Grout Columns Research Articles

Prediction of the diameter of jet grouting columns with artificial neural networks

The prediction of the diameter of columns is a fundamental step for the design of jet grouting applications, as harmful consequences may derive from an inadequate selection of the treatment setup. Starting from different perspectives, empirical or theoretical correlations between the mean diameter of columns, the treatment parameters and the mechanical properties of native soils have been provided in the literature. However, the margin of uncertainty with these relations is still relatively large, mostly because of arbitrary assumptions made in their formulation. In order to reduce as much as possible the role of preliminary choices, a method based on artificial neural networks (ANN) is proposed. It consists in training a computer code with a set of experimental observations and in using the established correlations between input and output variables to predict future occurrences. After a brief introduction of the principles and limitations of ANN’s, the paper describes the logical procedure followed for the selection of the variables which better describe the mechanism of columns formation. A database of more than 130 case studies, where jet grouting parameters, properties of soil and diameters are simultaneously reported, has been collected from the literature to train the network. Systematic analyses have been then performed, parametrically varying the structure of the network and the use of data, in order to improve the accuracy of prediction. The comparison with other methods recently published in the literature confirms the good predictive capability of the proposed method. For its practical application, a set of design charts has been produced where the mean diameters of columns are expressed, for all injection systems and soil types, as functions of the soil penetration index NSPT and the specific energy of treatment. Safety factors have been finally computed to take into account the inaccuracy of prediction.

Comparison of the seismic response of reinforced auger pressure grout and concrete columns

Despite the wide use of grout as a structural material due to easy construction and cost-effectiveness, its seismic performance has rarely been evaluated experimentally. In particular, reinforced grout columns which may experience significant lateral deformation need experimental evidence to validate their adequacy. This paper summarizes findings from a relevant experimental study, which consists of five cyclic tests and one hybrid simulation test conducted at the University of California, Berkeley. The results show that reinforced auger pressure grout columns under cyclic lateral load and high constant axial load can provide ductile and reliable behavior in flexure, comparable to that of similarly configured reinforced concrete (RC) columns. Therefore, these reinforced grout columns can be considered as an adequate alternative to RC columns subjected to medium to high compressive axial loads in regions of high seismicity.

Multiple Regression Model for the Prediction of Unconfined Compressive Strength of Jet Grout Columns

Jet grouting is one of the most widely used techniques in soil improvement because of its possibility to strengthen cut-off groundwater and provide structural rigidity with a single application by this technique. The effectiveness of the jet grouting process influenced by many factors or application parameters such as soil properties, lifting (withdrawal) and rotation speed, grout/water/air pressure, etc. Jet grout column properties (diameter and mechanical properties) are the most important parameters for designing the project. There is still no credible method that can predict the properties of jet grout columns before field application, except extreme secured empirical rules and designers generally assume the characteristics of jet grout columns by perception. This process may cause waste of time and money due to inconsistency between assumed and observed properties of jet grout columns. In the present study, it was aimed to establish a model predicting the unconfined compressive strength of jet grout columns by using multiple linear regression analysis to overcome this problem.

Jet grouting for mitigation of installation disturbance

To reduce the impact of installation of horizontal jet grouting columns on surrounding ground, a new horizontal jet grouting technique termed controlled discharge horizontal jet grouting is developed. A field trial programme is conducted to verify the application of the technique technology. Field measurements of ground surface displacement and induced excess pore-water pressures are obtained during implementation of the technique. Five trial jet grout columns are installed at 2 m below the ground surface and subsequently exposed for measuring and testing. The observed vertical displacements of the ground surface range from 0·4 to 9·4 mm, with maximum excess pore-water pressures generated during the field trial varying between 3·5 and 25·6 kPa. The diameters of the exposed jet grout columns range from 1·1 to 1·4 m. Core samples extracted from the trial jet grout columns indicate that the quality of the jet-grouted soil formed is good, with total core recovery of 70–95% and rock quality designation of 79–92%. Unconfined compressive strength tests show that the 28-d strength ranges from 0·9 to 1·5 MPa, and Young's modulus at 50% failure load (E50) is between 61·5 and 145·3 MPa. The field trial results confirm the applicability of the technique for achieving low-impact installation of horizontal jet grouting.

