Cement-mixed Soil Research Articles

Examining freeze/thaw effects on performance and morphology of a lightly cemented soil

The long-term hydraulic performance of lightly cemented soils is critical to engineering applications such as water infrastructure and/or remediation systems. Unfortunately there is a lack of literature that has related hydraulic performance of lightly cemented compacted soils (~5%) after freeze/thaw cycling to the morphology changes that result from this type of environmental loading. Previous studies on compacted clay materials have shown the underlying mechanisms responsible for hydraulic conductivity increases after freeze/thaw are attributed to initial cracking and subsequent frost lens formation. It is uncertain if the morphology changes and subsequent damage mechanisms for lightly cemented compacted soil will be similar to that of compacted clays or more similar to that of stronger, more brittle soil-cement reported in previous studies. The primary objective of this paper is to enhance the knowledge base on morphology changes that lightly cemented compacted soils undergo as a hydraulic barrier under freeze-thaw conditions. Laboratory testing is performed on six different compacted soil-cement mixes. The variables of the mix designs included cement content (3% or 6%) and compaction moisture contents (dry of optimum water content, optimum water content, or wet of optimum water content). The hydraulic performance of these samples is evaluated before and after three cycles of freeze/thaw. The mechanisms of freeze/thaw damage are then examined by studying the morphology changes in the samples via optical microscopy and mercury porosimetry. Hydraulic conductivity testing showed that increases in hydraulic conductivity after freeze/thaw cycling was primarily a result of cracking in the samples tested. Thin section results showed little evidence of ice lens formation in the samples after freeze/thaw exposure. However, formation of micro-cracks/cracks and matrix disruption after freeze/thaw were evident. The exception to this was observed for the 3% cement content sample compacted at wet of optimum conditions that appeared to undergo localized macropore increases. Mercury intrusion porosimetry failed to show consistent, small scale increases in porosity after freeze thaw, likely as a result of significant changes in the damaged areas not captured via the porosimetry scale.

Effect of Freeze/Thaw Cycles on the Performance and Microstructure of Cement-Treated Soils

AbstractIn this paper, the performance and structural changes in cement-treated soils under influence of freeze/thaw (f/t) exposure are investigated. Specimens from plastic and compacted soil-cement mix designs were exposed to different f/t scenarios to study the influence of f/t dimensionality (i.e., one-dimensional versus three-dimensional exposure) and specimens’ age at the time of f/t exposure on changes in their performance. Changes in hydraulic conductivity, unconfined compressive strength, and longitudinal resonant frequency of the specimens were studied under each exposure scenario. An examination of the microstructure of the f/t exposed and control specimens using transmitted light optical microscopy was also performed to evaluate how the soil-cement matrix was disrupted after exposure to f/t cycling. Observations showed increases in water content of the mix design (when wet of optimum water content), as well as increased specimen age at the time of exposure may increase f/t susceptibility. On th...

Hydraulic Conductivity of Residual Soil-Cement Mix

In Malaysia, although there are several researches on engineering properties of residual soils, however study on the hydraulic conductivity properties of metasedimentary residual soils is still lacking. Construction of containment walls like slurry wall techniques can be achieved with hydraulic conductivity of approximately 5 x 10-7cm/sec. The objectives of the study were to determine the physical properties of metasedimentary residual soils and to determine the influence of 1%, 3%, 5% and 10% of cement on hydraulic conductivity parameters. The coefficient of hydraulic conductivity of the soil naturally and soil-cement mixtures were determined by using the falling head test. According to the test, the hydraulic conductivity of the original soil was 4.16 x 10-8 m/s. The value decreases to 3.89 x 10-8 m/s, 2.78 x 10-8 m/s then 6.83 x 10-9 m/s with the addition of 1%, 3% and 5% of cement additives, respectively. During the hydration process, cement hydrates is formed followed by the increase in pH value and Ca(OH)2 which will alter the modification of pores size and distribution. When the quantity of cement increases, the pores size decrease. But, the addition of 10% cement gives an increased hydraulic conductivity value to 2.78 x 10-8 m/s. With 10%, the pore size increase might due to flocculation and agglomeration reaction. The generated hydraulic conductivity values will indirectly become a guide in the preliminary soil cement stabilization to modify the properties of the soil to become more like the properties of a soft rock.1. Introduction

