Teruhisa Masada

Soil Pressure Measured at Various Fill Heights Above Deeply Buried Thermoplastic Pipe

When a flexible pipe is installed in a dense soil fill, stress redistribution takes place around the pipe because of pipe-soil interaction. The degree of this interaction is considered to be influenced by the stiffness ratio between the pipe and its surrounding soil. Classical theory based on elastic solutions shows that in an ideal installation condition, the zone of the pipe-soil interaction may be confined to one to two pipe diameters from the pipe. In 1999 a research team from the Ohio Research Institute for Transportation and Environment installed a total of 18 instrumented thermoplastic pipes at the deep pipe burial project site in Albany, Ohio. These pipes were placed under either a 6.1-m or 12.2-m (20-ft or 40-ft) embankment fill. During the pipe backfilling and subsequent embankment fill placement, soil pressure cells were placed at different fill heights above selected test pipes to measure the vertical extent of the pipe-soil interaction zone. The field-measured vertical soil pressure compared well with the predictions made by the elastic solutions. Summarized here are the information and data related to the vertical soil pressure measurements made in the Ohio University field study.

Soil arching over deeply buried thermoplastic pipe

Soil arching associated with buried thermoplastic pipe is discussed. First, the soil arching phenomenon is described. Then two different approaches are mentioned from the literature to represent the degree of soil arching (or vertical arching factor). The elastic solutions of Burns and Richard are revisited to derive expressions for the vertical soil arching factor for buried pipe. Comparison of the elastic solutions and field soil pressure cell readings reveals the importance of incorporating a bending stiffness parameter. With this finding, the AASHTO method for calculating the load on buried pipe is evaluated against the elastic solutions. The analysis reveals that the AASHTO method is conservative, overestimating the load on thermoplastic pipe by up to 30%. Further evidence to support the finding is found within the strain gauge readings taken on the pipe walls in the field. Therefore, alternative equations derived directly from the elastic solutions are recommended to predict the load on buried thermoplastic pipe instead of the AASHTO method.

Profile-Wall High-Density Polyethylene Pipes 1050 mm in Diameter Under Deep Soil Cover: Comparisons of Field Performance Data and Analytical Predictions

Although the study of pipe–soil interaction has more than 80 years of history, a lack of long-term field performance data still exists when it comes to the structural performance of large-diameter, profile–wall thermoplastic pipes under deep soil cover. Field-monitored structural performance data were taken for 1050-mm (42-in.) diameter, corrugated high-density polyethylene (HDPE) pipes, which were subjected to 6.1-m (20-ft) and 12.2-m (40-ft) soil fill heights at the ORITE deep burial test site at the Ohio Research Institute for Transportation and the Environment. The field data accumulated over about 2 years indicate that these HDPE pipes are performing satisfactorily. None of the pipes deflected more than −2.5% vertically and 1% horizontally. Closer examinations of the field data obtained at the end of construction and a few months afterward provided insights into the HDPE pipe performance under deep soil cover. Among the analytical methods evaluated in light of the field data, the elastic solutions established by Burns and Richard were most promising in predicting the field performance of the HDPE pipes under deep soil fill.

New Inspection and Risk Assessment Methods for Metal Highway Culverts in Ohio

This paper first describes Ohios new statewide culvert management program, which aimed to reduce the risk of structural failure of culverts that serve major highways. The paper next describes a research project conducted by the Ohio Research Institute for Transportation and the Environment (ORITE) research team at Ohio University to validate the effectiveness of the approaches outlined in the new program. The new culvert program is supported by high-resolution field inspection and rating procedures for concrete, metal, and thermoplastic culverts. This paper focuses on the metal culvert components of the research project. The new field inspection procedure for metal culverts was applied at 25 sites to detect problems common to many metal culvert sites in Ohio. The data produced during the field inspection phase were analyzed statistically to evaluate the effectiveness of the new procedure and to verify the findings made by the previous study about the conditions of the metal culverts that serve Ohios maj...

