Method and apparatus for constructing buried pipeline systems

A method for reducing or eliminating frost heave in a buried pipeline system used for transporting product having a temperature less than 32.degree. F. through frost-susceptible soil having a surface, an upper layer of organic material, and a lower layer of non-organic material, said method comprising the following steps:

• excavating a trench through the surface and the upper layer and into the lower layer to a preselected depth;
• installing a pipeline in the trench so that the top of the pipeline is located essentially below the upper layer;
• filling the trench with heave resistant bedding material at least to a level substantially equal to that of the transverse horizontal centerline of the pipeline;
• installing fill material above the bedding material to a level substantially equal to that of the bottom of the upper layer;
• removing the upper layer of organic material over the pipeline and on both sides of the trench for a distance at least equal to the depth of the trench;
• and
• installing a blanket of granular, mineral material in place of the organic material which was removed.

A method for reducing or eliminating frost heave in a buried pipeline system used for transporting product having a temperature less than 32.degree. F. through frost-susceptible soil having a surface, an upper organic layer, and a lower non-organic layer, said method comprising the following steps:

• excavating a trench of a preselected width and having two sides and a bottom through the surface and the upper organic layer and into the lower non-organic layer to a preselected depth at least equal to the maximum seasonal freeze depth of the soil;
• removing the upper organic layer on one side of the trench for a preselected distance;
• constructing a work pad on the same side of the trench by installing a granular, mineral material in place of the organic layer which was removed;
• installing a pipeline in the trench so that the top of the pipeline is located below the adjacent upper organic layer and the bottom of the pipeline is located substantially above the bottom of the trench;
• filling the spaces between the pipeline and the sides and bottom of the trench with heave resistant bedding material, said bedding material extending upwardly from the bottom of the trench at least to a level substantially equal to that of the transverse horizontal centerline of the pipeline;
• installing a fill material above the bedding material, said fill material extending from the top of the bedding material upwardly to a level substantially equal to that of the bottom of the upper organic layer;
• removing the upper organic material on the side of the trench opposite the work pad for a distance at least equal to the depth of the trench;
• installing a blanket of granular, mineral material in place of the organic material which was removed, said blanket extending from the work pad, across the trench and outwardly and away from the trench;
• applying a heat absorbant coating to the top surface of the work pad and the top surface of the granular, mineral material;
• and
• erecting at least one snow fence on the blanket of granular, mineral material.

A buried pipeline system for transporting product having a temperature less than 32.degree. F. through frost-susceptible soil having an upper organic layer and a lower mineral layer, said system comprising:

• a trench of a preselected width excavated through the upper organic layer to a preselected depth;
• a pipeline located in the trench and substantially beneath the upper organic layer;
• heave resistant bedding material located in the trench and substantially surrounding the pipeline;
• and
• a blanket of granular, mineral material covering the trench and extending ouwardly and away from the trench on both sides thereof a distance at least equal to the depth of the trench, said blanket of granular, mineral material capable of increasing the heat input to the pipeline system from environmental sources over that which occurs naturally, thereby reducing frost heaving of the pipeline.

A buried pipeline system for transporting product having a temperature less than 32.degree. F. through frost-susceptible soil having a surface, an upper layer of organic material, and a lower layer of non-organic material, said system comprising:

• a pipeline buried substantially entirely beneath said upper organic layer;
• a zone of heave resistant bedding material extending below the pipeline at least to the maximum seasonal freeze depth of the soil and at least up to a level substantially at the transverse horizontal centerline of the pipeline, said bedding material supporting the pipeline and displacing the soil under the pipeline;
• a zone of fill material in the trench and above the pipeline, said fill material extending from the heave resistant bedding material to the surface above the pipeline;
• a blanket of granular, mineral material at the surface of the soil above the pipeline, said blanket being thick enough to retard the growth of vegetation in the area covered by the blanket;
• and
• a work pad on the surface of the soil, said work pad being parallel to and in contact with the blanket and being wide enough so that it and the blanket have a combined width at least equal to the depth of the bottom of the pipeline in the soil, said work pad also being thick enough to retard the growth of vegetation in the area covered by the work pad.