willemeulen
Civil/Environmental
- Aug 24, 2014
- 3
Hi,
Read some of the other thread's and found the consensus was that for bulk outfall sewer on can go up to slopes of 0.1 - 0.08%. The area I'm working in has dolomite; dolomite areas have the renowned sink holes. Most sink holes are cavities in the soil which can collapse, the collapse is mostly triggered due to water related activity and research has proven 96% of sinkholes are caused by human activity (water leaks, diverting of stormwater, lowering of water table etc.). Due to this dolomite the pipe materials have to conform to certain standards, the most important being that the pipe should be free of joints, pipe should be able to handle vertical stress/pull without joints being dislodged.
As you can guess for wet services either HDPE or Steel pipes are the options available.
First option would be HDPE (steel is costly and also not preferred with sewage).
My questions are the following:
Is HDPE a suitable material for the construction of flat slopes of 1:1000 (0.1%)?
In my experience HDPE can be nice and straight aligned in a trench in the morning until temperatures rise and expansion of the HDPE material causes it to look like a “snake” in a trench
How would one determine the allowance in alignment (dips) and how would this be quality checked?
My best guess would be laser and CCTV inspection.
Thanks in advance.
W
Read some of the other thread's and found the consensus was that for bulk outfall sewer on can go up to slopes of 0.1 - 0.08%. The area I'm working in has dolomite; dolomite areas have the renowned sink holes. Most sink holes are cavities in the soil which can collapse, the collapse is mostly triggered due to water related activity and research has proven 96% of sinkholes are caused by human activity (water leaks, diverting of stormwater, lowering of water table etc.). Due to this dolomite the pipe materials have to conform to certain standards, the most important being that the pipe should be free of joints, pipe should be able to handle vertical stress/pull without joints being dislodged.
As you can guess for wet services either HDPE or Steel pipes are the options available.
First option would be HDPE (steel is costly and also not preferred with sewage).
My questions are the following:
Is HDPE a suitable material for the construction of flat slopes of 1:1000 (0.1%)?
In my experience HDPE can be nice and straight aligned in a trench in the morning until temperatures rise and expansion of the HDPE material causes it to look like a “snake” in a trench
How would one determine the allowance in alignment (dips) and how would this be quality checked?
My best guess would be laser and CCTV inspection.
Thanks in advance.
W