In recent years, geosynthetics have been increasingly used to reinforce soil mass on PIPEs under static and repetitive loads. Soilbags are also effective for managing floods and various geotechnical applications, such as roadbeds, slope stability, and retaining walls. In this paper, the investigation of the BURIED PIPE’s behavior in the unreinforced trench and reinforced trench with soil bag is considered. Therefore, a series of tests were conducted on the unreinforced and reinforced trench (reinforced by one soil bag, two soil bags in columnar arrangement with and without spacing, and three soil bags in two layers of stepped arrangement) containing a PIPE with a diameter of 160 mm under static load. The results of the tests show the effect of the soil bag layer on reducing the bed settlement by enclosing the soil inside and preventing the lateral movement of the soil mass above the PIPE. Also, the bag, by distributing the stress on a wider surface and significantly reducing it in depth, reduces the transfer stress to the PIPE crown and as a result, reduces the deformation of the PIPE. Increasing the BURIED depth of the soil bag results in a reduction in deformation and pressure on the PIPE crown and an increase in soil surface settlement. The columnar arrangement of two layers of soil bags with spacing provides better performance in improving PIPE behavior compared to those without spacing. Moreover, the use of two layers of soil bag with a stepped arrangement leads to a reduction in surface settlement, pressure on the PIPE, and PIPE deformation compared to two layers of soil bag with a column arrangement. However, considering the lack of significant difference between the behavior of the stepped and column arrangements (with or without spacing), the use of a column system is recommended, as it saves 33% of the soil bag.

With increase in cities' population and development of urbane life, passing BURIED PIPElines near the ground's surface is inevitable in urban areas, roads, subways and highways. In this paper, the results of laboratory tests on exible PIPE with a 160 mm diameter, placed in reinforced-trench by a geogrid layer and an EPS geofoam block subjected to repeated load are investigated. The PIPE diameter change, strain and pressure acting over the PIPE were measured throughout the loading, unloading and reloading. The parameters inspected in the tests included the thickness (30, 60 and 100 mm) and width (160 and 240 mm) of EPS block and burial depth of PIPE (1. 2 and 1. 5 times the PIPE diameter). Based on the results, the values of the PIPE diameter change and PIPE strain swiftly increases during the early cycles of loadings and followed the stability trend with the gathering of load cycles. In the geogrid-reinforced system, the change in PIPE diameter and in PIPE's strain at the end of the loading cycles showed 19% and 20% reduction, respectively, as related to the unreinforced system. According to the results, the minimum PIPE diameter change and PIPE's strain were acquired by using EPS block with maximum width, thickness, and 30 kg/m3 density over the PIPE in addition to a geogrid layer representing values of, respectively, 0. 26 and 0. 3 times of the others acquired in the reinforced trench with a geogrid layer.

Engineering problem related to Expansive soils is their changes in volume by moisture. This soil tends to expand by absorbing water, so if they are not allow to expand and constrained pressure swelling pressure will create. Swelling pressure can cause settlement and damage to structures which are supported by this soil. There are different solutions for overcoming on this problem but utilizing of Geofoams (EPS) is one of the most innovative approaches. In this paper, the results of tests were conducted on BURIED flexible PIPE which supported by geofoam in the expansive soil are presented. In these experiments, two boxes have been used in such a way that a smaller box is placed inside a larger box and space between two box was filled by water. Flexible PIPE and geofoam (EPS) were located in the center of small box and then expansive soils were poured around the geofoam (EPS) and flexible PIPE. The expansive soil which was used in this research was sodium bentonite. Sodium bentonite expands when wet, absorbing as much as several times its dry mass in water. Because of its excellent colloidal properties, it is often used in drilling mud for oil and gas wells and boreholes for geotechnical and environmental investigations. The property of swelling also makes sodium bentonite useful as a sealant, since it provides a self-sealing, low permeability barrier. It is used to line the base of landfills, for example To investigating the influence of geofoam (EPS) in reduction of the swelling pressure and displacement was purpose of this experimental study. Four tests were done on flexible PIPE, in the first test, flexible PIPE was BURIED in expansive soil alone and in other tests geofoam (EPS) was used. Geofoams which used for protection of BURIED PIPE, have 4 mm, 20 mm and 40 mm thickness respectively. each test was conducted in 32 days, because after 32 days the dial gage did not show any changes. By comparison on the values of obtained swelling pressure and displacement, it became clear that using a geofoam (EPS) with thickness of 4mm and 20mm can decrease swelling pressure and displacement up to 50 and 80 percent, respectively. Also value of swelling pressure and displacement reduction for test with 40 mm thickness geofoam (EPS) was negligible. So it was found that increasing in geofoam (EPS) thickness can partially reduce swelling pressure and displacement of expansive soil, however, there is no direct correlation with increaseing the geofoams thickness.

