Interpretation of uplift pipeline-soil interaction behaviour using acoustic emission measurements

The objective of this study was to develop quantitative acoustic emission (AE) interpretation for uplift pipeline-soil interaction behaviour, enabling early warning of serviceability and ultimate limit state failures in the field. A series of large-scale uplift experiments was performed on a steel pipe in sand with different burial depths (i.e., stress levels), and varying rates of deformation were imposed. A suite of AE parameters was compared with the pipe force and displacement behaviour. Image-based deformation measurements were used to monitor the soil displacement field. AE generation was proportional to the imposed stress level and pipe displacement rate and related to the evolution of the pipe/soil failure mechanism. Relationships have been quantified between AE generation and stress level (R2 values of 0.99), and between AE generation rate and pipe velocity (R2 values ranging from 0.95 to 0.98), enabling interpretation of accelerating deformation behaviour that accompanies progressive ground failure processes. An example interpretation framework demonstrates how AE parameters can be used to identify the mobilisation of peak uplift resistance and quantify accelerating deformation behaviour during post-peak softening.

Uplift Performance of Plate Anchors in Cement-Stabilised Aeolian Sand

Comparative pullout tests were carried out on model plate anchors in uncemented aeolian sand (UAS) and cement-stabilised aeolian sand (CAS) with different embedment ratios of the embedment depth (H) to the width (D) of the plate to examine the effectiveness of the insertion of cement in aeolian sand to enhance the uplift performance of plate anchors. Experimental results demonstrated that significant increases in failure resistance and uplift stiffness can be achieved, irrespective of embedment ratios of H/D, when a relatively small amount of cement (an optimal cement content of 6% by weight of dry aeolian sand determined by direct shear test in this study) was added to the aeolian sand backfill. However, distinct load–displacement responses were observed in all the tests on the model plate anchors embedded in CAS and UAS backfills: two-phase of pre-peak and post-peak behaviour in CAS and three-phase of initial linear, nonlinear transition to peak uplift resistance, and post-peak behaviour in UAS; failure of the former started at tiny displacements and that of the latter appeared at large displacements. Therefore, the significant increases in uplift failure resistance and pre-peak uplift stiffness were limited to relatively low uplift displacements because of the brittle nature of the improved CAS backfills shear strength characteristics.

Uplift resistance capacity of anchor piles used in marine aquaculture

Anchor piles are widely used in marine aquaculture, and the safety is largely determined by the uplift resistance capacity,especially in harsh ocean environments. However, there are few practical guides to the design and installation of the anchor piles for mooring the body of marine aquaculture equipment. Laboratory experiments were conducted to investigate the effect of the initial tension angle, pile diameter, embedded depth, and pile configuration on the uplift resistance capacity of anchor piles under oblique loads. CCD camera and load cell were utilized to measure the corresponding displacement and load, respectively. The results show that increasing the initial tension angle of circular and square single piles can significantly improve the uplift resistance capacity. The failure load of the square single pile was slightly higher than that of the circular single pile. Increasing the pile diameter can effectively improve the failure load and delay the development speed of the pile top displacement. Increasing the embedded depth can effectively improve the failure load and increase the lateral displacement of the pile top. The uplift resistance capacity of the dual anchor piles was better than that of the single anchor piles. The layout configuration has little effect on the failure load, but has a large effect on the displacement development.

Uplift Resistance Capacity of Anchor Piles used in Marine Aquaculture

Anchor piles are widely used in marine aquaculture, and their uplift resistance capacity largely determines their safety, especially in harsh ocean environments. However, a practical guide on its design and installation is wanting. Laboratory experiments were conducted to investigate the effect of the initial tension angle, pile diameter, embedded depth, and pile configuration on the uplift resistance capacity of anchor piles for marine aquaculture under oblique loads. The results show that increasing the initial tension angle of circular and square single piles can significantly improve the uplift resistance capacity. The failure load of the square single pile was slightly higher than that of the circular single pile. Increasing the pile diameter can effectively improve the failure load and delay the development speed of the pile top displacement. Increasing the embedded depth can effectively improve the failure load and increase the lateral displacement of the pile top. The uplift resistance capacity of the dual anchor piles was better than that of the single anchor piles. The layout configuration has little effect on the failure load, but has a large effect on the displacement development.