CN103759996A - Low-strength tamped cement mortar model - Google Patents

Abstract

The invention provides a low-strength tamped cement mortar model which is prepared from sand, cement and water in a proportion of (9-30):1:(1-3.1). The model is prepared by the following steps: uniformly mixing cement and sand manually; pouring water into the mix for slow soaking; then manually and mechanically stirring twice, respectively; filling a steel mould with the mixed material for three times; tamping after filling every time; drawing the surface by a steel brusher; then filling with a model material; after a whole test piece is tamped, removing the steel mould to form a standard test piece; burying the test piece into wet sand with equal water content; and naturally maintaining. The model provided by the invention is used for detecting load and deformation processes of underground structural bodies under different geological rock bodies, and the measured mechanical parameters are of credibility and applicability.

Description

Low-intensity building type sand-cement slurry model

Technical field

The present invention relates to sand-cement slurry model, be specifically related to a kind of low-intensity building type sand-cement slurry model.

Background technology

Along with the development of production and construction and science and technology, increasing hypogee need to be built in the rock mass with complex geological structure, as tunnel, underground power station, oil cellar, mine etc.In order to study the security and stability of these buildings, the general method that adopts test.Test findings and the experimental phenomena of on-the-spot prototype full-scale laboratory test are directly perceived, but the test preparatory period is long, cost is large, can not observe the overall process of damage effect, can not repeat a certain breakoff phenomenon, be difficult to study in theory and in quantitative aspect, just, test findings and content measurement are had under the prerequisite of certain accurately prediction, just carry out site test and verify and revise.When carrying out principle, Research on Regularity, generally adopt Geotechnical Engineering indoor model test.In recent years along with the raising of tested number survey technology, geomechanical model test enters the quantitative test stage by the qualitative analysis stage, and because geomechanics model can reflect the loading characteristic of underground structure to greatest extent, and have the advantages that intuitive is strong, therefore, at construction of underground structure scientific research field, geomechanical model test method has become important research means at present.

Geotechnical Engineering model test, through the development and improvement of decades, more and more plays important and irreplaceable effect, is indispensable research means.Carry out ground model test and must observe relevant similarity relation criterion, wherein need the most critical maxim of relation of observing to be:

（1）

In above formula,

for cast material compressive strength and the ratio of former shaped material compressive strength;

for model physical dimension and the ratio of prototype physical dimension;

for cast material density and the ratio of prototype density of material;

for model acceleration of gravity and the ratio of prototype body acceleration of gravity.

Whether according to acceleration of gravity, change, "current" model test similarity theory has two kinds: copy similarity theory and Fu Luo get similarity theory.

(1) copy similarity theory

According to this theory, generally use former shaped material analogue formation,

=1,

=1

According to formula (1) requirement,

In model test, the physical dimension of structure is generally less than the size of prototype structure body,

< 1, therefore

> 1

Thereby, when copying similarity theory and test, need increased acceleration could meet gravity similarity requirement.Therefore, this test is only carried out on hydro-extractor.But, by hydro-extractor method, to carry out model test and also have some problems, these problems are mainly about moulded dimension.The typical length scale-up factor of centrifuge test is in 1/50 left and right, or less.Due to the restriction of hydro-extractor size, these small scale coefficients are essential.For making edge effect minimum, centrifugal case must be enough large, and case inner model body must be enough little.Carrying out in the test of rock-reinforcing engineering field, the size of overall dimensions and enhanced structure (as side slope and soil nailing, underground cavern and country rock anchor pole, anchor cable) must be proportional.When geometric proportion coefficient is 1/8 or 1/10 time, this requirement can relatively easily meet, and when geometric similarity coefficient is 1/50 or more hour, just becomes very difficult.Therefore, at present, more rock-reinforcing engineering field adopts Fu Luo get similarity theory to design and carries out model test.

(2) Fu Luo get similarity theory

Following the model test of Fu Luo get similarity theory, is to carry out in identical gravity field with prototype test,

Cast material can not be identical with former shaped material, need to be according to

requirement preparation cast material.

The physical dimension of model structure body is generally less than prototype structure body size,

< 1, the density of cast material is also less than the density of former shaped material,

< 1.

Known according to formula (1), the intensity of the cast material of choosing is less than the intensity of former shaped material,

.

The density of sand-cement slurry class material is 1.8 × 10 ³kg/m ³left and right, the density of medium tenacity prototype rock mass is 2.4 × 10 ³kg/m ³left and right,

=0.75, the geometric proportion coefficient of model and prototype structure body is

, according to formula (1), model and prototype structure body strength of materials ratio are:

=0.075-0.094.The intensity of medium tenacity rock mass is 10-20MPa, therefore, and the cast material uniaxial compressive strength of choosing: =0.75-2.82MPa.