Many BURIED structures, including tunnels and lifelines, have been severely damaged in recent earthquakes. It is noteworthy that the phenomenon of soil liquefaction has played a significant role in the occurrence of these damages. Damage caused by the uplift of lifelines has motivated the study of the uplift of BURIED structures. Therefore, in this study, an attempt has been made to the experimental study of the uplift of BURIED PIPEs in liquefiable soils by physical modeling at different depths. The soil used in this study is Gum Tape sand and shaking table has been used to simulate seismic load. Also, due to the importance of the deformation mechanism in this process, the particle image velocimetry method has been used to find out how the soil around the PIPE moves during liquefaction. BURIED PIPE at three depths: 1.5, 2.5 and 5 times the diameter of the PIPE has been subjected to seismic load and the degree of elevation and deformation mechanism have been investigated. The results show that with decreasing the BURIED depth of the PIPE, due to the relatively high pore water pressure in the lower depth of the soil, the overpressure created after dynamic loading tends to be wasted and flows towards the low-pressure points (surface part). And because in the surface areas, the flow is upward, so the uplift continues to some extent. Also, the displacement vectors on the sides of the PIPE are in the form of circular rings that try to raise the PIPE.

The bearing capacity and settlement of shallow foundations located on the PIPE are usually not acceptable in sandy soils. Therefore, in order to improve the performance of strip foundations, various methods are proposed, as a cost-effective alternative is to add skirts to the edges of the shallow foundation. the addition of the skirt to the edges of the shallow foundation increases the effective depth of the foundation and soil trapped within the skirts, and loads of the structure are transferred to the bottom depth at the level of the skirt tip. In recent years, performance assessment of skirted foundations has become one of the desired topics for civil engineers. In this article, the effect of the burial depth and horizontal distance from the center of the PIPE to a single load have been evaluated using numerical and experimental tests. Therefore, the skirted foundations located on the BURIED PIPE with skirts B and 2B (B is the width of the foundation) have been used. The results of the laboratory tests show that by using the skirted foundation with skirts of 2B, the bearing capacity can be increased by more than 300% compared to the strip foundation. A numerical comparison of the skirted foundation with semi-deep and embedded strip foundation shows that the bearing capacity of the skirted foundation was less than 10% different from the semi-deep foundation. Civil engineers can be led towards more economical and accurate designs by using the skirted foundation.

BURIED PIPElines are vital infrastructures and are mostly used to transport energy and other essential commodities. One of the most important seismic hazards on BURIED PIPElines is movement of faults crossed by them. In general, PIPEline can be simplified as a beam, while PIPE-soil interaction can be represented by soil springs in the axial, horizontal and vertical direction. Although this method has been implemented previously by ASCE and ALA guidelines the specifications of these springs are not well-defined. In this study, a full-scale tests were carried out on polyethylene PIPE BURIED in dense sandy soil (with 120. 5 mm of diameter). The response of the system (such as displacements and reaction loads) were recorded during the tests. A computer program was developed to optimize the specifications of the equivalent springs using Python scripts in MATLAB and ABAQUS environments. In this way, the deformation of the PIPE along its length would have the highest level of congruence with the experimental results. Using the proposed approach, the initial stiffness and maximum soil-PIPE interaction force have been calculated and compared to the criteria recommended by ASCE and ALA standards. The results showed that the value of yield force capacity and stiffnesses for the soil lateral equivalent springs, provided by ASCE and ALA codes, are determined to be in a great value of error. For polyethylene PIPE at the condition of strike-slip faulting, these values were too smaller than the values put forth by ASCE and ALA.

Large deformation causing damage due to uplift force is generated in BURIED PIPEline located in shallow trenches in marshes and saturated soils. In this paper, existing common methods of PIPEline anchorage are discussed and considering advantages and disadvantages of these methods, a new method of PIPEline anchorage are studied and presented. In this new developed method, geo-textile materials are used for anchorage of large diameter PIPEline. Laboratory and field experimental study are developed and effective parameters are deliberated considering load–displacement curves. Finally, a field study on a 30" diameter gas PIPE is performed to admit the laboratory tests. Considering the laboratory and field study results, the anchorage of PIPEline using geo-textile is recommended for anchorage of BURIED PIPEline in marshes and saturated soils. 

Risk analysis PIPElines in the quake as one of the most vital arteries in the current circumstances in the world is of special importance. in our everyday activities, used to underground structures such as PIPEs, tunnels, wells and so on for services such as transporting water, transportation, irrigation, drainage, sewage disposal, transporting oil and gas, carrying acid waste, industrial, household and so on. With regard to the huge investments structures, especially BURIED underground PIPEs, we need to study these constructs in response to the earthquake, is clearly felt. PIPElines used for transporting gas and other fluids, are widely distributed in all areas. These lines due to passing through the densely populated areas are always BURIED in the earth. Seismic behavior of these PIPEs as a result of the interaction between the soil and the PIPE is different from the above-ground structures. The manner of modelling of the effects of soil liquefaction on the PIPEs in this thesis is that two shear springs and a normal spring is defined between soil and the PIPE that in liquefaction mode minimize the friction shear strength.