Rafał F. Obrzud, Sébastien Hartmann and Krzysztof Podleś
This paper analyzes two approaches to serviceability limit state (SLS) verification for the deep excavation boundary value problem. The verification is carried out by means of the finite element (FE) method with the aid of the commercial program ZSoil v2014. In numerical simulations, deep excavation in non-cohesive soil is supported with a diaphragm wall. In the first approach, the diaphragm wall is modeled with the Hookean material assuming reduced average stiffness and possible concrete cracking. The second approach is divided into two stages. In the first stage, the wall is modeled by defining its stiffness with the highest nominal Young’s modulus. The modulus makes it possible to find design bending moments which are used to compute the minimal design cross-section reinforcement for the retaining structure. The computed reinforcement is then used in a non-linear structural analysis which is viewed as the “actual” SLS verification.
In the second part, the paper examines the same boundary value problem assuming that the excavation takes place in quasi-impermeable cohesive soils, which are modeled with the Hardening Soil model. This example demonstrates the consequences of applying the steady-state type analysis for an intrinsically time-dependent problem. The results of this analysis are compared to the results from the consolidation-type analysis, which are considered as a reference. For both analysis types, the two-phase formulation for partially- saturated medium, after Aubry and Ozanam, is used to describe the interaction between the soil skeleton and pore water pressure.
One of the key parameters essential for conducting numerical analyses of the geotechnical structure or to conduct its design calculations is the deformation modulus of the separated soil layer. The basis for determining the magnitude of the deformation modulus is the stress–strain relation obtained by an empirical study of the appropriately prepared soil sample. Traditionally, the test enabling the determination of the relationship between the states of stress and strain is the triaxial compression test conducted on cylindrical test specimens
Katarzyna Gabryś, Wojciech Sas, Emil Soból and Andrzej Głuchowski
Committee for Standardization (2013). Geotechnical investigation and testing - Identification and classification of soil - Part 2: Principles for a classification PN-EN 14688-2.
 SAS W., GABRYŚ K., SZYMAŃSKI A., Effect of Time on Dynamic Shear Modulus of Selected Cohesive Soil on One Section of Express Way No. S2 in Warsaw, Acta Geophysica, 2015, 63(2), 398-413, DOI: 10.2478/s11600-014-0256-z.
 SAS W., SOBÓL E., GABRYŚ K., MARKOWSKA-LECH K., Study of the cohesive soil stiffness in a modified resonant column, [in:] Materiały
accordance with the assumptions presented in Section 3 . In view of the assumed foundation depth for wind farms and the depth of the shallowest CPTU, the analysis was conducted in the depth range from 2 m to 8 m. Due to the varied thickness of the surface, which was a weak layer, apart from the investigation of the entire profile, analyses were additionally conducted separately in two depth ranges: 2–5 m and 5–8 m below the surface. In accordance with the principles of functional data analysis, the first step included smoothing of the function of the modulus depending on
, main central moment of inertia of the cross-section; W , elastic sectionmodulus; W pl , plastic sectionmodulus; σ dop25G2 , allowable stresses for S25G2 steel section; σ dopS480W , allowable stresses for S480W steel sections; σ dopS550W , allowable stresses for S550W steel sections.
Computer programs operating based on the FEM algorithm, in addition to displacements and internal forces, automatically calculate the stresses reduced according to the Huber–Mises–Hencky hypothesis according to the general dependence:
σ r e d = σ x 2 + σ y 2 + σ z 2 − σ x σ y
behaviour. The non-homogeneity of a granular pile is considered in terms of its deformation modulus with non-linear variation.
The essential steps of the analysis are described in the following sections.
The granular pile is discretised into n cylindrical elements acted upon by shear stresses τ, with the base having a uniform pressure p b . The granular pile base is assumed to be smooth, across which the load is uniformly distributed. The soil displacements of the nodes on the granular pile periphery and the centre of each element
Iman Faridmehr, Mohammad Reza YazdaniPour, Mohammad Javadi Jokar and Togay Ozbakkaloglu
injection” method, in addition to the economic and technical problems. Karkheh’s conglomerate foundation consists of water-resistant horizontal mudstone layers each having a thickness of 3 to 9 m. The permeability of these layers, which are bedded almost horizontally, is in the range of 10 −7 –10 −10 m/s. Geotechnical investigations revealed that these layers are continuous enough to provide different strata for each conglomerate layer confined by the mudstone layers. Fig. 2 and 3 show the cross and longitudinal sections of Karkheh Dam respectively.
, developed by Lee and Fenves [ 3 , 4 ]. The latter model is implemented by the author in the ZSoil software, in the modified form that includes creep and ageing [ 5 ]. The paper is organised as follows. A short description of the HS model used to represent the subsoil behaviour is given in Section 2 . Rheological aspects and implementation details of the modified Lee–Fenves model for concrete are given in Section 3 . The diaphragm wall case study based on the data collected from the Supersam project [ 2 ] is described and analysed in Section 4 . In the two subsections
calculated by choosing various value of modulus of elasticity E and by keeping the magnitude of the moment of inertia I constant. The effect of the EI on the lateral pile displacement, lateral soil pressure and corresponding p–y curve illustrated are discussed in this section. The pile slenderness ratios ( L/D ) are 10, 15, 20 and 25. The behaviours of lateral pile displacement with pile depth for two types of soil are given in Figures 10 and 11 . For lateral load of 450 kN at the pile tip, the lateral pile displacement for EI magnitudes of EI = 1.4 × 105 kN m
height of the sample, A is the area of horizontal cross-section of the sample and κ is the slope of the curve of compressive force to vertical deformations’ dependence, read in the range where the curve is close to a straight line. Results from this test are shown in Fig. 5a There were 14 cubic samples named K1–K14, but some tests were unsuccessful. The Young modulus varied from 10.136 to 24.768 GPa. Mean value was 15.745 GPa with standard deviation 4.819 GPa (31% of the mean value).
Results of the compressive tests: a) relation between the force and