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 CHEMICAL ENGINEERING TRANSACTIONS  
 

VOL. 66, 2018 

A publication of 

 

The Italian Association 
of Chemical Engineering 
Online at www.aidic.it/cet 

Guest Editors: Songying Zhao, Yougang Sun, Ye Zhou 
Copyright © 2018, AIDIC Servizi S.r.l. 

ISBN 978-88-95608-63-1; ISSN 2283-9216 

Study on Soil-Stone Interaction between Strength and 

Deformation Characteristics of Rock-soil Mixture 

Shiping Xu 

Lanzhou construction investment (holding) Group Co.Ltd, Lanzhou 730000, China 

GSLZXshp@163.com 

In order to explore the effect of different rock content on shear strength and soil-rock mixture, 21 large-scale 

single-shear tests were conducted using advanced large-scale single shear tester. A total of 7 test samples 

from 0% to 80% of stone content were designed and tested at three different normal pressures of 100, 200, 

and 300. Based on the experimental results, the relationship between stone content and shear strength, and 

shear characteristics of soil-rock mixture was analysed. The experimental results show that under the same 

normal pressure, the internal friction angle and cohesion of soil-rock mixture increase first and then decrease 

with the increase of stone content. When the soil-rock mixture is between 40% and 50%, the shear strength is 

the highest. The results show that the shear strength of soil-rock mixture is affected by the porosity ratio of 

soil-rock mixture, and at the same time, the structure and dominant particles in soil-rock mixture also change 

with the increase of stone content. When the content of stone is between 0% and 20%, the fine aggregate 

dominates in the soil-rock mixture, and the soil-rock mixture is suspended and compacted structure. At this 

time, the shear strength of the soil-rock mixture is similar to that of the matrix particles. When the content of 

stone is 20%~50%, the soil-rock mixture is a skeleton pore structure. With the increase of the amount of 

stone, the skeleton of the soil-rock mixture gradually forms and the occlusal force between the particles 

increases, making the cohesion and internal friction. The horns have been significantly improved; when the 

amount of rock content exceeds 50%, the soil-rock mixture exhibits a dense skeleton structure, the porosity 

starts to increase and the fine granules begin to drastically decrease, and the fine aggregate cannot fully fill 

the pores between the blocks. The shear strength of soil-rock mixture began to decline. 

1. Introduction 

Soil-rock mixture is a kind of non-homogeneous bulk material formed by mixing soil and rock. Its shear 

strength characteristics are mainly affected by factors such as water content, stone content, grain gradation 

and compaction degree. In the large-scale indoor direct shear test, on the basis of previous studies, the 

impact of grading parameters was considered. By controlling the mass and volume of the sample to achieve 

the level of compaction required for the test, the main parameters were analysed for the shear resistance of 

the soil-rock mixture. The effect of strength, the test results show that: with good grading, the shear strength of 

soil-rock mixture increases first and then decreases with the increase of non-uniform coefficient, and the non-

uniform coefficient reaches a peak around 22.99, while the curvature The coefficient has little influence on it; 

the shear strength of soil-rock mixture increases with the increase of stone content and compaction, but the 

trend of increase decreases with the degree of compaction exceeding 92.5%. For the growth, the shear 

strength increases first and then decreases, and reaches the peak value near the optimal moisture content. 

Based on the multiple linear regression analysis of MATLAB, the order of the influence of each factor on the 

shear strength of the soil-rock mixture is obtained. Stone content> moisture content> compaction> uneven 

Coefficient> curvature factor, obtained by nonlinear regression analysis formula for fitting the shear strength of 

each factor, and the correlation index R2 is greater than 0.9 (Abduljauwad and Gassous, 1991). 