格子状地盤改良工法における格子間隔簡易設定法の適用性

格子状地盤改良工法における格子間隔簡易設定法の適用性

Application of Water-Proof Curtain with High-Pressure Injection Concrete Piles in Foundation Pit

This paper introduces a design program for supporting of deep foundation pit through the actual example for Beijing Moisten the world Center project to solve the difficulties of high water content in foundation soil, sensitiveness to surroundings, and difficult control of quick sand and flowing mud in the process of supporting of foundation pit. This program adopts a supporting system with upper soil nailing wall and lower pre-stressed anchor pile and a comprehensive water-proof curtain (Retaining piles + Long spiral high pressure jet grouting & mixing piles) to effectively solve the above difficulties. It is indicated through actual monitoring that displacement and settlement of foundation pit meet the specification and design requirements with excellent water-proof effect. The successful application of this program provides a reference for foundation pit engineering with rich underground water, especially for engineering at hard soil layer and stratum with sand and gravel that are apt to the formation of cement-soil grouting and mixing piles, as well as engineering with limitation on dewatering of foundation pit.

Application of Cement Soil Mixing Pile for Transmission Line

The mechanism of soil liquefaction and the principle of enclosure method treating subgrade liquefaction are elaborated in this paper.It proves that the grid type cement soil mixing pile enclosing foundation can eliminate liquefaction based on amounts of datum and engineering case.And the means of design and construction are summarized.

Arresting Settlement of Peaty Soil in Built-Up Area

In Singapore, ground settlement is one of the major problems encountered in built-up area in housing, private and industrial estates. While the structure is not affected by the settlement as they are supported by piles. Some amount of settlement may occur on the ground surrounding the structures, thus affecting the service road, car park area and other underground services. This ground settlement, mainly secondary consolidation settlement will continue for long time due to presence of thick layer of soft peaty soil. Conventional ground improvement methods may not be suitable in solving such problem especially in built-up area. Hence, in present research, a new method called Liquefied Soil-cement Mix (LSM) method is developed to treat peaty soil and thus arrest the ground settlement in built-up area. This method involves injecting cement-clay slurry into peaty soil mass to fill the voids and fissures of peaty soil. The appropriate injection pressure is carefully designed to minimize ground disturbance during and after LSM treatment. In this study, a field trial was executed to treat the peaty soil at depth of 7 to 10 m by using this method. The field trial and laboratory tests were conducted to evaluate the efficiency of LSM method. The test results indicated that settlement was significantly reduced with LSM treatment.

A Field Trial Study on Jet Grouting to Improve the Subsoil in Ho Chi Minh City, Vietnam

This study attempts to fabricate a single Jet Grouting system from used machines and the machines were modified by the authors. The assembled jet grouting system was fabricated to create soil cement mixing by high pressure beams at pressure up to 30 MPa of cement slurry or water plus cement slurry. The two soilcrete columns were created using the above Jet Grouting system at the bank of Nhieu Loc canal, Binh Thanh District, Ho Chi Minh City, Vietnam. The diameters of the soilcrete columns vary from 0.8-1.3 m at the top and larger 0.4 m at the bottom. The lengths of the columns were 12 m and 4 m for the column 1 and 2, respectively. Characteristics of a soilcrete column are appreciably dictated by operating parameters of a Jet Grouting system.

Strength correlations of cement-mixed soils using data mapping

Development of comparisons and correlations between the unconfined compressive strength (UCS) and the undrained triaxial compressive strength, qu, is essential for generalising performance and optimising the design of cement-stabilised soils. This paper introduces current work in collecting and collating data from a number of research projects involving both laboratory strength tests performed on identical cement-stabilised soil samples. The research project on cement-stabilised Singapore marine clays at the National University of Singapore has been used as an example to explain the work on comparing and correlating results from both tests by normalising data and constructing contour plots. The effect of variables on strength comparison and correlations was evaluated. The variation in strength correlations was found to be dependent on a number of factors including: soil properties, cement content, curing time and stress, total water/cement ratio, confining stress and strain rate. The results showed that at ∼100 kPa confining stress, UCS and qu, had similar magnitudes. Correlations between strengths and other design variables are discussed and presented.

