Sliplining and Microtunneling of Large Diameter Pipelines Kimberly H. Paggioli, P.E., Vice President, Marketing and Quality Control Richard C. Turkopp, P.E., Vice President, Engineering HOBAS Pipe USA, 1413 Richey Rd., Houston, TX 77073 (281) 821-2200; (281) 821-7715 (F); kpaggioli@hobaspipe.com Introduction Deteriorating underground pipeline infrastructure is emerging as one of America s next crises. Aging pipes have already begun failing and will require replacement and significant upgrades just to maintain existing service levels. Expanding urban development means that additional pipeline capacity will be required. Major pipeline failures have been well documented in the media: natural gas line ruptures with fatalities in Rancho Cordova, CA in 2008; Plum Borough, Pennsylvania in 2008; Bergenfield, NJ in 2005; Carlsbad, NM in 2000, and a liquid propane line in Carmichael, MS in 2007 to mention just a few. Water and sewer line failures have affected numerous communities throughout the U.S. No area is immune. Major sewer and wastewater line failures have recently been reported in Culver City, CA and Thomasville, NC in 2010, and dozens of others in between over just the past few years. The EPA estimates that 1.2 million miles of underground wastewater pipelines are currently in place throughout the United States. The Freedonia Group and Water News Update reported in June 2011 that, "U.S. demand for water and wastewater pipe is expected to increase 6 percent annually to $19 billion in 2014, equivalent to approximately five billion feet. Stimulants include a rebounding residential building 2011 AREMA
construction sector, the growing obsolescence of sewer and drainage systems, and needs to upgrade municipal water systems. [Water News Update is a publication of the Clean Water Council, a coalition of 37 national organizations chaired by NUCA.] When the original pipelines were installed during the early days of urbanization, sparse development in most areas posed little challenge for contractors open cut trenching to install water and wastewater lines. These pipelines are now often underneath other existing infrastructure, including highways, airports and rail lines. Repairing pipelines located below railroads and within railroad rights of way by open cut methods can be cost prohibitive as well as very disruptive to surface mobility and system operation. Storm and other drainage culverts are some of the most likely candidates for pipelines needing rehabilitation under rail lines due to many factors. There are so many of them, they are sometimes poorly tracked and infrequently inspected, they may have been in service for decades, and the potential for catastrophic failure may be great. Pipelines as an out of sight asset have long been neglected. Often the repair cost of a failed culvert, including down time to associated infrastructure is much more costly than a repair prior to failure. Funds necessary to upgrade the nations infrastructure have only recently begun to enter the market and in limited quantities and with questionable effects. Owners struggle to make the most of their infrastructure investments, and invest in products that offer the lowest life-cycle cost. Disruption to transportation modes, whether it be rail, vehicular or aircraft is costly. Better methods by which these aging utilities can be replaced and rehabilitated need to be utilized routinely. Two options, sliplining rehabilitation of existing lines, and microtunneling (direct jacking) of new pipelines have proven to be very effective means for pipeline maintenance (rehabilitation) and expansion under rail lines. These two techniques will be discussed in this paper. Rehabilitation by Sliplining 2011 AREMA
Sliplining is a renewal method of installing a new, factory-made, structurally designed pipe into the existing host pipe. Sliplining is semi-trenchless and requires only minimal excavation. Generally, access pits are required at liner pipe insertion locations, allowing the above ground work zone to be located as far away from the operational rail lines as the existing pipe allows. Typically, the new factory-made pipe is pushed into place, adding one segment at a time to the train with a system of hydraulic jacks. In some cases, the new pipe liner can be pulled into the host pipe. A major benefit of sliplining is that it can usually be done live while the existing rail line is working and the pipeline is also in operation. Bypass pumping or a diversion for the existing line or culvert is usually not necessary. Examination