gout ad to be injected to contol te leak. Despite of tat, te volume actually gouted was 0.14gal o 42 % of wat was ecommended by te ASTM Te fact tat less gout volume was equied to seal te leak could be patly due to te contolled and confined natue of te 2D model used in tis study. Matematical Model Stating fom te point tat te sape of gouted sand bulb in te 2D lateal joint can be idealized as sown in Fig. 10. Based on te acylamide gout movement findings, te volume of injected gout based on void atio of soil and te sape of gouted sand bulb can be epesented as follows (Somasundaam, 2003). V G 2 1 k = 3 ( R ) 2 R 0 0 α πχ d 1+ e GS e. (1) 5

6 1600 Discage, Q (gpd/in. diam pipe) EPA's Limit 200 gpd/in.diam pipe Infiltaion Afte Gouting Wate Pessue, p (psi) Figue 3. Infiltation Flow Befoe and Afte Gouting (145 psi = 1 MPa) t: injection time t 1 t2 t 3 : Semi-majo Axis : Semi-mino Axis Figue 4. Te Ellipsoid Sape of Wate Movement in te 2D Model 6

7 P=3 psi p=7 psi p=10 psi R 0 pipe =1in 10 psi 7 psi 3 psi /Ro Injection Time, t (sec.) Figue 5. Te Effect of Injection Pessue and Injection Time on te Movement of Wate in te Semi-Mino () Diection (2D Model) (145 psi =1 MPa) P=3 psi p=7 psi p=10 psi R 0 pipe =1in 10 psi 7 psi 3 psi /R Injection Time, t (sec.) Figue 6. Te Effect of Injection Pessue and Injection Time on te Movement of Wate in te Semi-Majo () Diection (2D Model) (145 psi = 1 MPa). 7

8 Wee V G is te volume of injected gout, R 0 is te adius of te lateal pipe, k te semi-majo axis to te adius of te lateal pipe (/R 0 ), χ= semi-majo to semimino axis atio ( /), d GS =2 in. (wit of cambe) fo te 2D Lateal model, and te paamete α is te dilution facto wic was defined as follows: G V + V w α = G V (2) Wee V w is te volume of additional wate tat mixes wit te gout. Te 2D model pediction Eqn.1 on te gout volume fo vaious void atios and dilution factos and te actual injected volume ae sown in Fig. 11 and Fig. 12. Te volume of injected gout wic foms te gouted sand bulb influenced by sand s void atio, adius and eigt of te gouted sand bulb, and dilution facto (α). In te 2D model using 3 psi (21 kpa) injection pessue, 500 cm 3 (30 in 3 ) gout injection into sand wit void atio of 0.65 esulted in a gouted sand bulb wit χ = 0.56, and k= Assuming α=1, te volume of injected gout was calculated as 480 cm 3 (29.3 in 3 ) using te equation 1, and ence tis elationsip can be used in designing te extent of gouted sand bulb aound te pipe joint. CONCLUSIONS A 2D lateal joint model was used to investigate te pefomance of acylamide cemical gout in lateal pipe joint to contol leak. Te following conclusions ae advanced based on te pysical and matematical model studies: (1) Using te 2D model te gout movement in te sand suounding te lateal pipe joint was veified and modeled. Te expeiments sowed tat te movement of acylamide gout in te sand suounding te lateal pipe wen injected 3 psi (21 kpa), was ellipsoid saped wit / atio of 0.6. Tis atio did not vay significantly wen injection pessue was vaied fom 3 psi (21 kpa) to 10 psi (690 kpa). (2) Based in limited laboatoy tests, te 2D model can be used to veify te effectiveness of gout in contolling leak at lateal joints. Te acylamide gout used in tis study educed te infiltation to zeo. (3) Only 42% of te volume suggested by te ASTM standad was injected in tis study to educe te infiltation to zeo. Less gout was needed to eliminate te infiltation because of te two-dimensional (2D) and confined natue of te poblem. (4) Te matematical model was veified wit limited data to pedict te gout volume based on te gouted sand configuation aound te joint. 8

9 I=3 psi I=5 psi I=7 psi I=10 psi / Ratio 0.75 σ:standad Deviation Aveage= σ=0.06 σ=0.04 σ=0.09 σ= Injection Pessue, I (psi) Figue 7. Vaiation of / Ratios at Vaious Injection Pessues 1 3 Gouted sand font Gouted sand font 2 Gouted sand font 4 Figue 8. Acylamide Gout Movement in te 2D Model (Injection Pessue= 3 psi (21 kpa)) 9

10 Gouted sand bulbs 3.5 in. 3.5 in. 3.5 in in in. Figue 9. Gouted Sand Aound te Lateal Joint 2Ro. Cente of Gavity A GS Figue 10. Gouted Sand Aound te 2D Lateal Joint R 0 =1 in 2 in 10

11 Volume of Gout (V G /R0 3 ) Ro α =1, No Dilution χ=0.56 =χ k=/r 0 e=0.7 e=0.6 e=0.5 e=0.5 e=0.6 e=0.7 Actual Measued Figue 11. Effect of Void Ratio on te Pedicted Gout Volume Volume of Gout (V G /R0 3 ) Ro Void Ratio, (e)=0.65 χ=0.56 =χ α=1 α=1.5 α=2 α=1 α=1.5 α=2 Actual Measued k=/r 0 Figue 12. Effect of Dilution Facto on te Pedicted Gout Volume 11

12 ACKNOWLEDGEMENTS Tis wok was suppoted by te Cente fo Innovative Gouting Mateials and Tecnology (CIGMAT) wit funds fom NSF-Intenational and pivate companies. REFERENCES ASTM (2003) ASTM F Standad pactice fo eabilitation of sewes using cemical gouting, ASTM standad: 1-8. CIRIA (1997) Contol of Infiltation to Sewes, Constuction Industy Reseac and Infomation Association, Repot No. 175,. EPA (1970) Contol of Infiltation and Inflow into Sewe Systems, Repot #11022EFF12/70, Wasington, D.C. EPA (1977) Sewe System Evaluation, eabilitation, and New Constuction: A manual of Pactice, Repot # EPA600/277017d, Wasington, D.C. EPA (2002) EMS Integation Poject Final Repot wit WAF, Septembe, Wasington, D.C. ttp:// Gatuam, P. (2003) Population Based Model to detemine Life Cycle Cost of a Wastewate System, M.S.C.E. Tesis, Depatment of Civil and Envion. Engng, Univesity of Houston, Houston, Texas. Kaol, R.H. (1990) Cemical Gouting, 2 nd ed., Macel Dekkee, Inc., New Yok, NY. Somasundaam, S. (2003) Beavio of Flexible and Rigid Polyuetane Gouts Used fo Contolling Wate Leaks, M.S.C.E. Tesis, Depatment of Civil and Envion. Engng, Univesity of Houston, Houston, Texas. 12