In urban underground space development, the urban underground diaphragm wall, as a crucial component of deep foundation pit support and underground structures, directly impacts project safety. In modern urban underground diaphragm wall construction, rotary drilling rigs have become indispensable core equipment due to their unique advantages. This article provides a detailed analysis of the application value and technical essentials of rotary drilling rigsin urban underground diaphragm wall construction. 

I. Construction Challenges of Urban Underground Diaphragm Walls

With accelerated urbanization, urban underground diaphragm wall construction faces three core challenges:

1. Complex surrounding environments (adjacent to buildings/subway tunnels)

2. Variable ground conditions (interbedded soft soil, sand layers, and rock formations)

3. Strict environmental requirements (noise and vibration control) 

These challenges highlight the irreplaceability of rotary drilling rigs in urban underground diaphragm wall construction.

II. Technical Advantages of Rotary Drilling Rigs

To meet the special requirements of urban underground diaphragm walls, modern rotary drilling rigs offer the following outstanding advantages:

1. High-Precision Trenching

(1) Equipped with automatic verticality control systems, deviation can be limited to within 1/300

(2) Electronic depth measurement ensures trench depth accuracy of ±2cm

2. Strong Ground Adaptability

(1) Adapt to different strata by changing drill bits (roller cone bits, Bauer bits, etc.)

(2) Torque adaptive technology handles complex geological variations 

3. Green Construction

(1) Full hydraulic system keeps noise below 75 decibels

(2) Low-vibration design protects surrounding buildings

III. Typical Construction Process

Taking a subway station urban underground diaphragm wall project as an example, the standard construction process with rotary drilling rigs includes:

1. Guide wall construction (precision benchmark)

2. Unit panel division (typically 6m per section)

3. Rotary trenching (equipped with slurry wall protection system)

4. Hole cleaning and slurry replacement (specific gravity controlled below 1.15)

5. Reinforcement cage lifting

6. Concrete pouring 

Particularly in hard rock formations, the combined method of rotary drilling rigs with double-wheel trench cutters significantly improves the efficiency of urban underground diaphragm wall construction.

IV. Key Equipment Selection Criteria

When selecting rotary drilling rigs for urban underground diaphragm wall projects, consider: 

1. Core Parameters

(1) Torque ≥220kN·m (for hard rock formations)

(2) Maximum trenching depth ≥50m

(3) Trench width 600-1200mm 

2. Smart Features

(1) 3D trench monitoring system

(2) Automatic deviation correction

(3) Remote fault diagnosis 

3. Environmental Characteristics

(1) Complies with Stage V emission standards

(2) Low-noise cabin design

V. Future Development Trends

With the advancement of smart construction sites, urban underground diaphragm wall construction is evolving with new trends:

1. Digitalization: BIM technology integrated with rotary drilling rig data

2. Automation: Development of unmanned trenching systems

3. Greening: Pilot applications of electric rotary drilling rigs

Conclusion

For constructing urban underground diaphragm walls in densely populated areas, rotary drilling rigs have become the preferred solution for modern urban underground engineering due to their precision, efficiency, and environmental friendliness. Selecting suitable rotary equipment not only ensures project quality but also effectively controls construction risks.