Jet Grout Yönteminin Zemin İyileştirmesine Katkısının ve Bu Yöntemde Kullanılan Parametrelerin Etkilerinin İrdelenmesi

In this study, the relation between unconfined compressive strengths of jet grout columns which is generated with jet grouting method, parameters which are used in this method and soil properties before improvement were examined

A Novel Approach in Estimation of the Soilcrete Column’s Diameter and Optimization of the High Pressure Jet Grouting Using Adaptive Neuro Fuzzy Inference System (ANFIS)

For achieving optimized jet grout parameters and W/C ratio it is concluded to set trial tests in constant local soil as the conclusion depends on local soil and presence of the extensive range of the effective parameters. Considering the benefits, due to abundance of the involved variables and the intrinsic geological complexity, this system follows a great expense in the trial and implementation phases. Utilizing the soft computing methods, this paper proposes a new approach to reduce or to eliminate the cost of the trial phase. Therefore, the Adaptive Neuro Fuzzy Inference System (ANFIS) was utilized to study the possibility of anticipating the diameter of the jet grout (Soilcrete) columns on the trial phase based on the Trial and Error procedure. Data were collected from several projects and formed three sets of data. Consequently, parameters were held constant (as input) and the diameters of the Soilcrete columns were recorded (as output). To increase the precision, aforementioned data sets were combined and ten different data sets were created and studied, with all the results being assessed in two different approaches. Accordingly, Gaussian Function results in a huge number of precise and acceptable outcomes among available functions. Based on the measurements, Gaussian Function achieves the values of the R which are frequently more than 0.8 and lower values of the RMSE. Therefore, utilizing Gaussian Function, mainly a congruent relation between the R and RMSE is experienced and it leads to close proximity of the actual and predicted values of the Soilcrete diameter.

The numerical calculations of influence of underpinning on foundations settlement

Abstract The paper presents numerical calculations of the influence of implementation technology for underpinning the footing on settlement, with the use of finite element method. Three cases of underpinning methods were taken for calculations, depending on the diameter of the jet grouting column and the order of works. The intensity of settlement of the base of the footing foundation is significantly influenced by the growth of Young’s modulus and the jet grouting column with time, until its complete curing and reaching final technological parameters.

Support vector machines applied to uniaxial compressive strength prediction of jet grouting columns

Learning from data is a very attractive alternative to “manually” learning. Therefore, in the last decade the use of machine learning has spread rapidly throughout computer science and beyond. This approach, supported on advanced statistics analysis, is usually known as Data Mining (DM) and has been applied successfully in different knowledge domains. In the present study, we show that DM can make a great contribution in solving complex problems in civil engineering, namely in the field of geotechnical engineering. Particularly, the high learning capabilities of Support Vector Machines (SVMs) algorithm, characterized by it flexibility and non-linear capabilities, were applied in the prediction of the Uniaxial Compressive Strength (UCS) of Jet Grouting (JG) samples directly extracted from JG columns, usually known as soilcrete. JG technology is a soft-soil improvement method worldwide applied, extremely versatile and economically attractive when compared with other methods. However, even after many years of experience still lacks of accurate methods for JG columns design. Accordingly, in the present paper a novel approach (based on SVM algorithm) for UCS prediction of soilcrete mixtures is proposed supported on 472 results collected from different geotechnical works. Furthermore, a global sensitivity analysis is applied in order to explain and extract understandable knowledge from the proposed model. Such analysis allows one to identify the key variables in UCS prediction and to measure its effect. Finally, a tentative step toward a development of UCS prediction based on laboratory studies is presented and discussed.