Aiming at the difficulties in the analysis and calculation of parameters and models for the high-fill earth-rock 

mixture engineering, the apparatus of unsaturated soil was used to carry out 36 consolidation drainage shear 

tests to control the matric suction and net confining pressure, and the degree of compaction and matrix were 

quantitatively studied. The effect of suction and mix ratio on the strength and deformation characteristics 

                                

 
 

 

 
   

                                                  
DOI: 10.3303/CET1866077 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Please cite this article as: Xu S., 2018, Study on soil-stone interaction between strength and deformation characteristics of rock-soil mixture, 
Chemical Engineering Transactions, 66, 457-462  DOI:10.3303/CET1866077   

457



mixes was established. The modified algorithm expressions for shear strength, tangent deformation modulus 

and tangent bulk modulus of unsaturated compacted soils were established. The test results showed that the 

stress and viscosity were destroyed. The cohesive force increases linearly with the increase of suction force, 

and the change of suction force has little effect on the effective internal friction angle; the stress and strength 

parameters of failure increase with the increase of compaction coefficient; the failure stress and strength of 

soil sample with 4:6 soil-rock ratio. For soil samples with an overall parameter slightly higher than 2:8, the 

effective cohesion increases with the increase of the silty clay content. With soil samples with the same mix 

ratio and compaction coefficient, the greater the net confining pressure or suction, the greater the strength of 

the sample. Large, gradual change in body deformation; in soil samples with the same net confining pressure 

and suction force, the higher the compaction coefficient, the strain curve gradually changes from the strain 

hardening type to the ideal elastic modulus type. Some soil samples tend to be under the net confining 

pressure Variant unsaturated soils nonlinear Incremental Constitutive conform to the corrected fill large 

engineering practice, it can be used to calculate the slope stability and high fill GROUND HIGH FILL 

modification (Aziz et al., 2016, Cai et al., 2015). 

   

Figure 1: SEM images of TEG powder before (a) and after grinding (b, c) 

2. Material and method 

Soil-rock mixture is a kind of loosely-packed body with complex internal structure and a combination of block 

stones and soil particles formed during the Quaternary period under the dynamic coupling between the interior 

and exterior of the earth. This geological material has diverse material sources and complex geological 

origins. It is different from the general homogeneous soil and the general rock mass. It is a kind of special 

geological material between the soil and the fractured rock mass. Starting from the mesoscale, with the aid of 

mesoscopic calculation methods and mesoscopic tests, the characteristics of deformation and failure of soil-

rock mixture under load are revealed, the mechanism of earth-rock interaction of soil-rock mixture is 

ascertained, and the deformation and fracture mechanism is essentially described. The research is the need 

for the current project construction, and it is also the inevitable development of the modern fine-spot rock and 

soil mechanics (Chakrabortyv et al., 2014). 

 

Figure 2: Dependencies of the micro-stresses on the dispersity level of TEG particles 

In nature, the distribution of soil-rock mixture is very random. Even if the soil-rock mixture produced in the 

same area and originated from the same origin, the structure of the soil-rock mixture will show differences in 

the local area. The soil-rock mixture obtained based on image processing technology is also limited to the 

distribution of blocks in a section, and it cannot reflect the distribution of blocks in all sections of the soil-rock 

mixture. At the same time, even if it can truly reflect the local structural features, due to the regional 

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differences of the soil-rock mixture, the true structure characteristics of the local areas cannot fully reflect the 

structure characteristics of the entire site. Therefore, the establishment of a random structure model of soil-

rock mixture is more valuable than the establishment of a real scale model of soil-rock mixture, and it is more 

universally significant (Chakraborty et al., 2014). 

3. Result and discussion 

3.1 Accumulative settling characteristics of different packing slamming  

The coarse aggregate in the earth and rock-filling materials can be divided into sandstone aggregates and 

sand and mudstone mixtures. The single point concrete tests are performed on the two source materials 

respectively to observe the sag and sedimentation at single points. Quantities, to study the compaction effects 

of different types of coarse aggregate soil-rock mixture, and determine the best number of slamming. Taking 

into consideration the existing construction conditions, the single-shot tamping energy of the filling body 

treatment test is 3000. According to experience, the virtual shop thickness is 4.0 m, and the number of 

slamming hits is 20 hits (Park et al., 2015; Lohani et al., 2006). 

