Examkin

Question

Difficulty: HardDistinguishing Main Idea from Details

Subsurface micro-tunneling operations in dense urban environments require continuous ground stabilization to prevent structural settling. While high-pressure jet grouting is frequently deployed to consolidate loose sandy strata, engineers increasingly rely on artificial ground freezing for water-saturated soils. In this process, closed-loop refrigeration pipes circulate chilled brine at sub-zero temperatures, freezing pore water into an impermeable ice-soil matrix. Although the refrigeration units consume immense electrical power and require round-the-clock thermal monitoring, the frozen perimeter provides temporary compressive strength and absolute water cutoff. Ultimately, ground freezing provides a reliable, impermeable barrier that enables safe underground excavation where conventional chemical grouting methods fail.

Which of the following best expresses the main idea of the passage?

  1. A
    High-pressure jet grouting is deployed to consolidate loose sandy strata during micro-tunneling.
  2. Artificial ground freezing serves as an effective temporary stabilization method for tunneling through water-saturated ground.Answer
  3. C
    Closed-loop refrigeration pipes circulate sub-zero brine to freeze pore water into an ice-soil matrix.
  4. D
    Ground stabilization methods eliminate all geotechnical hazards and settlement risks in urban excavation.

Answer

Artificial ground freezing serves as an effective temporary stabilization method for tunneling through water-saturated ground.
The correct answer accurately expresses the overarching thesis of the passage: artificial ground freezing is presented as a vital, temporary solution enabling safe excavation in saturated soils where other methods fail. The remaining sentences in the paragraph—explaining the cooling mechanism, requirements, and limitations—all exist to substantiate this central point.

Step-by-Step Solution

1
Analyze the passage structure and identify the core topic
The text begins by establishing the necessity of ground stabilization in tunneling and concentrates predominantly on artificial ground freezing as a solution for saturated soils.
Determining the subject and problem-solution relationship establishes the scope of the paragraph.
2
Distinguish central assertions from supporting technical details
References to jet grouting, brine circulation pipes, electrical power consumption, and thermal monitoring serve as secondary facts and procedural descriptions supporting the primary claim.
Supporting details provide evidence or explain mechanisms, whereas the main idea synthesizes why those details are presented.
3
Select the statement that reflects the complete scope without being overly broad or narrowly focused
The statement summarizing artificial ground freezing as a reliable temporary stabilization technique for saturated soils encompasses the beginning, middle, and concluding synthesis of the text.
The correct main idea must encapsulate the full paragraph without being confined to a single sentence or making unwarranted generalizations.

Key Concept

Distinguishing the central thesis of an expository paragraph from subordinate factual details and scope distortions.
Estimated Time:1m 30s
Rate this question

Topics

Distinguishing Main Idea from Details

More questions from this topic