The Research on Applied of Cement-Soil Mixing Method Reinforcing Shallow Soft-Soil Foundation in Yinchuan Distric

Through tests and application, analyzes influential factors & reinforcement effect and application prospects & economic benefits of cement-soil mixing composite foundation, propounds some points of view for stabilizing & reinforcement soft-soil foundation by cement-soil mixing method especially in Yinchan District combined with constructive situation

Characteristics of Soil Grouting by Hydro-Jet Technology

The concept of physical bases for the grouting of soils by jet technology is discussed. Strength characteristics are cited for soil-cement mixes in jet-piles, which are attained during their formation as a function of volume replacement of soil by cement grout. Basic principles are outlined for calculation of the strength of soil-cement compositions in jet-piles on the basis of the density of the slurry removed.

Numerical Analysis of Slot Stability during the Supper-Deep Diaphragm Wall Construction

Two subway stations of line Z1 were built in Tianjin cultural center and Tianjin Yujiapu traffic hub. The diaphragm wall depth of the two stations was more than 60 m. The geological and hydraulic conditions were different in the two site. Keeping stability of slot wall was the key of supper-deep diaphragm wall construction to the both stations. Two 3D numerical models were built by ABQUS software to simulate the grooving process. The conditions of different slurry specific gravity and grooving depth were calculated. The deformation laws of the slot wall and ground settlement around the slot wall were studied. The results showed the upper soft silty clay and deeper silty sand layers were easy collapse. Finally, some technologies such as "] [" type guide wall, properly improving slurry specific gravity, soil cement mixing reinforcement were suggested to improve the stability during the diaphragm wall construction of the two stations.

D008 Automation of Soil Mixing for Soil Test by using Industrial Robot

This paper presents the automation of soil testing using an industrial robot with six degrees of freedom. Mixing soil and cement for soil testing imposes a heavy burden on workers. For shortening the soil test time, we focused on soil and cement mixing and developed a controllable mixing system using a robot and a motor unit to monitor and carry out soil-cement mixing, respectively. Using a software program, the system alters the mixing paddle revolution, rotation, position, and posture angle. As a result, the phenomenon that occurs during soil-cement mixing is evaluated using the system and the data for developing in demand.

An Investigation of Lateritic Soil Cement for Sustainable Pavements

Shortage of crushed rock as pavement base course for road construction and an increase in fuel cost have prompted the search for alternative materials. In this regard, improvements of the lateritic soil cement (LSC) have been investigated. Many researches have focused on study of the properties of the stabilized soil. However, more researches have to be done in order to explain how soil properties have improved. The production of crushed rock involves drilling, blasting, crushing and transportation, which are the cause of environmental problems. The objective is to use the improved lateritic soil instead of crushed rock as the base course material for highway pavement construction. In order to understand why the LSC has higher strength, microstructure of LSC composite was investigated by X-ray diffraction machine (XRD) and the Scanning Electron Microscope (SEM). The improvement of the unconfined compressive strength (UCS) of LSC composite was also evaluated. As regards the application aspect, the results show that cement mixed lateritic soils are suitable for base course construction. The investigation also shows that increase in UCS was attributed to the cement hydration within soil mass, resulting in the formation of reaction products as analyzed by XRD. It was also found that UCS was proportionally increased with the amount of the major reaction products such as calcium silicate hydrate (CSH).

SCM wall in sand: Numerical simulation and design implications

The full scale Soil Cement Mixing (SCM) wall was constructed to investigate viability of the wall. Long term behavior of the wall resulted in viability of the wall. However, design guidelines on SCM wall are limited due to its complex geometry. In this paper, the three dimensional finite element method is employed to study the influence of various design decisions for SCM wall. The numerical model is first calibrated with an instrumented case history. Then a parametric study is constructed. The results give information on the influence of the following factors on the wall behavior: size of column, column overlapping, column embedment, existence of relieving platform, and column strength. The implications in design are discussed.