The diameter of single, double and triple fluid jet grouting columns: prediction method and field trial results

In this paper, a simple expression to predict the average diameter of columns created with single, double and triple fluid jet grouting is proposed considering both the energy of the eroding jet and the resistance of the soil. The injection system (single, double or triple) and the composition of the injected fluids are taken into account on the basis of theoretical analysis of the turbulent diffusion of submerged jets. Instead of separately considering the energy of the air jet shrouding the eroding fluid, a simple parameter is introduced which represents the beneficial effect of air in reducing the energetic dissipation on the jet external surface. In this way, a new expression of the specific kinetic energy of the jet at any distance from the nozzle is proposed, which is a relevant step forward if compared with that at the nozzle or at the pump previously proposed, as it takes into account both the system characteristics and the composition of the eroding jet (either grout or water). In the expression proposed to predict the diameter of jet grouting columns, soil resistance is considered by way of the results of the standard penetration test and cone penetration test, in terms of NSPT and qc respectively. The expression has been calibrated on a number of experimental data, and in most cases proved its efficiency in predicting columns' diameter with a scatter of less than ±20%. The field trials results highlight that jet grouting is more effective in coarse-grained soils, as clearly shown by an efficiency parameter proposed by the authors. Design charts are drawn to quickly estimate the average diameter Da for different soils, injection systems and input energies.

Generalized Approach for Prediction of Jet Grout Column Diameter

This paper presents a generalized approach for predicting the diameter of jet grout columns based on the theoretical framework of turbulent kinematic flow and soil erosion. The proposed calculation method is applicable to all conventional jet-grouting systems and takes into account the full range of operational parameters, fluid properties, soil strength, and particle size distribution, including the effect of the injection time on erosion distance. It was demonstrated that the increase in the jet grout column diameter arising from the use of a compressed air shroud in the double and triple fluid systems is approximately 27–81% for the typical range of air pressure of 0.5–1.5 MPa. The proposed method was applied to four case histories involving four variants of jet-grouting systems, i.e., single fluid, double fluid, triple fluid, and an enhanced triple fluid system. Comparison between the calculated and the measured jet grout column diameters indicated that the proposed method can produce reasonable predictions for a variety of soil conditions. It was shown that jet grout columns formed by the enhanced triple fluid system are larger than those formed by the conventional triple fluid system by approximately 36% on average. The proposed generalized approach allows all the key variables to be considered and is a useful means for the design of ground improvement by jet grouting.

Jet grouting with a newly developed technology: The Twin-Jet method

The Twin-Jet method, a newly developed jet grouting technology for the instant solidification of soft ground, is presented. The basic principles of the Twin-Jet method are introduced and sodium silicate (water-glass) is selected as the binder to accelerate the hardening process of an admixture of grout and soil. Two case histories of the Twin-Jet Method, conducted in both a vertical (constructed in sandy soils) and a horizontal (constructed in clay soils) direction, are presented to show their effectiveness. Field construction shows that the admixture of grout and soil can be gelled within 5 to 10seconds. For the case history constructed in sandy soils, coring samples indicate that the jet grout columns are properly formed with a total core recovery of 80–100%, a rock quality designation (RQD) of 81–95% and a column diameter reaching 1.1m, while unconfined compressive strength (UCS) tests suggests that the 28-day UCS is within the range of 5.0–6.0MPa. For the case history constructed in clay soils, field cone penetration tests (CPT) suggest that the column diameter can reach 1.2m, and the UCS test results show that the 14-day UCS can reach 0.5MPa. All of these test results demonstrate the applicability of this newly developed technology in both sandy and clay soils.

Analysis of Foundations Reinforced with Jet Grouting

AbstractThe use of jet grouting columns to increase the bearing capacity and reduce the settlements of foundations is dealt with, the aim being to formulate a complete design procedure where theoretical analyses and site observations are combined. The study is based on experimental results reported in the literature, which show that jet grouting columns are able to transfer high vertical loads to the surrounding soil but also that structural collapse may locally occur because of a sudden narrowing of their cross sections and/or poor soil cementation. Noticeable attention has been then given to these aspects by interpreting the results of full-scale tests specifically performed to investigate the characteristics of jet grouting columns and their mechanical interaction with the surrounding soil. The results of this analysis form the basis of a numerical method developed to simulate the response of vertically loaded rafts supported by arrays of columns. The nonlinear load-settlement response of axially loade...

