8.1. Destruction of ancient building materials

All types of deformations of monuments can be divided for reasons of origin into 2 main groups:

1) deformations associated with the internal, initially laid defects in the structure or the base – monument system;

2) deformations caused by the action of external, secondary, unforeseen factors.

The causes of deformations in the first group can be:

- unstable natural or artificial base of foundations - timber, silt, subsiding and heaving soils, timbered distribution pads, wooden piles, various organics;

- landslide, karst, flooded or seismic nature of the site of ancient construction. The presence of springs, a similar level of groundwater;

- a weak (loose, finely laid, etc.) foundation of the structure, an area of ​​strip and columnar foundations that is disproportionate to the loads in various types of structures, for example, in churches of the cross-dome system.

- lateral pressure of the soil in the retaining walls, filling basement, basement and stepped structures;

- insufficient overall spatial rigidity of buildings (long-span and long structures, buildings with   highly located center of gravity of the masses); large deformability of compressed column elements, walls, vaulted ceilings;

- weak or open link frame;

- unperceived strut of arch-rack systems and vaulted ceilings;

- irrationally applied or excessive load on the floor; eccentric load of vertical load-bearing structures;

- the use of weak - fissured or unstable to the aggressive effects of the building material (unburned brick, raw wood);

- irrational orientation of blocks of anisotropic, for example layered, material; irregular nature of masonry;

- unfavorable destructive mode of operation of some durable building materials, for example Novgorod ferruginous limestone, in foundation structures collapsing in aggressive ground conditions, or elements of a metal bond frame, corrosive in a hygroscopic lime mortar of the old masonry;

- irrational drainage or snow retention form of roofing surfaces, imperfect waterproofing, contributing to wetting and defrosting masonry flooring structures (pokomomarnye cover, stepped roof with kokoshniki, flat roofs of open galleries, staircases, balconies, etc.);

- absence of deformation and construction joints in equal-sized, elongated or multi-temporal structures.

The causes of the deformations of the second group are usually the results of human activity: irrigation works, redevelopment and construction of the monument site, internal restructuring in order to adapt and various operational measures. The external causes of deformations also include the deliberate destruction of individual structures, the consequences of wars and natural disasters.

Secondary causes of deformities, in particular, are:

- change of hydrogeological conditions of the site of the monument during watering and draining of the territory with a decrease in the bearing capacity of the base (reduction of adhesion forces of saturated soil, rotting of wooden piles and other organic matter, formation of karst cavities, salinization of the soil);

- digging, ditches, bomb shelters, laying of various communications or subway lines near the monuments; the device of deep cellars and wells in the existing buildings;

- non-compliance with technology when laying the foundations;

- an extension to the monument of additional volumes with a great depth of the foundations or a significant load on the foundation;

- construction near the monument of the structures exerting lateral pressure on it;

- redevelopment and restructuring of buildings with a change in the initial working scheme (sizing and laying of openings; replacing vaulted ceilings with flat ones; dismantling existing floors or additional devices; dismantling air links, disassembling buttresses and counterforming extensions);

- change (increase, transfer) operational load;

- vibration impact of transport, driving and diving piles, the operation of engines, generators and fans inside the building; the use of percussion-drilling mechanisms for arranging blast-holes and wells for injection masonry reinforcement;

- defects of roofing, gutters, blind area; water and sewer leaks;

- violation of the optimum temperature and humidity conditions of the monument;

- shrinkage of wood, obmanie knots rod wood and combined systems;

- unorganized waste disposal of chemical and processing enterprises, air pollution with various compounds that are actively destroying the building material of monuments.

The division of causes into groups can be used in the diagnosis of deformation processes and in their "management" in the operation and repair of monuments.

In appearance, the deformations are divided into:

Vertical - sediments of foundations, individual structures or parts, buildings, shrinkage and crushing of masonry, crushing and drying of wooden bearing elements; destruction of main or temporary supporting structures;

Horizontal - shifts of the foundations and parts of the monument, displacement of the toes of individual arches, arches and spacing systems, the spreading of rafter legs with the loss of puffs, the separation of masonry during corrosion of the embedded metal, thermal deformations.

