Производство железобетонных труб для микротоннелирования: расчет на осевое продавливание и нормы DIN EN 1916

1. The Demanding Physics of Trenchless Pipe Jacking

In modern urban infrastructure, open-cut trench excavation is frequently impossible due to existing highway pavements, building foundations, water bodies, and subterranean metro tunnels. Trenchless pipe jacking (寰《绠?/ 椤惰繘鏂藉伐) propels a cutting shield head underground, with high-capacity hydraulic jacking rams in the drive shaft pushing the string of reinforced concrete pipes forward through the soil.

During driving, each pipe section acts as a structural column transmitting immense axial thrust forces鈥攐ften ranging from 1,500 kN on DN800 pipes to over 12,000 kN on DN2400/DN3000 pipes. Any minute irregularity in end-face squareness will concentrate thrust into point contact, causing catastrophic explosive spalling underground.

2. Jacking Joint Profiles: Steel Collar (F-Type) vs. In-Wall (J-Type)

Two joint architectures dominate international trenchless engineering:

1. Steel Collar Joint (F-Type / 閽㈠鐜帴澶?: A roll-formed Q345B carbon or stainless steel sleeve (thickness 10鈥?6 mm) is cast directly into the spigot end of the pipe. When jacked together, the steel sleeve slides over the adjacent pipe's rebated shoulder, encasing a wedge-shaped elastomeric profile gasket. Offers superior angular deflection tolerance (up to 1.0掳鈥?.5掳) without leaking.

2. In-Wall Rebated Joint (J-Type / 闃舵鎵挎彃鎺ュご): Fully concrete stepped joint with internal rubber gasket groove. Eliminates external steel collars, highly popular in non-aggressive soil environments.

3. Precision End-Ring Tolerances & Lathe Machining

Standard drainage pipe molds allow end squareness deviations of 卤3 mm to 卤5 mm. For jacking pipes, this would cause disastrous point loading under hydraulic ram forces.

4. Calculating & Resisting Extreme Axial Thrust Loads

Jacking pipe design must resist permissible jacking force (F_j) calculated per DIN 1610 / ATV-A 161 standards:

F_j 鈮?A_c 脳 f_cd 脳 k_1 脳 k_2

Where A_c is the concrete cross-sectional area, f_cd is the design compressive strength, k_1 accounts for cushion ring stress distribution (0.65鈥?.80), and k_2 accounts for angular deflection during curved driving.

HLY jacking pipe molds ensure the full annular bearing area is 100% planar, maximizing usable thrust capacity without local failure.

5. The Critical Role of Wooden Cushion Packing Rings

Between the concrete pipe faces, a wooden packing cushion ring (鏈ㄥ灚鍦? made from multi-layer marine plywood, chipboard, or fiberboard of 12鈥?8 mm thickness) must be installed. The wooden cushion crushes under early jacking pressure, redistributing uneven stress peaks across the full circumference.

6. High-Performance Concrete Mix: C50/C60 with Silica Fume

Jacking pipes require heavy-duty high-performance concrete (HPC):

鈥?Compressive Strength: Minimum C50 or C60 (50鈥?0 MPa at 28 days; 鈮?5 MPa before demolding).

鈥?Silica Fume / Slag Additions: 5% to 8% condensed silica fume (寰绮? added to refine pore structures, increasing surface abrasion resistance and chemical impermeability against underground slurry.

鈥?Low Water-Binder Ratio: Maintained between 0.30 and 0.34 with high-range polycarboxylate superplasticizers.

7. Frequently Asked Engineering Questions