Abstract
This paper studies the seismic response of buried oil and gas pipelines under the bidirectional nonuniform excitation. Based on the bidirectional shaking table array test, the loading and testing scheme is designed and developed, analyzing the strain response of the buried oil and gas pipeline under the bidirectional uniform and nonuniform seismic excitation, as well as the acceleration response and displacement response characteristics of the pipeline and the surrounding soil body and their change rule by the test. The test proves to show that the developed bidirectional laminar shear continuum model soil box can meet the requirements of the bidirectional nonuniform seismic excitation and continuous laminar shear deformation of the soil. The peak strains of the pipeline in axial and bending caused by nonuniform excitation are larger than those of the pipeline under uniform excitation, the degree of unevenness in the distribution along the axial direction is greater, and the strain curves are large in the middle and small at both ends along the axial direction of the pipe. The acceleration responses of the pipeline and the soil body under the bidirectional nonuniform excitation are larger than those under the uniform excitation. The acceleration response of both the pipe and the soil under the nonuniform excitation is larger than that under the uniform excitation, and the differences are shown in the transverse and axial directions, the peak acceleration response of the soil body under the nonuniform excitation is about three times that of the transverse direction, and more peak points appear in the axial and transverse acceleration responses of the pipe under the nonuniform excitation as the loading level increases, the peak displacement response of the soil body increases gradually with the height, but the fluctuation range of the peak displacement of the soil body nearby the pipe is larger. The soil displacement curve starts to smooth out when the loading level reaches 1.0 g, and the axial displacement decreases, which indicates that the interaction between the pipe and soil is more intense and the relative motion between the pipe and soil is more obvious under the nonuniform excitation, and the soil is more likely to be damaged and enter the nonlinear stage. Therefore, it is necessary to analyze and design the seismic performance of buried pipes considering the nonuniform seismic excitation.
Highlights
Buried oil and gas pipelines are called lifeline projects in oil and gas fields
With EPS backfilling, as opposed to ordinary backfilling, the lateral firmness of the pipe can be greatly reduced during earthquakes as the foundation moves, which has a significant effect on improving the seismic performance of buried pipes with elbows under the action of permanent ground deformation (PGD) important influence
Rahimi et al [8] conducted a series of shaking table tests on elbow buried pipes, and the results showed that under dynamic loads, small diameter buried pipes exhibited more suitable performance than large-diameter buried pipes, and buried pipes with high stiffness and low flexibility were subjected to higher stresses under dynamic loads
Summary
Buried oil and gas pipelines are called lifeline projects in oil and gas fields. A large number of earthquakes have shown that pipelines suffer direct damage during earthquakes and may produce serious secondary disasters such as fires, explosions, and environmental pollution, so it is important to ensure their safety and reliability under the effects of earthquakes [1, 2]. Rough the use of shaking table tests, understanding and verifying the pipe-soil dynamic model and analyzing the dynamic response characteristics and laws of buried pipelines under earthquake action have become an effective method of studying the seismic performance of buried pipelines [4, 5]. Junyan Han et al [10] developed a suspended continuum model box suitable for multiple arrays shaking table tests of long linear underground structures, carried out shaking table tests of buried pipelines with multipoint ground vibration inputs under different site conditions, conducted research on the selection of similar relationships in shaking table tests of long transmission buried pipelines and the study of test protocols, and analyzed the seismic response laws of pipelines and sites under consistent and noncoherent seismic effects. The pipeline is pressurized to simulate the actual operation of the pipeline, and the shaking table test is conducted under the bidirectional consistent and noncoherent seismic excitation to study the change process of seismic response of buried oil and gas pipeline under bidirectional noncoherent seismic excitation and reveal its seismic response characteristics and laws
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