Rock mass materials belongs to hard brittle material, its ultimate compression strength with the ratio of ultimate tensile strength (UTS) more than 10.At present, extensively adopt the simulation material of the composite materials such as gypsum and gypsum, zeyssatite, rock dust, flyash as rock mass both at home and abroad, the ultimate compression strength of this analoglike material below 10, with regard to requirement of strength, and is not suitable for the simulation material as rock mass with the ratio of ultimate tensile strength (UTS).And the character of this class gypsum class model material depends on the degree of drying of material, more responsive to the variation of humidity.Be generally to put into after drying room inner drying after model moulding, and at external coating varnish, prevent from can testing after moisture evaporation.Due to above-mentioned restriction, this class model material is generally applied to compared with in the model test of minimodel body, when model size is larger, is just not suitable for adopting above-mentioned material as cast material.

The ultimate compression strength of low intensive cement mortar material and ultimate tensile strength (UTS)

ratio be greater than 10, belong to hard brittle material, be relatively applicable to simulation rock mass, and its later stage gain in strength is slower, mechanical property tends towards stability, and is applicable to larger volume model test and adopts.

The minimum intensity label that existing construction cement mortar is conventional is Mu2.5 (uniaxial compressive strength 2.5MPa), and builds use, and workability is better, and water cut is high, is not suitable for the building moulding of model.

Summary of the invention

Technical matters to be solved by this invention is a kind of low-intensity building type sand-cement slurry model of design, utilizes this model can test out the stress deformation process of the underground structure body under different geology rock mass, tries to achieve its stability.

For solving the problems of the technologies described above, the technical solution used in the present invention is: a kind of low-intensity building type sand-cement slurry model, by sand, cement and water, formed, and wherein, sand, cement, water weight ratio example are 9-30:1:1-3.1;

Its method for making is:

(1) measure the water cut of selected sand;

(2) by cement, the artificial mix of sand evenly after, water is poured in mix, slowly infiltrate;

(3) once, machine mixing once for artificial mix; Once, machine mixing once for artificial mix again;

(4) uniform mix material is divided and inserted for three times in cylindrical steel mould, insert rear building at every turn, treat that this layer of building completes, with steel brush, by its surface galling, to avoid the generation of layering, then insert cast material, continue building, so altogether building three times;

(5) demoulding maintenance, after whole test specimen building completes, removes steel mold, forms wood property and tests needed standard specimen, this test specimen is imbedded in the damp sand equating with its water cut to natural curing.

The present invention adopts the designed low-intensity building type sand-cement slurry model of technique scheme, has following beneficial effect:

(1) according to the material of this low-strength cement cement mortar ratio preparation, can in mechanics parameter and physical property, meet the requirement of rock simulation material, guarantee scientific rationality and the correctness of model test result, the generation of the result of avoiding distorting.

(2) condition when moulding of test specimen, curing condition and model building is in full accord, makes the mechanics parameter recording have credibility and applicability.

(3), in the primary election stage of cast material, can save a large amount of cast material examination preparation time.

Accompanying drawing explanation

Fig. 1 represents the Changing Pattern of 7 days compressive strength of sand-cement slurry composite material of the present invention with proportioning;

Fig. 2 represents the Changing Pattern of sand-cement slurry composite material compressive strength of the present invention with curing time.

Embodiment

Below in conjunction with accompanying drawing, low-intensity building type sand-cement slurry model of the present invention is illustrated.

A kind of low-intensity building of the present invention type sand-cement slurry model, is comprised of sand, cement and water, and wherein, sand, cement, water weight ratio example are 9-30:1:1-3.1.

The embodiment 1 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 9:1:1, its medium sand 90kg, cement 10kg, water 11kg.

The embodiment 2 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 10:1:1.1, its medium sand 100kg, cement 10kg, water 11kg.

The embodiment 3 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 11:1:1.2, its medium sand 110kg, cement 10kg, water 12kg.

The embodiment 4 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 12:1:1.3, its medium sand 120kg, cement 10kg, water 13kg.

The embodiment 5 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 14:1:1.5, its medium sand 140kg, cement 10kg, water 15kg.

The embodiment 6 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 16:1:1.7, its medium sand 160kg, cement 10kg, water 17kg.

The embodiment 7 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 18:1:1.9, its medium sand 180kg, cement 10kg, water 19kg.

The embodiment 8 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 20:1:2.1, its medium sand 200kg, cement 10kg, water 21kg.

The embodiment 9 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 22:1:2.3, its medium sand 220kg, cement 10kg, water 23kg.