of Existing Pipe When considering sliplining, it is of vital importance to examine with some kind of survey the exact features of the existing host pipe. The engineer and/or installer must ascertain the diameter of the existing pipe as well as its bends or curves, and assess its condition. Often, it is not the tightness of fit but the offset joints, locations of undersized host pipes and directional changes that create the biggest challenges. In many cases, the existing line is not straight. It could be a monolithically poured curve, have angularly deflected pipe segments, a series of mitered fittings or deflected or mis-shapen pipes. Such surveys can be carried out with video cameras, closed-circuit television and more recently laser profiling methods. Choices of Pipe When evaluating a potential sliplining project, engineers must examine many considerations that will affect the outcome, from the nature and development of the area surrounding the pipe to be repaired to the different properties of various pipe materials. Concerns that affect pipe material choice are structural needs, corrosion considerations, hydraulics, and installation ease. 2011 AREMA
Several different types of pipe materials have been used successfully in sliplining including PVC, HDPE (Solid Wall and Profile wall) and FRPM. For the most part, gasket sealed segmental products are pushed into place, while fused joint products are pulled into place. Material Diameter Joint System Insert PVC 54" Gasket sealed - segmented Push - in HDPE- SW 54" Fused ends - continuous Pull - in HDPE- PW 144" Gasket sealed - segmented Push - in FRPM 120" Gasket sealed - segmented Push - in Sizing A general rule of thumb for relatively straight sections is that the liner pipe OD should be five percent less than the host pipe s ID, with an absolute minimum of one-inch difference on radius between the liner OD and host ID (or a two-inch difference in diameter). 2011 AREMA
For example, a 26-inch nominal diameter pipe with a 28-inch outside diameter could generally be slip lined into a 30-inch host pipe. That difference between 28 and 30 inches is seven percent. The difference on radius should be at least one inch, or two inches in diameter. One of the tightest fits ever recorded for a sliplining project with fiberglass pipe was in Los Angeles, where a 30-inch nominal pipe with 32-inch OD was inserted into a 33-inch clay sewer. That only allowed a ½-inch radial clearance. To add to the complexity of the project, not only was the diameter tight, but the existing joint lengths were quite short, at only 4-foot in length. The fiberglass liner pipe, installed in 10-foot joints, could potentially bridge across three of the existing clay pipe joints simultaneously. Here, the importance of an accurate survey is realized. For assurance, experts recommend pulling a test section of liner pipe or mandrell as proof or fit or liner passage. The proof pipe should be the same length as the segments the engineer is planning to use. For existing non-straight host pipe sections, segmental sliplining often resembles running straight railroad cars (pipe segments) around a curve in the tracks (host pipe). This creates a series of segments and angles rather than a uniform curve. For that reason, it is important to be sure that the joints will seal once the liner has found its final resting position. Navigation of the curve during sliplining is only one aspect to be considered. The designer needs to determine if the curve is uniform in radius. Also, it is important to know the required angle at each joint location. Whatever the existing alignment is, the designer will need to make sure that the liner joint capability is within the limits imposed by the host pipe. For sliplining around true curves, it is often possible to install shorter segments of pipe in the curves so that the joints will deflect slightly and the seals are maintained. Generally, depending on the manufacturer, liners can make one to two-degree bends at each joint and still maintain integrity of the joints. The more accurate the survey of the existing pipe and conditions, the higher the success rate in sliplining. 2011 AREMA