Behavior of Grouted Shaft Helical Anchors in Clay

AbstractSome years ago, a method was developed to incorporate a grout column around square-shaft helical screw-piles and anchors to increase shaft buckling resistance under compression loading. An additional benefit of this grouted shaft is to increase the load capacity in both compression and tension, depending on the geometry of the lead helical section and the soil conditions. Because of the unique construction procedure, the contribution of the shaft to the total capacity has largely been unknown. The behavior of grouted shaft helical anchors in clay was investigated by performing full-scale axial uplift (tension) load tests on a series of anchors installed at the University of Massachusetts Geotechnical Test Site. In order to isolate the contribution of the grouted shaft to the total load capacity, anchors were installed with a wooden dowel connection between the lead helical section and extension sections on three of the four anchors so that only the shaft resistance would be measured during the loa...

Innovative Construction Techniques used at North Shore Construction Project

AbstractThe North Shore Connector (NSC) project will extend the Allegheny County Port Authority’s Light Rail Transit System from downtown Pittsburgh below the Allegheny River to the North Shore via twin bore tunnels. Jet grouting, diaphragm walls, and soil mixing were selected as cost-effective technically viable ground improvement and support of excavation techniques.Jet grouting was specified to provide break-out (egress) and break-in (ingress) block sections at the tunnel boring machine (TBM) launching and receiving pits. Jet grout treatment was also used adjacent to buildings with shallow foundations and below retaining walls along the tunnel alignment. A new method for measuring jet grout column diameter based on electrical resistivity was employed on the project.New equipment was introduced in the U.S for constructing soil mix temporary support of excavation using a soil-mix technique termed Cutter Soil Mixing (CSM) due to the use of two vertical cutting wheels that have evolved from diaphragm wall ...

Application of data mining techniques in the estimation of the uniaxial compressive strength of jet grouting columns over time

Jet grouting (JG) is a soil treatment technique which is the best solution for several soil improvement problems. However, JG lacks design rules and quality controls. As a result, the main JG works are planned from empirical rules that are too conservative. The development of rational models to simulate the effects of the different parameters involved in the JG process is of primary importance in order to satisfy the binomial safety-economy that is required in any engineering project. In this paper, we present a new approach to predict the uniaxial compressive strength (UCS) of JG materials based on data mining techniques. This model was developed and verified using data from a JG laboratory formulation that involves the measurement of UCS. The results of the proposed approach are compared with the EC2 analytical model adapted to the JG material, and the advantages of the new approach are highlighted. We show that the novel data-driven model is able to learn (with high accuracy) the complex relationships between the UCS of JG material and its contributing factors.

Case studies on bermed excavation in Taipei silty soil

Bermed excavation (deep excavation supported by an excavation wall and a berm) can be an economical method for basement construction in urban areas if ground movement around the excavation is not the primary concern and the excavation site is large and (or) irregular in shape. This paper reviews three bermed excavation projects carried out in the Taipei Basin. One project was successful, one was successful after near failure, and one was a failure. Ironically, extensive ground improvement work had been done for the near-failure and failure cases; but no ground improvement was done for the successful case. It is of interest to find the similarities and differences among these bermed excavation projects. The causes of instability that result in unsuccessful bermed excavation projects and the applications of limit equilibrium analysis to the stability of bermed excavation are also discussed here. These three cases show that the existence of grout columns does not help to effectively increase the stability of the berm if the original safety factor against sliding of a berm slope is less than 1.0 and the improvement ratio of grout columns is low (say <20%).