The embodiment 10 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 25:1:2.6, its medium sand 250kg, cement 10kg, water 26kg.

The embodiment 11 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 27:1:2.8, its medium sand 270kg, cement 10kg, water 28kg.

The embodiment 12 of low-intensity building type sand-cement slurry model of the present invention, sand, cement, water weight ratio example are 30:1:3.1, its medium sand 300kg, cement 10kg, water 31kg.

In the various embodiments described above, sand adopts medium sand, and cement adopts general silicon P.O.32.5 cement, and the cast material test specimen of building is cylindric, its diameter is 5cm, and height is 15cm, and after building, test specimen is embedded in damp sand heap, keep moisture, maintenance at normal temperatures, its method for making is:

(1) measure the water cut of selected sand;

(2) by cement, the artificial mix of sand evenly after, water is poured in mix, slowly infiltrate;

(3) once, machine mixing once for artificial mix; Once, machine mixing once for artificial mix again;

(4) uniform mix material being inserted to diameter is 5cm, height is in the cylindrical steel mould of 10cm, insert the degree of depth is 4cm at every turn, then building, treats that this layer of building completes, with steel brush by its surface galling, to avoid the generation of layering, insert again cast material, continue building, so altogether building three times;

(5) demoulding maintenance, after whole test specimen building completes, removes steel mold, forms wood property and tests needed standard specimen, this test specimen is imbedded in the damp sand equating with its water cut to natural curing.

According to correlative study, show, for portland cement, within its 7 day length of time, discharge most of hydration heat, account for 75% of total amount of heat, within this length of time, the strength of materials increases the fastest, and cast material intensity is played a decisive role, and 7 days uniaxial compressive strengths of different proportionings of various embodiments of the present invention medium sand, cement, water are in Table 1:

Table 1

Proportioning (sand: cement: water)	7 days compressive strength (MPa)
		9:1:1	2.86
10:1:1.1	2.17
		11:1:1.2	1.99
12:1:1.3	1.2
		14:1:1.5	0.81
16:1:1.7	0.61
		18:1:1.9	0.55
20:1:2.1	0.45
		22:1:2.3	0.33
25:1:2.6	0.28
		27:1:2.8	0.22
30:1:3.1	0.2

7 days compressive strength of sand-cement slurry composite material is shown in Fig. 1 with the Changing Pattern of proportioning.

From table 1 and Fig. 1, can find out, along with the minimizing of cement content, 7 days compressive strength of sand-cement slurry composite material reduce rapidly, and the matching relational expression of its 7d uniaxial compressive strength and sand and cement proportion is:

In formula, for the 7d uniaxial compressive strength of composite material, unit: MPa;

for the weight ratio (>=9) of sand and cement, watering quantity is 1/10 of cement, sand compound weight.

The cement mortar specimen uniaxial compressive strength of 7 days, 14 days, 28 days is the number percent of 7 days strength increases of strength ratio of recording in Table number percent in 2(table bracket),

Table 2

Sand-cement slurry composite material compressive strength is with Fig. 2 between the Changing Pattern of curing time.

From table 2 and Fig. 2, can find out:

(1). in first 7 days of natural curing, cement mortar specimen intensity rises rapider.

(2). between 7d～14d and 14d～28d, the strength increase of each proportioning test specimen is than basic identical, and wherein during 14d～28d, the number percent of strength increase is slightly large, and for 18:1 test specimen, its intensity increases by 35% and 45% successively; For 22:1 test specimen, its intensity increases by 36% and 70% successively; For 25:1 test specimen, its intensity increases by 46% and 61% successively.This is that curing time is long due between 14d～28d curing period on the one hand, is 14 days, and on the other hand, test specimen is building moulding, and its moisture is less, and intensity rises slower.

Claims (1)

1. a low-intensity building type sand-cement slurry model, is characterized in that being comprised of sand, cement and water, and sand, cement, water weight ratio example are 9-30:1:1-3.1;

Its method for making is:

(1) measure the water cut of selected sand;

(2) by cement, the artificial mix of sand evenly after, water is poured in mix, slowly infiltrate;

(3) once, machine mixing once for artificial mix; Once, machine mixing once for artificial mix again;

(4) uniform mix material is divided and inserted for three times in cylindrical steel mould, insert rear building at every turn, treat that this layer of building completes, with steel brush, by its surface galling, to avoid the generation of layering, then insert cast material, continue building, so altogether building three times;

(5) demoulding maintenance, after whole test specimen building completes, removes steel mold, forms wood property and tests needed standard specimen, this test specimen is imbedded in the damp sand equating with its water cut to natural curing.

Images