CEP INCLINOMETER CASING

Application

CEP’s inclinometer casings are typically installed in boreholes for use in slope stability surveys.  It may also be embedded in fills, surcharge, cast into concrete in bored piles or diaphragm walls.

CEP’s inclinometer casings are made from high-impact ABS plastic and are suitable for long term contact with all types of soils, grouts and ground water.  The inclinometer casing has 4 external self alignment spines.

Casing Diameter Selection

The diameter of the inclinometer casing affects the useful life of an inclinometer installation.  Larger diameter casing offers longer life and is recommended for most applications where large vertical and lateral soil movements are expected.

• CEP1-1-85mm Casing is recommended for long term monitoring or where large lateral soil movements are expected.
• CEP1-1-70mm Casing is suitable for most construction projects where a moderate degree of lateral movement is expected.
• CEP1-1-60mm Casing is for installation in small diameter bore holes in competent soils or rock where anticipated deflections are small.

Inclinometer Coupling Joints Selection

The type of coupling joints to be used for an inclinometer bore hole installation depends on the strength of the sub-soils in which the casings are to be installed. The weakest link in the inclinometer casing installation is the coupling joint. Correct selection of the type of coupling joints is very important to avoid:-

• Crushing and buckling of the joints and inclinometer casing caused by large vertical force due to soil settlement.
• Dislocation and misalignment of the joints due to lateral squeezing and migration of the soft sub-soil during construction.

Correct coupling selection helps to prevent the inclinometer sensor from jumping grooves at the joints during bore hole survey caused by failure of the joints.

Standard, Slip-On or Fixed Couplings

Standard, slip-on or fixed couplings are available in 200mm length.  Fixed connections are used in competent soil or where the SPT of the soil is greater than 10 blows per 300mm, or where the total vertical or lateral movements of the inclinometer installations are less than 50mm.

Telescopic And Fixed Coupling

For projects e.g. basement, tunnels, slope stability etc where the soil strength increases with depth, the inclinometer bore holes are subject to some vertical settlement instead of purely lateral movements.  To get a better lateral profile from the inclinometers, it is good engineering practice to use telescopic couplings where the SPT N values of the soil are relatively low.

In order to take into account vertical movements of less than 60mm (from ground level to a depth of 12m B.G.L.), telescopic couplings each with a telescopic range of +/- 30mm should be used in the top 12 meter of an inclinometer BH.

Telescopic Couplings

Telescopic couplings which permit vertical and lateral movements of the inclinometer bore hole must be used in:-

• Soft sub-soils where SPT of the soil is less than 10 blows per 300mm.

• Reclamation projects.

• Sub-soil Improvement projects.

• Basement projects where total vertical or lateral movements are expected to exceed 50mm.

Spiral of Casing

In Singapore, a large scale land reclamation and soil improvement project was carried out in Changi and the specifications state that a spiral sensor should be used to measure the spiral of all the installed inclinometers. CEP inclinometer casings with telescopic couplings of +/- 75mm range were used for the project. (Deepest bore holes exceed 70m). The spiral sensor used was supplied by SLOPE Indicator Co., USA. All the spiral readings of the installed inclinometers were within the contract specification.