Study of ground collapse induced by large-diameter horizontal directional drilling in a sand layer using numerical modeling
Bibliographic record
Abstract
With large-diameter horizontal directional drilling (HDD) becoming the preferred method to construct oil and gas pipelines and utility pipelines beneath rivers, the issue of potential ground collapse arises when drilling in loose geological layers such as sand. Ground collapse is a result of borehole collapse and may cause significant damage to the topography and nearby facilities. The present investigation considered the potential causes of ground collapse induced by an actual 1.219 m diameter HDD river-crossing project, using the FLAC3D numerical modeling tool. The analysis showed that the failure zone first developed at the crown of the borehole, resulting in subsequent borehole collapse due to instability of the sand above, and eventually leading to ground collapse. Sequential reaming cycles have been simulated and the results indicate very little effect in comparison with a single reaming cycle. The risk of borehole collapse, and consequent ground collapse, increases with borehole diameter. Parametric numerical modelling has also been conducted to study the influence of soil parameters and drilling mud pressure on the stability of the ground surface above the borehole. The results show that soil cohesion and friction angle have a large influence on stability of the borehole and ground surface, while elastic modulus and Poisson’s ratio have relatively little effect. It was also determined that mud pressure is a very important factor in maintaining stability of the borehole, and therefore the ground surface as well.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".