Posts by Kanwarjot Singh

Soils can experience over-compaction if the compactor makes too many passes over it. In fact, relative soil compaction test results over 100% do not necessarily mean over-compaction because the relative compaction is based on the maximum dry density of the soil obtained by the Proctor test and this does not necessarily refer to absolute maximum dry density.

Over-compaction is considered undesirable because it may eventually create cracks in the underlying compacted material so that it results in a decrease in density. Moreover, it causes waste of machine power and manpower which is undesirable.

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.

For the construction of diaphragm walls adjacent to buildings, previous experience showed that excess slurry head above groundwater level had to be maintained to limit the ground settlements during the construction of diaphragm walls. In fact, the excess slurry head can be achieved by the following methods. The first one is to construct a ring of well points to lower the piezometric level to achieve a higher excess slurry head in diaphragm walls. Alternatively, guide walls may be raised above ground level to accommodate the slurry column.

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 functions of diaphragm walls are as follows:

(i) It is designed to retain soils during the construction of underground structures.

(ii) It helps to control the movement of ground during construction.

(iii) It is intended to take up high vertical loads from above ground structures during construction (e.g. top-down approach). In addition, during the servicing of the completed structures, the diaphragm walls, internal piles and basement raft act together as a single unit to perform as piled raft.

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 use of tiebacks in deep excavation allows uninterrupted earth moving within the excavation zone owing to the absence of interior obstructions. The spacing of tieback should not be placed too close as this may impair the capacity of tieback because of the interference between adjacent grouted zones.

A tieback is made first by drilling a hole by a drill rig, followed by placing a bar in the drilled hole. Concrete is then poured in the hole and the connection of tieback with wall is made lastly. A tieback anchor consists of an anchorage located in a bearing layer and the anchor is tensioned at the front face of the wall. The portion of the anchor which transmits the force to the surrounding soil is called the “fixed length”. One the other hand, the “free length” of tieback transfers the force from the fixed length through the anchor head to the wall.

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.

When excavation work is carried out in grounds with highly permeable soils, other than the installation of well points to lower down the groundwater table, consideration may be given to the injection of grout to the soils.

The purpose of the injection of grout is to fill the pore spaces and cavities of soils with grout and to reduce the permeability of soils. The method of grouting is effective in coarse soils but not for sands. In essence, “grout curtain” is constructed around the excavation by installation of several rows of injection holes for grouting.

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.

Diagonal strutting is sometimes used at the corners of excavation to leave a large working space at excavation level. Sometimes, raking struts are observed in long flying shores across excavation and these struts serve to decrease the span length of struts.

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.

Following table shows unit weight of materials used at construction site. Please note this is for reference purpose only and may vary from place and type of material.

We are thankful to Engineer Ravi Verma for submitting this very useful information to us. If you also have any other formula and shortcuts which can be used on construction site do submit it to us using the submit form here

S.No	Material	Theoretical Weight in(KG/M³)	Approx Weight at Site in		Remarks
			Kg	Per
1	Cement	1440	50	Bag
2	Steel	7850	d²/162		d -dia in mm
3	Sand-
	Dry	1600	50 to 55	farma	1 farma=1.25cft
	River	1840	57 to 63	farma	1 farma=1.25cft
4	Stone(basalt)	2850 to 2960	48 to 52	farma	metal 12mm to 20mm
5	Water	1000	1	liter
6	PCC	2240	8.24 to 8.5	Cube mould	cube mould size=15x15x15cm
7	RCC 2% Steel	2420
8	Bricks	1600 to 1920	1.9 to 2	no	9x4x2 3/4″
			4.8 to 4.9	no	9x6x3 3/4”
9	Brick Masonry	1920
10	Soil(damp)	1760	50 to 55	cft	Black cotton
11	Cement concrete block(solid)	1800	18 to 20	cft	30x15x20 cm
			10 to 11	no	30x10x20 cm
12	Cement Mortar	2080	57 to 62	cft
13	Lime Mortar	1760	48 to 52	cft
14	Lime	640	30	bag
15	Glass	2530	0.9 to 0.95	sft	4mm tk plain
16	Teak Wood	670 to 830	18 to 20	cft
17	Sal Wood	990	22 to 24	cft
18	Marble mosaic tile		2.8 to 3.2	no	25x25x22mm
			4.8 to 5.2	no	30x30x25mm
19	Chequered tile		2.5 to 2.8	no	25x25x22mm
20	Glazed tile15x15cm		0.20 to 0.25	no	5mm tk
21	Marble Stone	2620	5.1	sft	3/4″tk
22	Granite Stone	2460-2800	5.35	sft	3/4″tk
23	Coddappa	2720	6.4	sft	1 1/4″tk
24	A.C.sheet corrugated	16	1.2	sft
25	Bitumen	1040	220	Drum	200liter drum
26	Window frame (simple design)		1.9 to2.1	sft
27	Door Frame
	a)3’00×7’0		25 to 27	no	section 4″x2 1/2″
	b)2’6″x7’0		24 to 26	no	section 4″x2 1/2″

Following are the IS codes which are used for Wood And Other Lignocellulosic Products. These IS Codes include standardization in the field of Wood Products including Composite Wood Products

IS 303:1989 Specification for plywood for general purposes

IS 652:1960 Specification for wooden separators for lead-acid storage batteries

IS 709:1974 Specification for medium strength aircraft plywood

IS 710:1976 Specification for marine plywood

IS 848:2006 Specification for synthetic resin adhesives for plywood (pnenolic and aminoplastic)

IS 851:1978 Specification for synthetic resin adhesives for construction work (non-structural) in wood

IS 852:1994 Specification for animal glue for general wood working purposes

IS 1328:1996 Specification for veneered decorative plywood
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Preloading in struts in braced excavation helps eliminate the potential movement. The application of preload decreases the shear stress in soils established previously by excavation. As a result of stiffening of soils, the soil movement is declined accordingly.

However, the use of very high preloads in struts may not be desirable because the local outward movement at struts may cause damage to nearby utilities.

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 use of active and at-rest theory is not applicable in braced excavation. In essence, upper struts tend to be more heavily loaded while lower struts appear to be less loaded when compared with active pressure theory.

Peck then measured the bracing loads which were converted back to soil pressures. For example, the pressure envelope for non-cohesive soils is 0.65rHK_a
where
r=soil density
H=height of excavation
K_a=active pressure coefficient

Some engineers consider r as total soil weight without applying any water pressure. However, Peck has said “the earth pressures are essentially effective active pressures multiplied by a factor and redistributed as a
rectangle or a trapezoid.” Hence, effective weight of soils should be used for r with water pressures added separately.

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.