Flexural - a curvature of eccentrically loaded posts, thin walls and other elements, deflections of beams and floor slabs, sagging of farm belts, local flattening of masonry arches.

Mixed - representing a combination of several types of deformations.

Each type of deformation has its own characteristic external feature - the opening of cracks or seams, breaking of bonds, the formation of gaps in the nodes of the trusses, etc. Plastic masonry can deform without cracking - with   smooth tilt and curvature of the seams or even their disclosure. Complicated deformations of spatial structures are sometimes accompanied by the opening of a whole system of variously oriented cracks on the facades and in the interior, indicating the stagedness of the process or the “hierarchy” of elements converging in the deformation block (Fig. 8.1).

Natural methods. Full-scale tests carried out directly in the buildings. Wherein   investigate, for example, the level of noise or heat-humidity conditions in the premises. The objective conclusions are substantiated by the testimony of special devices that record the numerical values ​​of the parameters under study. The natural method of testing the structures of buildings and structures is performed by means of instrumental measurement of the actual stresses arising in the structures.

Diagnostic Tools. Diagnostics of deformations is a form of engineering research that identifies the causes of deformations of buildings and assigns these or other methods of strengthening. Obviously, in the complex process of restoration, the diagnosis of damage and the assessment of the technical condition of monuments are the most important aspects that determine the degree of engineering intervention in the existing constructive scheme of ancient buildings. There are examples of technical solutions implemented on the basis of an erroneous understanding of the operation of structures or incomplete diagnostics, which do not take into account the effect of any hidden factor or the “overlay” of several obvious factors. In these cases, temporarily hidden defects again manifested themselves and, as they progressed, led to an even more complex state that required new expensive fortification works, often distorting the appearance of the monument.

Any kind of destruction and deformation of structural elements is preceded by either one reason, or, as a rule, a whole chain of interrelated causes acting in a certain sequence and affecting many intermediate connections. Therefore, in order to properly assess the technical state of the method of strengthening, it is necessary to identify and construct the whole chain of destructive causes.

The complex interrelation of structures in combination with the action of changing natural and other factors also requires a clear understanding of the functions of each element or phenomenon in the initial, intermediate and modern stages of the system. The greatest difficulty is the diagnosis of damage and the assessment of the carrying capacity of ancient spacer structures - arches and vaults, which is explained by: the specifics of the vaults as spatial systems having a masonry structure; their dependence on the state of the vertical bearing elements and the bond frame; a variety of possible transformations and redistribution of load, the variability of the working scheme.

The basis of the diagnostics is, first of all, the study of the static state of the building - its structural system, the nature of the deformations, and the comparison of the data obtained with the data of engineering and geological surveys. In addition, in some cases, they resort to the study of the dynamics of deformations by collecting information on the state of the monument in the past, repeated geodetic measurements of increased accuracy and the installation of beacons on cracks. The beacons are made of mortar, gypsum or other materials and are provided with inscriptions containing the date and order number, after which the beacons are periodically inspected and the results of the observation are recorded in special journals.

Laboratory methods. Laboratory studies can be brought in for such research and restoration tasks as finding out a building history and developing restoration proposals on this basis.

With their help, the identity of the clutches in different parts of the monument or their different times can be established. Sometimes in this way it is possible to directly determine the age of buildings or its individual parts. When external or internal decoration of the monument is restored by laboratory tests, the pigments and binders used in the past are identified, on the basis of which the original color of the dyes is restored, even if they are in the form of insignificant residues that have lost their previous shade and intensity.

With the help of laboratory research information can be obtained on the composition of colored glazed tiles, on the technology of its application and firing. Without which it is impossible to replenish lost parts. Sometimes analyzes help find out very subtle moments of the monument's truss history. So, according to the remains of microflora on the surface of the masonry under plaster or painting covering it, it is possible to judge whether this layer is applied immediately during construction or after some time, and accordingly imagine the original character of the wall texture. In the course of studying the monument, many other problems may arise, which require the help of a research laboratory.

If engineering and technical laboratory studies can be entrusted to specialists of relevant professions and the architect retains basically the functions of general work coordination, then for the architectural research group itself, the role of the architect is decisive. He sets the research task, he selects the samples himself or outlines the places for their selection, draws final conclusions based on the conclusions of the laboratory.