Soil Inclusions in Jet Grout Columns

Jet grouting has increasingly become one of the ground improvement technologies used to address seepage concerns and to provide strength improvement of soils. The technique of jet grouting uses high pressure/velocity jet fluids to erode the existing soil and then to mix the cuttings with cement slurry to form soilcrete. Excess slurry or spoil is ejected to the surface. If the native soil is not completely mixed with slurry, the resulting columns will have soil inclusions which can reduce the strength of the column and/or increase the permeability of the column. A jet grout test program at Tuttle Creek Dam shows that the completed large diameter columns contain perhaps 40 to 50% or more of native soil that was not broken up and mixed during the jet grout process. The test program included excavation of full-scale columns to a depth of 35 ft (10.7 m) for visual inspection and testing. Additionally, six of the columns were cut or sectioned to investigate the interior of the columns. The observed inclusions include significant amounts of both fine grained (silts and clays) and coarse grained (fine sands and sands) soils. Evidence suggests at least two explanations: (1) fine grained soils can be difficult to erode and break up into small enough particles that can be ejected to the surface, especially if at low natural water content, and (2) when large diameter columns are being excavated, the excavated roof of the cylindrical cavity may be unstable and may collapse. With this roof instability large slabs of material can break off, fall into the slurry and escape the cutting and mixing action of the rotating jets. This paper describes the Tuttle Creek Dam test program, inclusions observed in the completed columns, and suggests potential causes of the inclusions.

Anisotropic Strength Characteristics of Composite Soil Specimen Under Cubical Triaxial Conditions

AbstractThis paper provides 41 cubical triaxial test results to examine the influence of the stress path angle and the improvement ratio on the anisotropic strength of the composite soil specimens consisting of remolded soft clay and grout columns. Pictures of failed samples shown in this paper are especially enlightening in demonstrating failure mechanisms. Results from this study can be summarized as follows. The composite soil specimens exhibited different failure patterns depending on the stress path angle, axial compression failure for 0°, 30° and 60°; lateral compression for 120° and 150°; and axial extension for 90° and 180°. Consistently, diagonal shear cracks through the grout column were observed for axial compression failure samples. On the other hand, tension cracks were observed for samples which failed due to lateral compression and axial extension. The composite soil specimens exhibited apparent anisotropic behavior. In general, the anisotropic strength ratio increased with the improvement ratio. The equivalent strength formula commonly used in practice may give erroneous results, especially when the stress paths are those of tension failure. In such a case, the anisotropic strength ratio suggested in this paper can significantly improve its accuracy.

CCB-based encapsulation of pyrite for remediation of acid mine drainage

Acid mine drainage (AMD) from abandoned coal mines continues to be one of the most significant environmental problems. Remediation of AMD requires an addition of lime source to decrease the acidity, and grouting the entire mine and encapsulating the pyrite by calcium-rich additives is often employed. Utilization of alkaline coal combustion by-products (CCBs) has gained acceptance in such remediation applications because of their cost-effectiveness. A study was conducted to investigate the effectiveness of CCBs to abate acid mine drainage by encapsulation of pyrite. Geomechanical, hydraulic, and environmental tests were performed on grouts prepared with various ratios of CCBs as well as an alternative free lime source, lime kiln dust (LKD). The results indicated that the mechanical properties of grouts were dependent on their free lime contents. Hydraulic conductivities of pyrite–grout columns were relatively high due to the coating of the pyrite rock with the grout rather than the filling of all of the void spaces, as commonly experienced in field applications. The leaching tests indicated that the presence of high amounts of lime in a grout is not solely sufficient to improve the quality of AMD, since the rate of dissolution of a high lime content grout may be slow due to its rapid hardening. Therefore, it is recommended that grouts be selected with consideration of their hardening capacities, as well as the percentage of lime content present in the mixture.

Nondestructive Evaluation of Installed Soil Nails

This paper presents the findings from a research study that evaluated nondestructive test (NDT) methods that may be useful for quality assurance purposes during construction of soil nail retaining walls. More specifically, the new NDT procedure will be used to evaluate the integrity of the grout column surrounding the steel tendon and to measure the grouted length of the installed soil nail. A preliminary evaluation of the existing NDT methodologies was undertaken to identify candidate NDT methods. The selected NDT methods, sonic echo and impact echo, were subjected to a detailed evaluation through three series of full-scale field NDT testing. The findings from the sonic echo tests are presented in this paper. The field studies demonstrated that the sonic echo method can be used successfully to detect major defects in installed soil nails. The nail condition predictions from sonic echo tests were confirmed by actual nail conditions observed after all the soil nails were exhumed.