Proceedings of the International rilem conference Materials, Systems and Structures in Civil Engineering 2016

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International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

CONTROL OF EARLY AGE CRACKING IN A MASSIVE TUNNEL 

STRUCTURE BASED ON EXPERIMENTAL INVESTIGATIONS AND 

NUMERICAL SIMULATIONS 

 

Wibke Hermerschmidt 

(1)

, Martin Laube 

(2)

, Alex-W. Gutsch 

(2)

, Hartmann Alberts 

(2)

, 

Robert Teuber 

(2)

, Eckart Thoms 

(3)

 

 

(1) Technische Universität Braunschweig, iBMB, Germany 

(2) MPA Braunschweig, Germany 

(3) Senate Department for Urban Development and the Environment, Berlin, Germany 

 

 

 

Abstract 

In massive tunnel structures, early age cracking can lead to a loss of serviceability of the 

structure due to leakage. Therefore, a realistic calculation of the temperature and stress 

development caused by heat of hydration is necessary to ensure an economic design. This 

paper presents an application example for the control of early age cracking in a massive 

tunnel structure. Experimental investigations are carried out to characterize the 

thermomechanical behaviour of the concrete at early ages. This includes the testing of the 

adiabatic heat release, the development of the mechanical short term properties (compressive 

strength, tensile strength and Young's modulus) and the autogenous shrinkage. The 

experimental results are used to perform numerical simulations of the temperature and stress 

development in the tunnel structure. In addition, the temperatures and strains in the structure 

are metrologically monitored to validate the simulation results. 

 

 

1. Introduction 

 

In massive concrete structures, the temperature development caused by heat of hydration in 

combination with restraint of the structure can cause cracking at early ages. To avoid cracking 

or limit the crack width with reinforcement, a realistic calculation of the temperature and 

stress development is needed. For such a calculation, several factors affecting the material and 

the structural behaviour have to be taken into account. These factors have been studied 

extensively in the last decades to improve the description of the material properties since early 

ages, e.g. [1-4]. Several different modelling approaches and numerical tools for the 

description of the thermo-chemo-mechanical behaviour of concrete structures have been 

derived from these studies, e.g. [5-10]. Numerical models that account for all the influencing 

factors provide a realistic description of the structural behaviour but are at the same time 

computationally expensive and need an advanced theoretical knowledge from the user to 

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40

International RILEM Conference on Materials, Systems and Structures in Civil Engineering 

Conference segment on Service Life of Cement-Based Materials and Structures 

22-24 August 2016, Technical University of Denmark, Lyngby, Denmark 

 

produce reliable results. Therefore, in engineering practice it is more common to use 

simplified modelling strategies due to their easier inclusion into the planning process. 

The present paper describes the application of such a simplified modelling strategy for the 

control of early age cracking in a massive tunnel structure. In the course of the extension of a 

highway in Berlin, a part of this highway is built as a tunnel with four lanes in each direction. 

The tunnel is constructed as cut-and-cover tunnel, where the excavation is supported with 

slurry walls and an underwater concrete slab founded on piles. The cross section of the tunnel 

is shown in fig. 1. The tunnel is built in independent segments with a length of 10 m. Each 

segment is constructed in three stages: First, the foundation slab is cast, followed by the 

middle wall. The outer walls and the top slab are cast together in the third stage. 

 

 

Figure 1: Cross section of the tunnel structure 

 

As the tunnel is exposed to groundwater, special attention has to be paid to the water tightness 

of the structure. Due to the large thickness of the walls and slabs there is a high risk of 

cracking due to restraint stresses caused by heat of hydration and shrinkage. To avoid leakage 

of the structure, the evolution of restraint stresses has to be taken into account for the design 

of the reinforcement.  

Hence, a comprehensive experimental program has been carried out to obtain an accurate 

description of the concrete’s material behaviour at early ages. This includes the testing of the 

adiabatic heat release, the evolution of the compressive strength, the tensile strength and the 

Young's modulus and the autogenous shrinkage.  

The experimental results act as input parameters for the subsequently performed numerical 

simulations. Staggered temperature-stress simulations with three dimensional finite element 

models were performed. With the results of the numerical simulations, the cracking risk due 

to restraint stresses can be estimated and an economic design of the reinforcement needed for 

crack width control can be ensured. 

 

 

2. Material 

properties 

 

2.1  Concrete mix design 

A concrete of strength class C35/45 is used for the tunnel construction. Table 1 shows the 

mixture for 1 m³ fresh concrete. For reasons of fire protection, an amount of 2 kg/m³ 

polypropylene (PP) fibres is added to the mix. These fibres reduce the risk of explosive 

concrete spalling due to fire impact, because they melt at about 170°C and increase the gas 

permeability of the concrete [11]. In this relatively small dosage applied here, PP-fibres do 

not influence the properties of the hardened concrete, but the fresh state properties. The 

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