Application of Cement-Soil Mixing Pile with Bearing Load Plate

In order to treat efficiently with the soft multi-layers in the middle of ground, the improved cement-soil double mixed pile is developed and the pile diameter is enlarged in the soft soil layer depth to form the cement-soil mixed column with bearing load plate. The installation mechanism, deep mixing machine, and pile installation procedure of the soil-cement mixed pile with bearing plate is presented. The field test results show that the cement-soil mixing pile with bearing load plate construction technology can ensure the cement mix content and mixing uniformity. The pile strength is greatly higher than conventional cement-soil pile, so it can be used to improved soft multi-layered ground economically and effectively, and it has a good potential application for practice.

Research on Load Transfer Behavior of Cement-Soil Mixing Piles by Load Test

The pile axial strains were measured according to the results of static loading test. The axial force and side friction of pile were calculated, and load transfer behaviors were researched. Analysis of the data shows that cement-soil mixing pile has the characteristics of friction piles. The rapid reducing of the upper pile axial force and friction show that load passed within a certain range. Horizontal crack occurred at the upper of the pile. Before and after the destructing of the pile load transfer mechanism is different.

Case Study of Oh-hara Dam Embankment Rehabilitated by Cement-mixed Muddy Soil for Seismic Resistant-Reinforcement

大原ダムは堤体が老朽化により断面不足や漏水により耐震性が不足していたため，耐震補強と漏水防止のための改修を行った事例である。大原ダムでは，ダムサイト付近で入手可能な築堤土による堤体改修法は，斜面勾配を既設堤体よりも緩くする必要から，大量の築堤土が必要となるだけでなく貯水容量の減少も著しく現実的な改修が不可能であったため，貯水池内に堆積した底泥土を築堤土に利用できる砕・転圧盛土工法が採用された。本稿では大原ダムにおける耐震補強と漏水防止のための砕・転圧盛土工法による堤体ゾーニングと，それを築造するための設計・施工法について述べる。大原ダムは貯水量の減少を防ぐために改修後の堤体を既設堤体内に入るようにゾーニングした。また，池内の底泥土に既設堤体などからの掘削土を加えた混合泥土を砕・転圧盛土工法に利用したことで，工事発生土の場外処分を無くすと同時に底泥土を約26,000m3除去し，結果として貯水量を約30,000m3増加させることができた。

Properties of Cement-Treated Soils During Initial Curing Stages

The engineering properties of cement-treated soils manufactured by the so-called “Pipe Mixing Method” and “Super GeoMaterial (SGM) Method” were studied. In these methods, clayey soils with high water contents are mixed with cement and used as fill material. Since the cement-mixed soils are transported through a pipeline, whose length at times exceeds 2 km, the properties of the treated soil during the initial stages of the hardening process are important. Bender element, vane shear and fall cone tests were performed to obtain such engineering properties as the shear modulus and the shear strength. The study revealed the following: 1) The minimum shear wave velocity of treated soils is detectable at around 2.8 m/s, corresponding to a shear modulus of about 12 kPa. 2) A linear correlation between the shear modulus and the shear strength exists even in the very early stages of curing, approximately G =300 s , where G and s are the shear modulus and the shear strength, respectively. This relation is similar to that for natural clays. 3) The “setting time” observed for concrete is also apparent in cement-treated soil materials. 4) Fall cone tests comprise a useful and simple technique for measuring very low levels of shear strength.

Creep failure of geomaterials and its numerical simulation

It is shown that creep failure of geomaterials can be simulated by a non-linear three-component elasto-viscoplastic model. The model is described in the case of a single stress variable and the isotach viscous property type, although the model can be applied to more general three-dimensional stress conditions and viscous property types other than isotach. Various trends of viscous behaviour, including stress relaxation and creep deformation with and without creep failure, are illustratively simulated to show that creep failure is one specific aspect of the whole viscous behaviour that can be simulated by a single model. Creep failures observed in drained triaxial compression tests on compacted moist cement-mixed gravelly soil and saturated soft clay are simulated.