Question

In: Civil Engineering

A _____________ dredger essentially consist of a graph suspended from cable. Select one: a. Hydraulic b....

A _____________ dredger essentially consist of a graph suspended from cable.

Select one:

a. Hydraulic

b. Bucket

c. Grab

d. Ladder

Solutions

Expert Solution

Answer:   option (c): Grab

Explanation

Dredger

  • It is a marine vessel.
  • It has a device or devices to scrap depositions such as sand, gravel, sediments, and etc. over sea bed.

Types of dredgers

Dredgers are mainly divided into three types: Hydraulic, mechanical and other dredgers (dredgers other than Hydraulic and mechanical dredgers)

(i) Hydraulic dredger:

  • Principle: Addition of large amounts of process water in order to change original structure of sediments.
  • It uses moving water to suction up the deposited materials.
  • Common form: consists of onboard pump to suck material up using tube lowered to bottom of water and is then pumped through a pipeline to a different location.

(ii) Mechanical dredger:

  • Suitable for working in confined areas.
  • It is used to remove the hand-packed materials.

Mechanical dredgers can be further divided into four types: Bucket Dredger, Bucket Ladder Dredger and Grab Dredger and Backhoe dredger.

(A): Bucket Dredger

  • Fixed on anchors (stationary dredgers.
  • Movement is possible along the semi-arcs during dredging using winches.
  • It has an endless chain of buckets.
  • Buckets are used to scrap off and fill the loose dredged material.
  • The completely filled buckets are emptied into barges by turning them upside down over barges.

(B): Bucket Ladder Dredger (modified bucket dredger)

  • It has a series of buckets mounted on a wheel used to pick sediments.
  • Limitation: low production, high level of noise

(C): Grab (clamshell) dredger

  • Stationary dredgers fastened on with anchors or using spud-poles.
  • Cutting tool- grab consisting of wire operated two half-shells.
  • Half-shells after being filled get loaded in barges.
  • Grab can be mounted on a dragline or a hydraulic excavator.
  • Grabs are of different types: open grab, closed grab and watertight grab.
  • Grabs are useful in: removal of material from corners of dock and basin, easy excavation close to quay walls.
  • Grab dredger is a revolving crane and is fitted with a grab which is placed on a hopper vessel or pontoon.
  • A grab can lowers, closes, and raises a single bucket using flexible cables.
  • It makes use of a bivalve grab suspended from a crane which can be opened or closed using a cable or by using hydraulic cylinders. (Thus, the answer is option (c): grab).
  • Characteristics of the grab
  • Shape of grab – scooper like a circle’s quadrant
  • Normal position opening
  • When grab is lowered to bottom, Grab dig to the mud and gets closed with the help of suitable arrangements.

(D) Backhoe Dredger

  • Useful in: harbour maintenance and shallow dredging.
  • They are hydraulically driven excavators.
  • It consists of a half-open shell or a digging bucket.
  • Half-open shell or a digging bucket is capable of digging across a wide range of materials.

Related Solutions

B) 3 - phase system, consist of three lines is suspended by a string of 3...
B) 3 - phase system, consist of three lines is suspended by a string of 3 similar insulators. When the voltage across the line unit is 30 kV, calculate • The line to neutral voltage, when the shunt capacitance between each insulator and earth is 0.111 of the capacitance of the insulator itself. The string efficiency for the three insulators When you have 4 insulators How can you derive (V).
The corpus luteum does what? Select one: a. releases the secondary oocyte. b. forms from a...
The corpus luteum does what? Select one: a. releases the secondary oocyte. b. forms from a Graafian follicle after ovulation and secretes mainly progesterone. c. degenerates into a zygote if pregnancy does not occur. d. secretes progesterone. e. forms from a Graafian follicle after ovulation. During the female menstrual cycle what hapens? Select one: a. the fimbriae wall thickens over the course of the cycle. b. there are three phases: menarche, amenorrhea, and luteal. c. estrogen levels peak at ovulation....
26. Select the odd one out Select one: a. Zone control b. Paint strips c. Imbedded...
26. Select the odd one out Select one: a. Zone control b. Paint strips c. Imbedded wire d. dead reckoning 27. An AGV has an average speed of 50 m/min. how much distance it can travel in an hour given that it is working in a factory layout in which it has availability factor of 0.9 and traffic factor of 0.95 Select one: a. 3 km b. 2.5 km c. 3.5 km d. 2 km 28. In which of the...
Select the incorrect statement about ADH. Select one: a. It stimulates reabsorption of water b. It...
Select the incorrect statement about ADH. Select one: a. It stimulates reabsorption of water b. It is not secreted if the body consumes large amounts of water c. It is secreted if the body fluids become hypertonic d. It is produced by the distal tubule e. It is also called vasopressin
What should be subtracted from GDP to calculate national income? Select one: A. indirect taxes B....
What should be subtracted from GDP to calculate national income? Select one: A. indirect taxes B. net factor payments to the rest of the world C. personal income taxes D. depreciation
Basic renal processes include? Select one: a. Filtration from Bowman's capsule into the glomerulus. b. Secretion...
Basic renal processes include? Select one: a. Filtration from Bowman's capsule into the glomerulus. b. Secretion from the tubule into the peritubular capillaries. c. Reabsorption from the capillaries into the tubular lumen. d. Filtration from Bowman's capsule into the glomerulus and secretion from the tubule into the peritubular capillaries. e. None of the choices are correct
Select any one of the one anothers from the reading, such as “Be Kind to One...
Select any one of the one anothers from the reading, such as “Be Kind to One Another.” Think about why practicing this particular one another is important in your own spiritual life and what you might have to change or give up to practice it. As the week progresses, focus on practicing this one another. In your journal for this week: Record each day: Your experiences Your learning Your growth related to your selected one another Answer the following question:...
The current in an inductor Select one: a. is in phase with the voltage b. lags...
The current in an inductor Select one: a. is in phase with the voltage b. lags behind the voltage by 90 degrees c. leads the voltage by 90 degrees The current in an resistor Select one: a. leads the voltage by 90 degrees b. lags behind the voltage by 90 degrees c. is in phase with the voltage What is an AC circuit? Select one: a. A circuit in which the applied voltage is constant as a function of time...
Select the TRUE statement from the following: Select one: a. The outermost electrons of Fe3+ are...
Select the TRUE statement from the following: Select one: a. The outermost electrons of Fe3+ are more energetic than the outermost electrons of Fe0 b. When the Cr atom loses electrons to become positively charged, the first electrons lost are from the 3d subshell. c. For any given element, the anion will be smaller than the neutral atom. d. For any given element, the cation will be smaller than the neutral atom.
One kind of elevator has the elevator car hanging from a cable, which then passes over...
One kind of elevator has the elevator car hanging from a cable, which then passes over a pulley and connects to a counterweight. The mass of a fully-loaded elevator (that is, the elevator and all its passengers) is 1850 kg , the mass of the counterweight is 1750 kg , and the pulley has a radius of 0.5 mm and a mass of 450 kg . A motor drives the motion of the elevator by exerting a torque on the...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT