Experimental Evaluation of Soil-Pipe Friction Coefficients for Coated Steel Pipes

Abstract

Significant thrust forces can be generated on a pressurized pipeline wall or fitting due to internal pressure, momentum forces, surge forces, and/or thermal changes. The produced thrust force can lead to longitudinal movement of a pipeline and its connections. Soil frictional resistance, which is a function of the pipe's surface area and coating material, depth of cover, and soil characteristics, plays a key role in restraining such axial movements. Thus, soil frictional resistance is an important factor in designing restrained buried pipes that operate under internal pressure. When soil conditions are stable, considerable economies could be realized by utilizing the embedment soil to restrain the pipe. A series of controlled laboratory tests were performed, aimed at establishing friction coefficient values for combinations of selected soil types and three external coating systems, namely, Cement mortar, per AWWA C205; Polyurethane, per AWWA C222; and Prefabricated Polyethylene tape, per AWWA C214 (used in conjunction with steel pipes). The work was performed using the Trenchless Technology Center's (TTC) soil chamber testing apparatus (6 ft wide × 12 ft long and 5 ft deep), which is equipped with an air bladder and a stiff steel lid capable of applying a uniformly distributed load of up to 18 psi on the soil surface. The internal diameters of the pipes were 14" for the specimens coated with polyurethane and prefabplastic tape and 12" for the specimen coated with cement mortar lining. This was done to obtain a comparable external surface area for the pipe specimens. The pipes were pulled through the soil using a horizontally mounted 150,000 lb servo-controlled hydraulic actuator. The embedment materials were compacted to the level of the crown of the pipe, for conservatism. Earth pressure cells placed in the vicinity of the pipe registered stress changes in the soil medium due to longitudinal movement of pipe. All embedment materials underwent an array of laboratory soil characterization tests to establish key characterization parameters. Test results were compared with predictions provided by appropriate clauses in the current version of the AWWA M11 design manual for steel pipe design.

Axial friction response of full-scale pipes in soft clays

“…The results in Fig. 16 show that the friction coefficient decreases with the increase of the normalized buried depth, which is consistent with the finding of Alam et al [15].…”

“…In attempting to obtain the friction coefficient of pipelines, theoretical and experimental researches are available. Many researches focused on the interaction of pipe with cohesionless soil over the past several decades [2,[10][11][12][13][14][15]. Only a minority of scholars studied the pipe-clay interaction using model tests.…”

A low-cost simple lysimeter soil retriever design for retrieving soil from small lysimeters

“…It is attributed to the sliced bottom face of the topsoil block, where it was flatter for high-moisture soil and crooked for low-moisture soil. The high variation in subsoil was associated with the soil losses during retrieval; larger for low moisture and smaller for high moisture soil (Alam et al 2013). The findings suggested that the lifting and slicing mechanism was effectively operated without adversely affecting the shape and height of the soil blocks.…”

“…This study considered a cutting method which is slicing the soil using a cutting blade. The selection of cutting force and mechanism depends on the characteristics of the root system of the plant, soil type, soil moisture level and foreign materials in the soil such as gravel or stones (Alam et al 2013, Jain 2013. The reconstructed soil column used in this study was free of foreign materials like stones and pebbles, easy to slice without deformation for the soil block shape when the soil moisture is high.…”

Large-scale experimental evaluation of soil saturation effect on behaviour of buried pipes under operational loads

“…Jung et al (2013) studied the buried pipe response under lateral loads in dry and unsaturated soils using FE modelling and large-scale tests. They found that the lateral loads on pipes in unsaturated conditions were significantly different from Alam et al (2013) Study soil-pipe friction coefficient for different soil types and moisture contents Anderson et al (2005) Evaluate soil-pipe interaction in polyethylene pipelines Shmulevich et al (1986) Study soil stress distribution around buried pipes Tokyo Gas, PERL laboratory experiments (Robert 2010) Study lateral soil load on pipe with different saturations Note: PERL, Pipeline Engineering Research Laboratory.…”