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INNOVATIVE SOLUTIONS IN
GEOTECHNICAL ENGINEERING

STABILITY AND EARTHQUAKE RESISTANT ENGINEERING STRUCTURES

Earthquake resistant foundation
stability structures

For the earthquake-resistant stability constructions, the difference in supporting stability potential by using the new approach is over 30-50%. Unfortunately for these constructions, it bears a negative sign; it is therefore necessary and urgent to revise the eartquake-resistant regulatory procedure for laying the foundations of buildings.

A conventional earthquake-resistive design method may include a pseudo-static analysis, or dynamic analysis, wherein the latter may include a response at which an earthquake-resistive matches an external vibration-force. The conventional earthquake-resistive design method may not provide an exact earthquake force, that needs to be balanced with an amount of a resistive force of a horizontal connecting surface arranged between a foundation and a building structure.

As shown by the pictures of the recent earthquake events in Turkey and Taiwan, the collapse of most of the mostly shallow-founded structures was caused in most cases by the yielding of the foundation or the yielding of the resistive of the structural connection of the structure to the foundation. Both are the result of an unsubstantiated earthquake force. Buildings that have collapsed and have not been demonstrated to be stable with the added effect of kinetic forces from the earthquake could have occurred even with compliance with current regulations, because the regulations do not require "primary" proof of the impact of kinetic forces or "mechanical impedance". All previous evidentiary procedures have a secondary character because their approximation to the real state of equilibrium is indirect. In the case of earthquake-resistant various basic building structures, there is a large difference in a dimensioned earthquake force compared to previous calculations, that it is a sufficient cause of global earthquake disasters.

Thus, the conventional earthquake-resistance design method may not provide an exact earthquake resistance of the building structure.

Laying the foundation on insufficiently
load-bearing soil

Regarding the basic piling construction, the real values of its constructive parameters can finally be proven, which bear a positive sign in terms of stability potential by using the said approach. This also confirms the ancient value of the said construction.

Laying the foundation on insufficiently load-bearing soil has already been solved in ancient times by the construction collectively named "piling", implying aggregate action, or resistance. Thomas Whitaker (1976) said, "Piling is a form of construction of great antiquity, and an almost instinctive trust in piles for overcoming difficulties runs throughout foundation work".

To this day (2024), "piling" does not have a better purposeful alternative, and the alternative "is not even necessary", because, at the same time, it is the best eathquake-resistant construction. The said building construction has not been represented with a primary structural approach so far.

In most cases, it is unnecessary and irrational, and in terms of earthquakes also harmful, to search for a deep load-bearing layer using "piers or caissons" as a substitute for "piling", unless liquefaction is present.

Retaining engineering structure

Unlike first two procedures, the third one, the Retaining Engineering Structure or RES, EP 3827133, thanks to the discovered stability potential being over 30-50%, but with a positive sign, is already in practical application and implementation, and has references.

The excavation stability in water-bearing and a not water-bearing soil has so far been solved according to the least resistance principle in seeking solutions, so that the horizontal action is stabilized by horizontal "long" anchors, or heavy gravity walls, or disruptive supports. Neither can be considered an engineering solution due to the obvious spatial awkwardness in dimensions, weight, and reactive stability adverse activity.

The new solution applied by us, the new "Retaining Engineering Structure" construction (European patent, EP 3827133) eliminates anchors and gravity walls. It is introduced into the regular construction practice.

Laying the foundation on sloping
or landslide-prone terrain

Laying the foundation on sloping, or landslide-prone terrain, has so far been solved similarly as the excavation stability, with inevitable harmful consequences. The new construction, "Retaining Engineering Structure", simultaneously solves the foundation stability, and earthquake-resistant action. Such a stable combination is impossible to achieve with any other construction. This solution is particularly relevant for infrastructure facilities – roads and railways, which, in natural conditions of increased landslide instability, require the upgrade of basic solutions.

APPROACH

A stability engineering construction is a set of elements or forces [F] which is simultaneously in the mass gravity element [γh], forming together the energy field [Fs] of elements or forces. Elements or forces of such an energy field [Fs] can therefore be expressed in equilibrium state as energy stress, inertial and gravitational forces [Nm]. If such a statement is made for known characteristic energy points or field surfaces, then it is possible to write balance equations of energy forces for these points or surfaces by solving which we get the scalar magnitudes of forces [N] necessary to dimension the equilibrium state of the structure in the field [Fs]. Known energy points or surfaces are simply those for which we know some of the characteristic energy values, displacement, velocity or acceleration. If the energy field elements [Fs] receive kinetic energy such as an earthquake, then a kinetic energy force [Nm/s] is attached to the field element. Since it is a kinetic energy force, in this case the question of the character of the interaction of these forces in the field [Fs] arises.