From the point of impact of on-site slamming effect, the coarse aggregate of the filler in the depth of the 

bottom of the pit was broken within 0.5m, and the average number of super heavy-duty gravity hits of the soil 

and stone mixed with sand and mudstone as the coarse aggregate was 6.4 hits. Less than the depth of the 

deep filling of the heavy-duty gravity hits, after the powerful ramming pit 0.5m below the padding of the super-

heavy hitting the number of dynamic hits in the 7.2 ~ 8.7 hits, after the dynamic compaction to fill the 

foundation to reach the state of dense, deep foundation The density is greater than the shallow density. The 

average number of heavy heavy-duty gravity hits within a depth of 0.5m with ground-stone mixture of 

sandstone and coarse aggregate is 8.4 hits, and the average value is significantly smaller than that of deep-

filled heavy-duty gravity hits. The number of super heavy-duty dynamic strikes hitting the following fillers was 

8.7 to 13.2 hits, and the compacted land after compaction reached a dense-to-dense state. The deepness of 

the foundation was greater than that of the shallow layer. 

1
ar g max | (1 （) , ）|

i k
j r b


                                                                                                                         (1) 

1
（ , , ）

i k b
m r w k


                                                                                                                                 (2) 

The increase of compactness increases the elastic modulus and deformation modulus of the filler, and the 

shear strength of the filler increases, which is conducive to enhancing the stability of the filling slope and 

reducing the deformation of the filling foundation. This chapter mainly analyses the influence of packing 

density on the stability and deformation of the filling body under complex terrain conditions in the mountain 

area. The deformation of the building is analysed by taking the two-dimensional valley filling body as an 

example. The deformation displacement vector of the filling soil on the centre of the valley and on the slopes 

on both sides of the valley is different, and the gravity of the soil around the hillside on both sides is different. 

In addition to the vertical displacement, there is also a horizontal displacement component. The larger the 

vertical displacement component, the larger the horizontal displacement component. The smaller the degree 

of compaction, the greater the vertical component of the displacement of the building body, and hence the 

greater the horizontal component. A is a double-sided slope, and b is a single-faced slope. When the 

compactness is small when the slope is filled, the vertical displacement component and horizontal 

displacement component will be larger and more unstable. 

 

Figure 3: Micro-hardness dependencies on an applied load on indentor for the samples of initial TEG  

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The soil-rock mixture medium has the characteristics of high heterogeneity, significant structural effect and 

size effect, which makes its physical and mechanical properties complex. In this paper, according to the 

deformation and influencing factors of the shear band in the shearing process of soil-soil mixture, a self-

developed RSM-1000 motor servo control large-scale earthwork shear strength test system is adopted to 

consider different stone contents (0, 30%, (50%, 70%), overburden pressure, block size (L1, L2, L3), three 

main structural control factors, shear deformation test of soil-rock mixture, drilling through the inside of the 

sample The method of wire and dry ash monitors the characteristics of the shear belt. The results show that 

when the content of stone is less than 30%, the deformation of the sample is less affected by the stone, a nd 

the strength mainly depends on the strength of the sand. When the content of stone reaches 50%, the 

skeleton structure has been formed in the sample. Affected by the block rock, the strength is caused by the 

joint action of the block stone and the sand. When the content of the rock reaches 70%, the block-stone 

overhead structure has been formed in the sample. In the case of high stone content and large grain size 

stone, the block stone sample with a penetrating shear plane develops with the shear deformation, and the 

block stone undergoes extrusion and inversion phenomenon; the sample of rock stone distributed near the 

shear face, With the development of the shear deformation, the block rock is dominated, and the block stone 

undergoes extrusion, angular shearing and misalignment. The shear deformation of the specimen can be 

compared with the failure characteristics of a landslide that is deformed by backwards and forwards or a 

composite landslide that deforms from the front to the back, that is, the trailing edge of the slope produces 

cracks under the action of active earth pressure, and then sinks. Compaction, slippage and slipping; creep 

deformation of the leading edge of the foot slope; shear loss of the rock and soil in the slope to progressive 

expansion of the sliding surface, the final shear plane through, the formation of the overall destruction. The 

research results are of great significance for revealing the formation and evolution rules of the landslide shear 

zone of the soil-rock mixture, the failure modes, and the disaster prevention and mitigation of landslides 

(Nataraj et al., 2015). 