THERMOPLASTIC PIPE DEEP-BURIAL PROJECT IN OHIO: INITIAL FINDINGS

The paper reviews a project that: monitored the pressure distribution around the perimeter of the thermoplastic pipes subjected to deep burial; detected vertical extent of the soil-pipe interaction zone through readings of pressure calls placed at various heights above the test pipes; monitored the deflection profile around the pipe perimeter and circumferential shortening of the pipes subjected to deep burial; monitored the pipe responses as a function of time; and evaluated reliability of empirical, theoretical, and numerical methods developed for the analysis and design of buried pipe in light of the latest field performance data.

Modified direct shear study of clay liner-geomembrane interfaces exposed to landfill leachate

Abstract Direct shear tests have been utilized to quantify interface friction existing within the multi-layer solid waste landfill system. In this study, modified direct shear tests were performed for interfaces between compacted clay and three types of geomembrane materials (smooth HDPE, textured HDPE, and smooth PVC). Tests included clay samples saturated with leachate to simulate possible in-situ conditions in the landfill. Also, some geomembranes were submerged in leachate for up to 30 days prior to testing to simulate aging effect. Prolonged exposure of the geomembranes to the landfill leachate reduced the interface friction angle. The clay liner-PVC geomembrane interface was more susceptible to the leachate effect.

Effect of Rib Spacing on Deformation of Profile-Wall Plastic Pipes Buried in Coarse Granular Backfill

Several different types of plastic pipe products were instrumented, buried in coarse granular backfill, and subjected to monotonic, distributed load in the field. During each field test, data were recorded from strain gages, linear variable differential transformers, and earth pressure cells by computerized data acquisition units. Review of the deflection data from 14 tests revealed a pattern on the initial deflection that can be explained by considering a dimensional ratio between the rib spacing, S, and maximum particle size, d max . Earth pressure cell readings taken in the springline region appeared to support this. Based on this observation, a recommendation was made that the S/d max ratio should be either less than 0.6 or larger than 2.6 to prevent excessive initial deflection under relatively low levels of loading.

Field Service Conditions of the Oldest Corrugated HDPE Pipe Culvert under Ohio’s Roadway

AbstractA research institute at Ohio University recently conducted a comprehensive study on highway culvert structures for the Ohio Department of Transportation. During the study, a number of thermoplastic pipe structures under Ohio’s highways were inspected and rated. One of the thermoplastic pipe structures was a 0.61-m-diameter (24-in.-diameter) corrugated high-density polyethylene (HDPE) pipe under State Route 145 in Noble County, Ohio. What was unique about this pipe structure was that it was the oldest thermoplastic pipe culvert in service in Ohio. The pipe was installed under a shallow cover in 1981. The Ohio University team visited the culvert site in 2004 and inspected the pipe structure thoroughly. It was inspected again in June 2010. Drainage water entering the culvert was acidic, indicating the influence of a nearby surface coal-mining operation. The pipe structure had moderate amounts of deflection under the roadway, but overall it appeared to be in satisfactory condition. In 2004, a short pi...

Field Demonstration Test on Construction and Strength of Flexible Pipe Drainage System Using Flowable Fill

A team at Ohio University recently completed a research project related to flowable fill. The main objective of the project was to evaluate the feasibility of constructing an economical drainage pipe system using a flexible thermoplastic pipe and flowable fill. The project tasks were divided into three phases (laboratory characterization tests, field demonstration tests, and engineering analysis). This technical paper summarizes mainly data obtained during one of the Phase 2 field demonstration tests conducted at the load frame site, utilizing a corrugated HDPE pipe, flowable fill, and a variety of sensors. The test results confirmed many previously cited advantages of using flowable fill as pipe backfill material and also showed that some potential problems could be overcome easily. Finite element analysis simulated the field performance of the flexible pipe-flowable fill system reasonably well. In summary, it was concluded that it was quite feasible to construct a sound subsurface drainage system using flexible pipe and flowable fill.

Inspection and Risk Assessment of Mechanically Stabilized Earth Walls Supporting Bridge Abutments

AbstractUsing a mechanically stabilized earth (MSE) wall as a bridge abutment has become an attractive option to the traditional cast-in-place wall abutment. The use of an MSE wall abutment notably...