ENGINEERING-GEOLOGICAL PROPERTIES OF UPPER CARBONIFEROUS

KARSTED ROCKS ON THE TERRITORY OF MOSCOW

É. Yu. Nesynova1 and A. I. Yudkevich1

Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 3, March 2006, pp. 38 – 41.

The thickness of the stratum of Jurassic clays is a criterion of sinkhole danger.

Engineering-geological prospecting and design of build-

ings and structures on the territory of Moscow necessarily in-

cludes estimation of the danger of sinkholes and internal ero-

sion of the region studied. This requirement is stipulated by a

special instruction of the Moscow Government [2]. In accor-

dance with this instruction any program of engineering-geo-

logical prospecting for a new construction site includes deep

boring (80 – 120 m) with opening of monolithic limestone to

a depth of 5 – 10 m and geophysical studies. The main task is

the determination of “karst cavities and strongly crushed

cracked and tectonic zones” [2]. The main danger in the re-

gions of karst manifestation (and its potential possibility) is

the presence of cavities in karst rocks. The instruction re-

quires their elimination by plugging or compaction of the

above-lying rocks. The erected construction “should be

checked by computation that allows for... the formation... of

a sinkhole 6 m in diameter under the building or the struc-

ture” [2]. The experience in prospecting acquired by the

“Gidroproekt” Institute in various regions of Moscow shows

that the Upper Carboniferous karsted rocks have some spe-

cial features that do not fully meet the requirements of the

active instruction.

When prospecting a region for complex development

Gigroproekt specialists have studied the geological structure

of the Zakharkovo floodplain in the valley of the Moskva

River at the west boundary of the city. A large ancient ero-

sion zone passes under the recent left-bank floodplain zone.

In the Moscow Region it is known as Central Preglacial Val-

ley [1]. A fossil saddle lies at a depth of 40 – 45 m below the

Holocene riverbed. Upper Carboniferous rocks are opened in

depression flanges to a depth of 84 – 114 m (Fig. 1). They

are represented by alternating limestone and clay strata that

are arranged in three horizons, i.e., the Dorogomilovskii,

Khamovnicheskii, and Krevyakinskii (from top to bottom).

Each horizon consists of two strata (members), i.e., a lower

carbonaceous stratum and an upper argillaceous stratum. The

section of the Zakharkovskaya floodplain consists of the Me-

shcharinskaya stratum (C3mð), the Perkhurovskaya carbona-

ceous stratum (C3pr), the combined Neverovskaya and

Voskresensk argillaceous stratum (C3nv + vs), and the Suvo-

rovskaya carbonaceous stratum (C3sv). Middle Carbonifer-

ous limestone of the Myachkovsk horizon (C2mè) lies still

lower.

Sinkholes in the carbonaceous rocks have been studied

by boring and by a set of geophysical methods that included

electrometry (the method of vertical electric probing and

seismic profiling) and the correlation method of refracted

waves. The geophysical study was performed for solving the

following problems: mapping of the boundaries of an ancient

erosion incision, determination of the position of the roof of

Jurassic clays and of their thickness, study of the trace of the

roof of the limestone stratum from the surface (the Perkhu-

rovskaya member C3pr), and determination of weakened

(karsted) regions in them.

The electrometric data made it possible to amend the

contour of an ancient erosion depression. The top boundary

of the bearing high-resistivity geoelectric horizon was used

for determining the range of occurrence of the Perkhurov-

skaya limestone in a section of the stratum. Weakened zones

primarily occurring near the flanges of the ancient incision

were singled out according to the reduced values of electrical

resistivity in the Perkhurovskaya limestone.

Results of seismic prospecting were used to determine

with sufficient accuracy the boundaries of a stratum of loose

alluvial quaternary sediments (aQ4) and of the roof of the Su-

vorovskaya limestone (C3sv) with characteristic high veloci-

ties of elastic waves (3.1 – 3.2 m/sec).

The strongly karsted state of the Perkhurovskaya lime-

stone determined by geophysical methods has been con-

firmed by boring. The Perkhurovskaya stratum was bored in

14 places. In virtually all cases the composing rocks had

traces of intense leaching that manifested itself by a macro-

pore texture and numerous caverns in the limestone. The

caverns were from 1 – 2 mm to 0.5 cm in size or even larger.

In addition to the caverns the rocks contained pockets of lime

Power Technology and Engineering Vol. 40, No. 3, 2006

148

1570-145X�06�4003-0148 © 2006 Springer Science + Business Media, Inc.

