Upheaval buckling is a potentially serious problem especially for buried pipelines operating at high temperatures and pressures and routed in High sand dune areas. When a pipeline is operated at a temperature and pressure higher than ambient, it will try to expand. If the line is not free to expand, as in the case of buried pipelines, the pipe will develop an axial compressive force. When a curvature is present, this axial force causes to exert lateral force to soil. If the force exerted by the pipe on the soil exceeds the vertical restraint against uplift movement created by the pipe’s weight, its bending stiffness and the resistance of the soil cover, the pipe will tend to move upward, and considerable vertical displacement may occur resulting overstressing and or failure of pipelines. This is the phenomenon of upheaval buckling. Similar case of buckling in the lateral direction is the phenomenon of lateral buckling. TRE is cable of doing this specialized calculation as per Dr.K.Peters method which is being widely followed in UAE, other Gulf countries and in other regions of the world. The calculations provide the maximum permitted change of angle and also generates smooth graded route profile which can be transferred to alignment sheets in the design stage. It also calculates the extra soil cover for any location along the route for avoiding buckling.
These calculations are already completed by TR in many major projects successfully and include all buried lines in ADCO’s Sahil-Asab-Shah(SAS) & Qusahwira FFD, Rumaitha/Shanayel Facilities, Gasco’s Shah Gas Development(SGD), Shah Gas project & Integrated Gas Development Expansion(IGDE) projects in UAE and for other major Clients like TouatGaz of Algeria.
In addition to K.Peters method, TRE is also specialized in buckling calculations as per OTC-6335 & and DEP-31.40.10.16-Gen.
TRE has developed an internal software program for the upheaval buckling calculations. The program used for Dr.Peters method of calculations has the following features:
1. It calculates the maximum permitted change of angle for avoiding upheaval or lateral buckling for any given soil cover (constant or varying)
2. Program reads survey data from excel sheet and automatically generates smooth graded profile which avoids buckling and is made available in the design stage itself and construction becomes easier and saves lot of hours.
3. The output of the program can easily be exported to AutoCAD (by creating a .DXF file) to include in alignment sheets.
4. It predicts extra soil cover required if any, at any point along the route.
5. The calculations done for vertical & lateral directions for normal terrain, sand dune, sabkha sections etc.
6. It accepts fixed or varying soil covers with different compaction level specified along the route.
7. It calculates the volumes of soil cutting and soil filling. This is very useful, to plan the schedule of construction, EPC cost estimation during bidding etc. The volume of soil cutting will be equal/almost equal to the volume of soil filling.
8. It has option to select Tresca or Von-mises criteria.