Risk Prediction of Sinkhole Occurrence for Different Subsurface Soil Profiles due to Leakage from Underground Sewer and Water Pipelines

Abstract

A sinkhole is a ground surface depression that may occur with or without any indications on the surface and often pose danger to both properties and people. Leakage from underground pipe mains in urban areas may cause sudden ground subsidence or sinkholes. For a long time, researchers have been working on the hazard and risk assessment of sinkhole formation, especially natural sinkholes. However, much less work has been done on risk prediction and the mechanism of manmade sinkholes. In this study, different versions of small-scale sinkhole physical models were used in experiments to monitor ground surface settlement or collapse due to leakage from an underground pipeline. The factors under consideration were the type of subsurface soil profile, type of water flow, and leakage position in the pipeline. The ultimate goal was to use this information to predict the risk of sinkhole occurrence due to leakage from sewer or water pipelines under different subsurface soil conditions. The experimental results and statistical analysis showed that the subsurface soil strata conditions dominated the mechanism of sinkhole occurrence, although other factors also have contributed to the settlement. Then, this analysis was used to predict the sinkhole risk level under different conditions. The development of a reliable sinkhole risk prediction system can potentially minimize the risk to human lives and infrastructure. These findings can be applied to the development of a sinkhole risk index (SRI) that considers various other factors influencing sinkhole occurrence.

Data on manmade sinkholes due to leakage in underground pipelines in different subsurface soil profiles

“…The first stage of the experiment was to design the architecture in the laboratory. The overall architecture of the experimental setup is shown in [1] . Water was supplied to the system from a water tank (Tank 2) with a capacity of 227 L. The water passing through the pipeline was collected at the outlet, allowing measurement of the quantity of water seeping into the model box due to leakage.…”

“…In total, 200 L of water was placed into the water tank for each case. As the pressure of the water flow at the inlet declines steadily with the water level inside the water tank, another water tank (Tank 1) was used to maintain the water level in Tank 2 to control the drop in water pressure, as shown by [1] . A solenoid valve was fixed at the bottom of each water tank to manually control the flow of water inside the pipeline.…”

“…A PVC pipeline with an external diameter of 40 mm and an internal diameter of 36 mm was used. Artificial leakage was created by creating a hole in the pipeline, as shown by [1] . The model box used for the experiment had dimensions of 700 mm (width) × 600 mm (length) × 330 mm (height) with a hole at the center of the bottom for drainage.…”

“… The materials adopted for the 12 different soil profile models in the laboratory included sandy clay, limestone, sugar cubes, and gravel. Coarse aggregate (gravel) was used to represent bedrock, limestone powder was used to represent limestone, and sugar cubes were used to represent artificial cavities, as shown by [1] . Ali and Choi [1] represented the four different soil profiles under consideration in this study as A, B, C, and D. In each of the 12 cases, the soil was compacted in two layers, each 160 mm in thickness.…”

“…Four cases for each condition shown in Tables 1 , 2 , and 3 (total 12 cases), as presented in [1] show the progression of settlement under various conditions with time.…”