1“Gidroproekt” Institute, Moscow, Russia.

dust, clay layers, and other features of dissolution. Three

wells (21% of the total number) opened considerable (up to

5 m in size) ancient sinkholes corresponding to the total

thickness of the Perkhurovskaya stratum. The limestone has

been fully removed from them and replaced by secondary

products of karst formation or by a filler drawn from the out-

side (lime dust, clay, gravel). Cases of boring tool dropping

or of the presence of free-flowing, plastically flowing, and

Engineering-Geological Properties of Upper Carboniferous Karsted Rocks on the Territory of Moscow 149

TABLE 1

Test Soil

Parameters of properties

W

density, g�cm3

e Sr

plasticityIl

ñ ñd

ñs

WL

Wp

Ip

1Clay

0.171 2.21 1.89 2.78 0.473 1.005 0.363 0.195 0.17 – 0.14

2 0.235 1.97 1.60 2.74 0.718 0.897 0.414 0.213 0.20 0.11

Fig. 1. Geological-lithological section.

other weak rocks in the secondary filler of the voids (karst

deposits kst) have not been observed. As a rule, karst depos-

its were withdrawn in the form of normal and dense enough

drill cores. The parameters of physical properties of the clay

filler are presented in Table 1. It seems that the deposits of

kst are quite ancient and dense. For example, the clay from a

sinkhole opened by one of the wells has a compacting factor

of 1.09. Some cases in which the karst can be characterized

by marked weakening of the rocks and by the presence of

pockets of lime dust are an exception.

Limestone of the Suvorovskaya stratum (C3sv) and the

seat rocks of the Middle Carboniferous Myachikovskii hori-

zon (C2mè) are preserved somewhat better than the Perkhu-

rovskaya stratum. This can be inferred from the state of the

drill cores, from the growth in the velocity of seismic waves

(in the Suvorovskaya limestone it is 3.1 – 3.5 km/sec against

150 É. Yu. Nesynova and A. I. Yudkevich

1 2 3 4 5

6 7 8

Mosc

ow

Riv

er

Zakharkovo

village

3176400 3176600 3176800 3177000 3177200 3177400 3177600 3177800 3178000 3178200 3178400 3178600 3178800

6170800

6171000

6171200

6171400

6171600

6171800

6172000

6172200

6172400

6172600

6172800

6173000

6173200

6173400

6173600

6173800

6174000

6174200

V-1

V-2

V-3

V-4

V-5

V-6

V-7

V-8

V-9

V-10

V-11

V-12

V-13

V-14

V-15

V-16

V-17

V-18

V-19

V-20

V-21

V-22

V-23

V-24

V-25

V-26

V-27

V-28

V-30

V-31

V-32

V-33

V-34

V-35

V-36

V-37

16I

17I

11*

12*

13*

14*15*

16*17*

18* 19*

20*21*

22*

23*

25*

26*

27*

28*

29*

30*

31*

hole-1

hole-10

hole-11

hole-12

hole-13

hole-14hole-15

hole-2

hole-3

hole-4

hole-5

hole-6

hole-7

hole-8hole-9

S-1

S-10S-2

S-3

S-4

S-6S-7

S-8

S-9

S-C

S-AS-B

GP-4

TZ-3

TZ-4

1

2

3

4

5

67

8

14

20

27

28

29

30

31

32

33

34

35

43

61

62

52

70

76

TZ-1

TZ-2

TZ-3

TZ-4

TZ-5

TZ-6

TZ-7

TZ-8

TZ-9

TZ-10TZ-11

TZ-12

TZ-13

TZ-14

TZ-15

TZ-16

TZ-17

TZ-18

TZ-19

TZ-20

TZ-21

TZ-22

TZ-23

TZ-25

Fig. 2. Map of sinkhole danger: 1, drill hole; 2, probing point; 3 – 4, boundary of erosion of: 3, Jurassic deposits, 4, Perkhurovskaya limestone;

5, area of erosion of Perkhurovskaya limestone; 6 – 8, zones of sinkhole danger: 6, dangerous, 7, potentially dangerous, 8, safe.

the 2.1 – 2.6 km/sec in the Perkhurovskaya stratum), and

from the results of laboratory tests of withdrawn rock sam-

ples (Table 2). At the same time, they have traces of leaching

and regions of crushed rock. A case of dropping of a drilling

tool into a sinkhole 0.9 m high has occurred in the

Suvorovskaya limestone.

Thus, regions of strongly karsted rock have been deter-

mined on the territory of the Zakharkovskaya floodplain.