If the field element velocities differ, then the interaction expression of these forces is no longer possible based on the elements rigidity.

But based on the elements impedance:

EARTHQUAKE

An earthquake is an earth mehanical wave, which consists of a cyclic exchange of potential and kinetic energy of particles of a wave material, particle mass flow q [kg/s], particle velocity v [m/s] and acceleration ag [m/s2]. This change propagates in the form of a wave, longitudinally or transversely at constant velocity C [m/s] according to the well-known law of elasticity,

The inertial force F1 of a building structure, which response to the acceleration of the earthquake wave ag is transferred to the building structure as a further acting active force of the building structure. At the same time, the inertial force F2 is created in a wave field, thus creating impedance conditions of the two elements, a first element 1 and second element 2.

In the field of forces, there are the following elements of a stability construction:

Object 1- a first element 1 of the field being the building structure - an element with a mass M1, received force F1 from the earthquake wave, acceleration a1, velocity v1 and displacement u1, F1, a1, v1, u1
Horizontal connecting surface 3 – common element of the field being an element with resultant confrontation force Q or a resultant earthquake force,
Object 2 - a second element 2 or transmission medium of the field – an element with a mass M2, transferred force F2 from the first element, acceleration a2, velocity v2 and displacement u2

Distribution of shear inertial forces Fi along the height of the building structure 1 may be calculated as follows

where Μi (Μj) are floor masses and zi (zj) are heights of the masses above the connecting surface 3.

Distribution of force Q by possible resistive forces RQ2 of foundation structures must be as follows

iThe former s the resistive force of the horizontal connecting surface 3 and in the foundation slab structure may be calculated as follows:

with added passive resistance where may be calculated as follows

where is gravitational resistive force of the passive resistance. Said RPAS is resistive force existing in a case when the first element 1, i.e. above ground object comprises underground structures such as garages or/and basements, said underground structure generates gravitational resistive force RPAS.

in the foundation slab structure may be reinforced with adding a Retaining Engineering Structure - RES where (M2) may be calculated as follows

where RRES is a resistive force generated by a Retaining Engineering Structure.

The Retaining Engineering Structure is described in European patent application no. 18 759 997.2 which application is incorporated herein in its entirety by reference.

According to the present invention, the Retaining Engineering Structure is implemented for the building structure 1 without underground structures, and in addition to the foundation slab structure 2.

Thus, the resistive force is present when in addition to the foundation slab structure 2 the building structure 1 comprises the retaining engineering structure, wherein the retaining engineering structure is implemented for the building structure 1 without underground structures.

PILING FOUNDATON STRUCTURE

When piles are necessary to avoid heavily controlled subsidence, it is historically implied that this is the resistant action of a pile group or piling.

Piles are vertical columns, built with the purpose of transfer the load of the building into deeper better-bearing soil layers. To avoid difficult-to-control soil settlements, due to the resistive action of a group of piles it is necessary to use pile foundations.

With reference to figure 3, the building structure 1 arranged above the connecting surface 3 is the first element 1 with defined mass Μ1, the group of piles 2 arranged below the connecting surface 3 is the second element 2 with defined mass M2, where an outer perimeter of the group of piles 2 structure determines the mass M2.

Piles in the constructive group are determined with space s x s, depth D, pile diameter d, anchored depth of pile hs=D/3,

and with pilot-ground sliding surface with resultant angle amount,

where s is distance between piles, D is embedment depth of piles, d is diameter of piles and, where deformation – tension force δ- NP for one pile may be calculated as follows ,

NP [N] a tension force in one pile may be calculated as follows

Equilibrium equations on a surface where y=D may be calculated as follows

RETAINING ENGINEERING STRUCTURE

By installing batter piles at an optimum angle of 15° to 20° coupled with the vertical structures of the retaining walls, several useful advantages are achieved. The structures used so far, because of their horizontal dimension, are difficult to adapt to adjacent spaces and structures. According to the new solution, the horizontal anchor is replaced with a batter pile, which reduces the horizontal dimension of the structure by 3 to 5 times and because of the interactive effect an excess of useful structural stability potential is created, therefore increasing the safety by 1.2 to 1.25 times. Stability analysis procedure, as well as the results of the already performed test structures, confirm the above.