If the angle of shearing resistance is 60° then the product of active earth pressure

If the angle of shearing resistance is 60°, then the product of active earth pressure coefficient and passive earth pressure coefficient will be

A) 0

B) 1/3

C) 1

D) 3

Coefficient of Active Earth Pressure Coefficient :-

Ka=1−sin(ϕ)1+sin(ϕ)=tan2(45−ϕ2)$K_a=\frac{1-\sin \left(\varphi \right)}{1+\sin \left(\varphi \right)}={\tan }^2\left(45-\frac{\varphi }{2}\right)$

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Coefficient of Passive Earth Pressure Coefficient :-

Kp=1+sin(ϕ)1−sin(ϕ)=tan2(45+ϕ2)$K_p=\frac{1+\sin \left(\varphi \right)}{1-\sin \left(\varphi \right)}={\tan }^2\left(45+\frac{\varphi }{2}\right)$

Calculations:

Point to be remembered:

For any value of shearing angle, the product of active earth pressure coefficient and passive earth pressure coefficient will always equal to 1.

Ka×Kp=1−sin(ϕ)1+sin(ϕ)×1+sin(ϕ)1−sin(ϕ)=1$K_a\times K_p=\frac{1-\sin \left(\varphi \right)}{1+\sin \left(\varphi \right)}\times \frac{1+\sin \left(\varphi \right)}{1-\sin \left(\varphi \right)}=1$

Alternate Solution:

For ϕ = 60°

Ka=tan2(45−602)=0.0718$K_a={\tan }^2\left(45-\frac{60}{2}\right)=0.0718$

Ka=tan2(45+602)=13.928$K_a={\tan }^2\left(45+\frac{60}{2}\right)=13.928$

Therefore,

Ka × Kp = 0.0718 × 13.928 = 1

The quantitative statement of the balance water gains and losses

 The quantitative statement of the balance water gains and losses in a certain basin during a specified period of time is known as which one of the following?

A) Water budget

B) Hydrologic budget

C) Groundwater budget

D) None of the above

Water - Budget Equation :-

The Water - Budget equation is based on conservation of mass in a closed system and states that any water entering a system, must be transferred into either evaporation, surface runoff or stored in the ground.

A general water balance equation is

Mass inflow - Mass outflow = Change in storage

or

P = R + E + ΔS

where

P is precipitation (gain)

E is evapotranspiration (loss)

R is streamflow (loss)

ΔS is the change in storage 

Hence, it can be concluded from the above that the balance water gains and losses in a certain basin during a specified period of time is Water - Budget equation.

Quick lime

 

• Quicklime (CaO) reacts with water to form slaked lime {Ca(OH)2}.
• The addition of a limited amount of water to quick lime is called slacking of lime.
• When Calcium oxide is mixed with water it forms Calcium Hydroxide.
• The above reaction can be written as

⇒ CaO + H2O → Ca(OH)2

• Calcium Hydroxide is used in the preparation of Mortar.

 

Common Name	Chemical formula/Compound name
Lime Stone	CaCO3/Calcium Carbonate
Chloride of Lime	Ca(OCl)2/Calcium Hypochlorite
Chalk Powder	CaCO3/Calcium Carbonate

Question related to Quick Lime

Fill in the blank with the most appropriate option.

Quicklime reacts with water to form ______.

A) limestone

B) slaked lime

C) chloride of lime

D) chalk powder

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consolidated drained (CD) test

consolidated drained (CD) test  

In the consolidated drained (CD) test on a saturated soil sample, drainage is permitted throughout the test, during the application of both normal as well as shear stress so that full consolidation occurs and no excess pore pressure is set up at any stage of the test. Generally, it takes 2 to 5 days.

Important Points:

In the unconsolidated-undrained (UU) test, no drainage is permitted either during the consolidation stage or the shear stage. Therefore, there is no dissipation of pore pressure during the test and test can be conducted in a few minutes (5 minutes to 10 minutes).

In the consolidated-undrained (CU) test, drainage is permitted under the initially applied normal stress only and fully primary consolidation is allowed to take place and no drainage is allowed in the shear stage. Generally, it takes 24 hours.

Hence, pore water pressure is zero during both consolidation and shearing stage.

Question related to consolidated drained (CD) test 

In the consolidated drained test on a saturated soil sample, pore water pressure is zero during

A) Consolidation stage only

B) Shearing stage only

C) Both consolidation and shearing stage

D) Loading stage

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Carpet area

Carpet area

Carpet area of a building is a useful area or liveable area or lettable area

It is the total floor area minus the circulation area, verandahs, corridors, passages, staircase, lifts, entrance hall, etc. and minus other non-useable areas as sanitary accommodations, air conditioning room etc.

Carpet Area For office Building :-

Carpet area is the lettable area or usable area.

Carpet Area For Residential building :-

Carpet area is the liveable area and should exclude the kitchen, pantry, stores and similar other room which are not used for living purposes.

question related to carpet area :-

Carpet area does not include ________.

A) bathroom and lavatory

B) storeroom

C) pantry

D) all of the above

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Bogue’s Compounds or Portland cement compounds

 Bogue’s Compounds or Portland cement compounds

The setting and hardening of cement after addition of water is due to hydration of some of the constituent compounds of cement such as Tricalcium aluminate, Tricalcium silicate, Dicalcium silicate, and Tetra calcium aluminoferrite.

These compounds are known as Bogue’s Compounds.

Hydration of Bogues Compounds

Tricalcium aluminate (C3A) :-

Celite is the quickest one to react when the water is added to the cement. It is responsible for the flash setting. The increase of this content will help in the manufacture of Quick Setting Cement. The heat of hydration is 865 J/Cal.

Tricalcium silicate (C3S) :-

This is also called as Alite. This is also responsible for the early strength of the concrete. The cement that has more C­­­­3S content is good for cold weather concreting. The heat of hydration is 500 J/Cal.

Dicalcium Silicate (C2S) :- 

This compound will undergo reaction slowly. It is responsible for the progressive strength of concrete. This is also called as Belite. The heat of hydration is 260 J/Cal.

Tetra calcium Alumino ferrite (C4AF) :-

This is called as Felite. The heat of hydration is 420 J/Cal. It has the poorest cementing value but it responsible for long-term gain of strength of the cement.

For the rate of hydration is highest for C4AF and heat of hydration is highest for C3A.

From the above, the decreasing order of rate of hydration of Portland cement compounds is

C4 AF > C3 A > C3 S > C2 S.

For the heat of hydration, decreasing order of heat of hydration of portland cement is

C3 A > C3 S > C4 AF > C2S

Note: Heat of Hydration and Rate of Hydration is different

Question related to bogus compound

Which of the following shows the CORRECT decreasing order of rate of hydration of Portland cement compounds?

A) C3 A > C4 AF > C3 S > C2 S

B) C3 A > C4 AF > C2 S > C3 S

C) C3 A > C3 S > C2 S > C4 AF

D) C4 AF > C3 A > C3 S > C2 S

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