In Los Angeles, for example, on a project for Los Angeles County Sanitation District, the installation contractor pushed 17 pipe segments, each 2.5 feet long, at the beginning of a 3,500-foot run. The entire project included three such curves with a 45-foot radius. In this case, they could gain access to evaluate the curves, but they were not directly accessible for installation so push shafts were located at the end of the straight sections. Shorter segments, the 2.5-foot lengths, were installed first and pushed through the straight sections to end in the curve. The success of this complex installation was largely due to the knowledge of the host pipe size and orientation. In areas where angles are not navigable through pushing pipes and where pit locations are convenient, fiberglass fittings can be manufactured to fit the existing sewer. These custom pieces can be simple elbows or more complex fittings such as branch wyes, crosses and other non-standard configurations. Hydraulic Efficiency Flow capacity is affected by the relative sizes of pipes and their respective hydraulic characteristics. In many cases, especially for large diameter pipes, the capacity can be maintained or improved even with a reduction in diameter. The roughness of a pipe wall is expressed as an n value that is utilized in Manning s formula to predict flow. The Manning value of many plastic and fiberglass pipes is between 0.009 and 0.011. By contrast, the value for new concrete is somewhat rougher, at 0.013. Old concrete can range from 0.018 to 0.020 or even worse, depending on the level of deterioration. Wall "t" Typ. Dia. Material vs. Dia. Reduction Flow Change FRPM 2% - 3% 10% > PVC 3% - 4% 12% > HDPE - SW 4% - 5% 14% = 2011 AREMA
HDPE - PW 6% - 8% 19% < One can calculate the reduction in diameter that is possible with the liner pipe in order to maintain flow. By manipulating Manning s formula as a function of flow, the designer can determine the ratio of the liner flow (Q1) to the host flow (Q2). If the ratio of the liner flow to the host flow is 90 percent, for example, the liner has resulted in a 10 percent reduction in flow. But if the ratio of Q1 over Q2 is greater than one, flow has improved. Q = (1.49/n) A R 2/3 S 1/2 Reducing Two Simultaneous Equations on the Same Slope Q 1 / Q 2 = (n 2 /n 1 ) * (D 1 /D 2 ) 8/3 Where Q1 is the liner and Q2 is the host. Depending on the existing pipe diameter and the liner pipe chosen, a step down in liner size is typically four to 12 inches less than the host pipe. This depends on the strength of the liner pipe, its thickness and the resulting OD and ID. A liner with a Manning s value of 0.009 can be 13 percent smaller than the host with a Manning s of 0.013 and maintain equal flow. The more efficient the cross-section of pipe, the greater is the potential for flow recovery or even increase capacity. Installation Questions Many factors affect the distances that are possible to push the liner pipe. Aside from the obvious alignment issues, the presence of flow in the line, host condition, and the distance to be relined are considerations. Displaced flow will lift up the liner, and the flow in the liner plus the pipe weight will press it downward. Buoyancy considerations include the flow depth in the host, the liner pipe weight and the ability to control the depth in the liner pipe by means such as a nose cone or weir on the push ring that 2011 AREMA
affects the flow depth in the liner during insertion. The more neutrally buoyant is the liner, the less friction encountered. The distance that the liner may be pushed is also a function of equipment. Relining short sections, for example culvert spans of 100 feet in length, would generally require simple equipment, vs. a large diameter half mile long storm sewer outfall. Hydraulic jacking systems are probably the most commonly used equipment for lengthy sliplining projects. But simple winch systems and even ordinary construction equipment can be used as well, usually for shorter runs. The force that it takes to install the liner is dependent upon the friction. The maximum load that may be placed on the liner pipe and its weight are specifications that are available from the pipe manufacturer. With this information, and an appropriate factor of safety (3.0 is common), the safe push distance can be calculated. Friction factors are installation-specific but are commonly in the 0.3-0.5 range. For example, with 164 tons of force, a contractor can jack 48-inch pipe 5,800 feet with a friction factor of 0.4 in the host. That pipe weighs 141 pounds per foot. In one project for the Los Angeles County Sanitation District, 51-inch and 57-inch fiberglass liner pipes were sliplined into 57-inch and 63-inch reinforced concrete pipes, respectively. Maximum pushing force was about 100 tons on all drives, including curves, angles and offsets. The average friction factor was 0.3 and the longest single push in one direction was 5,600 feet. In short, sliplining can provide leak-free service, eliminate corrosion deterioration and restore structural integrity to old pipes. When properly designed and evaluated, a liner can be installed safely with a minimal amount of downsizing, and capacity can be maintained or even improved. Additionally, the potential for pushing thousands of feet means that surface disruption is minimized, too. 2011 AREMA