3.2 The influence of compactness on deformation of filling body 

(1) Based on the heterogeneity, non-linearity, non-continuity, and other characteristics of the "soil" and "block 

stone" that make up the soil-rock mixture, the concept of "calculation of the mechanics of the soil-soil mixture" 

is proposed, and the soil-rock mixture is defined. The key scientific issues that the mechanics of scale 

computational mechanics must solve are that the soil-rock mixture is regarded as a three-phase composite 

medium consisting of a soil matrix, a block stone, and a soil-stone interface. Based on the mechanical 

numerical test method based on the finite element principle and damage statistical mechanics, the effects of 

orientation, random distribution, rock mass, and soil-cement bonding characteristics on the deformation and 

cracking of soil and rock are comprehensively considered, and the soil-rock mixture is analysed. Under the 

condition of progressively progressive failure, the damage can be divided into three grades: the failure of 

earth-rock interface slip, the failure of soil cracking, and the misalignment of block stone (for low-strength 

schist, slate, etc.) (Tsukamoto, 2006). 

1

(1 ) *
i

r
N W B 



                                                                                                                                (3) 

 1 1
( | , )

k k k k
x p x x a                                                                                                                                (4) 

Table 1: Statistical table of super gravity sounding test after dynamic compaction 

Test setup 
Buried depth  
0~0.5m 

Buried depth  
0.5~1.0m 

Buried depth  
1.0~2.0m 

Buried depth  
2.0~3.0m 

Buried depth  
>3.0m 

Sand mud mix filler 

6.6 7.2 7.2 7.9 8.2 

6.7 6.5 7.4 8.5 8.7 

5.8 7.0 7.1 7.9 7.9 

Sandstone filler 
7.9 8.7 9.4 11.8 13.2 

8.8 9.1 9.0 8.1 9.9 

 

(2) Ultrasonic testing technology was introduced into the research field of soil-rock mixture. Test systems for 

axial and radial soil-rock hybrids were developed to study the variation of acoustic parameters under the 

uniaxial loading conditions of soil-soil mixture. The comparative analysis of rock acoustic test results reveals 

the unique characteristics of soil-rock mixture that distinguish it from “soil body” and “block stone”. Axial 

ultrasonic test was used to study the stress dependence of soil-rock mixture. The results show that the wave 

velocity, transmission coefficient and internal pore change law and the soil, block stone have obvious essential 

differences; at the same time, the axial compaction of soil-rock mixture is deduced. The expression of porosity 

reduction in the process. The radial ultrasonic test is used to analyse the damage-cracking characteristics of 

460



soil-rock mixture, and the evolution law of the crack width in the loading process is deduced according to the 

change of ultrasonic velocity. The evolution equation of the segmented nonlinear damage constitutive 

equation is established (Youwai and Bergado, 2003). 

 

Figure 4: The young modulus diagram for the samples of compacted TEG with average particle sizes  

Complex landforms in mountainous areas often have strong restraining effect at the bottom of valleys, which is 

conducive to stability. As the height of valley increases, the restraint effect weakens. Although there is a weak 

silty clay layer at the bottom of the area, due to the strong constraints, the bottom of the gully has good 

stability; due to the weak constraint, the displacement of the upper part of the gulch centre elevation of 330m 

is relatively large. Potential slip. In the process of filling the upper part of the elevation of 360.0m, due to the 

self-gravity and the constraints of rock slopes in the downhill slope, the amount of slip on the high-speed side 

to the high-speed side of the upper filling body is large, and the elevation is 360.0m below the elevation. The 

slope has an effect. 

