Week 8 Challenge

Question :1

Calculate the loads as per IRC 6 assuming bridge in Bangalore on the pile group of the below given bridge for the abutment.(ignore temperature and wind)

Answer:

• Girder Cross sectional Figure of Box  girder:

Question :2

 List all the components of the well foundation and list the minimum kg/cumec(poundage) in them mentioning clauses from IRC codes.

Also list their functionality in respect to bridges loadings.

Draw a sketch for each component to the scale.

Answer:

 <!-- [if !supportLists]-->·        <!--[endif]-->Well Foundation:

In India, a "well foundation" refers to a specific type of deep foundation used in civil engineering and construction, especially in bridge construction. Well foundations are commonly employed in areas with soft or loose soil conditions, such as riverbeds or areas prone to flooding. It Provide a solid and massive structure & can resist large horizontal forces and vertical loads.

Well foundations consist of several key components, which are essential for their construction and functionality.

The main components of a well foundation in the construction field include:

<!-- [if !supportLists]-->·        Cutting Edge

 The cutting edge, also referred to as the bottom plug, is the lowermost section of the well foundation. It is usually made of reinforced concrete and is designed to penetrate the underlying soil or bedrock, providing stability, and preventing settlement.

The mild steel cutting a shall be a strong enough and not less than 40kg/m. (IRC:78-2014, Cl.708.6.1) to facilitated sinking of the well. The type of strata expected to be encountered without suffering any damage.

<!-- [if !supportLists]-->·        <!--[endif]-->Bottom Plug: (IRC:78-2014, Cl.708.8)

The bottom plug shall be provided in all wells and the top shall be kept not lower than 300mm. In the centre above the top of the curb.

The concrete makes used in bottom plug shall have a minimum cement content 330kg/m3 and slump of about 150mm to be permit Easy flow to concrete throw tremie to the place fill up all cavities. (IRC:78-2014, Cl.708.8.2)

For under water concreting the concrete shall be placed by Timmy. Under steel water condition and the cement content of mix be increased by 10%. (IRC:78-2014, Cl.708.8.2)

Thickness of bottom plug should not be less than the half of the dredge hole diameter nor less than the Calculated using following formula as given below:

                                                          </> < class>Where,

 W          =             Total bearing pressure at the base of well.

F_c            =             Flexural strength of concrete in bottom plug.

<!-- [if gte msEquation 12]>ϑ<![endif]--><!-- [if !msEquation]--><!-- [if gte vml 1]> <![endif]--><!-- [if !vml]--><!--[endif]--><!--[endif]-->             =             Poisson’s ratio for concrete. (As taken0.18 & 0.20)

<!-- [if !supportLists]-->·        <!--[endif]-->Filling the well: (IRC:78-2014, Cl.708.8.10)

The fling of the well is considered necessary above the bottom plug Shall be done with sand or excavated material free from organic matter.

Sand filling provide stability of well reduced tensile stress produced by bending moment and distributes the load of superstructure to the bottom plug.

<!-- [if !supportLists]-->·        <!--[endif]-->Intermediate Plug: (IRC:78-2014, Cl.708.8.10.1)

After the filling of materials such as sand or excavated materials,

then 300mm thick plug of M15 cement concrete shall be provided over it.

<!-- [if !supportLists]-->·        Well Curb: (IRC:78-2014, Cl.708.7.3)

The well curb, also known as the outer casing, is the outermost part of the well foundation. It serves to retain the surrounding soil and protect the interior during excavation. The well curb is typically made of reinforced concrete or steel. The minimum reinforcement to be provided is 72kg/m³. The inner portion of the staining should have a slope of 2:1 guidance.

The internal angle of the curb should be kept at about 30 degrees to 37 degrees. (IRC:78-2014, Cl.708.7.2)

<!-- [if !supportLists]-->·        <!--[endif]-->Intermediate Plug:

It's possible that the term "intermediate plug" may be used informally or regionally to refer to a component or stage of construction within a well foundation,

<!-- [if !supportLists]-->·        <!--[endif]-->Well, Steining: (IRC:78-2014, Cl.708.2.1)

It is the main body of the well Who is tennis for load to the base of the foundation It’s basically reinforced concrete. Minimum grade of concrete used in staining is M20 with cement content not less than 310 kg m^3.

It is the wall or shall of the well, made of R.C.C. and which transfer the load to the curb. It acts as an enclosure for excavating the soil for the penetration of well. The facilitated well sinking an offset of 75mm to 100mm is provided in well staining at its junction with the well curb. The thickness should be sufficient to overcome skin friction developed during sinking by its own weight.

The minimum reinforcement in the oil is staining should be 5 to 6kg/m³of which 75% is to be provided as vertical and 25% as lateral ties or hoop rings.

<!-- [if !supportLists]-->·        <!--[endif]-->For Brick masonry:

The minimum thickness is 450mm or 1/8 of the external Dia. Of well.

The thickness is increased by 120mm /3m depth after sinking.

<!-- [if !supportLists]-->·        <!--[endif]-->For cement Concrete:

The minimum thickness is 1/10 of the external Dia. Of well.

The thickness is increased by 150mm /6m depth after sinking.

The thickness of oil staining should not less than 450 mm and not less than the following equation as given below:

                                                            T=KD√L

Where,

T             =             The minimum thickness of concrete staining in metre.

D             =             The external diameter of the circular well or dump bell shaped well or plan dimension of twin D Well metre.

L             =             Depth of Well in metre below LWL or top of well cap, whichever is greater

 K            =             A constant depending on the nature of subsoil and staining material.

                              Taken as:

                                             For Circular well,                               k=0.30

                                             For Twin D well                                 k=0.039

                                                            straining in sandy strata and 10% more than the corresponding value in the case of clay soil. (IRC:78-2014, Cl.708.2.3.1)

The recommended thickness is as tabulated:

          D(m)                                                   3                            5                            7

                              T(m)                                                    0.75                      1.2                        2.0

<!-- [if !supportLists]-->·        <!--[endif]-->Top Plug:

The term "top plugging" in the context of well foundation construction typically refers to the process of sealing or closing off the top of the well foundation structure. This is an important step in the construction of a well foundation, as it ensures that the well is properly sealed and prepared for the placement of the superstructure.

The minimum grade of concrete used in top plug is M15.

It is placed under well cap and its help transferring the load through the granular materials into the steining.

PCC top Plug        :  Placed on the filling materials. (Full filling by sand)

RCC Top Plug       :  When water is present on intermediate plug.

<!-- [if !supportLists]-->·        <!--[endif]-->Well Cap or Top Slab: (IRC:78-2014, Cl.708.11)

The well cap, or top slab, is the uppermost part of the well foundation. It forms a stable platform for supporting the structure that will be constructed above the well foundation. The top slab is designed to distribute the load from the superstructure to the underlying soil or bedrock.

Thickness of Well cap is usually between 1500m & 2000 mm The recommended minimum thickness is, 0.75 metre.

The construction of well foundations is a complex process that demands careful consideration of soil conditions, hydrology, and structural requirements. Well foundations are commonly used in areas with soft or loose soil to transfer heavy loads to deeper, more stable layers of soil or bedrock. Proper design and construction are crucial to ensure the longevity and effectiveness of well foundations and the structures they support.

•  Figure of the well foundation components:

< /></> <> </> <> <><>></> </> <>< /></> <> < alt>