Alternatively, in sewers where bypass pumping is possible and the sewer alignment prevents sliplining in the traditional way, segments of pipes and fittings can be carried into the sewer and installed much like traditional tunnel carrier pipes. Microtunneling Installation of new pipes may also be accomplished via a trenchless method such as direct jacking, also known as microtunneling. Microtunneling a method of installing a new, factory made, structurally designed pipe in a trenchless technique by pushing the pipe through the soil. Choices of Pipe Selection of a proper pipe is critical to the success of any installation, but even more so for jacking. Good jacking pipes have many common characteristics and the most successful possess most or all of the key attributes. Jacking pipes must possess high axial load capacity to withstand the frequently very large thrust forces applied during installation. Of near equal importance are small, consistent dimensional tolerances related to OD, roundness and straightness control in order to minimize increasing the jacking thrust loads unnecessarily. Of further benefit is a resilient pipe wall material that aids in distributing uneven thrust loads around the pipe circumference. All jacking pipes must have a reliable, leak-free joining system (preferably gasket-sealed for quick assembly) to resist annulus lubrication injection, potentially high ground water pressures, contact grouting (when used) and system service conditions. Finally, since some pipe damage during jacking is inevitable, a pipe that is permanently repairable in-place is at least an economic windfall, if not an absolute necessity for project success. Jacking Pipe Characteristics 2011 AREMA
Several different types of materials are used including RCP, Polymer Concrete Pipe and Centrifugally Cast Fiberglass. Generally accepted criteria for quality jacking pipes, includes a circular shape with a flush surface (including the joint area), strength sufficient to withstand both installation and in-place loading, durability (abrasion and corrosion resistance) and water-tight joints. In addition to the other external factors that affect jacking loads, which will be discussed later, dimensional consistency of the jacking pipes can affect jacking performance. The table below provides general ranges of products as well as desirable limits. Tolerances outside the limits may require a higher jacking load safety factor. From the ASCE Standard, Construction Guidelines for Microtunneling The dimensional tolerances for fiberglass jacking pipe can achieve: - OD... +/- 0.05% of diameter - Straightness... maximum 0.06 deviation / 10 length 2011 AREMA
- Roundness... +/- 0.10% of diameter - End squareness... +/- 0.06 - Length... +/- 0.25 s Meaning of Tonnage Rating The stated tonnage rating (allowable jacking thrust) is the ultimate axial load capacity divided by the chosen safety factor. The load capacity is determined in a compressive test by applying a uniform, square load to the entire pipe end. The test is designed to determine the true material strength including any influence from the joint ends which may have a reduced cross-section and contain groove(s) for the sealing gaskets. The tonnage rating is NOT a guarantee of field performance due to the non-uniform loading and / or reduced end-to-end contact that may be experienced during actual jacking operations. Factors Affecting Actual Jacking Loads: The combined effects of many factors determine the magnitude of the actual jacking loads experienced during a drive. Generally, the factors may be divided into two groups: (1) Conditions and Operations and (2) Pipe Characteristics. Conditions and Operations Factors - Drive distance - Soil type(s) - Annulus overcut - Annulus lubrication - Ground water - Alignment and grade control - Machine advance rate In general, a longer drive results in higher jacking loads; collapsing gripping native soils (typically granular) generate higher loads; smaller overcut (annulus) produces higher 2011 AREMA
