Posts by Kanwarjot Singh

The factor of safety for the embankment constructing on soft clay is minimum at the end of construction. After that consolidation takes place, thereby increasing the shear strength of foundation soils. Reinforcement is normally introduced to maintain the stability owing to the following reasons:

(i) The reinforcement at the clay surface, which is capable of carrying tensile forces, generates shear stresses to resist the lateral deformation of clay and improves its bearing capacity.

(ii) The reinforcement could also hold in equilibrium the lateral trust developed by the fill above so that it reduces the stresses which tends to cause failure of clay foundation.

(iii) The reinforcement has a tendency to drive the failure mechanism deeper in the soft clay, which should possess higher shear strength because its strength generally increases with depth.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

By
Naveen G.M ¹, Vinay Kumar B.M²
1. Lecturer, Dept. of civil Engg, V.V.I.E.T, Mysore.
2. Lecturer, Dept. of civil Engg, V.V.I.E.T, Mysore.

Abstract
Sound comes from the vibrations in molecules, and is always traveling through a substance, whether it is a solid, liquid, or gas. Sound cannot travel through a vacuum because there are no molecules for the sound to travel through. Noise pollution (or environmental noise) is displeasing human-, animal- or machine-created sound that disrupts the activity or balance of human or animal life. A common form of noise pollution is from transportation, principally motor vehicles. Noise health effects are both health and behavioral in nature. The unwanted sound is called noise. This unwanted sound can damage physiological and psychological health. Noise pollution can cause annoyance and aggression, hypertension, high stress levels, hearing loss, sleep disturbances. In the present study, attempts are made to study the noise level range at different roads of the Mysore city. Traffic behaviour and characteristics at various roads near schools, hospitals, railway tracks, offices, courts, etc. using “Sound Level Meter”. Then, the maximum value of noise level in decibels is Estimated.

Keywords: Noise and Sound level meter.
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The idea of Observational Method was first discussed by Peck in the Rankine Lecture in 1969. The Observational Method is commonly adopted in geotechnical works in construction phase, though it is also feasible in design stage.

In essence, in the conforming design by engineers during planning stage, the design is usually based on over-conservative approach or most unfavourable conditions owing to a lack of precise and actual site information. During subsequent construction, with precise site information and condition available the Observational Method is adopted in which the original design is revised based on most probable conditions with instrumentation monitoring. If the monitoring results show that performance of the revised design approaches the limit of acceptable level of risk, then it shall be reverted to planned modification which is based on most unfavourable conditions and hence the level of risk is lowered back to the original design. Otherwise, the revised design shall continue and this results in cost reduction without comprising safety of works.

However, care should be taken in implementing Observational Method when rapid deterioration of the site may occur so that there is insufficient time for carrying out the planned modification. For instance, rapid deterioration can result from development of high pore water pressure in heavy rainfall or burst watermain.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

To reduce the effect of soil liquefaction, it is intended to reduce the pore water pressure induced during earthquake shaking. This can be achieved by providing better drainage in soils (e.g. wick drains, sand drains etc. ) and densification of soils (e.g. vibroflotation, dynamic compaction etc.).

Liquefaction hazards can be reduced by improving the drainage ability of the soil. If the pore water within the soil can drain freely, the build-up of excess pore water pressure would be reduced accordingly.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

In liquefaction, the pore water pressure builds up steadily and eventually approaches a value equal to the confining pressure. In an earthquake, however, there is not enough time for the water in the pores of the soil to be squeezed out. Instead, the water is trapped and this avoids the soil particles from moving closer together. Consequently, this results in an increase in water pressure which reduces the contact forces between the individual soil particles, thereby softening and weakening the soil. Eventually, soils particles lose contact with each other and behave like a liquid.

Hence, the type of soils which is susceptible to liquefaction is the one like sand whose resistance to deformation is mobilized by frictional forces between particles under confining pressure. In case the soil is fine grained, cohesive forces tends to develop between these fine particles and it is difficult to separate them. Therefore, sand with increasing content of fines tends to increase its resistance to liquefaction.

The consequence of liquefaction is that the subsequent settlements after liquefaction may damage the overlying structures. Moreover, for sloping ground lateral flow may result which is undesirable. Liquefaction only occurs to saturated soils.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Where soil nails are intended for improving the slope stability of existing ground, sheets or geo-grids can hardly replace reinforcing elements in soil nails. Practically speaking, the reinforcing of existing slopes limits the types of reinforcing elements to be adopted. For instance, sheets or geo-grids do not have sufficient bending stiffness to be inserted into exiting slope and they are usually placed in soils as soil layers are built up. The reinforcing element of exiting ground requires steel bars with good tensile strength.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

The passive nature of soils nails requires a small movement for the nails to take up loading. During this process, it is understood that the grout annulus around the nail would crack to allow for these small displacements.

Therefore, the tensile capacity of grout is normally ignored in design and only compressive capacity might be considered.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

As Per Indian Guidelines Only.

Clear cover to main reinforcement in
Footings : 50 mm
Raft foundation Top : 50 mm
Raft foundation Bottom/ sides : 75 mm
Strap Beam : 50 mm
Grade Slab : 20 mm
Column : 40 mm (d>12mm) 25 mm (d= 12mm)
Shear Wall : 25 mm
Beams : 25 mm
Slabs : 15 mm or not less than diameter of the bar.
Flat Slab : 20 mm
Staircase : 15 mm
Retaining Wall on Earth : 20/ 25 mm
Water retaining structures : 20 / 30 mm
Sunshade (Chajja) : 25 mm

Hook for stirrups is 9D for one side

No. of stirrups = (clear span/Spanning) + 1

For Cantilever anchorage length for main steel is 69D

“L” for column main rod in footing is minimum of 300mm

Chairs of minimum 12 mm diameter bars should be used.

