RU2504707C2 - Method for burial of pipeline to design levels - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method involves uncovering of a pipeline on one side of a trench below design depth so that a groove is created. Then, the pipeline is buried to design levels under action of gravity force and movement of grounds (sand clay, sand) to the groove side. In order to provide the pipeline burial to the required value, gravity depth h_g is determined by the following formula:

where h_bur - pipeline burial depth before works are performed, m; h_reg - required pipeline burial depth to the pipe top, m; k - safety margin accepted for loose grounds k=1.2 and for binder grounds k=1.25; a - width of ground section under the pipeline that is offset after the trench development to the gravity side, which is equal to outside diameter D_o of the pipeline, m; b - width of the trench at the bottom, m. In case of dense binder grounds, the ground is extracted from under the pipeline with an excavator.

EFFECT: reduction of costs and labour intensity owing to reducing the number of working operations and working personnel.

2 cl, 4 dwg

Description

It is known that in accordance with SNiP 2.05.06-85 * the deepening of the pipeline to the top of the pipe is accepted within h _add = 0.6 ÷ 1.1 (SNiP 2.05.06-85 * "Main pipelines" approved by the resolution of the USSR Gosstroy from March 30, 1985, as amended on January 8, 1987, July 13, 1990, November 10, 1996, instead of SNiP II-45-75, the effective date is January 1, 1986). In the process of diagnosing the technical condition of the oil and gas pipeline, sections of pipelines laid above design marks are identified. That is revealed areas with depth of laying the pipeline _zag h <h _ext.

To deepen the pipeline to design elevations, a method is known for repairing sagging and washed out sections of an underwater pipeline without stopping product pumping, which includes opening the washed-out and adjacent sections in parts equal to the length of the intersection line of the water horizon with the point of the trench to be torn off in the direction of its rise, and a fragment of the trench along the pipeline is deeper than the design elevation with an increase in the disclosure of adjacent sections, the extraction of soil from under the pipeline in sections and ensuring an acceptable radius of bending and the pipeline, filling the trenches with water with the formation of jumpers that remove, which lengthens the span of the pipeline in the water, unloading the gas pipeline from the center of the eroded section on both sides with filling the trench (Patent RU 2081366 C1 of 06/10/1997, patent holder: Research and Design Institute "Severnipigaz").

The disadvantage of this method is the high complexity, the ability to use this method only in areas of underwater crossings, the need to fill the trench with water, the high cost of money.

The objective of the invention is to reduce the complexity and reduce the cost of deepening the pipeline to design levels.

A method for deepening a pipeline into a trench to design elevations under the action of gravity of the pipeline itself without stopping pumping of the product is proposed.

Figure 1 and figure 2 shows the scheme of opening the pipeline in weak loose soils (sand, sandy loam, etc.), in which a trench 2 is excavated on one side of the pipeline 1 below the design elevation with the formation of a recess 3. Under the influence of the gravity of the pipeline, the soil begins move down in the direction of arrow 4 and to the right in the direction of arrow 5 in the direction of the recess, gradually filling it. The pipeline 1 slides down and takes the necessary position, while the laying depth reaches the design marks h _add .

To ensure the deepening of the pipeline to the required value of the depth of the trench h _add , the depth of the excavation h _and in the presence of weak soils

determined by the formula derived by the authors, based on practical experience and the geometric parameters of the trench:

where h _in - the depth of the excavation, m;

h _zag - the depth of the pipeline before work, m;

h _add - the required depth of the pipeline to the top of the pipe, m;

k is the safety factor taken for soft soils k = 1.2, for cohesive soils k = 1.25;

a is the width of the cross section of the soil under the pipeline, which after the development of the trench 2 is shifted towards the excavation, equal to the outer diameter D _{n of the} pipeline 1, m;

b - width of trench 2 along the bottom, m.

Figure 3 and figure 4 shows a diagram of the opening of the trench with the subsequent deepening of the pipeline to design elevations under the action of gravity in the presence of dense cohesive soils (loam, clay, loess, etc.), in which a trench 2 is excavated on one side of the pipeline 1. Pipeline 1 under the influence of gravity cannot accept the position laid down in the project. For its deepening, it is necessary to excavate 3 from under the pipeline with a single-bucket excavator 6.

In the presence of dense cohesive soils, excavation from the pipeline by the excavator is carried out to the required depth of the pipeline h _ext .

As a result of using this method of deepening the pipeline to design levels, there is a significant decrease in the complexity of the work and the cost of the work by reducing the number of work operations and reducing the working staff.

Claims (2)

1. The method of deepening the pipeline to design elevations, including opening the pipeline, deepening the trench to the design elevations, opening without stopping pumping the product below the design elevation with the formation of a excavation, characterized in that the autopsy is carried out on one side of the trench, then by gravity the pipeline is deepened to design marks, while the depth of the excavation is determined by the formula:

where h _in - the depth of the excavation, m;
h _zag - the depth of the pipeline before work, m;
h _add - the required depth of the pipeline to the top of the pipe, m;
k is the safety factor taken for weak pounds k = 1.2, for cohesive soils k = 1.25;
a - the width of the cross section of the soil under the pipeline, which after the development of the trench is shifted towards the excavation, equal to the outer diameter D _{n of the} pipeline, m;
b - the width of the trench along the bottom, m 2. The method of deepening the pipeline to design elevations according to claim 1, characterized in that in dense, cohesive soils, excavation is carried out from under the pipeline by an excavator.

Images