loads; less annulus lubrication creates higher loads; a faster machine advance rate causes higher loads, and quicker, more frequent direction (grade and / or alignment) changes means higher loads. Pipe Characteristics Factors - OD control - Roundness control - Straightness control - End squareness control - Weight - Exterior surface smoothness Generally, larger dimensional tolerances create higher jacking loads; greater weight produces higher loads, and a rougher exterior surface results in higher loads. Summary By taking a proactive role in pipeline management, which includes sewers and culverts, the investment in infrastructure can be better persevered and will lead to a safer more cost effective operation. Both sliplining rehabilitation of existing lines, and microtunneling (direct jacking) of new pipelines are cost effective, performance proven, semi-trenchless methods of installing new factory-made pipeline below railroads and within railroad rights-of-way. 2011 AREMA
Kimberly Paggioli, P.E. VP, Quality Control & Marketing HOBAS Pipe USA
Overview Sliplining Basic Procedure & Design Considerations for Fiberglass Pipe Overview Jacking / Microtunneling Basic Procedure & Design Considerations for Fiberglass Pipe Summary / Q & A 2
Materials Glass fibers, thermosetting resin and aggregates Diameters 12-inch to over 120-inch diameter
Flexible Pipe AWWA Design Basis M45 ASTM D3262 Covers fiberglass gravity applications 8 156. Originally Approved in 1973
Semi Trenchless Method limited excavation 5
New, Factory Made Pipe Within an Old Pipe 6
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Existing Pipe Preparation Verify Actual Host Pipe Diameter Assess Existing Pipe Condition (video) Excavate Access Shaft(s) Open Host Line Remove Debris & Obstructions (clean) Perform Point Repairs (if needed) Mandrel Proof 8
Lining Process Insert Liner Pipe Confirm Successful Insertion (video) Reinstate Any Laterals Grout Annulus Final Acceptance (video) 9
Liner Corrosion Protection Leak Prevention Hydraulics Structural Reinforcement Installation 10
Segmented Systems (gasket sealed) Live Insertion Small Access Shafts Fast Assembly Quick Insertion 11
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26 CCFRPM (28 OD) into 30 (7%) Diameter Differences Generally a 5% Decrease in Diameter is Successful Minimum of About 1 on R 13
NC DOT Existing pipe Leaking joints Corrosion from saltwater exposure 30-inch diameter sliplined with 28- inch fiberglass pipe 14
Determining if the Pipes Will Pass Through PI s, Curves, Offsets Accurate Survey Pipe Dimensions (Raised or Flush Bell) Simply Geometry Mandrel Proof Determining if Pipes Will Seal if They Pass Worst Case if Liner Pipe Joints Occur at Host PI s 15
Pipes & Fittings Carried In 16
McAllen, TX Deteriorating line Off set joints PI s Leaks 72-inch concrete pipe sliplined with 63-inch fiberglass pipe 17
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Function of Diameters & Pipe Hydraulic Characteristics Even With a Diameter Reduction, Typically Improved Flow Capacity 19
Q = (1.49/n) A R 2/3 S 1/2 Reducing Two Simultaneous Equations on the Same Slope Q 1 / Q 2 = (n 2 /n 1 ) * (D 1 /D 2 ) 8/3 20
4 12 Inch Typical Step Down Depends On Wall t and Clearance Liner Host Manning's n Diameter for equal flow 0.009 13% Reduction vs. 0.013 0.011 13% Reduction vs. 0.016 17% Reduction vs. 0.018 21
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Buoyancy Flow Depth Control & Effects Equipment Friction Pipe Weight 24
Primary casing with liner Twin storm sewer lines Newark, NJ 42-inch fiberglass liner, 48-inch concrete and 60-inch casing
Trenchless Method of New Pipe Installation 26
One Pass Installation of New Pipe Or Two Pass System 27
Geotechnical Investigation Soil Types Groundwater Location Method Determination Auger Microtunnel Slurry Microtunnel Traditional (Muck Car) 28
Shaft Requirements Locations & Quantity Type & Dimensions
Loads Distances Pit Locations Reliability of Method Predicted vs. Actual Inspection After Installation Pipe and Joints Ground Monitoring 30
Ground Conditions: Types of Soil, uniform / consistent Size, Type and Dimensions of Material Installed
Distance Jacked Construction: Steering, Overcut & Lubrication
Pipe Capacity Based on Materials Compressive Strength w/ FS Based on Straight Uniform Loads
Predicted Load Decreased by Intermediate Jacks 34
Segmental Sliplining Restore Structural Integrity Leak Free Limited Surface Disruption Limited Environmental Impact Jacking & Microtunneling High Strength Composite with Low Jacking Loads Non Metallic Construction Resilient & Reliable Material
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