Minimum diameter of dowel bars should be 12 mm

Lap slices should not be used for bar larger than 36 mm.

In steel reinforcement binding wire required is 8 kg per MT.

Lapping is not allowed for the bars having diameters more than 36 mm.

Minimum number of bars for a square column are 4 and for circular column are 6.

Longitudinal reinforcement should not be less than 0.8% and more than 6% of gross C/S.

Weight of rod per meter length = d²/162 where d is the diameter in mm

All reinforcement shall be free from mill scales, loose rust & coats of paints, oil or any other substances.

Main bars in the slabs shall not be less than 8 mm (HYSD) or 10 mm (Plain bars) and the distributors not less than 8 mm and not more than 1/8 of slab thickness.

In case of spacing of bars
Provide the diameter of the bar, if the diameter of the bar are equal.
Provide the diameter of the larger bar, if the diameter are unequal.
5mm more than the nominal maximum size of the coarse aggregate.

Things Site Engineers Must Know

Check out the Unit Weights and Conversion which will be required on construction site here

We at engineeringcivil.com are thankful to Er Vikrant for submitting this construction site check list which is of great use to all civil engineers.

Minimum thickness of slab is 125 mm.

Water absorption should not be more than 15 %.

Dimension tolerance for cubes + – 2 mm.

Compressive strength of Bricks is 3.5 N /mm²

Maximum Free fall of concrete allowed is 1.50 m.

In soil filling as per IS code for every 100 sqm 3 sample for core cutting test should be taken.

Electrical conduits shall not run in column

Earth work excavation for basement above 3 m should be stepped form

Any back filling shall be compacted 95% of dry density at the optimum moisture content and in layers not more than 200mm for filling above structure and 300 mm for no structure

F soling is specified the soling stones shall be laid at 45° to 60° inclination (and not vertical) with interstices filled with sand or moorum.

A set of cube tests shall be carried out for each 30 cum of concrete / each levels of casting / each batch of cement.

Water cement ratio for different grades of concrete shall not exceed 0.45 for M20 and above and 0.50 For M10 / M15 contractor

For concrete grades M20 and above approved admixture shall be used as per mix design requirements.

Cement shall be stored in dry places on a raised platform about 200mm above floor level and 300mm away from walls. Bags to be stacked not more than 10 bags high in such a manner that it is adequately protected from moisture and contamination.

Samples from fresh concrete shall be taken and at least a set of 6 cubes of 150mm shall be prepared and
cured. 3 Cubes each at 7 days and 28 days shall be tested for compressive strength. The test results
should be submitted to engineer for approval. If results are unsatisfactory necessary action/rectification/remedial measures has to be exercised.

Water used for both mixing and curing shall be clean and free from injurious amounts of oils, acids, alkalies, salts, sugar and organic materials or other substances that may be deleterious to concrete or steel. The ph shall be generally between 6 and 8.

Cement shall be tested for its setting.
1. The initial setting time shall not be less than 30 minutes.
2. The final setting time shall not be more than 10 hours.

Slump IS 456
Lightly reinforced 25 – 75 mm
Heavily reinforced 75 – 100 mm
Trench fill (insitu & Tremie) 100 – 150 mm (For Tremie no need of vibrator)

Curing Days Required
Super Sulphate cement : 7 days
Ordinary Portland cement OPC : 10 days
Minerals and Admixture added cement : 14 days

Cube Samples
1 – 5 M³ : 1 No.
6 – 15 M³ : 2 No’s
16 – 30 M³ : 3 No’s
31 – 50 M³ : 4 No’s
Above 50 M³ : 4 + 1 No of addition sample for each 50 M³.

Things Site Engineers Must Know About Reinforcement and Steel Bars

Check out the Unit Weights and Conversion which will be required on construction site here

We at engineeringcivil.com are thankful to Er Vikrant for submitting this construction site check list which is of great use to all civil engineers.

Accuracy of measuring equipment in batching plant.
Cement : + – 2%
Aggregate : + – 3%
Admixture : + – 3%
Water : + – 3%
Mixing time : 2 minutes for one mixing. (Mixing which is being done on site)

Tolerance in Form work
In C/S for columns & Beams deviation is = + 12mm more (or) – 6mm less in size
In footing plan = + 50 mm more (or) – 12 mm less size
In depth = + – 0.05 D (specified thickness).

Tolerance in Reinforcement
For effective depth D < = 200mm = +- 10mm For effective depth D > 200mm = +- 15mm
For Cover to reinforcement = + 10mm
Maximum freefall of concrete = 1.50 m height.

Tolerance on diameter in length
0-25mm = +- 0.5 %
25-35mm = +- 0.6 %
35-50mm = +- 0.8 %

Tolerance on weight per metre
0-10mm = +- 7%
10-16mm = +- 5%
16 and above = +- 3%

Tolerance for cutting Length
A) When the specified length is not given = + 75mm (or) – 25 mm
B) When the minimum length is specified = + 50 mm (or) – 0 mm

We are thankful to Er. Vikrant for submitting this to us.