These are limestones and dolomites of the Upper Carbonifer-

ous Perkhurovskaya stratum (C3pr) lying in a 103 – 114-m

range of absolute marks; their roof is situated at a depth of

16 – 24 m from the surface. The thickness of the karsted stra-

tum reaches 6 m. The cavities formed in the stratum are

filled with secondary products; in some cases the limestone

has been fully removed due to the karst process. The distri-

bution of the karst over the area is nonuniform. According to

the data obtained by drilling and by geophysical studies the

most karsted rocks occur in the flanges of the preglacial ero-

sion valley and partially outside its boundaries over the

northern end of the recent-day floodplain. The part of the

area where the drill holes have opened filled cavities in the

Perkhurovskaya limestone and where the geophysical study

has shown the presence of numerous cavities is singled out

as a karst-dangerous territory.

According to the active standards the potential karst dan-

ger is determined by the thickness of Jurassic clays. They

serve as a protective layer that hinders vertical circulation of

the underground water and reduces the activity of karst for-

mation. When the thickness of this layer is less than 10 m (or

they are absent), the territory is assumed to be potentially

dangerous with respect to sinkholes [3].

An analysis of propagation of Jurassic clay deposits over

the territory has shown that their thickness is variable. Within

the contours of the ancient erosion incision the Jurassic clay

has fully degraded. Under the high terrace the thickness of

Jurassic clays reaches 20 m. On the Zakharkovskaya flood-

plain it fluctuates from 0.5 to 8.5 m (in the latter case we im-

ply the opened thickness of the rock). In accordance with the

active standards the part of the area characterized by low

thickness of Jurassic clays (the opened thickness is less than

7 m) is classified as potentially dangerous with respect to

sinkholes. A map of the sinkhole danger of the region is pre-

sented in Fig. 2.

It should be noted that the karst developed in the Perkhu-

rovskaya limestone is quite ancient. Judging by the confine-

ment in an ancient erosion scour, it was formed in the

preglacial period (presumably several hundreds of thousand

years ago). The formation of karst was primarily stimulated

by the special features of the paleoaccidence. The existence

of a deep erosion incision predetermined the hydrodynamic

conditions required for its development. At the present time

the process of karst formation has ended fully or to a consid-

erable degree. The cavities formed have been filled with a

clay material. Today the accidence does not promote active

circulation of underground water. A major (or at least a con-

siderable) part of the easily soluble carbonates has leached.

External features of active karst formation are absent.

The floodplain does not bear erosion pools, settled soil,

riverbed deformation, or other manifestations of karst forma-

tion. This gives us grounds to classify the karst encountered

in the section of the Zakharkovskaya floodplain as a fossil

kind (paleokarst).

The active standards do not differentiate between paleo-

karst and karst though it is obvious that the active karst and

the paleokarst present different dangers for construction. Un-

der the conditions of paleokarst occurring at a depth of 20 m

and having a thickness of not more than 3 m, formation of

sinkholes is virtually impossible. The example of the Zakhar-

kovskaya floodplain shows that the karsted limestone on a

territory classified as sinkhole-dangerous according to the

active instruction has been virtually fully substituted by sec-

ondary deposits (kst)C3

that often have high enough plastic

characteristics. Construction and design in this zone does not

require special antikarst measures, but the elevated voidage

of the limestone and of the dolomite should be taken into ac-

count by using lower strength parameters of the rocks in the

design and by thoroughly studying the properties of the filler

of sinkholes treating it as an independent engineering-geo-

logical element. In this connection it is expedient to treat the

regions with developed paleokarst as a special zone and to

develop special requirements for this zone.

REFERENCES

1. B. M. Dan’shin, The Geological Structure and the Mineral

Wealth of Moscow and Its Neighborhoods [in Russian], Mosk.

Obshch. Lyubitelei Prirody, Moscow (1947).

2. Instruction for Designing Buildings and Structures in the Regions

of Moscow Characterized by Manifestations of Karst and Inter-

nal Erosion [in Russian], Izd. Mosgorispolkom – GlavAPU –

Mosproekt-1 – Mosgorgeotrest, Moscow(1984).

3. Moscow. The Geology and the City [in Russian], Izd. IGÉ

RAN – Mosgorgeotrest, Moscow (1997).

Engineering-Geological Properties of Upper Carboniferous Karsted Rocks on the Territory of Moscow 151

TABLE 2

Stratigraphic

indexRock

Parameters of properties

Wm

Wu

ñm

, g�cm3 ñu, g�cm3 R

comp, MPa R

tens, MPa

C3pr Limestone002 005

0045

. .

.

� 004 008

005

. .

.

� 203 222

213

. .

.

� 215 231

223

. .

.

� 2 4 115

72

. .

.

� 05 21

135

. .

.

�

C3sv Dolomitized limestone003 004

0035

. .

.

� 004 005

0045

. .

.

� —

.2 46

256 258

257

. .

.

� 368 658

513

. .

.

� 31 45

38

. .

.