Table 2: Result of compactness test 

Coarse 

aggregate type 

Average dry 

density(g/cm3) 

Maximum dry 

density(g/cm3) 

Average degree of 

compaction 

Solid volume 

rate 

Sand mud 

2.258 2.376 95.5% 84.4% 

2.257 2.376 95.4% 84.4% 

2.258 2.376 95.3% 84.3% 

Sandstone 
2.227 2.331 95.3% 84.7% 

2.228 2.331 94.8% 84.7% 

3.3 Effect of compactness on deformation and stability of fill building 

(1) The results of comprehensive axial ultrasonic testing and radial ultrasonic testing confirmed that the stone 

content is the most important index affecting the mechanical properties of soil-rock mixture. The P-wave 

velocity decreases with the increase of stone content, and the attenuation characteristics increase with the 

increase of stone content. With the increase of stress, the coupling effect between soil and rock becomes 

stronger, the wave-like velocity of axial wave velocity and transmission coefficient increase slowly; the radial 

relative wave velocity decreases with the increase of stress, and the cumulative width of cracks in the sample 

increases continuously. 

(2) Using the combination of the uniaxial compression test and the real-time CT scan test of the macroscopic 

soil-rock mixture, the CT number characteristics of the region of interest (ROI) inside the sample are 

quantitatively analysed, and the damage cracking of the sample is further clarified. Mechanism; In addition, 

based on mathematical morphology statistical principles to extract the crack geometry and analysis of its 

spatial distribution characteristics, the crack length, area and average width of the quantitative description, 

more conducive to the sample deformation cracking mechanism and research, It also helps to further establish 

the mesoscopic damage evolution equation. 

(3) In order to overcome the defect that the porosity value is uncertain due to the threshold value 

segmentation method, starting from the CT image itself, the porosity of the sample is calculated by mining the 

variation law of the number of CT images, and the porosity extraction is proposed. Gray level method. The 

gray value of the whole CT image is divided into two parts: the matrix and the pore. Through the determination 

461



of the matrix and pore CT number threshold, the porosity of the sample can be quickly calculated to analyse 

the damage cracking mechanism from the perspective of mesoscopic pore evolution. 

(4) Based on CT number-based damage variable definition method, the damage characteristics of soil-rock 

mixture samples under uniaxial loading are analysed, and the damage evolution equation and damage 

constitutive model of soil-rock mixture are obtained. The calculation shows that the damage variable and the 

principal strain have an exponential function in the loading process of the soil and rock samples, and the 

calculated results of the theoretical prediction model are in good agreement with the measured results. 

4. Conclusion 

Soil-rock mixture is a complex geotechnical material composed of two materials with different properties (soil 

medium and block stone), showing a strong non-uniformity, non-continuity, macroscopic mechanical 

properties and the amount of stone contained in the block stone. The structures such as morphological 

characteristics and spatial distribution are closely related. This paper takes the establishment of the mixture 

structure model as the starting point, and mainly completes the following work and obtains the following 

conclusions: Through the image acquisition device, the digital image data of the block stone is collected, and 

the image processing technology is used to identify the boundary pixels of the block stone, and then With the 

concept of "straight-forward music", a geometric method for obtaining linear boundaries and corner points of 

block stones was proposed, which not only eliminated the jaggedness of the boundary, but also obtained the 

boundary shape of block stones without losing the shape information of block stones. Two new parameters for 

the shape of block stone are proposed: the area difference ratio CPS, the angular index AI, and its effect on 

the mechanical properties of the soil-rock mixture. The study shows that when the content of stone is 50%, the 

shear properties of the soil-rock mixture are determined by the fine material and the block stone. The area 

difference CPS and the angular index AI indicate the surface shape characteristics of the block stone, and the 

mechanics of the soil-rock mixture. Less impact on performance. Based on the idea of "substituting an arc for 

straightness" and the principle of "allowing particles to overlap", an algorithm for filling irregular block stones 

(MCOS algorithm) was proposed, and the control conditions for filling accuracy were proposed, and a block 

suitable for discrete elements of particles was established. Stone basic unit. 

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