How do we carry out Trench Excavation in Sand near sea for a depth of 4 meters? The working space is narrow and road width available is 5 meters. The Trench work is for a Under Ground Drainage work and RCC pipes are used. Well Point de-watering is used for de-watering. But the sand is collapsing.
We are executing UGD projects in Karwar and Mangalore for KUIDFC under KUDCEMP Project. In Karwar we have used well point dewatering equipments to carry out trench excavation in sand and silty strata. The water table is very high in Karwar due to its proximity to sea. However, we did the trench excavation upto a depth of 3.5 mtrs. The earth is highly collapsible to even the vibrations of JCB Excavator, Shoring and strutting also do not work. We did excavation by leaving Earth Braces in between at every 6 to 8 mtrs.
Now we are doing work in Surathkal Mangalore, where the sand is very dry and powdery not like karwar where sand is mixed with silt and little stable. When we started trenching here, we started with a width of 1 mtrs, but as excavation progressed, the sand kept on collapsing and the width was almost 3 mtrs. This was a open site, but the maximum work has to be carried on roads with 4 to 5 mtrs width and existing utilities.
I am attaching some photos of both Karwar and Suratkal works for your reference. Photos 819 and 822 are of Suratkal site.
Hemant Maloo
hemant.maloo@gmail.com